ABSTRACT
Many species of bacteria “form complex communities, hunt prey in groups and secrete chemical trails for the directed movement of thousands of individuals” (Shapiro 1988). As they grow, divide, and multiply, they reflexively release a species-typical signaling molecule known as an autoinducer. At low levels of concentration, autoinducers rapidly diffuse; but they are reliably detected as their concentration increases. When Alvibrio fischeri detect their species-typical autoinducers, they express genes that evoke bioluminescence (Bassler 2010; Camilli and Bassler 2006; Rutherford and Bassler 2012). Bobtail squid have evolved to exploit the bioluminescent properties of these bacteria. They hunt at night, in clear, shallow water. By monitoring the moonlight, and adjusting the shutters on their light organ, they can cancel out their shadows and hunt in stealth mode. But each morning, they expel most of the bacteria in their light organ and bury themselves in the sand. The lights turn off. But the remaining bacteria multiply throughout the day. And as night falls, the lights come on. The squid hunts. And the cycle repeats.
