Electrochemical potential enables dormant spores to integrate environmental signals

The dormant state of bacterial spores is generally thought to be devoid of biological activity. We show that despite continued dormancy, spores can integrate environmental signals over time through a preexisting electrochemical potential. Specifically, we studied thousands of individual Bacillus subtilis spores that remain dormant when exposed to transient nutrient pulses. Guided by a mathematical model of bacterial electrophysiology, we modulated the decision to exit dormancy by genetically and chemically targeting potassium ion flux. We confirmed that short nutrient pulses result in step-like changes in the electrochemical potential of persistent spores. During dormancy, spores thus gradually release their stored electrochemical potential to integrate extracellular information over time. These findings reveal a decision-making mechanism that operates in physiologically inactive cells. Bacterial spores can spend years in a dormant, biochemically inactive state, yet they retain the ability to process information from cues that can release them from dormancy and allow them to undergo germination. Kikuchi et al . present a mathematical model and experimental evidence that bacterial spores use an electrochemical potential caused by a gradient of potassium across the spore membrane (see the Perspective by Lombardino and Burton). Pulses of nutrient, which can combine to release spores from dormancy, caused changes in the electrochemical potential that could be integrated over time to allow the spore to monitor such cues with a mechanism that does not require energy production in the dormant spore. —LBR A study shows how dormant bacterial spores process cues to resume growth.