Chapter 18, Problem 15TYU

SYNTHESIZE YOUR KNOWLEDGE

The flashlight fish has an organ under its eye that emits light, which serves to startle predators and attract prey, and allows the fish to communicate with other fish. Somc species can rotate the organ inside and then out, so the light appears to flash on and off The light is actually emitted by bacteria (of the genus Vibrio) that live in the organ in a mutualistlc relationship with the fish. (The bacteria receive nutrients froin the fish.) The bacteria must multiply until they reach a certain density in the organ (a "quorum"; see Concept 11.1), at which point they all begln emittlng light at the same time. There is a group of six or so genes, called lux genes, whose gene produets are necessary for light formation. Given that these bacterial genes are regulated together, propose a hypothesis for how the genes are organized and regulated.