Bacteria will go to great lengths to cope with difficult times. They build a fortress-like structure around their DNA, and shut off all other signs of life. Even so, these dormant organisms can be revived when conditions improve.
But “you gotta be careful when you decide to come back to life,” says Peter Setlow, a biochemist at UConn Health in Farmington. “Because if you get it wrong, you die.” How is a spore to tell?
For spores Bacillus subtilisThe solution is easy: It matters.
These “living rocks” sense it’s time to revive, or germinate, by essentially counting how often they encounter nutrients, researchers report in a new study in the Oct. 7 Science.
“They appear 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 spores’ cores contain positively charged potassium atoms, and because these atoms can move around without the cell using energy, the team suspected that potassium could be involved in shocking the cells awake.
The team is exposed B. subtilisTo track the movement and distribution of potassium from the core, spores were transformed into nutrients using colorful dyes. As the core was exposed to more potassium, its electrical charge changed to be more negatively with each exposure. Once the spores’ cores were negatively charged enough, germination was triggered, like a champagne bottle finally popping its cork. Different spores have different exposure requirements to trigger germination. Just like corks that require more twisting to pop, so does the number of exposures required to trigger germination. Spores whose potassium movement was hamstrung showed limited change in electric charge and were less likely to “pop” back to life no matter how many nutrients they were exposed to, the team’s experiments showed.
The tree of Life is affected by changes to the electrical charge of cells. They are crucial for everything, from the ability to send messages between brain cells to one another to the ability to detect when they stop communicating with each other. Snapping a Venus flytrap (SN: 10/14/20). Finding that spores also use electrical charges to set their wake-up calls excites Süel. “You want to find principles in biology,” he says, “processes that cross systems, that cross fields and boundaries.”
Spores are fascinating for their extreme biology and practical applications. Some “can cause some rather nasty things” from food poisoning to anthrax, says Setlow, who was not involved in the study. Understanding spores’ germination may help us bring them back to health.
Still, there are many unanswered questions about the “black box” of how spores start germination, like whether it’s possible for the spores to “reset” their potassium count. “We really are in the beginnings of trying to fill in that black box,” says Kaito Kikuchi, a biologist now at Reveal Biosciences in San Diego who conducted the work while at University of California, San Diego. However, it is exciting to discover how spores track their environment when they are dead or alive.
