How dormant bacteria spores sense when it’s time to come back to life

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Bacteria go to extreme lengths to deal with tough times: they hunker down, build a fortress-like shell around their DNA, and extinguish any signs of life. And yet, when times improve, these dormant spores can rise to apparent death.

But “you have to be careful when deciding whether to come back to life,” says Peter Setlow, a biochemist at UConn Health in Farmington. “Because if you’re wrong, you die.” How’s a spore to say?

For bacteria spores Bacillus subtilisThe solution is simple: It matters.

These “living rocks” sense that it’s time to revive or germinate, essentially counting how often they encounter nutrients, researchers report in a new study Oct. 7. Science.

“They seem to have literally no measurable biological activity,” says Gürol Süel, a microbiologist at the University of California, San Diego. But Süel and his colleagues knew that spore nuclei contain positively charged potassium atoms, and because these atoms can move around without the cell using energy, the team suspected that potassium might be involved in the process. shocking awakening of cells.

Thus, the team exposed B. subtilis spores to nutrients and used colored dyes to track the movement of potassium out of the nucleus. With each exposure, more potassium left the core, shifting its electrical charge to be more negative. Once the spore nuclei were sufficiently negatively charged, germination was triggered, like a bottle of champagne that eventually pops its cork. The number of exposures needed to trigger germination varied between spores, just as some plugs require more or less twisting to burst. Spores whose potassium movement was crippled showed limited change in electrical charge and were less likely to ‘come back’ to life no matter how many nutrients they were exposed to, the team’s experiments showed. .

Changes in a cell’s electrical charge are important in the tree of life, from determining when brain cells send messages to each other, to the snapping of a Venus flytrap (SN: 10/14/20). Discovering that the spores also use electrical charges to trigger their wake-up calls excites Süel. “You want to find principles in biology,” he says, “processes that cross systems, that cross fields and borders.”

Spores are not only interesting for their unique and extreme biology, but also for practical applications. Some “can cause some pretty nasty things” ranging from food poisoning to anthrax, says Setlow, who was not involved in the study. Since spores are resistant to most antibiotics, understanding germination could lead to a way to bring them back to life in order to kill them for good.

Yet there remain many unanswered questions about the ‘black box’ of how spores begin germination, such as whether it is possible for spores to ‘reset’ their potassium levels. “We’re really in the early days of trying to fill that black box,” says Kaito Kikuchi, a biologist currently at Reveal Biosciences in San Diego, who led the work at the University of California, San Diego. But finding out how the spores manage to keep up with their surroundings when they’re more dead than alive is an exciting start.

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