Monday, January 18, 2021

444 - Strange Sequence Stops Cell Subjugation

T4 Bacteriophage
By Victoramuse,
CC BY-SA 4.0
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


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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Monday, January 11, 2021

443 - Gut Group Gives Gamma Guard

Lachnospiraceae
By Public Health Image Library
Attribution
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


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.

Other interesting stories:

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.