This time of year, to many people, blinking lights and stress mean holidays. But to scientists at Caltech, they reveal a new understanding of how bacteria respond-at the genetic level-to a certain type of stress. To track this response, scientists studied the sigma B protein in bacterial cells. When triggered by extreme temperature, starvation or other stressors, sigma B can activate more than 150 genes. The researchers inserted a fluorescent sensor into bacterial cells so that the cells would glow green when sigma B sprang into action. Then they doused the bacteria with a chemical stressor that essentially saps the cells' energy. As expected, sigma B flipped on. But then, just as quickly, it flipped off, even though the chemical remained in the environment. This on-off behavior, which appeared as a blinking green light, reveals that bacteria may "hedge their bets" when exposed to energy stress. This could help bacterial populations survive in changing conditions. Rather than dedicating all their resources for an extended period, the cells offer a brief, dramatic response, then return to their normal state, ready for a different environmental stressor. Because sigma B controls the disease-causing abilities of some bacteria, this research could help us better understand the genetics-and potential weaknesses-of organisms that cause a host of potentially deadly infections.

Featured in the December 15, 2011, issue of Biomedical Beat.