444: Strange Sequence Stops Cell Subjugation

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.


Other interesting stories:



Bacteria can make biodegradable plastics from waste sludge




 


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com. Thanks for listening!


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