In “Bacteria Flash Like Christmas Lights,” Sara Reardon (Science NOW, 14 July 2011) tells us:
Like little batteries, bacteria have two charges: positive on the outside of their cell membranes, negative on the inside. And as with batteries, this division of charge is their power source. By pumping protons across their membrane, bacteria can make energy, spin their flagella so they can swim, and drive the pumps that bring in food. Researchers have now found that Escherichia coli drop this voltage difference for a brief moment and depolarize, much as neurons do when they fire. The phenomenon could help explain how some bacteria resist antibiotics.
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On a whim, postdoc Joel Kralj placed some bacteria on a slide and looked at them under a microscope. He was shocked to see them blinking on and off like Christmas lights, suggesting that they lost their charge altogether rather than using the stable charge difference to pump ions across the membrane. Even though the bacteria had all grown together in the same flask and were supposedly identical, each cell flashed at a different rate. Some blinks lasted for a fraction of a second, others for several seconds. Why the bugs flash at different rates is unclear, the researchers say in their paper published online today in Science, but when the researchers counted the flashes and graphed them, the pattern looked similar to the electrical activity of a neuron when it fires.
Or a cell phone? 😉