By attaching fluorescent proteins to the genetic circuit responsible for B. subtilis's stress response, researchers can observe the cells' pulses as green flashes.
In response to a stressful environment like one lacking food, B. subtilis activates a large set of genes that help it respond to the hardship. Instead of leaving those genes on as previously thought, researchers discovered that the bacteria flip the genes on and off, increasing the frequency of these pulses with increasing stress.
From a November 2011 Caltech news release. (http://media.caltech.edu/press_releases/13470) - NIH/NIGMS image gallery
Credit: Michael Elowitz, Caltech University
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