BacterioFiles

477: Hijackers Hitchhike on Hyphal Highways Mar 27, 2023

This episode: Bacteriophages can hitch a ride on bacteria they don't infect to travel through soil on fungal filaments, potentially helping their carriers by infecting and killing their competitors!

Download Episode (7.1 MB, 10.3 minutes) Show notes: Microbe of the episode: Epinotia aporema granulovirus

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Takeaways For tiny bacteria, partially dry soil can be like a vast system of caverns, with particles of soil separated by air-filled spaces much bigger than individual bacteria. Not all bacteria can swim through liquid, and those that can’t simply try to thrive as best they can wherever they may be. But for those that can swim, fungi and other filamentous organisms can form bridges between soil particles that motile bacteria can swim across, reaching new places. In this study, phages were found to hitch a ride on bacteria they don’t normally infect, crossing fungus-like filaments to new places and infecting the bacteria they find there. The bacteria carrying them can also benefit from this interaction, since the phages help the carrier bacteria compete and establish a colony in the new location. Journal Paper: You X, Kallies R, Kühn I, Schmidt M, Harms H, Chatzinotas A, Wick LY. 2022. Phage co-transport with hyphal-riding bacteria fuels bacterial invasion in a water-unsaturated microbial model system. 5. ISME J 16:1275–1283.

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476: Bamboo Breakdown Benefits Beetle Babies Mar 13, 2023

This episode: Beetles inoculate bamboo with a fungus that consumes the bamboo sugars to feed the beetle larvae!

Download Episode (7.7 MB, 11.2 minutes) Show notes: Microbe of the episode: Saccharomyces cerevisiae virus L-BC (La)

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Video: Lizard beetle laying its egg

Takeaways The structural polymers that make up plants, such as cellulose, can be difficult for many organisms to digest. Some kinds of bacteria and fungi can do it, and some animals (cows, pandas, termites) partner with these microbes to be able to eat otherwise indigestible plant material. This includes insects such as leaf-cutter ants that farm external gardens of microbes, providing them plant material and then eating the resulting microbial growth. In this study, the lizard beetle lays its eggs in bamboo and inoculates the walls of the bamboo with a fungus that provides food to the larvae. Chemical analyses suggest that the fungus only consumes the simple sugars in the bamboo rather than breaking down the tougher polymers, which raises questions about the evolution of this interaction. Journal Paper: Toki W, Aoki D. 2021. Nutritional resources of the yeast symbiont cultivated by the lizard beetle Doubledaya bucculenta in bamboos. Sci Rep 11:19208.

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475: Modifying Mixed Microbiota Feb 27, 2023

This episode: New techniques allow specific modifications in certain members of a complex community of microbes, without isolating them in pure culture first!

Download Episode (11.5 MB, 16.7 minutes) Show notes: Microbe of the episode: Tomato golden mosaic virus

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Takeaways The technology for understanding and manipulating microbial genetics has come a long way in a short time. It used to take years even to sequence a small genome, and now thousands can be sequenced in just a few days. The technology to change and even create genetic sequences is also much further advanced now than just a few decades ago. But still, many analyses and modifications require a pure culture of a microbe to carry out. This study tested a method for modification of single or multiple species in a community of many. The method allows for identification of which species were successfully modified in targeted ways, and can allow the modified species to be extracted and studied individually. Journal Paper: Rubin BE, Diamond S, Cress BF, Crits-Christoph A, Lou YC, Borges AL, Shivram H, He C, Xu M, Zhou Z, Smith SJ, Rovinsky R, Smock DCJ, Tang K, Owens TK, Krishnappa N, Sachdeva R, Barrangou R, Deutschbauer AM, Banfield JF, Doudna JA. 2022. Species- and site-specific genome editing in complex bacterial communities. 1. Nat Microbiol 7:34–47.

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474: Stalker Cells Stop Seafood Sickness Jan 23, 2023

This episode: Predatory bacteria could protect lobster farms from disease-causing bacteria!

Download Episode (4.8 MB, 7 minutes) Show notes: Microbe of the episode: Gordonia rubripertincta

Takeaways Antibiotics have done wonders for controlling bacterial pathogens. Many people have lived that would otherwise have died, and some industries have produced much more than they would have, particularly those involved in animal farming. However, more and more targeted pathogens are developing resistance to the antibiotics we have, and new ones are harder to discover, so alternative approaches are needed. Here, predatory bacteria take the place of antibiotics in a study on farmed spiny lobsters. These predators swim after and attach to prey bacteria, hollowing out their contents to use as nutrients to make more predators. They do not hurt the lobsters, but the study finds they do reduce the number of pathogenic prey organisms injected into the lobsters at the same time. Journal Paper: Ooi MC, Goulden EF, Smith GG, Bridle ARY 2021. 2021. Predatory bacteria in the haemolymph of the cultured spiny lobster Panulirus ornatus. Microbiology 167:001113.

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473: Bacteriophage Bunks in Bacterial Barriers Dec 26, 2022

This episode: A bacteriophage that overcomes the bacterial CRISPR/Cas immune system by interrupting the CRISPR DNA with its own genome!

Download Episode (6.8 MB, 10 minutes) Show notes: Microbe of the episode: Wenzhou mammarenavirus

Takeaways Bacteria have many ways to resist being exploited by bacteriophage viruses, including the adaptable CRISPR/Cas system that uses a piece of viral nucleic acid sequence to target and destroy incoming phages. But phages also have many ways to evade and disrupt bacterial defenses. In this study, a phage is discovered that inserts its own genome into the CRISPR/Cas sequence in the bacterial genome, disrupting the bacterial defenses. To escape the defenses while it is doing this insertion, it carries genes for previously-unknown anti-CRISPR proteins. But inserting and removing a viral sequence from the bacterial genome is not always a clean procedure. Journal Paper: Varble A, Campisi E, Euler CW, Maguin P, Kozlova A, Fyodorova J, Rostøl JT, Fischetti VA, Marraffini LA. 2021. Prophage integration into CRISPR loci enables evasion of antiviral immunity in Streptococcus pyogenes. 12. Nat Microbiol 6:1516–1525.

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Great article on the history of phage therapy

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472: Caulobacter Condensates Compartmentalize Kinase Nov 21, 2022

This episode: Bacteria can use blobs of disordered proteins to quickly adapt to new conditions!

Thanks to Dr. Saumya Saurabh for his contribution!

Download Episode (10.9 MB, 15.9 minutes) Show notes: Microbe of the episode: Drosophila melanogaster Micropia virus

Takeaways Bacteria can adapt to environmental fluctuations via mechanisms operating at the various levels of the central dogma, or metabolism (stringent response). Recently, researchers at Stanford University discovered a mechanism that allows bacteria to sense and rapidly adapt to nutrient fluctuations by simply tuning protein self-assembly as a function of nutrient availability. Termed membraneless organelles or condensates, these proteinaceous assemblies can dynamically sequester key signaling enzymes within them in response to environmental cues. Biophysical adaptation mediated by organelles is fast, reversible, and facile; thereby representing a crucial step in the mechanistic understanding of microbial adaptation. Journal Paper: Saurabh S, Chong TN, Bayas C, Dahlberg PD, Cartwright HN, Moerner WE, Shapiro L. 2022. ATP-responsive biomolecular condensates tune bacterial kinase signaling. Sci Adv 8:eabm6570.

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471: Phage Fight Foils Fitness Aug 29, 2022

This episode: A phage both kills bacterial pathogens and selects for reduced virulence!

Download Episode (6.3 MB, 9.9 minutes) Show notes: Microbe of the episode: Helminthosporium victoriae 145S virus

News item Takeaways Using bacteria-killing viruses to treat bacterial infections, or phage therapy, can be a good alternative to antibiotics in some situations when there are no effective antibiotics for a particular infection. But bacteria can evolve resistance to phages as well as antibiotics, often with little cost to their fitness. In this study, a phage not only could treat an infection by attacking the bacteria, but the bacterial hosts that do evolve resistance to the phage do so by getting rid of certain structures that help them to cause more serious infection. Thus, therapy with this phage may both reduce the bacterial load and also make those remaining less virulent. Journal Paper: Kortright KE, Done RE, Chan BK, Souza V, Turner PE. 2022. Selection for Phage Resistance Reduces Virulence of Shigella flexneri. Appl Environ Microbiol 88:e01514-21.

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470: Super Small Symbionts Soothe Symptoms Jul 11, 2022

This episode: Tiny bacteria that live on larger bacteria reduce the inflammation and gum disease the bigger microbes cause in the mouths of mice!

Download Episode (6.3 MB, 9.2 minutes) Show notes: Microbe of the episode: Actinomadura viridilutea

Takeaways Even bacteria can be hosts to smaller symbionts living on them. Some kinds of these extremely tiny bacteria live in various parts of our bodies, and are sometimes associated with inflammation and the resulting disease. But being associated with something isn't necessarily the same as causing that thing. In this study, tiny bacteria living on other bacteria in the mouths of mice were found to reduce the inflammation caused by their bacterial hosts, resulting in less gum disease and bone loss in the jaw. Even when the tiny bacteria were no longer present, their former bacterial hosts were still less disruptive to the mouse mouth. Journal Paper: Chipashvili O, Utter DR, Bedree JK, Ma Y, Schulte F, Mascarin G, Alayyoubi Y, Chouhan D, Hardt M, Bidlack F, Hasturk H, He X, McLean JS, Bor B. 2021. Episymbiotic Saccharibacteria suppresses gingival inflammation and bone loss in mice through host bacterial modulation. Cell Host Microbe 29:1649-1662.e7.

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469: Prophage Provides Partial Protection Apr 04, 2022

This episode: A virus lurking in a bacterial genome protects its host population from infection with other phages, by killing off infected cells!

Download Episode (7.6 MB, 11.0 minutes) Show notes: Microbe of the episode: Olive latent ringspot virus

Takeaways Many bacteriophages just go in and gobble up all their host's resources to make a bunch of new viruses right away. Others play a longer game, splicing into and lurking in the host's genome across multiple generations until conditions are right to multiply more rapidly. It is beneficial to these latter kind when their host is resistant to the fast-killing variety, but how can bacteria be resistant to some phages but not others? In this study, one prophage (the phage genome integrated into the bacterial genome) carries a gene that does this in an interesting way. It prevents invading phages from replicating and kills the host cell so the infection can't spread, protecting the population (and all the other cells containing the prophage). It also contains an immunity element that allows the prophage to replicate itself without interference. Journal Paper: Owen SV, Wenner N, Dulberger CL, Rodwell EV, Bowers-Barnard A, Quinones-Olvera N, Rigden DJ, Rubin EJ, Garner EC, Baym M, Hinton JCD. 2021. Prophages encode phage-defense systems with cognate self-immunity. Cell Host Microbe 29:1620-1633.e8.

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468 - Commensal Can Kill Cholera Feb 28, 2022

This episode: Harmless gut microbes resist cholera with good defense or better offense!

Download Episode (5.8 MB, 8.4 minutes) Show notes: Microbe of the episode: Streptomyces corchorusii

News item Takeaways The community of microbes in our guts is highly diverse, yet generally they all coexist relatively peacefully. Some pathogens can invade this community and cause massive disruptions. Cholera is a disease caused by a pathogen that injects its competing bacteria with toxins and disrupts the health of the gut, leading to very watery diarrhea that can quickly dehydrate victims. This study found that some microbes commonly found harmlessly existing in the gut can resist destruction by the cholera pathogen. One of these resists by striking back with its own toxin injection system; the other creates a barrier of slime around itself that keeps the invader's toxins from reaching it. Such resistant gut microbes could help to reduce the threat of diseases such as cholera. Journal Paper: Flaugnatti N, Isaac S, Lemos Rocha LF, Stutzmann S, Rendueles O, Stoudmann C, Vesel N, Garcia-Garcera M, Buffet A, Sana TG, Rocha EPC, Blokesch M. 2021. Human commensal gut Proteobacteria withstand type VI secretion attacks through immunity protein-independent mechanisms. Nat Commun 12:5751.

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467: Prion Pivots Productive Pathways Dec 27, 2021

This episode: Prions in yeast can allow better adaptation to changing conditions!

Download Episode (9.5 MB, 13.9 minutes) Show notes: Microbe of the episode: Hepatovirus F

News item Takeaways Prions can be deadly. They're misshapen proteins that cause a cascade of misfolding of similar proteins if they get into the nervous system, resulting in neurodegeneration in mammals. But in other organisms, they are not always so scary; some fungi use prions to regulate their behavior in varying conditions. In this study, a prion allows yeast to switch between a fast-growing lifestyle with shorter reproductive lifespan that can be beneficial in conditions where nutrients are often plentiful, and a slower-growing but more enduring lifestyle that helps in more scarce conditions. Journal Paper: Garcia DM, Campbell EA, Jakobson CM, Tsuchiya M, Shaw EA, DiNardo AL, Kaeberlein M, Jarosz DF. 2021. A prion accelerates proliferation at the expense of lifespan. eLife 10:e60917.

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Modified yeast probiotic could tune its effects as needed by sensing bowel inflammation

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466: Microbes Mining Mars Minerals Dec 06, 2021

This episode: Bacteria are able to extract metals from rocks for industrial use, even in microgravity!

Download Episode (6.2 MB, 9.0 minutes) Show notes: Microbe of the episode: Decapod ambidensovirus 1

News item Takeaways As humanity makes progress toward becoming an interplanetary species, consideration is needed on how travelers can survive and thrive in distant places. These methods may look very different from what works well on Earth, with differences in gravity, atmosphere, and access to resources. For example, mining for materials for construction may not be feasible using methods common on Earth. An alternative may be biomining, using microbes that can selectively extract and purify specific metals from minerals. In this study, the European Space Agency tested the ability of several microbes to extract vanadium from rocks in different gravity conditions, on the International Space Station. Two out of three microbes were able to extract twice as much vanadium as was extracted in the absence of microbes, both on a planet and up in space. Journal Paper: Cockell CS, Santomartino R, Finster K, Waajen AC, Nicholson N, Loudon C-M, Eades LJ, Moeller R, Rettberg P, Fuchs FM, Van Houdt R, Leys N, Coninx I, Hatton J, Parmitano L, Krause J, Koehler A, Caplin N, Zuijderduijn L, Mariani A, Pellari S, Carubia F, Luciani G, Balsamo M, Zolesi V, Ochoa J, Sen P, Watt JAJ, Doswald-Winkler J, Herová M, Rattenbacher B, Wadsworth J, Everroad RC, Demets R. 2021. Microbially-Enhanced Vanadium Mining and Bioremediation Under Micro- and Mars Gravity on the International Space Station. Front Microbiol 12:663.

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A prokaryote with internal metabolic compartments (paper)

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465: Partners Produce Predator Prevention Nov 22, 2021

This episode: Bacteria living inside soil fungus produce toxins that can protect their host from tiny predators!

Download Episode (7.7 MB, 11.2 minutes) Show notes: Microbe of the episode: Mycobacterium virus DLane

Takeaways Soils have many different organisms cooperating and competing for resources. Some little worms called nematodes prey on fungi in the soil, while fungi may effectively defend themselves or strike back with toxins or traps that catch and kill the worms. On top of these interactions are other organisms that interact in various ways. In this study, bacteria living inside a kind of soil fungus produce toxins that defend the fungus against predatory nematodes. Journal Paper: Büttner H, Niehs SP, Vandelannoote K, Cseresnyés Z, Dose B, Richter I, Gerst R, Figge MT, Stinear TP, Pidot SJ, Hertweck C. 2021. Bacterial endosymbionts protect beneficial soil fungus from nematode attack. Proc Natl Acad Sci 118:e2110669118.

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Sequencing stomach bacteria to find out how prehistoric populations migrated

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464: Prodding Pollen's Popping Process Nov 09, 2021

This episode: Certain nectar-dwelling bacteria can induce pollen to germinate to access their tasty proteins!

Download Episode (6.0 MB, 8.8 minutes) Show notes: Microbe of the episode: Clostridium oceanicum

News item Takeaways Nectar in flowers seems like it would be a great place for microbes to live, since it has so much sugar, but it's actually somewhat difficult to thrive solely in and on nectar. The carbon in sugar is only one essential element for life, and there's enough of it that it can be overwhelming to the osmotic balance of many microbes. Pollen could provide more nutrients in the form of protein and the nitrogen that comes with it, but it is difficult to penetrate its hard shell. In this study, certain kinds of bacteria that live in nectar were able to access more pollen protein than other microbes by inducing pollen to germinate, growing out of its shell, or burst and release the protein directly. These microbes only benefited from pollen that were still alive and able to germinate, and not from those that had been disabled. Journal Paper: Christensen SM, Munkres I, Vannette RL. 2021. Nectar bacteria stimulate pollen germination and bursting to enhance microbial fitness. Curr Biol 31:4373-4380.e6.

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Bacteria recycling plastic into vanilla flavor

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463: Selectively Stimulating Cell Squatters Sep 20, 2021

This episode: Bacteria produce a compound that causes a phage lurking in the genome of a competing species to wake up and start killing that competitor!

Download Episode (8.2 MB, 12.0 minutes) Show notes: Microbe of the episode: Zaire ebolavirus

News item Takeaways Some bacteriophages infect and immediately destroy their hosts in a burst of new viruses, while others can be stealthier, integrating their genome into the genome of the host and remaining there quietly even over multiple generations of the bacteria. When something stresses the host, such as DNA damage, these integrated phages (prophages) become active and start producing new viruses, killing their host like the other kind does. In this study, one kind of bacteria release a chemical that wakes up phages in a competitor species of bacteria. This is helpful for competition, but even more interesting is that out of the six prophages in the competitor species, the chemical wakes up only one of them. Such selective phage induction could be interesting to study. Journal Paper: Jancheva M, Böttcher T. 2021. A Metabolite of Pseudomonas Triggers Prophage-Selective Lysogenic to Lytic Conversion in Staphylococcus aureus. J Am Chem Soc 143:8344–8351.

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Lab-evolved fungus strain could protect honeybees from mites

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462: Super Ciliate Symbiont Set Sep 13, 2021

This episode: A eukaryote has symbionts living in it: green algae and also purple bacteria, a combo never seen before!

Download Episode (6.1 MB, 8.8 minutes) Show notes: Microbe of the episode: Staphylococcus virus phiETA

News item Takeaways Having bacteria as endosymbionts is fairly common in life on Earth: almost all eukaryotes have them in the form of mitochondria and sometimes chloroplasts. These former bacteria somehow got inside the ancestral eukaryote, either as parasites or as prey, and ended up as integral parts of their host's metabolic functions. Some organisms, especially insects, obtained bacterial endosymbionts more recently, that help them balance their metabolic needs when living on limited diets. Algae have been known to be endosymbionts also, performing photosynthesis for their host. But in this study, a ciliate with both algae and purple photosynthetic bacteria as endosymbionts was discovered. Purple bacteria as symbionts is rare, and this combination has not been observed before. Interestingly, though algae produce oxygen through their photosynthesis, the ciliate prefers living in low-oxygen sediment at the bottom of a pond. The symbionts and their host seem to adjust their metabolisms as needed depending on the needs at the time; they may each perform photosynthesis, fermentation, or respiration if light, organic carbon, or oxygen are available. Journal Paper: Muñoz-Gómez SA, Kreutz M, Hess S. 2021. A microbial eukaryote with a unique combination of purple bacteria and green algae as endosymbionts. Sci Adv 7:eabg4102.

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Oxygen-producing microbes could help treat acute strokes

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461: Ingrained Invader Inhibits Infectors Sep 06, 2021

This episode: Training a phage strain on bacteria can increase its ability to control those bacteria for much longer than an untrained phage!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Pepper yellow leaf curl Indonesia virus

News item Takeaways With resistance to antibiotics spreading more and more among deadly bacteria, finding alternatives to treat infections is becoming more important. One option is phage therapy, using viruses that infect bacteria to weaken or wipe out pathogens, but this can be tricky. Sometimes it takes too long to prepare an effective population of phage for treatment, and sometimes the target pathogen evolves resistance to the phage too quickly In this study, a phage that was trained, or pre-evolved, to infect specific bacteria more effectively, was able to dominate the population consistently and prevent it from becoming fully resistant. For comparison, against an untrained strain of the same phage, the bacteria developed almost complete resistance after several days. Journal Paper: Borin JM, Avrani S, Barrick JE, Petrie KL, Meyer JR. 2021. Coevolutionary phage training leads to greater bacterial suppression and delays the evolution of phage resistance. Proc Natl Acad Sci 118.

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Engineered gut bacteria could sense and indicate bowel inflammation

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460: Prokaryote Publicity Prevents Protist Processes Aug 16, 2021

This episode: A bacterial communication signal makes algae stop growing, which helps them survive virus attacks!

Download Episode (5.3 MB, 7.7 minutes) Show notes: Microbe of the episode: Veillonella parvula

Takeaways Many interesting interactions between microbes take place in the ocean. As single-celled organisms lacking complex sensory organs, many such interactions and communications are mediated by chemical signals. Some bacteria, for example, each produce small amounts of certain chemicals and release them into the environment. When the concentration of the chemical signal builds up to a certain point, the bacteria change their behavior to take advantage of their high numbers that must be present to produce so much of the signal. This process is called quorum sensing. Some of these chemical signals can affect the behavior of organisms other than bacteria also. In this study, a common marine algal species was found to stop growing in response to a certain bacterial signal. This chemical inhibits an enzyme required for the algae to produce nucleotides to replicate their genomes. As a result, the algae are able to resist destruction by a virus that would otherwise decimate their populations. Journal Paper: Pollara SB, Becker JW, Nunn BL, Boiteau R, Repeta D, Mudge MC, Downing G, Chase D, Harvey EL, Whalen KE. 2021. Bacterial Quorum-Sensing Signal Arrests Phytoplankton Cell Division and Impacts Virus-Induced Mortality. mSphere 6:e00009-21.

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Comparing ancient gut microbes from fecal fossils to modern gut communities / also this one

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459: Prokaryotes Provide Polyp Perserverance Aug 02, 2021

This episode: Transplanting microbes from some corals to others could help the corals survive high temperatures!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Streptomyces olivaceoviridis

News item Takeaways The ever-rising temperatures of our modern world are putting more and more stress on various ecosystems. This is true even on the ocean floor: record-high temperatures damage reefs by causing coral bleaching, in which corals lose their photosynthetic endosymbionts. If conditions do not improve, these corals eventually die. Corals have microbial symbionts other than the phototrophs, also. We know from ourselves and from plants that microbes can have big effects on their hosts, so it seemed worth testing whether symbionts from more heat-resistant corals could transfer heat resistance to more vulnerable individuals. Recipients of this treatment did show enhanced heat resistance, but the microbial community composition did not always change after the treatment. Journal Paper: Doering T, Wall M, Putchim L, Rattanawongwan T, Schroeder R, Hentschel U, Roik A. 2021. Towards enhancing coral heat tolerance: a “microbiome transplantation” treatment using inoculations of homogenized coral tissues. Microbiome 9:102.

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Tiny bacterium kills larger bacterium that makes troublesome foam

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458: Slimy Cells Stop Sinking Jul 19, 2021

This episode: Bacteria can resist the force of gravity in liquid culture by covering themselves with goopy sugar polymers like parachutes!

Download Episode (10.4 MB, 15.2 minutes) Show notes: Microbe of the episode: Brevicoryne brassicae virus

Takeaways Put bacteria in a centrifuge, and most of the time you end up with a compact pellet of cells at the bottom of the tube, and mostly cell-free liquid above it. Bacteria do have ways to remain suspended in liquid, even without constant stirring or shaking of the container, but swimming, for example, consumes energy. In this study, artificial selection allowed the discovery of bacteria that could resist centrifuging speeds up to 15000 times the force of gravity, remaining suspended in liquid instead of forming a pellet. Production of polysaccharide was important, but not sufficient; for the most resistance to sinking, bacteria had to attach the polysaccharide to their cell surface, to act as a sort of parachute. Journal Paper: Kessler NG, Caraballo Delgado DM, Shah NK, Dickinson JA, Moore SD. 2021. Exopolysaccharide Anchoring Creates an Extreme Resistance to Sedimentation. J Bacteriol 203(11):e00023-21.

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Engineered probiotic yeast could help prevent vitamin A deficiency

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457: Small Cell Studies: Superior Scoops Jun 28, 2021

This episode: Newspapers report on scientific studies about microbiomes a fair amount, but certain kinds of studies are more likely than others to show up in the news!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Cafeteriavirus-dependent mavirus

Takeaways Research into the human microbiome has generated a lot of interest, even among non-scientists. This is especially true since the beginning of the Human Microbiome Project in 2007. But sometimes things are lost in translation from published studies into general news. This study is a survey of microbiome studies reported in six different news sources from three different countries, either general news or business news. General news did a better job reporting on different kinds of microbiome studies proportionally, but certain kinds of studies were reported on proportionally more or less frequently than they were published. Journal Paper: Prados-Bo A, Casino G. 2021. Microbiome research in general and business newspapers: How many microbiome articles are published and which study designs make the news the most? PLOS ONE 16:e0249835.

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Gut microbes in C-section babies can be similar to non-surgical births after several years

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456: Invader Induces Increased Immensity Jun 21, 2021

This episode: A virus of archaea stops cells from dividing, so they just keep getting bigger and releasing more viruses!

Download Episode (6.9 MB, 10.1 minutes) Show notes: Microbe of the episode: Streptomyces caelestis

Takeaways Viruses affect their hosts many different ways: instant hostile takeover of cellular machinery, lurking unseen in the genome for generations, inducing reduced cell division or excessive cell division, and more. Archaeal viruses are relatively unknown in their genetic abilities and lifestyles, but we do know that they tend not to destroy their hosts through explosive viral reproduction, and that some archaea have eukaryote-like cell cycle phases. In this study, some viruses infecting a thermophilic archaeon interrupt its cycle in the growth phase, so hosts expand in size up to around 17 times normal, continuously releasing new viruses over time. Eventually some archaea in the population gain resistance to the viruses via their CRISPR/Cas systems, and normal-sized cells dominate the population again. Journal Paper: Liu J, Cvirkaite-Krupovic V, Baquero DP, Yang Y, Zhang Q, Shen Y, Krupovic M. 2021. Virus-induced cell gigantism and asymmetric cell division in archaea. Proc Natl Acad Sci 118:e2022578118.

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Chocolate is a fermented food

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455: Marine Microbes Make Megapascal Management Molecule Jun 07, 2021

This episode, in honor of World Ocean Day: Bacteria that may move between high and low pressure areas in the ocean use a particular molecule to protect their cells from being crushed!

Download Episode (6.6 MB, 9.5 minutes) Show notes: Microbe of the episode: Rickettsia rickettsii

News item Takeaways Life in the ocean can have many challenges, depending on the organism and where it lives. Microbes can be found in almost every region, from the warmest to coldest, brightest to darkest, and shallowest to deepest. Sometimes microbes are carried from shallow to deep regions, where the weight of so much water causes immense pressure, which can inhibit cellular structural integrity and function. So life in the deep sea must have ways to deal with this pressure to survive. In this study, bacteria transform a fairly common chemical into a molecule that cushions and protects their cellular structures from the effects of high pressure, allowing them to survive lower down than they would otherwise. Journal Paper: Qin Q-L, Wang Z-B, Su H-N, Chen X-L, Miao J, Wang X-J, Li C-Y, Zhang X-Y, Li P-Y, Wang M, Fang J, Lidbury I, Zhang W, Zhang X-H, Yang G-P, Chen Y, Zhang Y-Z. 2021. Oxidation of trimethylamine to trimethylamine N -oxide facilitates high hydrostatic pressure tolerance in a generalist bacterial lineage. Sci Adv 7:eabf9941.

Other interesting stories:

Engineering microbes to produce petroleum product precursor isoprene

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454: Hitchhiking Horticultural Helpers May 31, 2021

This episode: Spores of some bacteria latch onto the tails of other bacteria and ride along as they move around in the soil!

Download Episode (5.5 MB, 8.0 minutes) Show notes: Microbe of the episode: Bohle iridovirus

News item Takeaways The soil is a complex environment, and microbes that live in soil need complex lifestyles to thrive. There are many examples of cooperation, competition, and other adaptations to highly varied situations. In this study, bacteria that grow like filamentous fungi don't have the mechanisms to move autonomously, but their spores can hitch rides on other kinds of bacteria that swarm through the soil using their propeller-like tails called flagella to push themselves toward the plant roots they prefer to grow near. Journal Paper: Muok AR, Claessen D, Briegel A. 2021. Microbial hitchhiking: how Streptomyces spores are transported by motile soil bacteria. ISME J.

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"How microbes in permafrost could trigger a massive carbon bomb"

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453: Phenazine Faciliates Phosphorus Feeding May 24, 2021

This episode: Some bacteria produce antibiotics that can also help them gather more nutrients!

Download Episode (5.0 MB, 7.3 minutes) Show notes: Microbe of the episode: Diadromus pulchellus toursvirus

News item 1 Takeaways Antibiotics have saved a lot of lives since they were discovered and used to treat many previously untreatable bacterial infections. But bacteria themselves have been making antibiotics much longer than we have, to help compete in their environment. However, sometimes these compounds are not produced in large enough concentrations to act as antibiotics, killing or inhibiting rival bacteria. Why waste energy on this sublethal production? Are there other functions these molecules can perform? In this study, bacteria produce an antibiotic called phenazine that can damage cell components by redox reactions, transferring electrons. But it can also help liberate the essential nutrient phosphorus from being bound to insoluble particles, allowing the bacteria to grow better even in the absence of competitors. Journal Paper: McRose DL, Newman DK. 2021. Redox-active antibiotics enhance phosphorus bioavailability. Science 371:1033–1037.

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Bacterial proteins stuck to tumor cells could be targeted

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452: Prokaryotic Partner Powers Protist May 03, 2021

This episode: Single-celled eukaryotes can thrive without oxygen with the help of bacterial endosymbionts that respire nitrate the way our mitochondria respire oxygen!

Thanks to Jon Graf for his contribution!

Download Episode (12.4 MB, 18.1 minutes) Show notes: Microbe of the episode: Brenneria salicis

News item 1 / News item 2 Takeaways The combination of a bacterium and other microbe into the first eukaryote was a big advance in evolutionary history; it made possible the huge variety of different body shapes and sizes we see today. This is thanks to the bacterial endosymbiont, the mitochondrion, taking on specialized metabolic tasks for the cell. We already knew about endosymbionts that help with oxygen respiration, with photosynthesis (chloroplasts), and with amino acid synthesis (certain endosymbionts in insects). But bacteria have other metabolic abilities that are very useful in certain conditions; do these bacteria ever team up with other organisms? The answer is yes! In this study, ciliates were discovered at the bottom of a lake in oxygen-free waters. These protists have an bacterial endosymbiont that helps them respire, not oxygen, but nitrate instead, generating more energy than most anaerobic ciliates. Journal Paper: Graf JS, Schorn S, Kitzinger K, Ahmerkamp S, Woehle C, Huettel B, Schubert CJ, Kuypers MMM, Milucka J. 2021. Anaerobic endosymbiont generates energy for ciliate host by denitrification. Nature.

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Bacterial cellulose film is very good at separating oil and water

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451: Phototrophs Fancy Floating Feasts Apr 19, 2021

This episode: Despite being photosynthetic, some kinds of algae engage in predatory behavior, hunting and consuming live bacteria!

Download Episode (4.9 MB, 7.1 minutes) Show notes: Microbe of the episode: Paramecium bursaria Chlorella virus 1

News item Takeaways Although most of them are microscopic, algae perform a significant portion of the photosynthesis on the planet, because there are so many of them. But even though photosynthesis seems like a reliable way of acquiring energy, there are conditions under which even algae benefit from gathering energy and nutrients from other organisms. This is called phagomixotrophy, when algae hunt and consume bacteria. In this study, scientists developed fluorescence methods for detecting and studying this predation in a group of algal phytoplankton that's not well-studied, prasinophytes. They found that all five species they looked at engaged in bacterivory under nutrient-depleted conditions, and that they preferred live bacteria to killed ones. Journal Paper: Bock NA, Charvet S, Burns J, Gyaltshen Y, Rozenberg A, Duhamel S, Kim E. 2021. Experimental identification and in silico prediction of bacterivory in green algae. ISME J.

Other interesting stories:

Fecal microbe transplant seems to help mice recover from spinal cord injury (paper)

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450: Subterranean Spotlights Support Cyanobacteria Apr 05, 2021

This episode: Lighting in caves open to tourists supports the growth of unwanted photosynthetic bacteria!

Download Episode (6.6 MB, 9.5 minutes) Show notes: Microbe of the episode: Dill cryptic virus 2

Takeaways Caves can contain amazing beauty, intricate geological formations formed by minerals, water, and time. Some, such as Carlsbad Caverns in New Mexico, have been fitted with instruments to allow tourists to pass through and see the wonders within; definitely a worthwhile experience. Caves also have their own natural microbiota that can live within them, in the dark, somewhat cold, and nutrient-poor conditions. But with the lighting installed to allow tourism, photosynthetic microbes have been able to take hold in the communities of these show caves. These microbes can outcompete the natural microbes, and can cause discoloration and unwanted growths on cave formations. They are difficult to remove without much effort and the risk of damaging the cave formations themselves. This study looked at the effects of the color of lighting in the caves, as well as other factors, on the growth of these so-called "lampenflora." It supports new efforts and methods to control the issue. Journal Paper: Havlena Z, Kieft TL, Veni G, Horrocks RD, Jones DS. 2021. Lighting Effects on the Development and Diversity of Photosynthetic Biofilm Communities in Carlsbad Cavern, New Mexico. Appl Environ Microbiol 87.

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449: Paralyzed Poisons Push Power Mar 29, 2021

This episode: Deep-sea bacteria can detoxify cadmium and convert it to light-capturing particles!

Download Episode (5.8 MB, 8.4 minutes) Show notes: Microbe of the episode: Arthrobacter virus Sonny

Takeaways Hydrothermal vents can have thriving communities, despite being too deep for much light to penetrate. Microbes can derive energy from chemicals coming out of the vent, and form the foundation of the food chain. But toxic heavy metals also come out of the vent, including lead, mercury, and cadmium. The microbes in this study were found to be resistant to cadmium, which they can detoxify by combining it with the sulfur found in the amino acid cysteine. This forms cadmium-sulfur nanoparticles, which can function as light-absorbing semiconductors, allowing the bacteria to harvest light energy. Journal Paper: Ma N, Sha Z, Sun C. 2021. Formation of cadmium sulfide nanoparticles mediates cadmium resistance and light utilization of the deep-sea bacterium Idiomarina sp. OT37-5b. Environ Microbiol 23:934–948.

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448: Myxomycete Makes Mycelial Memories Mar 22, 2021

Finally found some good stories, so we're back! This episode: How slime molds encode and use memories built into their own bodies!

Download Episode (4.6 MB, 6.7 minutes) Show notes: Microbe of the episode: Aeromonas salmoncida

News item Takeaways Despite being single-celled organisms, slime molds have fairly complex behavior, including a basic form of memory. They often grow as a network of tubes of cytoplasm branching out from one place to find and exploit new sources of food in their environment. When these tubes connect to new food, other less productive branches of its body shrink away. As it turns out, this body form serves a role in memory also. This study determined that the slime mold's tubes undergo constant squeezing, which moves cell contents around and also shrinks them. When tubes are connecting to a food source though, they secrete a softening agent that allows the pressure to expand the tubes instead of shrinking them. These larger tubes consequently are capable of transporting more softening agent farther away to newer food sources, so the history of food discoveries is recorded in the slime mold's own body, which also influences its responses to new discoveries. Journal Paper: Kramar M, Alim K. 2021. Encoding memory in tube diameter hierarchy of living flow network. Proc Natl Acad Sci 118.

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447: Big Bacteria Bank Behaviors Feb 08, 2021

This episode: Giant bacteria with many chromosomes in each cell carry extra genes to help them live in many different environments!

Download Episode (8.7 MB, 12.7 minutes) Show notes: Microbe of the episode: Propionibacterium virus SKKY

News item Takeaways We think of bacteria a certain way: too small to see and having mostly just a single large chromosome with all the genes they need for their lifestyle and not much more. And most bacteria are like that. But not all! Giant bacteria exist, some of which can be so large that individual cells can be seen without a microscope. Achromatium species are one such kind of bacteria. They form clumps of minerals that take up most of their internal volume, but their cells are big enough to see and handle. In order to supply all parts of their vast innards with proteins, they have many copies of their chromosome distributed throughout their cytoplasm. In this study, a survey of Achromatium genomes from all different kinds of ecosystem revealed that even different species in very different environments all seem to share one set of genetic functions, but only use the ones they need for their particular lifestyle while archiving the rest. Journal Paper: Ionescu D, Zoccarato L, Zaduryan A, Schorn S, Bizic M, Pinnow S, Cypionka H, Grossart H-P. Heterozygous, Polyploid, Giant Bacterium, Achromatium, Possesses an Identical Functional Inventory Worldwide across Drastically Different Ecosystems. Mol Biol Evol https://doi.org/10.1093/molbev/msaa273.

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446: Biofilm Benefits Bone Braces Feb 01, 2021

This episode: The biofilm that probiotic bacteria can leave behind on a titanium implant seems to help it integrate better with the existing skeleton, with less inflammation and risk of infection!

Download Episode (5.5 MB, 7.9 minutes) Show notes: Microbe of the episode: Methylobacterium organophilum

News item Takeaways Skeletal implants make it a lot easier for many people to stay mobile as they age, but the surgical procedure of implanting is risky. Its invasive nature puts stress on the immune system, which puts stress on other systems, and the spread of antibiotic resistance is increasing the risk of a hard-to-treat infection. In this study, probiotic bacteria grow in a biofilm on titanium implants before being inactivated, leaving only the biofilm behind on the implant. This biofilm-coated implant showed improved bone integration, antimicrobial resistance that was not toxic to the body's own tissues, and reduced inflammation when implanted into rats. Journal Paper: Tan L, Fu J, Feng F, Liu X, Cui Z, Li B, Han Y, Zheng Y, Yeung KWK, Li Z, Zhu S, Liang Y, Feng X, Wang X, Wu S. 2020. Engineered probiotics biofilm enhances osseointegration via immunoregulation and anti-infection. Sci Adv 6:eaba5723.

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445: Living Lurking Landmine Locators Jan 25, 2021

This episode: Engineered bacteria encapsulated in little beads sense chemicals from landmines and give off light!

Download Episode (6.4 MB, 9.3 minutes) Show notes: Microbe of the episode: Bifidobacterium pullorum

Takeaways Landmines are a good way to take an enemy by surprise and do some damage. They're so good that some places in the world still aren't safe to go decades after a conflict, due to intact landmines hidden in the area. In order to detect them from a distance to aid in disarming efforts, we need something very good at detecting the faint odor they give off—something like bacteria! In this study, bacteria are engineered to detect breakdown products of TNT in landmines and produce light—bioluminescence. These bacteria are encapsulated in polymer beads and are stable for months in the freezer, and could accurately pinpoint a landmine buried in sand for a year and a half. Journal Paper: Shemer B, Shpigel E, Hazan C, Kabessa Y, Agranat AJ, Belkin S. Detection of buried explosives with immobilized bacterial bioreporters. Microb Biotechnol https://doi.org/10.1111/1751-7915.13683.

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444: Strange Sequence Stops Cell Subjugation Jan 18, 2021

This episode: An interesting bacterial genetic element protects against viruses in a unique way!

Download Episode (7.1 MB, 10.3 minutes) Show notes: Microbe of the episode: Mongoose associated gemykibivirus 1

News item Takeaways Even single-celled, microscopic organisms such as bacteria have to deal with deadly viruses infecting them. And while they don't have an immune system with antibodies and macrophages like we do, they still have defenses against infection, mostly based on sensing and destroying viral genomes. Restriction enzymes cut viral genomes at specific places, and CRISPR/Cas targets and destroys specific viral sequences. Knowing this, when microbiologists contemplate a strange genetic element of unknown function in bacteria, it's worth considering that it may be relevant to defense against phages. The strange element in this case is retrons: a special reverse transcriptase enzyme takes a short non-coding RNA transcript and transcribes it into DNA, then links the RNA and DNA sequences together. These retrons are found in a variety of forms in a variety of microbes, and their function has been unknown up till now. In this study, one specific retron was found to defend bacteria against a number of phages. By comparing viruses, they discovered that this retron functions by sensing viruses' attempts to defeat another bacterial defense, a sort of second level of defenses. How common such a system is, what variants may exist, and how we may be able to use it for research or biotech purposes remain to be determined. Journal Paper: >Millman A, Bernheim A, Stokar-Avihail A, Fedorenko T, Voichek M, Leavitt A, Oppenheimer-Shaanan Y, Sorek R. 2020. Bacterial Retrons Function In Anti-Phage Defense. Cell 183:1551-1561.e12.

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Bacteria can make biodegradable plastics from waste sludge

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443: Gut Group Gives Gamma Guard Jan 11, 2021

This episode: Certain gut microbes protect mice from harmful effects of high-energy radiation!

Download Episode (7.3 MB, 10.6 minutes) Show notes: Microbe of the episode: Solenopsis invicta virus-1

News item Takeaways High-energy radiation can be very dangerous. Besides a long-term increased risk of cancer due to DNA damage, a high enough dose of radiation can cause lethal damage to multiple systems in the body, especially the gastrointestinal tract and the immune system. Finding new ways to treat or prevent damage from radiation would be very helpful for improving the safety of space travel, nuclear energy, and radiotherapy for cancer. In this study, some mice exposed to a typically lethal dose of radiation survived without ill effects, thanks to certain microbes in their gut. Transferring these microbes to other mice helped those mice survive radiation as well, and even just the metabolites that the bacteria produced were helpful for protecting the cells in the body most affected by radiation. Journal Paper: Guo H, Chou W-C, Lai Y, Liang K, Tam JW, Brickey WJ, Chen L, Montgomery ND, Li X, Bohannon LM, Sung AD, Chao NJ, Peled JU, Gomes ALC, van den Brink MRM, French MJ, Macintyre AN, Sempowski GD, Tan X, Sartor RB, Lu K, Ting JPY. 2020. Multi-omics analyses of radiation survivors identify radioprotective microbes and metabolites. Science 370:eaay9097.

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442: Fossil Phototroph Phagocytosis Dec 28, 2020

This episode: Algae surviving impact that killed the dinosaurs seem to have consumed other organisms to make it through the dark times!

Download Episode (7.1 MB, 10.3 minutes) Show notes: Microbe of the episode: Chaetoceros tenuissimus RNA virus 01

News item Takeaways Being able to look through time and learn about what might have happened to creatures throughout Earth's history is what makes paleontology great. Everyone knows about dinosaurs and what happened to them at the end of the Cretaceous period thanks to science. But what we can learn is not limited just to large organisms; there are ways to learn about microorganisms of the past as well, including by looking at fossils! In this study, fossils of hard-shelled algae from around the end of the dinosaurs show that many of these microbes in the oceans went extinct at the same time due to the massive space impact. Debris blocked out sunlight for years, making it difficult for photosynthetic organisms to survive. So some of these algae appear to have survived by preying on smaller organisms, pulling them in through a hole in their shell. Journal Paper: Gibbs SJ, Bown PR, Ward BA, Alvarez SA, Kim H, Archontikis OA, Sauterey B, Poulton AJ, Wilson J, Ridgwell A. 2020. Algal plankton turn to hunting to survive and recover from end-Cretaceous impact darkness. Sci Adv 6:eabc9123.

Other interesting stories:

Phages could help treat diabetic wound infections without harming microbiota (paper)

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441: Hyphal Hijacker Helps Harvests Dec 21, 2020

This episode: A fungus-infecting virus transforms the fungal foe into a friend of its host plant!

Download Episode (6.1 MB, 8.9 minutes) Show notes: Microbe of the episode: Hepacivirus J

News item Takeaways Viruses can be useful for treating various diseases, especially bacterial infections and cancer. Their ability to target certain cell types specifically makes them great at hunting down and killing disease-causing cells without harming the body's healthy tissue. And just as bacteriophages can work to treat bacterial disease in us, fungal viruses could help to treat serious fungal infections in crop plants. In this study, a fungus-infecting virus goes beyond treating a deadly fungal disease in rapeseed plants. Fungus infected with this virus no longer causes disease, but lives in harmony with the host plant, protects it from other fungal diseases, and even helps it to grow better. Journal Paper: Zhang H, Xie J, Fu Y, Cheng J, Qu Z, Zhao Z, Cheng S, Chen T, Li B, Wang Q, Liu X, Tian B, Collinge DB, Jiang D. 2020. A 2-kb Mycovirus Converts a Pathogenic Fungus into a Beneficial Endophyte for Brassica Protection and Yield Enhancement. Mol Plant 13:1420–1433.

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440: Prokaryotes Pay for Passage Dec 14, 2020

This episode: Bacteria pay for the privilege of cruising around soil on fungus filaments!

Download Episode (7.7 MB, 11.2 minutes) Show notes: Microbe of the episode: Clostridium acetobutylicum

News item Takeaways In the complex environment of soil, many different kinds of organisms coexist. Some compete with each other, while others cooperate in fascinating interactions. One example is how bacteria can swim through a film of water surrounding the filaments of fungi, allowing them to traverse more quickly and reach new locations. In this study, an interaction between fungus and bacterium is discovered in which the bacteria benefit from the fungus in enhanced ability to travel, and the fungus benefits by absorbing vitamins that the bacteria produce. Journal Paper: Abeysinghe G, Kuchira M, Kudo G, Masuo S, Ninomiya A, Takahashi K, Utada AS, Hagiwara D, Nomura N, Takaya N, Obana N, Takeshita N. 2020. Fungal mycelia and bacterial thiamine establish a mutualistic growth mechanism. Life Sci Alliance 3(12):202000878.

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439: Microbes Mitigate Mushroom Morbidity Nov 30, 2020

This episode: Bacteria protect farmed mushrooms from damage by other bacteria by breaking down their toxins!

Download Episode (4.9 MB, 7.1 minutes) Show notes: Microbe of the episode: Tomato mosaic virus

Takeaways

Almost all organisms are vulnerable to pathogenic microbes that make them sick or cause damage. Most also have other microbes that help them grow better or protect them from pathogens. This includes animals, plants, and also fungi.

In this study, bacterial pathogens produce a toxin that causes button mushrooms to turn brown and rot. However, other bacteria can degrade this toxin and protect the fungus, and can also degrade molecules the pathogens produce to help them swarm to new places, restricting their movement.

Journal Paper: Hermenau R, Kugel S, Komor AJ, Hertweck C. 2020. Helper bacteria halt and disarm mushroom pathogens by linearizing structurally diverse cyclolipopeptides. Proc Natl Acad Sci 117:23802–23806.

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438: Bacteria Bait Bug Babies Nov 16, 2020

This episode: Actinomycete bacteria are often helpful to insects, but some can be deadly yet still attractive!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Streptomyces corchorusii

News item Takeaways Actinomycete bacteria do a lot of interesting things. They grow like fungi, with mycelia and spores, and produce many interesting compounds, including antibiotics and other useful pharmaceuticals. They often team up with insects, producing such compounds to assist them in competing with other organisms or resisting disease. But such amazingly helpful powers of chemistry can also be amazingly harmful. In this study, multiple strains of these bacteria were able to kill fruit fly larvae that ingested their spores. The toxin the bacteria produced was a chemical that interferes with cells' DNA-protein interactions. The bacteria also produced an odor that, in certain concentrations, lured the larvae to their doom. Journal Paper: Ho LK, Daniel-Ivad M, Jeedigunta SP, Li J, Iliadi KG, Boulianne GL, Hurd TR, Smibert CA, Nodwell JR. 2020. Chemical entrapment and killing of insects by bacteria. Nat Commun 11:4608.

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Also news, Feedspot ranked BacterioFiles in the top 5 virology podcasts! Check out the list for other good shows about viruses.

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437: Balmy Bacteria Build Bone Nov 09, 2020

This episode: Warmth helps mice build stronger bones, mediated by bacteria producing certain compounds!

Download Episode (6.8 MB, 9.9 minutes) Show notes: Microbe of the episode: Aquaspirillum serpens

News item Takeaways Bones aren't just solid, structural supports for the body's tissues. They're active and alive, housing important components of the immune system, and also capable of being broken down and built up in response to changes in the body's interactions with the environment. Various things can affect bone mass and health, including nutrition, temperature, age, and even the body's microbes. In this study, two of these effects are found to interact. Warmth leads to increased bone density in mice, and this effect can be attributed to the microbes in the mice, and transmitted from one mouse to another just by transplanting microbes adapted to warmth. Even the particular chemicals the microbes produce that mediate this effect are discovered. Journal Paper: Chevalier C, Kieser S, Çolakoğlu M, Hadadi N, Brun J, Rigo D, Suárez-Zamorano N, Spiljar M, Fabbiano S, Busse B, Ivanišević J, Macpherson A, Bonnet N, Trajkovski M. 2020. Warmth Prevents Bone Loss Through the Gut Microbiota. Cell Metab 32:575-590.e7.

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436: Copper Concentrates Culture Current Oct 26, 2020

This episode: Copper electrodes, rather than killing bacteria in microbial fuel cells, allow them to generate higher densities of electric current!

Download Episode (5.0 MB, 7.2 minutes) Show notes: Microbe of the episode: Xipapillomavirus 2

News item Takeaways Copper is widely used as a way to make surfaces and materials antimicrobial, to cut down on the spread of pathogens in hospitals and other environments. Among other mechanisms, it reacts with oxygen to form reactive oxygen species that are very harsh on microbial proteins. But copper is also a good electrical conductor, which would be useful to use in microbial fuel cells, which exploit bacterial metabolism to generate electricity. Microbes form biofilms on an electrode and transfer electrons to it as a way for them to generate energy. Most such fuel cells have used graphite electrodes to avoid toxicity. In this study, fuel cell bacteria grew well on a copper electrode in an oxygen-free environment. The copper actually allowed them to increase the amount of current they produced per unit of area, as ionic copper diffused through the biofilm and allowed electrons to flow through the biofilm to the electrode from layers farther from the electrode that otherwise would not have access. Even graphite electrodes could be improved by adding these copper ions to the biofilm directly. Journal Paper: Beuth L, Pfeiffer CP, Schröder U. 2020. Copper-bottomed: electrochemically active bacteria exploit conductive sulphide networks for enhanced electrogeneity. Energy Environ Sci 13:3102–3109.

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435: Invader Introducing Infrared Invokes Immunity Oct 19, 2020

This episode: Combining Salmonella with something called photoimmunotherapy to attack tumors in multiple ways!

Download Episode (8.2 MB, 11.9 minutes) Show notes: Microbe of the episode: Shimwellia blattae

Takeaways Distinguishing healthy from unhealthy tissue is one of the big challenges when dealing with cancer. Since cancer is derived from healthy tissue, there are many similarities between them that make it hard to target it specifically. This is especially important when cancer is spread in multiple places throughout the body, as opposed to a single tumor that can be removed locally. In this study, bacteria modified to make them safer were injected into mice with tumors. The bacteria alone were capable of doing some damage to the tumors, and this damage happened to make the tumors darker. Using this color change, the scientists targeted the tumors with lasers to heat them up and kill them in an isolated manner. This had the added benefit of inducing an immune response against the cancer that could target it throughout the body. Journal Paper: Yi X, Zhou H, Chao Y, Xiong S, Zhong J, Chai Z, Yang K, Liu Z. 2020. Bacteria-triggered tumor-specific thrombosis to enable potent photothermal immunotherapy of cancer. Science Advances 6:eaba3546.

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434: Killer Carries Compact Cas Sep 28, 2020

This episode: Large phage discovered that contains a compact version of the CRISPR/Cas defense/gene editing system!

Download Episode (5.9 MB, 8.6 minutes) Show notes: Microbe of the episode: Stenotrophomonas virus IME13

News item Takeaways CRISPR/Cas systems have made a lot of things in gene editing much easier in certain organisms. It's almost as easy as just getting the cells to produce the Cas protein and putting in an RNA sequence to tell it where to go! But in some cases, these requirements are too much to work well. In this study, a more compact version of CRISPR/Cas was discovered in large bacteriophages. These systems help the viruses compete with other viruses and defend against host defenses sometimes. The Cas protein is half the size of the standard Cas most used in gene editing, and it has fewer other requirements to function in new cells, so it could be better in versatility and potential in applications with strict space constraints. Journal Paper: Pausch P, Al-Shayeb B, Bisom-Rapp E, Tsuchida CA, Li Z, Cress BF, Knott GJ, Jacobsen SE, Banfield JF, Doudna JA. 2020. CRISPR-CasΦ from huge phages is a hypercompact genome editor. Science 369:333–337.

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433: Probiotic Promotes Pathogen Peacefulness Sep 21, 2020

This episode: A probiotic can protect intestine-like cell growths from destruction by pathogens, but it can also be infected by a virus that makes it more harmful to intestinal cells!

Download Episode (6.9 MB, 10.1 minutes) Show notes: Microbe of the episode: Euphorbia yellow mosaic virus

News item Takeaways There are many strains of Escherichia coli. Some are pathogenic, in the gut or the urinary tract, and a subset of those are very dangerous, such as the enterohemorrhagic O157:H7 strain. Many others are commensals, living peacefully as part of our gut community. And some strains can be beneficial to the host, protecting from and reducing the severity of disease. One such strain is called E. coli Nissle. This study used an advanced model of human intestines called organoids, where stem cells are induced to develop into hollow spheres of intestinal epithelium in which all cell types of a normal intestinal wall are represented. E. coli pathogens typically destroy these organoids and escape from inside, but Nissle was able to prevent this destruction and enable coexistence between the pathogen and the host cells. Nissle suffered for this protection though; O157:H7 carries a toxin-encoding phage that can infect and kill susceptible E. coli strains. Those Nissle cells that survived this infection could resist the phage, but were not as beneficial to the organoids due to the toxin they now produced. Journal Paper: Pradhan S, Weiss AA. 2020. Probiotic Properties of Escherichia coli Nissle in Human Intestinal Organoids. mBio 11(4):e01470-20.

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432: Moses Microbes Maintain Moisture Sep 07, 2020

This episode: Bacteria living in the driest place on earth have ways to extract water from the mineral structures of rocks!

Download Episode (3.7 MB, 5.4 minutes) Show notes: Microbe of the episode: Irkut lyssavirus

News item Takeaways Microbes living in extremely dry conditions have it tough. Water is important both for the chemistry and structure of all cells. Desert microbes are very good at acquiring and holding on to the water they can find, but in places such as the Atacama Desert in Chile, there's almost none available. However, microbes can be very resourceful. In this study, phototrophs were discovered that can actually extract water molecules bound up in the crystalline structure of the mineral gypsum, and this allows them to survive in hyperarid regions. They do this by secreting organic acid molecules to etch the rock and release the water, converting gypsum to anhydrite, which is a mineral with the same chemical structure except without the water. Journal Paper: Huang W, Ertekin E, Wang T, Cruz L, Dailey M, DiRuggiero J, Kisailus D. 2020. Mechanism of water extraction from gypsum rock by desert colonizing microorganisms. Proc Natl Acad Sci 117:10681–10687.

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431: Conductive Cables Control Carbon Aug 31, 2020

This episode: Cable bacteria around rice roots transport electrons and help prevent formation of methane!

Thanks to Vincent Scholz for his contribution!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Vibrio alginolyticus

News item Takeaways Transforming other things into methane is a great way to make a living for some kinds of microbes. These tend to live under still water, like in rice fields or wetlands, or in the guts of cattle. And while this methane could be useful as natural gas if collected, it's a much more potent greenhouse gas than carbon dioxide when released into the atmosphere. In this study, cable bacteria were inoculated into rice pots in the lab. Cable bacteria transfer electrons from deeper down in the ground up to the surface to generate energy, and in the process generate sulfate. This sulfate allows other microbes to outcompete the methane producers, reducing the amount of methane produced from rice cultivation in the lab. This may be helpful to reduce greenhouse gas emissions from rice agriculture. Journal Paper: Scholz VV, Meckenstock RU, Nielsen LP, Risgaard-Petersen N. 2020. Cable bacteria reduce methane emissions from rice-vegetated soils. 1. Nat Commun 11:1878.

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430: Dextrose Deposits Delay Dormancy Aug 24, 2020

This episode: Bacteria that can store sugar as glycogen have multiple advantages when food is only available sporadically!

Download Episode (7.2 MB, 10.4 minutes) Show notes: Microbe of the episode: Carnivore bocaparvovirus 3 Takeaways

Almost all habitats experience some sort of change and fluctuation; very few are totally stable, depending on the timeframe. So strategies to change and adapt with changing conditions can greatly help an organism thrive. For example, methods of storing energy are helpful when food is only available sporadically. Some bacteria, like humans, can store sugar in a polymer called glycogen, which can be quickly produced when food is abundant and quickly broken down to ease a transition to fasting. In this study, bacteria that could produce and use glycogen were able to stay active longer and grow better in the face of intermittent starvation. They were even better able to acquire new food when more became available. Journal Paper: Sekar K, Linker SM, Nguyen J, Grünhagen A, Stocker R, Sauer U. 2020. Bacterial Glycogen Provides Short-Term Benefits in Changing Environments. Appl Environ Microbiol 86.

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429: Springtails Smell, Spread Streptomyces Aug 17, 2020

This episode: Bacteria in soil produce smells to attract arthropods that eat them but also spread their spores!

Download Episode (6.2 MB, 9.0 minutes) Show notes: Microbe of the episode: Blotched snakehead virus

News item Takeaways Soil, especially after a rain, often has a characteristic "earthy" smell. This soil smell is actually the result of certain bacteria producing a volatile chemical called geosmin. Many geosmin producers are in the Streptomyces genus, which produces a large variety of interesting chemicals, but geosmin is one of the few that is nearly universal in the genus. This study found that insect-like arthropods called springtails are attracted to geosmin. These animals usually feed on fungi, but they will also eat bacteria when available. Despite this result, the bacteria continue to produce the chemical, which is linked to their sporulation cycle. The study found that springtails carry intact bacterial spores to new places stuck to the insides and outsides of the animal, and this enhances the dispersal ability of the bacteria. Journal Paper: Becher PG, Verschut V, Bibb MJ, Bush MJ, Molnár BP, Barane E, Al-Bassam MM, Chandra G, Song L, Challis GL, Buttner MJ, Flärdh K. 2020. Developmentally regulated volatiles geosmin and 2-methylisoborneol attract a soil arthropod to Streptomyces bacteria promoting spore dispersal. 6. Nat Microbiol 5:821–829.

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428: Microbes May Manage Mysteries Aug 10, 2020

This episode: The skin microbes that people leave behind may be used to identify them, even after other people have touched the same surface!

Download Episode (5.4 MB, 7.9 minutes) Show notes: Microbe of the episode: Actinobacillus lignieresii Takeaways

The microbial communities in and on our bodies are highly complex and highly varied between people; this complexity has raised the question of whether the microbes that people transfer onto things they touch could be used in forensics, to track their movement and activity, like fingerprints or DNA evidence. One difficulty with this approach is that microbe communities are constantly changing as conditions change or other microbes are introduced. This study simulated such microbial tracking in a couple of scenarios, such as touching door handles in an office building and touching various surfaces in a home in a mock burglary. Tracking a person on door handles worked fairly well for up to an hour after the contact, even if other people had also touched the same door handles. However, the accuracy of identifying the "burglar" in a home was not very high, but modifying the analysis from looking at the community as a whole to only rare microbes relatively unique to an individual improved the results.

Journal Paper: Hampton-Marcell JT, Larsen P, Anton T, Cralle L, Sangwan N, Lax S, Gottel N, Salas-Garcia M, Young C, Duncan G, Lopez JV, Gilbert JA. 2020. Detecting personal microbiota signatures at artificial crime scenes. Forensic Sci Int 313:110351.

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427: Simple Cells Stay Strong Aug 03, 2020

This episode: Bacterial cells with their genomes removed can still be active and useful!

Download Episode (10.2 MB, 14.9 minutes) Show notes: Microbe of the episode: Rosavirus A Takeaways

Microbes have amazing biochemical transformation abilities, creating and breaking down many compounds and proteins. This makes them great candidates for many purposes, in medicine, industry, and environmental remediation. In some of these purposes, though, there are risks associated with adding foreign microbes, especially engineered ones, that can replicate themselves and possibly persist, into new places. To avoid this risk, this study turns intact bacteria into SimCells, simplified entities with most of their genetic material removed, leaving only the proteins and other components and just enough DNA to accomplish desired tasks. These SimCells were able to continue performing tasks for around 10 days before running out of the cellular resources needed to keep going. One of these tasks was producing a compound that damaged cancer cells in a dish but left non-cancerous cells unharmed.

Journal Paper: Fan C, Davison PA, Habgood R, Zeng H, Decker CM, Salazar MG, Lueangwattanapong K, Townley HE, Yang A, Thompson IP, Ye H, Cui Z, Schmidt F, Hunter CN, Huang WE. 2020. Chromosome-free bacterial cells are safe and programmable platforms for synthetic biology. Proc Natl Acad Sci 117:6752–6761.

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426: Sensory Cilia Supply Susceptibility Jul 27, 2020

This episode: A fungus paralyzes its tiny worm prey by acting on the worm's own sensory hairs!

Download Episode (6.0 MB, 8.7 minutes) Show notes: Microbe of the episode: Bat associated cyclovirus 9 Takeaways

Not all predators are fast or agile; some are sneaky, or good trap builders, or just good chemists. The predator club includes animals but also plants and even fungi. For example, the oyster mushroom fungus can paralyze roundworms in the soil that touch its filaments, then degrade their bodies and consume their nutrients. The mechanism of this paralysis has been a mystery, but it's one step closer to being solved. This study found that intact sensory cilia, little hairs on the worm's head that help it sense its surroundings, are required for the paralysis to work. Worms with mutations in the structure of their cilia were protected from paralysis. How exactly the fungus acts on these cilia and the neurons they connect to, though, is still unknown.

Journal Paper: Lee C-H, Chang H-W, Yang C-T, Wali N, Shie J-J, Hsueh Y-P. 2020. Sensory cilia as the Achilles heel of nematodes when attacked by carnivorous mushrooms. Proc Natl Acad Sci 117:6014–6022.

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425: Paired Predators Prevent Pathogen Persistence Jun 22, 2020

This episode: This episode: A bacteriophage and bacterial predator can wipe out a population of bacteria that could develop resistance to each individually!

Thanks to Laura Hobley, J. Kimberley Summers, and Jan-Ulrich Kreft for their contributions! Also a note: I will be taking a short break from podcasts while I rebuild my collection of awesome microbiology stories to talk about.

Download Episode (6.8 MB, 9.9 minutes) Show notes: Microbe of the episode: Blackbird associated gemycircularvirus 1 Takeaways

Bacteriophages and bacterial predators that prey on other bacteria are both very good at killing large numbers of bacteria. But bacteria as a whole are also very good at surviving being killed in large numbers; there are almost always a few that have the right genes to overcome whatever is doing the killing. This is what makes the threat of antibiotic resistance so scary, and why phage therapy is both very promising and very limited. In this study, however, a combination of phages and the bacterial predator Bdellovibrio bacteriovorans is able to completely eradicate a population of bacteria, or at least reduce their numbers below a detectable level. A mathematical model based on these data predicts that despite the two killers working independently, they can effectively eliminate all the individual prey organisms that would otherwise be able to resist killing by either one alone.

Journal Paper: Hobley L, Summers JK, Till R, Milner DS, Atterbury RJ, Stroud A, Capeness MJ, Gray S, Leidenroth A, Lambert C, Connerton I, Twycross J, Baker M, Tyson J, Kreft J-U, Sockett RE. 2020. Dual Predation by Bacteriophage and Bdellovibrio bacteriovorus Can Eradicate Escherichia coli Prey in Situations where Single Predation Cannot. J Bacteriol 202.

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424: Stranger Cells Switch Stable States Jun 15, 2020

This episode: Certain bacteria can greatly affect the makeup of a microbial community, even if they quickly disappear!

Thanks to Dr. Daniel Amor for his contribution!

Download Episode (6.3 MB, 9.2 minutes) Show notes: Microbe of the episode: Gadgets Gully virus News item Takeaways

Microbial communities show more than just competition between species. Stable assemblies of many species can exist for long periods in places like the human gut, despite constant minor shifts in conditions. More major shifts, or invaders like pathogens coming in and taking over, can cause big disruptions in the community and lead to long-term gut dysbiosis, which can be, interestingly, also a stable community. This study shows that invaders into a community, even if they don't persist for very long, can cause a shift from one stable state to another, by favoring the dominance of a species or group that was not dominant before, for example by changing the pH of the environment. So competition is always present. This could be helpful to know for efforts to intentionally shift community structures.

Journal Paper: Amor DR, Ratzke C, Gore J. 2020. Transient invaders can induce shifts between alternative stable states of microbial communities. Sci Adv 6:eaay8676.

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423: Roundworm Riders Route Rootworm Resistance Jun 08, 2020

This episode: Helping insect-killing bacterial symbionts of nematodes evolve resistance to chemicals that major corn pests use to defend themselves!

Download Episode (10.0 MB, 14.0 minutes) Show notes: Microbe of the episode: Listeria virus PSA Takeaways

Interactions between species and even kingdoms in nature can be complex and multilayered. This means that when we want to intervene to cause a particular outcome, there may be multiple points at which we can act, but the consequences may be hard to predict. In this study, action was taken to counteract the damage the Western corn rootworm causes to corn crops, using a tiny roundworm that attacks the insect pest with deadly bacteria. The rootworm defends itself by accumulating plant-produced toxins that inhibit the bacteria. Directed evolution was used to make the bacteria more resistant, and this led to more effective killing of the pest.

Journal Paper: Machado RAR, Thönen L, Arce CCM, Theepan V, Prada F, Wüthrich D, Robert CAM, Vogiatzaki E, Shi Y-M, Schaeren OP, Notter M, Bruggmann R, Hapfelmeier S, Bode HB, Erb M. 2020. Engineering bacterial symbionts of nematodes improves their biocontrol potential to counter the western corn rootworm. 5. Nat Biotechnol 38:600–608.

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422: Frigid Phototrophs Fuel Fords Jun 01, 2020

This episode: Producing both biodiesel and bioethanol fuels from cold-loving Arctic algae!

Download Episode (8.7 MB, 12.6 minutes) Show notes: Microbe of the episode: Royal Farm virus Takeaways

Renewable fuels such as biofuels can allow existing infrastructure and vehicles to continue to operate in a more sustainable manner, which could reduce the cost and impact of switching to new/different systems of transportation like electricity. Economically competitive methods of producing biofuels are still being explored and developed. In this study, Arctic algae are grown in cold temperatures using only light, carbon dioxide, and a few minerals, and then broken down to produce biodiesel and bioethanol, which can be used as fuel in many different internal combustion engines. The amounts produced are comparable to other algae-based systems being researched, and use of the cold-loving organisms could reduce the cost of production in colder latitudes and seasons.

Journal Paper:

Kim EJ, Kim S, Choi H-G, Han SJ. 2020. Co-production of biodiesel and bioethanol using psychrophilic microalga Chlamydomonas sp. KNM0029C isolated from Arctic sea ice. Biotechnol Biofuel 13:20.

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421: Nucleocapsids Navigate Nano Nuggets May 25, 2020

This episode: Using phages to target gold nanoparticles to infecting bacteria, then using light to heat the nanoparticles just enough to kill the bacteria! Thanks to Raymond Borg and Huan Peng for contributing!

Download Episode (10.6 MB, 15.4 minutes) Show notes: Microbe of the episode: Pantoea agglomerans News item Takeaways Viruses that infect bacteria, bacteriophages, are often very good at overcoming bacterial defenses and killing them. This raises the possibility, and many times actuality, of using phages to treat bacterial infections that are no longer treatable with antibiotics. But bacteria can evolve resistances to viruses as well as drugs, and using multiplying, evolving entities as treatments in people raises questions about the safety and consistency of the treatment. This study circumvents these questions by using phages for delivery and targeting of bacteria rather than the therapeutic agent itself. The actual treatment is done with tiny rods of gold, gold nanorods, bound to the phage surface. When a certain wavelength of light hits these nanorods, they vibrate enough to generate enough heat in their immediate surroundings to render nearby bacteria nonviable. Thus the infection is treated in a very localized, targeted way that doesn't leave any active bacteria or phages behind. The authors have plans to study this approach as a topical treatment of wounds. Journal Paper: Peng H, Borg RE, Dow LP, Pruitt BL, Chen IA. 2020. Controlled phage therapy by photothermal ablation of specific bacterial species using gold nanorods targeted by chimeric phages. Proc Natl Acad Sci 117:1951–1961.

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420: Cell Societies Stay Stable May 18, 2020

This episode: Simplified gut communities growing in bioreactors grow and metabolize reproducibly, with only moderate variations, even when individual members of the community are absent!

Download Episode (8.2 MB, 11.9 minutes) Show notes: Microbe of the episode: Citrobacter virus Merlin Takeaways The community of microbes in our guts is highly complex, with thousands of species all interacting with each other, with our own cells, and with the contents of our diet. Each region of the gut has a different collection of microbes as well. Many questions remain to be answered about the functions and fluctuations of these communities. How can we study such a complex system? Which species, if any, are most important for its continued function? In this study, a simplified community of only 14 species is grown repeatedly in bioreactors, and one species at a time is left out of the community to see what will change in its absence. This reveals effects different species have on the overall growth, carbon source consumption, and production of various metabolites relevant to gut health. Some microbes have large effects, but none of them appears to be crucial for the overall function and stability of the community. Journal Paper: Gutiérrez N, Garrido D. 2019. Species Deletions from Microbiome Consortia Reveal Key Metabolic Interactions between Gut Microbes. mSystems 4:e00185-19.

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Some archaea can survive for a while trapped inside salt crystals (paper)
Bacteria degrade BPA in soil (paper)

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419: Marine Methane Microbe Multiplication May 11, 2020

BacterioFiles is back! This episode: Measuring how quickly marine methane-consuming microbes become active when new methane enters an area!

Download Episode (9.0 MB, 13.0 minutes) Show notes: Microbe of the episode: Torque teno midi virus 6 Takeaways Oceans and the organisms living in them have a large effect on the planet, in terms of climate and gases they absorb from or release into the atmosphere. They are a source of much of a potent greenhouse gas, methane, but microbes living in ocean sediments also consume large amounts of methane. These anaerobic methanotrophic archaea generate energy for themselves by transforming methane and sulfate into carbonate and sulfide. In this study, however, methane-consuming microbes were only found active at sites of methane seepage. Even in sites where methane had previously been present, only few of these microbes were present and active. After enriching samples of these sediments for up to 8 months, still the only activity that was seen was from actively methane-consuming communities. So once dispersed, such communities seem slow to regenerate as the locations of methane seepage shift. Journal Paper: Klasek S, Torres ME, Bartlett DH, Tyler M, Hong W-L, Colwell F. 2020. Microbial communities from Arctic marine sediments respond slowly to methane addition during ex situ enrichments. Environ Microbiol 22:1829–1846.

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418: Special Sea Species Swallows Cells Mar 16, 2020

This episode: A newly discovered species of bacteria consumes other bacteria as prey by engulfing them!

Download Episode (8.7 MB, 12.6 minutes) Show notes: Microbe of the episode: SARS-CoV-2! This is the coronavirus responsible for COVID-19, the current pandemic. For more up-to-date information, please refer to the American Society for Microbiology, This Week in Virology, and other reputable sources. Stay healthy! Takeaways There are bacteria living almost every different lifestyle you can think of, including predatory, preying on other bacteria. Since bacterial cells are usually quite rigid, bacterial predators usually consume others either by burrowing inside them or digesting them from outside, rather than engulfing prey like eukaryotes often do. The study here discovers a new kind of bacteria, in the group called Planctomycetes, known for having unusually flexible cells and internal compartments like eukaryotes. This new species does engulf its prey, including bacteria and even tiny algae, and digests them inside itself. It possesses multiple adaptations that suit it for this lifestyle. Journal Paper: Shiratori T, Suzuki S, Kakizawa Y, Ishida K. 2019. Phagocytosis-like cell engulfment by a planctomycete bacterium. Nat Commun 10:1–11.

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417: Bacteriophage Blocks Bacterial Bouncers Mar 09, 2020

This episode: A phage defends its genome against bacterial host defenses by building a wall to keep them out!

Download Episode (7.0 MB, 10.2 minutes) Show notes: Microbe of the episode: Myroides odoratus and M. odoratimimus News item Takeaways Parasites and their hosts are constantly in arms races with each other, each thriving best when it acquires new and more effective methods of attack, defenses, defenses against defenses, and so on. Bacterial defenses against viruses that infect them mostly involve cutting up viral genomes, either by the indiscriminate specific-cutting restriction enzymes, or by adaptive, sequence-sensing CRISPR/Cas systems. Bacteriophages have proteins that can defend against the CRISPR/Cas system, but they mostly require the sacrifice of multiple failed infections before the proteins build up enough to defeat the defense. In this study, a phage is discovered that can immediately defend against all DNA-cutting systems, by constructing a nucleus-like protective compartment inside the host. Journal Paper: Mendoza SD, Nieweglowska ES, Govindarajan S, Leon LM, Berry JD, Tiwari A, Chaikeeratisak V, Pogliano J, Agard DA, Bondy-Denomy J. 2020. A bacteriophage nucleus-like compartment shields DNA from CRISPR nucleases. Nature 577:244–248.

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416: Oxygen Or Other Oxidizes Iron? Mar 02, 2020

This episode: Earth's iron deposits could have been created by anaerobic light-harvesting microbes instead of those that make oxygen!

Download Episode (9.3 MB, 13.5 minutes) Show notes: Microbe of the episode: Streptomyces avidinii News item Takeaways In the ancient earth, the sun was dimmer, the world was colder, and oxygen was rare because photosynthesis had not yet evolved. Without oxygen to oxidize it, iron remained in its soluble, more accessible form, and many organisms took advantage of it for anaerobic metabolism. But was it photosynthesis and the oxygen it created that transformed most of the planet's iron into its insoluble form, creating large iron deposits in the ground? This study explores the possibility that it was another form of light-harvesting metabolism, called photoferrotrophy, that uses light and the transformation of iron to generate energy. This hypothesis is found to be consistent with the evidence we have about what the early earth was like. Journal Paper: Thompson KJ, Kenward PA, Bauer KW, Warchola T, Gauger T, Martinez R, Simister RL, Michiels CC, Llirós M, Reinhard CT, Kappler A, Konhauser KO, Crowe SA. 2019. Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans. Sci Adv 5:eaav2869.

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415: Global Glomus Growth Guesses Feb 24, 2020

This episode: A global estimate of plants and their root fungi shows how agriculture may have greatly affected soil carbon storage over time!

Download Episode (5.7 MB, 8.3 minutes) Show notes: Microbe of the episode: Rhizobium virus RHEph4 News item Takeaways Even small organisms can have a big effect on the climate of the planet if there are enough of them. This includes trees, which are small relative to the planet, and also includes the fungi that attach to the roots of trees and other plants. These mycorrhizal fungi thread subtly through the soil, some occasionally popping up mushrooms, and transfer valuable nutrients they gather to the trees in exchange for carbon fixed from the air. Knowing how big an effect a given kind of organism has requires knowing how much of it is around. This study collates data from various surveys of global plant populations and the fungi that interact with their roots, to estimate a global picture of the fungi below our feet. It estimates that a kind of fungus that stores more carbon in the soil may have been replaced in many areas with fungi that store less, or no fungi at all, due to the transformation of land from wild areas to farmland. Journal Paper: Soudzilovskaia NA, van Bodegom PM, Terrer C, Zelfde M van’t, McCallum I, Luke McCormack M, Fisher JB, Brundrett MC, de Sá NC, Tedersoo L. 2019. Global mycorrhizal plant distribution linked to terrestrial carbon stocks. Nat Commun 10:1–10.

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414: Producing Proton Power Perpetually Feb 17, 2020

This episode: Microalgae can produce hydrogen, but other metabolic pathways take priority, except when special engineered hydrogenase enzymes can overcome this limitation!

Download Episode (8.4 MB, 12.2 minutes) Show notes: Microbe of the episode: Alphapapillomavirus 11 Takeaways There are many options being explored as ways to replace fossil fuels. Electricity and batteries are good, but they have their limitations, especially for long-distance high-energy travel such as airplanes. Hydrogen is one good option: high energy density, clean-burning, simple to produce. Microbes can produce hydrogen through various metabolic pathways, including fermentation, nitrogen fixation byproduct, and photosynthesis. However, competing metabolic pathways make microbial hydrogen production less efficient. In this study, scientists engineer a hydrogenase enzyme for hydrogen production in microalgae that can compete better with carbon fixation as a destination for the electrons and protons that hydrogen production requires. This engineered enzyme allowed the algae to produce hydrogen continuously, even during photosynthesis. Journal Paper: Ben-Zvi O, Dafni E, Feldman Y, Yacoby I. 2019. Re-routing photosynthetic energy for continuous hydrogen production in vivo. Biotechnol Biofuels 12:266.

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413: Finding Fire Fungi Footholds Feb 10, 2020

This episode: Some fungi only form fruiting bodies after forest fires; where do they hide the rest of the time? At least for some of them, the answer is: inside mosses! Thanks to Daniel Raudabaugh for his contribution!

Download Episode (6.2 MB, 9.0 minutes) Show notes: Microbe of the episode: Nocardia brevicatena News item Takeaways Forest fires can do a lot of damage, but life grows back quickly. Certain kinds of plant seed actually only germinate after a fire, and a similar thing is true of certain kinds of fungi: they only form fruiting bodies (like mushrooms, for spreading spores) after a fire. For plants, the advantage may come from increased access to light with some or all of the canopy burned away, and fungi may benefit from less competition on the ground. But in between burn events, these fire-loving (pyrophilous) fungi seem to disappear. Where do they go? The study here sought an answer, suspecting an association with some mosses that reappeared soon after a forest fire in North Carolina in 2016. They looked for fungi lurking as endophytes inside moss and other samples, both by growing them on agar and by DNA sequencing, and they found a number of different known pyrophilous fungi. Some of these were in soil, or samples from outside the burned area, but the majority were inside mosses growing in the recently burned zone. Journal Paper: Raudabaugh DB, Matheny PB, Hughes KW, Iturriaga T, Sargent M, Miller AN. 2020. Where are they hiding? Testing the body snatchers hypothesis in pyrophilous fungi. Fungal Ecol 43:100870.

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412: Carbon Concentration Complicates Crop Cooperation Feb 03, 2020

This episode: Looking at the effects of almost doubling CO2 concentrations on the interaction between wheat varieties and beneficial fungi!

Download Episode (8.1 MB, 11.8 minutes) Show notes: Microbe of the episode: Lato River virus News item Takeaways As the world's population grows, feeding everyone will grow more challenging. Advances in technology in the past have made today's population possible, but future advances may be needed, especially in the face of an increasing concentration of carbon dioxide in the atmosphere. Soil microbes that partner with crop plants for the benefit of each may be part of the solution. One option to explore is a group called mycorrhizal fungi, which associate with plant roots to extend their nutrient-gathering ability, in exchange for carbon compounds produced by photosynthesis. This study examined the influence of increased carbon dioxide in the atmosphere on the interaction of several varieties of wheat with these fungi. Journal Paper: Thirkell TJ, Pastok D, Field KJ. Carbon for nutrient exchange between arbuscular mycorrhizal fungi and wheat varies according to cultivar and changes in atmospheric carbon dioxide concentration. Glob Change Biol.

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411: Parasite Produces Partial Plant-like Predator Jan 27, 2020

This episode: Giant virus in newly discovered microscopic marine predator encodes several light-harvesting proteins!

Download Episode (7.8 MB, 11.4 minutes) Show notes: Microbe of the episode: Dolphin mastadenovirus A News item Takeaways Giant viruses are distinct in many ways from other viruses, even aside from their size. One way is the large number and variety of genes they carry in their genome. Though many of their genes are unknown in origin and function, many others appear to take the place of essential reproductive functions, such as translation and protein synthesis. This allows them to assume more control of their host's metabolism and control its resources more optimally. In this study, the sequence of a giant virus was discovered seemingly infecting a newly discovered microscopic marine predator. The eukaryotic cell feeds on smaller microbes such as bacteria, but strangely, the virus carries genes for several light-harvesting proteins, possibly converting a heterotrophic predator into a partial phototroph. Journal Paper: Needham DM, Yoshizawa S, Hosaka T, Poirier C, Choi CJ, Hehenberger E, Irwin NAT, Wilken S, Yung C-M, Bachy C, Kurihara R, Nakajima Y, Kojima K, Kimura-Someya T, Leonard G, Malmstrom RR, Mende DR, Olson DK, Sudo Y, Sudek S, Richards TA, DeLong EF, Keeling PJ, Santoro AE, Shirouzu M, Iwasaki W, Worden AZ. 2019. A distinct lineage of giant viruses brings a rhodopsin photosystem to unicellular marine predators. Proc Natl Acad Sci 116:20574–20583.

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410: Microbes Modify Muscle Measurement Jan 20, 2020

This episode: Mice that got a microbe transplant from humans with higher physical function performed better in certain ways than mice receiving microbes from humans with lower physical function!

Download Episode (6.7 MB, 9.8 minutes) Show notes: Microbe of the episode: Stenotrophomonas maltophila News item Takeaways Our bodies and our microbe communities are closely interconnected, with effects going both ways. Studies had previously shown that making changes to the microbe communities of mice could even affect the physical function and body composition of the mice. This study aimed at addressing the same question in humans. There were certain consistent differences in microbial communities between elderly people with high ability to function physically, compared with low functioning people. These differences carried over in transplants of microbes from people to mice, and mice receiving microbes from high-functioning humans did better in tests of grip strength than mice receiving microbes from low-functioning people. Journal Paper: Fielding RA, Reeves AR, Jasuja R, Liu C, Barrett BB, Lustgarten MS. 2019. Muscle strength is increased in mice that are colonized with microbiota from high-functioning older adults. Exp Gerontol 127:110722.

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409: Marine Methane Mostly Munched Jan 13, 2020

This episode: Microbes in low-oxygen zones in the ocean consume significant amounts of methane anaerobically!

Download Episode (5.2 MB, 7.6 minutes) Show notes: Microbe of the episode: Mojiang henipavirus News item Takeaways Methane is a much more potent greenhouse gas than carbon dioxide. Fortunately there's not as much of it in the atmosphere, but even smaller amounts can have significant effects on the climate. One source of methane is low-oxygen zones in the ocean, where certain kinds of archaea make methane as part of their energy metabolism. This study found that other anaerobic microbes in the same areas consume much of this methane, preventing it from reaching the atmosphere. Journal Paper: Thamdrup B, Steinsdóttir HGR, Bertagnolli AD, Padilla CC, Patin NV, Garcia‐Robledo E, Bristow LA, Stewart FJ. 2019. Anaerobic methane oxidation is an important sink for methane in the ocean’s largest oxygen minimum zone. Limnol Oceanogr 64:2569–2585.

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408: Currents Carry Cloud Creators Jan 06, 2020

This episode: Ocean bacteria brought up from the sea floor into the air can help create clouds!

Download Episode (6.1 MB, 8.9 minutes) Show notes: Microbe of the episode: Streptomyces thermodiastaticus News item Takeaways The ocean is an important player affecting the climate of the planet, in many ways. Its effects on clouds influence the amount of solar radiation reflected back into space or trapped as heat, and microbes play a role in this effect. Certain microbes make particles that form the nucleus of water droplets or ice crystals that make up clouds, and other microbes can perform this nucleation themselves. In this study, an unusual combination of a phytoplankton bloom and strong winds and currents, all in the right places, led to a large number of ice-nucleating bacteria being fed and then brought up from the sea floor and launched into the air, possibly affecting weather patterns in the Arctic. Journal Paper: Creamean JM, Cross JN, Pickart R, McRaven L, Lin P, Pacini A, Hanlon R, Schmale DG, Ceniceros J, Aydell T, Colombi N, Bolger E, DeMott PJ. 2019. Ice Nucleating Particles Carried From Below a Phytoplankton Bloom to the Arctic Atmosphere. Geophys Res Lett 46:8572–8581.

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407: Fungus Facilitates Phototroph Feeding Dec 23, 2019

Probably the last episode of the year. See you in the next! This episode: Fungus living inside plants helps them form partnerships with nitrogen-fixing bacteria!

Download Episode (5.9 MB, 8.5 minutes) Show notes: Microbe of the episode: Prevotella intermedia Takeaways Plants are very good at acquiring carbon, but they can often use some help with other nutrients. Many form partnerships with microbes such as nitrogen-fixing bacteria or mycorrhizal fungi that can help gather nutrients from the soil better than the plants' own roots. In this study, legume plants could form a partnership with nitrogen-fixing bacteria in its roots, but a fungus living inside the plant could enhance this partnership even more, increasing the amount of nitrogen acquired and influencing the community of microbes around the plant roots in ways favorable to all partners. Journal Paper: Xie X-G, Zhang F-M, Yang T, Chen Y, Li X-G, Dai C-C. 2019. Endophytic Fungus Drives Nodulation and N2 Fixation Attributable to Specific Root Exudates. mBio 10:e00728-19, /mbio/10/4/mBio.00728-19.atom.

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406: Different DNA Destroys Disease Drivers Dec 16, 2019

This episode: DNA from related species can kill certain pathogens when they incorporate it into their genome!

Download Episode (7.9 MB, 11.5 minutes) Show notes: Microbe of the episode: Ungulate tetraparvovirus 3 Paper summary (paywall) Takeaways Neisseria gonorrhoeae, the bacteria that cause gonorrhea, have the unusual ability of taking up DNA from their surroundings at any time and making use of it in their own genome. This helps them acquire useful traits that help them survive better, such as antibiotic resistance. But it turns out that the ability is also a secret weakness! This study showed that when N. gonorrhoeae takes up DNA from harmless, commensal species of Neisseria in the body, the DNA is similar enough to be incorporated into the genome but different enough that it kills the pathogen. This effect also occurs with a serious pathogen in the same genus, N. meningitidis. Journal Paper: Kim WJ, Higashi D, Goytia M, Rendón MA, Pilligua-Lucas M, Bronnimann M, McLean JA, Duncan J, Trees D, Jerse AE, So M. 2019. Commensal Neisseria Kill Neisseria gonorrhoeae through a DNA-Dependent Mechanism. Cell Host Microbe 26:228-239.e8.

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405: Coated Colonizers Counteract Corrosion Dec 09, 2019

This episode: Coating metal surfaces with artificial biofilms could help keep the surfaces corrosion-free even in the ocean!

Download Episode (6.3 MB, 9.1 minutes) Show notes: Microbe of the episode: Hymenopteran ambidensovirus 1 Takeaways The ocean can be a harsh place for metal surfaces. Between the water, the salt, and oxygen (near the surface), corrosion is a common reality. Microbes in the ocean can contribute to this too, degrading metal structures to obtain energy for their metabolism. They colonize surfaces in biofilms that can be difficult to remove, a process called biofouling. In this study, instead of trying to remove or prevent biofilms on surfaces, artificial biofilms were created by coating the surfaces and specially selected bacterial cells with polymers. This approach did not prevent colonization by other organisms in the sea, but preliminary results suggested that the community that did take up residence was not as corrosive as the communities found on uncoated steel. Journal Paper: Rijavec T, Zrimec J, Spanning R van, Lapanje A. 2019. Natural Microbial Communities Can Be Manipulated by Artificially Constructed Biofilms. Adv Sci 6:1901408.

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404: Phages Force Food Finding Nov 25, 2019

This episode: Another climate-related story: Cyanobacteria infected by viruses continue taking up nutrients from their environment, using it to make more viruses than would otherwise be possible!

Download Episode (6.3 MB, 9.2 minutes) Show notes: Microbe of the episode: Microcystis virus Ma-LMM01 News item Takeaways Though global warming is a global problem, accurate models for predicting where things are headed need to incorporate the activity of even the smallest organisms, if they're numerous enough. Photosynthesis and other activities of microbes in the oceans are a big sink for carbon, but cycles of other nutrients and also viruses can affect the carbon cycle. In this study, phages infecting photosynthetic ocean bacteria were able to continue their host's uptake of nitrogen from the environment even after mostly shutting down the host's own protein production and growth. This has implications for how viruses affect carbon cycling by cyanobacteria and how quickly populations of these bacteria may grow or die off. Journal Paper: Waldbauer JR, Coleman ML, Rizzo AI, Campbell KL, Lotus J, Zhang L. 2019. Nitrogen sourcing during viral infection of marine cyanobacteria. Proc Natl Acad Sci 116:15590–15595.

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403: Mercury Modifies Microbe Metabolism Nov 18, 2019

This episode: First episode of a climate-related arc! Considering microorganisms is important when predicting the amount of carbon coming from soil as temperature increases!

Download Episode (4.7 MB, 6.75 minutes) Show notes: Microbe of the episode: Streptomyces virus Zemlya News item Takeaways Soil as a whole has a big influence on the climate of the planet, by enabling the communities of organisms that live in it to interact and grow, taking up gases from the atmosphere and putting others back in. Even aside from plants that grow in it, the other organisms in soil can respire and break down compounds to produce CO2, adding to what's in the atmosphere already. There has long been observed a relationship between ambient temperatures and this respiration in soil, such that more heat means more activity and more gases released from the soil, but today's study found that the microbial biomass in a given piece of land can have a big effect on the temperature/respiration relationship. Journal Paper: Čapek P, Starke R, Hofmockel KS, Bond-Lamberty B, Hess N. 2019. Apparent temperature sensitivity of soil respiration can result from temperature driven changes in microbial biomass. Soil Biol Biochem 135:286–293.

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402: Microbe Membranes Mobilize Microglia Nov 11, 2019

This episode: Gut microbes can stimulate immune cells in mouse brains to fight off viral infections!

Download Episode (9.0 MB, 13.0 minutes) Show notes: Microbe of the episode: Streptoverticillium mobaraense News item Takeaways The central nervous system, including the brain, is a protected area of the body. Pathogens that get in can do a lot of damage, including memory loss, paralysis, and death, so there's a strict barrier in healthy people that keeps most things out of this area: the blood-brain barrier. The immune system is also kept separate, so special cells called microglia do the patrolling and protection of the brain. Nevertheless, microbes in the gut can influence the function of the immune system in the brain, even from a distance. In this study, mice lacking gut microbes did not have as effective an immune response to a virus infecting the brain, and it was found that molecules from bacterial outer membranes were sensed by microglia to activate their defensive response. Journal Paper: Brown DG, Soto R, Yandamuri S, Stone C, Dickey L, Gomes-Neto JC, Pastuzyn ED, Bell R, Petersen C, Buhrke K, Fujinami RS, O’Connell RM, Stephens WZ, Shepherd JD, Lane TE, Round JL. 2019. The microbiota protects from viral-induced neurologic damage through microglia-intrinsic TLR signaling. eLife 8:e47117.

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401: Phototrophs Fill Fungal Filaments Nov 04, 2019

This episode: In this partnership between fungus and algae, the algae eventually take up residence inside their partner!

Download Episode (8.4 MB, 12.1 minutes) Show notes: Microbe of the episode: Erwinia tracheiphila News item/Summary article Takeaways Partnerships and cooperation between otherwise free-living organisms is common in the natural world. Partnering with a photosynthetic organism is a smart approach, allowing the partner to get its energy from the sun and making gathering nutrients easier for the phototroph, and possibly offering protection as well. But in most partnerships, each partner stays separated by its own cell membrane. In this study, a fungus and an alga grow well together, exchanging carbon for nitrogen, similar to how lichens operate. But after a month or so of co-culture, the algae apparently enter the cells of the fungus somehow and live inside it, happily growing and dividing, turning the fungus green. Journal Paper: Du Z-Y, Zienkiewicz K, Vande Pol N, Ostrom NE, Benning C, Bonito GM. 2019. Algal-fungal symbiosis leads to photosynthetic mycelium. eLife 8:e47815.

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400: Considering Consumables' Community Correlations Oct 21, 2019

This episode: Figuring out how gut communities change with changes in diet!

Download Episode (6.1 MB, 8.8 minutes) Show notes: Microbe of the episode: Hepacivirus A News item Takeaways Diet can play a big role in our health. It's not a magic pill that can cure or prevent anything, but a good diet can significantly reduce many health risks for the average person, compared with a bad diet. Diet also has a big effect on the community of microbes in our gut, and this may play a role in the health effects we see from diet, so understanding how food and microbes interact is important. This study looked at the diet quality of participants in several food categories, and correlated this with various kinds of microbes found inside them. Journal Paper: Liu Y, Ajami NJ, El-Serag HB, Hair C, Graham DY, White DL, Chen L, Wang Z, Plew S, Kramer J, Cole R, Hernaez R, Hou J, Husain N, Jarbrink-Sehgal ME, Kanwal F, Ketwaroo G, Natarajan Y, Shah R, Velez M, Mallepally N, Petrosino JF, Jiao L. 2019. Dietary quality and the colonic mucosa–associated gut microbiome in humans. Am J Clin Nutr 110:701–712.

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399: Conductor Creating Carbon Canvases Oct 14, 2019

This episode: Bacteria can aide the production of the useful material graphene, using their ability to add electrons to external surfaces!

Download Episode (7.7 MB, 11.3 minutes) Show notes: Microbe of the episode: Brevibacterium frigoritolerans News item Takeaways Advanced materials often take advanced techniques to create, but they offer numerous benefits: increased strength and flexibility, smaller size, more options. One such material is graphene, which is basically a sheet of carbon atoms linked together like chainmail. It is only a single atom thick but is amazingly strong, mostly transparent, and good at conducting heat and electricity. The trick is, it's hard to make in large quantities cheaply and easily. Sheets of carbons can be obtained from blocks of graphite, but these sheets are graphene oxide, which lack the desirable properties of graphene. Chemical methods can be used to remove the oxidation, but they are harsh and difficult. Luckily, bacteria are great at microscopic remodeling. In this study, electron-transferring bacteria are able to reduce the graphene oxide to graphene with properties almost as good as are achieved by chemical reduction. Journal Paper: Lehner BAE, Janssen VAEC, Spiesz EM, Benz D, Brouns SJJ, Meyer AS, van der Zant HSJ. 2019. Creation of Conductive Graphene Materials by Bacterial Reduction Using Shewanella oneidensis. ChemistryOpen 8:888–895.

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398: Marathon Microbes Maximize Mileage Oct 07, 2019

This episode: Bacteria found in the guts of serious athletes help mice exercise longer by transforming their metabolic waste!

Download Episode (7.3 MB, 10.6 minutes) Show notes: Microbe of the episode: Aggregatibacter (Actinobacillus) actinomycetemcomitans News item Takeaways Our gut microbes affect many aspects of health, and many aspects of how we live affect our microbes. One such aspect is physical exertion, which has been associated with enrichment of various microbes in the guts of athletes. This observation led to the question: are these microbes just benefiting from the high levels of exertion, or are they able to contribute also? This study found that certain such bacteria, when given to mice, enabled the mice to run for a longer period on a treadmill. These microbes break down lactic acid, which is generated in our bodies when we push our physical limits, but the study provided evidence that the longer run times were due not to removal of this waste product, but to the propionate compound produced by its degradation. Journal Paper: Scheiman J, Luber JM, Chavkin TA, MacDonald T, Tung A, Pham L-D, Wibowo MC, Wurth RC, Punthambaker S, Tierney BT, Yang Z, Hattab MW, Avila-Pacheco J, Clish CB, Lessard S, Church GM, Kostic AD. 2019. Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nat Med 25:1104–1109.

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397: Plant Promotes Pathogen-Prohibiting Partner Sep 30, 2019

This episode: Plants stimulate their root bacteria to compete better, and these bacteria help the plants resist disease!

Download Episode (7.3 MB, 10.6 minutes) Show notes: Microbe of the episode: Bacillus circulans Takeaways In some ways, plants' roots are like our gut. They both absorb nutrients, and they both have complex communities of microbes living alongside the host cells. These microbes can assist their hosts in various ways, and get fed in return. In this study, one species of root bacterium is able to compete against others by producing an antimicrobial compound. The plant stimulates this production with chemical signals, and benefits from its symbionts' increased competitiveness because the bacterium helps the plant resist infection. Journal Paper: Ogran A, Yardeni EH, Keren-Paz A, Bucher T, Jain R, Gilhar O, Kolodkin-Gal I. 2019. The Plant Host Induces Antibiotic Production To Select the Most-Beneficial Colonizers. Appl Environ Microbiol 85:e00512-19.

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396: Bacteria Boost Blood Bank Budgets Sep 23, 2019

This episode: Bacterial enzymes could convert donated blood to be compatible with more people in need!

Download Episode (8.0 MB, 11.7 minutes) Show notes: Microbe of the episode: Cucumber leaf spot virus News item Takeaways Blood transfusions using donated blood save many lives. Unfortunately, most donations can't be given to just anyone that needs blood; there must be a match in blood type between donor and recipient, or else a life-threatening reaction could occur in the recipient's body. So type A can't donate to type B, or vice versa, but type O is compatible with the other types. In this study, bacterial enzymes found in human gut microbes have the ability to cleave off the unique type A and B sugars on the surface of red blood cells. This could allow the conversion of all donated blood to type O, greatly increasing the blood bank supply, but more testing is needed to develop the process. Journal Paper: Rahfeld P, Sim L, Moon H, Constantinescu I, Morgan-Lang C, Hallam SJ, Kizhakkedathu JN, Withers SG. 2019. An enzymatic pathway in the human gut microbiome that converts A to universal O type blood. Nat Microbiol 4:1475–1485.

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395: Many Microbiome Mindsets Sep 16, 2019

This episode: Five different ways of thinking about our relationship with our microbes!

Download Episode (20.4 MB, 29.8 minutes) Show notes: Microbe of the episode: Tuhoko rubulavirus 3 News item Takeaways The microbiome by itself is an amazingly complicated community of many different species, with different lifestyles and metabolisms, all living together in competition and cooperation. On top of that, interactions between the microbiome and our body and our lifestyle multiply the complexity even more. This article explores five different views of the microbiome and how it fits into our body (or how the body fits in with the microbiome). From the organ view to the ecosystem view, each is a different way of looking at the different functions, dynamic patterns, and integration of the microbiome in its host, and each provides guidance for how to approach treatment of disease and maintenance of health. Journal Paper: Morar N, Bohannan BJM. 2019. The Conceptual Ecology of the Human Microbiome. The Quarterly Review of Biology 94:149–175.

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394: Skinny Cell Structure Supports Aug 26, 2019

This episode: Not as simple as it sounds—how rod-shaped bacteria maintain their shape! Thanks to Dr. Ethan Garner for his contribution!

Download Episode (6.3 MB, 9.2 minutes) Show notes: Microbe of the episode: Erwinia virus M7 News item Takeaways Microbes seem like they should be a lot simpler than large multicellular organisms, but even what seems like it should be a simple system in microbes can be surprisingly complex. In this case, the system bacteria maintaining their particular cell shape. Spherical cells have it easier: just add more cell material at every point. But for rods, they must make the cell longer without making it wider. How do they accomplish this? Two groups of proteins work together to help rod-shaped species grow, but how they work wasn't specifically known. In this study, it was found that one group of proteins adds more cell material as it moves around the circumference, while the other adds structure to the cell that allows it to maintain shape. The more of these structural proteins present, the thinner the cell can stay. Journal Paper: Dion MF, Kapoor M, Sun Y, Wilson S, Ryan J, Vigouroux A, van Teeffelen S, Oldenbourg R, Garner EC. 2019. Bacillus subtilis cell diameter is determined by the opposing actions of two distinct cell wall synthetic systems. Nat Microbiol 4:1294–1305.

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393: Prokaryote Partner Prevents Pathogen Potency Aug 12, 2019

This episode: Bacterial symbionts of amoebas help them survive bacterial infection, and prevent pathogens from spreading to others as much!

Download Episode (7.5 MB, 8.1 minutes) Show notes: Microbe of the episode: Eubacterium dolichum News item Takeaways Amoebas are free-living, single-celled organisms, but they have some things in common with some cells of our immune system (macrophages). For example, certain bacterial pathogens can infect both in similar ways. So it can be useful to study the interactions of amoebas and bacteria to learn about our own immune defenses. In this study, the amoeba Acanthamoeba castellanii has another bacterial symbiont that helps it resist killing by the bacterial pathogen Legionella pneumophila. Once the amoebas recovered from the infection, they were more resistant to future challenges. Even better, the symbiont prevented the pathogen from transforming into a more spreadable form like it does when infecting amoebas alone. Journal Paper: König L, Wentrup C, Schulz F, Wascher F, Escola S, Swanson MS, Buchrieser C, Horn M. 2019. Symbiont-Mediated Defense against Legionella pneumophila in Amoebae. mBio 10:e00333-19.

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392: Magnetic Microbes Maneuver Marine Manager Aug 05, 2019

This episode: A marine protist can orient itself along magnetic fields thanks to bacterial symbionts on its surface that make magnetic nanoparticles!

Download Episode (7.2 MB, 7.9 minutes) Show notes: Microbe of the episode: Chlorocebus pygerythrus polyomavirus 3 Takeaways Various kinds of bacteria can orient their movement along a magnetic field. These are called magnetotactic, and they use this ability to swim toward or away from the surface of their aquatic habitat, to adjust their oxygen exposure according to their preference. No eukaryotic microbes have yet been discovered that can sense and react to magnetic fields like these prokaryotes. In this study, however, a protist was discovered that can do it via its partnership with ectosymbionts, or bacteria attached to its surface, that sense magnetism and orient their host's movement. In return, factors of the host's metabolism may feed its symbionts. Journal Paper: Monteil CL, Vallenet D, Menguy N, Benzerara K, Barbe V, Fouteau S, Cruaud C, Floriani M, Viollier E, Adryanczyk G, Leonhardt N, Faivre D, Pignol D, López-García P, Weld RJ, Lefevre CT. 2019. Ectosymbiotic bacteria at the origin of magnetoreception in a marine protist. Nat Microbiol 4:1088–1095.

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391: Slime Stores Sodium Sensibility Jul 15, 2019

This episode: Slime molds can learn to get used to salt and hold on to that memory even after a period of dormancy!

Download Episode (8.9 MB, 9.7 minutes) Show notes: Microbe of the episode: Nocardia transvalensis News item Takeaways Slime mold Physarum polycephalum has many surprisingly intelligent abilities, despite being only a single cell. Studying how these abilities work in the cell can teach us new ways that life can do things. The ability of interest here is habituation, or learning not to avoid a chemical that seems unpleasant to the cell but is not necessarily harmful, especially with a food reward. The slime mold can become habituated to salt, in this case, learning to tolerate it enough to pass through a gradient of increasing concentration to get to some food as quickly as it crosses the same distance with no salt present. The scientists here learned that the cell takes up sodium into itself as it habituates, and holds onto both sodium and its memory through a period of hibernation. Journal Paper: Boussard A., Delescluse J., Pérez-Escudero A., Dussutour A. 2019. Memory inception and preservation in slime moulds: the quest for a common mechanism. Phil Trans R Soc B 374:20180368.

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390: Friendly Phages Find Foes Jul 08, 2019

This episode: Bacteria carry deadly phages and use them against rival strains!

Download Episode (9.4 MB, 10.2 minutes) Show notes: Microbe of the episode: Bifidobacterium bifidum News item Takeaways Bacteria such as Escherichia coli live in environments such as the gut with many other types of microbes, and often develop communities of microbes cooperating and/or competing with each other for resources. But in order to cooperate or compete, bacteria must first be able to identify and discriminate between themselves and others. Sometimes microbes do this by exchanging membrane molecules, or secreting chemical signals that only partners can detect, or transferring plasmids or producing antimicrobial compounds that kill competitors. In the current study, scientists discovered a strain of E. coli that carries around phages that help them distinguish other strains and compete with them. When this strain encounters another, the phages it carries attack and destroy cells of the other strain, while leaving the carrier strain mostly unharmed. This strategy is not without cost, though; the viral proteins take resources to produce, and when there's no competing strains around, the virus can attack its carrier to some extent. Journal Paper: Song S, Guo Y, Kim J-S, Wang X, Wood TK. 2019. Phages Mediate Bacterial Self-Recognition. Cell Reports 27:737-749.e4.

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E. coli adjusts its swimming to get around obstacles

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389: Prokaryotes Pacify Protein Problem Jul 01, 2019

This episode: Engineered bacteria could help people digest an essential nutrient when they can't digest it themselves!

Download Episode (8.5 MB, 9.3 minutes) Show notes: Microbe of the episode: Kadipiro virus News item (paywall) Science-Based Medicine blog article about phenylketonuria, Synlogic, and engineering bacteria to treat this disorder, with lots of good detail Takeaways Treating genetic disorders can be very difficult. Sometimes they can be managed, with lifestyle, diet, or medication, but cure has almost always been out of the picture. With a disorder such as phenylketonuria (PKU), for example, in which the body is unable to fully metabolize the amino acid phenylalanine, diet and medication may work to some extent. In an effort to provide better options for PKU, scientists at Synlogic, Inc have created a strain of Escherichia coli that produces phenylalanine-degrading enzymes in the gut. The hope is that ingesting this bacterium could allow PKU patients to be less restrictive with their diet. Journal Paper: Isabella VM, Ha BN, Castillo MJ, Lubkowicz DJ, Rowe SE, Millet YA, Anderson CL, Li N, Fisher AB, West KA, Reeder PJ, Momin MM, Bergeron CG, Guilmain SE, Miller PF, Kurtz CB, Falb D. 2018. Development of a synthetic live bacterial therapeutic for the human metabolic disease phenylketonuria. Nat Biotechnol 36:857–864.

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388: Floor Fungi Fracture Phthalates Jun 17, 2019

This episode: Microbes in household dust help degrade potentially harmful plasticizer chemicals! Thanks to Ashleigh Bope for her contribution!

Download Episode (6.7 MB, 7.3 minutes) Show notes: Microbe of the episode: Rosa rugosa leaf distortion virus News item Takeaways Modern life and technology comes with modern challenges, including exposure to chemicals in building materials and such that humans didn't encounter much before the last few generations. Phthalate esters, found in PVC and other materials, can accumulate in homes and cause some problems, especially in children. Modern life is also new to microbes, but they are very adaptable and versatile. In this study, microbes in household dust show some ability to break down the phthalates over time. Whether this activity is significant and beneficial to residents remains to be discovered. Journal Paper: Bope A, Haines SR, Hegarty B, Weschler CJ, Peccia J, Dannemiller KC. Degradation of phthalate esters in floor dust at elevated relative humidity. Environ Sci: Processes Impacts.

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Native fungi tag team to kill invasive insect pest (paper)

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387: Carbonate Creators Combat Cracking Jun 10, 2019

This episode: Bacteria strengthen concrete while helping to prevent damage from road salts!

Download Episode (6.8 MB, 7.4 minutes) Show notes: Microbe of the episode: Azospirillum brasilense News item Takeaways Winter is a bad time for concrete outside. Water seeps into cracks and freezes, causing bigger cracks that widen into potholes. Even the road salts used to keep water from freezing can react with compounds in the cement to break down the structure of the concrete. This study looks to bacteria for a solution for protecting concrete from these reactions. Sporosarcina pasteurii, given the right nutrients, can take the harmful salt compounds and turn them into minerals that strengthen the concrete instead of weakening it. Journal Paper: Ksara M, Newkirk R, Langroodi SK, Althoey F, Sales CM, Schauer CL, Farnam Y. 2019. Microbial damage mitigation strategy in cementitious materials exposed to calcium chloride. Construction and Building Materials 195:1–9.

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Developing way for bacteria to make mother-of-pearl, a tough and useful material

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386: Cupola Contaminant Cleaners Jun 03, 2019

This episode: Bacteria help gently clean residue off artworks painted on stone!

Download Episode (5.6 MB, 6.1 minutes) Show notes: Microbe of the episode: Cellulophaga virus Cba171 Takeaways More and more cleaning products these days contain an ingredient called "enzymes." These are proteins that break down contaminants biologically instead of just removing them chemically, in a targeted manner. In a similar approach, this study explores applying bacteria directly to classic artwork painted directly on stone, to clean up residues on the surface. These bacteria can produce enzymes on site and degrade the contaminants while leaving the underlying paint intact. Journal Paper: Ranalli G, Zanardini E, Rampazzi L, Corti C, Andreotti A, Colombini MP, Bosch‐Roig P, Lustrato G, Giantomassi C, Zari D, Virilli P. 2019. Onsite advanced biocleaning system on historical wall paintings using new agar-gauze bacteria gel. J Appl Microbiol 126:1785–1796.

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385: Prokaryotes Protect Paper May 27, 2019

This episode: Bacteria produce antifungal compounds that can protect paper from fungal deterioration!

Download Episode (6.8 MB, 7.4 minutes) Show notes: Microbe of the episode: Acetobacter aceti Takeaways Paper is a very useful information storage medium, but it is also somewhat delicious for microbes that can break it down as food, degrade the quality, and cause indelible stains and discoloration under the right conditions. Preventing this usually requires careful control, such as keeping humidity low, for storing paper for long periods. In this study, scientists tested the ability of the bacterium Lysobacter enzymogenes to protect paper via the antifungal compounds it produces. This first required filtering out the pigments that the bacteria produced, to prevent them from discoloring the paper. Once a method for this filtering was in place, they found the bacterial culture supernatant could significantly reduce fungal growth on various kinds of paper, and protect the paper from staining and degradation. Journal Paper: Chen Z, Zou J, Chen B, Du L, Wang M. 2019. Protecting books from mold damage by decreasing paper bioreceptivity to fungal attack using de-coloured cell-free supernatant of Lysobacter enzymogenes C3. J Appl Microbiol 126:1772–1784.

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384: Moss Materials Modify Microbiota May 20, 2019

This episode: Contact with soil materials and moss causes significant, though short-term, changes in the skin microbiota! Thanks to Dr. Mira Grönroos for her contribution!

Download Episode (7.1 MB, 7.75 minutes) Show notes: Microbe of the episode: Leonurus mosaic virus Takeaways Exposure to microbes throughout life is thought to help calibrate the immune system to some extent, reducing the risk of allergies and asthma without losing defense against pathogens. In this study, rubbing soil or packets of moss on the skin changed the composition of the skin microbiota temporarily, so this may be a way to help with this important type of exposure, but it is not yet known how to achieve optimal long-term effects. Journal Paper: Grönroos M, Parajuli A, Laitinen OH, Roslund MI, Vari HK, Hyöty H, Puhakka R, Sinkkonen A. 2019. Short-term direct contact with soil and plant materials leads to an immediate increase in diversity of skin microbiota. MicrobiologyOpen 8:e00645.

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383: Communities Carry Communicable Communities May 13, 2019

I'm back! This episode: Looking at how people in different villages share microbes!

Download Episode (6.5 MB, 7.0 minutes) Show notes: Microbe of the episode: Cristispira pectinis Takeaways Our microbiota, the communities of microbes living in and on our bodies, are incredibly diverse and varied. Each person's is different, and they can change drastically over time with changes in location, diet, lifestyle, and other factors. Learning how our microbiota forms and changes and functions is important, because it can affect many aspects of health. In this study, villagers in the islands of Fiji share microbes with others in the same and other villages, but not always in patterns that might be expected. Journal Paper: Brito IL, Gurry T, Zhao S, Huang K, Young SK, Shea TP, Naisilisili W, Jenkins AP, Jupiter SD, Gevers D, Alm EJ. Transmission of human-associated microbiota along family and social networks. Nat Microbiol.

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382: Small Scavengers Suck Sizable Cells Apr 15, 2019

This episode: Fungus-hunting amoebas have different strategies for detecting and preying on single-celled and filamentous fungi! Also, a personal note: I'm going to be taking a few weeks off the podcast to be able to take full advantage of spring, but I'll be back as soon as the weather gets too hot.

Download Episode (7.5 MB, 8.2 minutes) Show notes: Microbe of the episode: Chondromyces catenulatus Takeaways Amoebas in the microbial world are like powerful predators, going around gobbling up whatever they find that's small enough, by a process called phagocytosis, in which they surround their prey with their cell membrane and engulf it. It's similar to macrophages or white blood cells as part of our immune system in our bodies. The prey of amoebas includes bacteria, large viruses, and single-celled fungi called yeasts. In this study, scientists showed that some yeasts make great food sources for a certain kind of amoeba called Protostelium aurantium, while others either lack nutritional value or hide from the predators by covering up certain recognition molecules on their cell wall. They found that the amoebas could also consume the spores of filamentous fungi, and could even attack the filaments, or hyphae. In this latter case, instead of engulfing the large filaments, they pierced the cells and extracted their contents, an approach named ruphocytosis, from the Greek for suck or slurp. Journal Paper: Radosa S, Ferling I, Sprague JL, Westermann M, Hillmann F. The different morphologies of yeast and filamentous fungi trigger distinct killing and feeding mechanisms in a fungivorous amoeba. Environ Microbiol.

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Finding potential antimicrobials from ant bacteria

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381: Chlorophyll Can Convey Cancer Characteristics Apr 08, 2019

This episode: Pigmented bacteria can be used in a cancer imaging technique that combines light and sound!

Download Episode (8.9 MB, 9.75 minutes) Show notes: Microbe of the episode: Streptomyces bellus Takeaways Because "cancer" is a general term that describes many different forms of disease affecting different cells in different parts of the body, effective cancer treatment relies on understanding the location and physiology of the cancer in a given patient. New imaging technologies for diagnosis and analysis of cancer and for cancer research can be very valuable, especially if they don't require big investments of money and space. One promising imaging technology is called multispectral optoacoustic imaging, or MSOT. This uses pulses of light to create vibrations as pigments in tissues absorb the light and undergo thermal expansion; these vibrations are then detected by ultrasound technology. This approach allows good resolution and depth of imaging without large equipment like MRI machines, but the best results require adding pigments into the body. In this study, scientists showed that the photosynthetic pigments of purple non-sulfur bacteria can be useful in this optoacoustic imaging, providing a somewhat long-term, nontoxic approach. It proved especially interesting when they discovered that the wavelength spectrum changing over time was an indication of macrophage activity in the tumors. Journal Paper: Peters L, Weidenfeld I, Klemm U, Loeschcke A, Weihmann R, Jaeger K-E, Drepper T, Ntziachristos V, Stiel AC. 2019. Phototrophic purple bacteria as optoacoustic in vivo reporters of macrophage activity. Nat Commun 10:1191.

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Figuring out the structure of bacterial nanowires

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380: Plant Promoter Produces Polymer Apr 01, 2019

This episode: A microbe that boosts plant growth needs to make storage polymers for both itself and the plant's sake!

Download Episode (7.1 MB, 7.75 minutes) Show notes: Microbe of the episode: Suid gammaherpesvirus 3 Takeaways Bacteria that promote plant growth are fascinating and not too hard to find. Plants and microbes make good partners by each contributing something the other needs. Plants make sugars via photosynthesis that microbes can use as food, and microbes can gather nutrients that plants can't make, can drive off pathogens, and can contribute to plant growth in other ways. However, plants aren't making sugars all the time, because the sun goes down every day. So what do partner microbes do at these times? In this study, a beneficial microbe Herbaspirillum seropedicae was found to produce a storage compound called polyhydroxyalkanoate, or PHA, that it could use to store food for times of scarcity. Mutants of this microbe that could not make the storage compound weren't very beneficial for their plant partners. Journal Paper: Alves LPS, Amaral FP do, Kim D, Bom MT, Gavídia MP, Teixeira CS, Holthman F, Pedrosa F de O, Souza EM de, Chubatsu LS, Müller-Santos M, Stacey G. 2019. Importance of Poly-3-Hydroxybutyrate Metabolism to the Ability of Herbaspirillum seropedicae To Promote Plant Growth. Appl Environ Microbiol 85:e02586-18.

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379: Photons Facilitate Faster Flourishing Mar 25, 2019

This episode: Light increases the growth even of some bacteria that don't harvest its energy!

Download Episode (9.0 MB, 9.75 minutes) Show notes: Microbe of the episode: Methylococcus thermophilus News item Takeaways Light from the sun is one of the fundamental sources of energy for life on this planet. Plants and other phototrophs—photosynthetic organisms that get their energy mainly from light—form the foundation of the food web, and organisms that feed on them or that feed on organisms that feed on them are all dependent on the ability to capture the sun's rays. There are other ways to benefit directly from the sun's energy, besides photosynthesis—some microbes have enzymes that use light energy to repair damage to DNA (the same damage that is caused by ultraviolet light), and we use sunlight to synthesize vitamin D. In this study, however, microbes are discovered to grow faster in the presence of light despite not being phototrophs or producing any light-harvesting proteins. The scientists discover some possible light-sensing proteins, though, that could regulate these microbes' behavior, allowing them to synchronize their growth cycles to phototroph partners in aquatic environments.

Journal Paper: Maresca JA, Keffer JL, Hempel P, Polson SW, Shevchenko O, Bhavsar J, Powell D, Miller KJ, Singh A, Hahn MW. Light modulates the physiology of non-phototrophic Actinobacteria. J Bacteriol JB.00740-18.

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378: Medusa Makes Marble Microbes Mar 18, 2019

This episode: Newly discovered giant virus from a hot spring turns its amoeba hosts to stone!

Download Episode (6.7 MB, 7.3 minutes) Show notes: Microbe of the episode: Listeria virus P70 News item Takeaways Viruses come in endless different shapes, sizes, and genetic configurations. Even within the group called giant viruses there is a large amount of variety. Many of their genes are unknown, without homology to any other sequences we have acquired in other areas of life. There is great potential to learn interesting things from these viruses. In this study, a new giant virus is discovered. Like many others, this infects amoebas, and causes them to transform from dynamic, shape-shifting cells into hard little cyst-like circles. This ability gave it the name Medusavirus. It's the first giant virus found in a relatively hot environment (a hot spring), and among other interesting features, it shows signs of multiple instances of gene transfer to and from its amoeba host. Journal Paper: Yoshikawa G, Blanc-Mathieu R, Song C, Kayama Y, Mochizuki T, Murata K, Ogata H, Takemura M. 2019. Medusavirus, a novel large DNA virus discovered from hot spring water. J Virol JVI.02130-18.

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