Monday, August 29, 2022

471 - Phage Fight Foils Fitness

Shigella phage A1-1
By Kortright et al., 2022.
AEM 2022, 88(e01514).
CC BY-4.0
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
 
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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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Monday, July 11, 2022

470 - Super Small Symbionts Soothe Symptoms

Tiny symbiont Saccharibacteria (yellow-green)
on host bacteria (red)
By Utter et al.,
CC BY-SA 4.0


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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Monday, April 4, 2022

469 - Prophage Provides Partial Protection

Salmonella invading cells
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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Monday, February 28, 2022

468 - Commensal Can Kill Cholera

Vibrio cholerae
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

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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.

Other interesting stories:

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

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