Glow and Be Eaten: Marine Bacteria Use Light to Lure Plankton and Fish

(Science Daily (Feb. 26, 2012) — "Not all that glitters is gold. Sometimes it is just bacteria trying to get ahead in life. Many sea creatures glow with a biologically produced light. This phenomenon, known as bio-luminescence, is observed, among others, in some marine bacteria which emit a steady light once they have reached a certain level of concentration (a phenomenon called "quorum sensing") on organic particles in ocean waters."

In terms of science, the fact that bacteria and other organisms produce light both in and out of the ocean has been known for quite some time already.

However, since this time, the purpose of these behaviors "remained unclear".

"Now, in an article published recently in the Proceedings of the National Academy of Sciences (PNAS), researchers of the Hebrew University of Jerusalem have unraveled the mystery of why the marine bacteria glow. It has to do with what might be called 'the survival of the brightest.'"

The studies showed that light emitted by the bacteria attracts predators (zoo plankton) which consume them but can not digest them. The bacteria glow within the zoo plankton, causing it to glow brightly, attracting its predators (fish), which can easily spot them.

"In experiments conducted by the researchers in total darkness, they found that nocturnal fish were easily able to detect the glowing zooplankton and eat them, while, on the other hand, the fish were not attracted to zooplankton that had swallowed bacteria that had undergone genetic mutation and thus did not glow."

The light-emitting bacteria find paradise in the nutrient rich internal organs of fish. Bacteria glow because they want to be eaten (not digested), and make their would-be predator into a meal.

"In the dark, deep ocean the quantity of food is very limited, therefore it is worthwhile for the zooplankton to take the risk of becoming glowing themselves when contacting and consuming the particle with glowing bacteria, since the profit of finding rare food there is greater than the danger of exposing themselves to the relatively rare presence of predatory fish," explained Prof. Genin.