(ORDO NEWS) — Many microbes form dense biofilms, living in close and mutually beneficial communities.
However, if conditions change, mechanisms of regulated death are triggered in some of the old bacterial cells. This signals to younger microbes that it is time to move to more favorable places.
Bacteria often do not live alone, but as part of numerous communities. Their dense and durable biofilms can cover sewers, coastal rocks, or the surface of teeth.
This strategy provides them with many benefits, including additional protection against toxins and antibiotics. However, over time, it can turn into a negative side.
If environmental conditions change and become less favorable, it would be beneficial for bacteria to move to a new place. However, it is almost impossible for cells firmly attached to the substrate to do this.
Then they can “sacrifice themselves” so that younger bacteria closer to the surface of the biofilm leave it in search of a more suitable place to live.
Back in 2010, University of Montreal professor Yves Brun and his colleagues showed that biofilm-forming Caulobacter crescentus cells secrete free DNA when they die.
It is she who serves as a signal that prevents young cells from attaching to the biofilm and stimulates them to “go in search of new places.” In the new work, Brun et al studied how and why some cells die.
It turned out that this does not happen randomly, but as a result of the activation of the mechanisms of programmed cell death.
At the same time, the “toxin-antitoxin” system is triggered , which includes a set of two genes, one of which encodes a “poison” protein, and the other is an “antidote” to it.
When it’s time to die, the production of the second protein is suppressed, and the accumulated toxin kills the cell.
Scientists have shown that the activation of the toxin-antitoxin system is triggered by oxygen deficiency.
When the biofilm becomes too thick or conditions are unfavorable, less and less of this gas penetrates to the depth where the oldest cells are.
Then some of them take over the death by secreting extracellular DNA and stimulating younger cells to move to form new biofilms in a more favorable place.
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