Bacteria use small molecules to slam the brakes on their own growth
[2020-04-29] An international research team under the lead of scientists at the Umeå Center for Microbial Research (UCMR) and The Laboratory for Molecular Infection Medicine Sweden (MIMS) have uncovered a new kind of regulatory system of toxin and antitoxin proteins in bacteria that could be a defense system against viral attack. The bioinformatic identification of the proteins and their experimental validation are now published in the high impact journal Proceedings of the National Academy of Sciences of the US (PNAS, 28 April 2020)
When bacteria get stressed e.g. through antibiotic treatment or the lack of nutrients, they slow down their growth mechanism by small signaling molecules called Alarmones. The Atkinson and Hauryliuk labs at Umeå University have worked on the proteins that make and degrade alarmones for over a decade. They previously revealed the ubiquitous presence of small proteins that make alarmones, called small alarmone synthetases or SASs, encoded in bacterial genomes.
It was an unanswered question why bacteria carry SAS proteins in addition to their standard tool-set for alarmone synthesis and degradation. Now, Gemma C. Atkinson, Vasili Hauryliuk and their colleagues found an explanation. They showed that some SASs are components of so-called toxin-antitoxin (TA) systems.
Toxin-antitoxins genes are enigmatic components of microbial genomes. What toxins of TA systems all have in common is that they slam the brakes on growth and reproduction. This is counteracted by their antitoxins which are encoded by adjacent genes. Antitoxins can also work in different ways, either binding to the toxin to stop its action, or counteracting the effect of the toxin in an indirect way.
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