439 - Microbes Mitigate Mushroom Morbidity

Button mushrooms
By chris_73, CC BY-SA 3.0

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

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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.

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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438 - Bacteria Bait Bug Babies

Drosophila fruit fly
By André Karwath
CC BY-SA 2.5

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

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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.

Other interesting stories:

• Eukaryotes borrowed viperin genes for proteins that prokaryotes use to fight viruses (paper)
• Bacteria can break down plastic even faster with newly discovered enzyme

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

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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437 - Balmy Bacteria Build Bone

Porous interior of bone
By Daniel Ullrich Threedots
CC BY-SA 3.0

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

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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.

Other interesting stories:

• Salt-tolerant bacteria could help plants grow in coastal areas (paper)
• Fire ants like to nest near potentially antifungal bacteria

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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436 - Copper Concentrates Culture Current

Geobacter sulferreducens
By Mantapia11147,
CC BY-SA 4.0

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

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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.

Other interesting stories:

• Lizard gut microbes are affected by temperature, and may affect lizard heat tolerance (paper)
• Phages in ice show evidence of trading genes easily to adapt to new environments

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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435 - Invader Introducing Infrared Invokes Immunity

Mouse with darkened tumor
By Yi et al. 2020,
Sci Adv 6:eaba3546
CC BY-NC 4.0

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

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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.

Other interesting stories:

• Bacteria could help make nylon more sustainably
• Glowing bacteria living in nematodes that kill insects may also interact with and protect plant roots (paper)

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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434 - Killer Carries Compact Cas

T4 bacteriophage
By Victoramuse
CC BY-SA 4.0

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

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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.

Other interesting stories:

• Example of how cooperation becomes more beneficial than independence
• Programming bacteria to detect and kill specific other microbes in a mixed community (paper)

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

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433 - Probiotic Promotes Pathogen Peacefulness

E. coli in lumen of organoid
From Pradhan and Weiss, 2020
mBio 11(4):e01470-20
CC BY 4.0

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.

Other interesting stories:

• Certain gut microbes can help people resist cholera
• Photosynthetic microbes engineered to produce spider silk

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: Apple Podcasts, Google Podcasts, Android, or RSS. Support the show at Patreon, or check out the show at Twitter or Facebook.