From the first moments of
its life, the squid circulates bacteria-infested seawater through a
hollow chamber in its body. Only the Vibrio fischeri cells are caught
by the squid's tiny cilia. Henceforth, the squid provides his
microscopic "prisoners" with oxygen and amino acids - and they
reciprocate with emitted light.
The squid constantly monitors to what extent the night sky is
illuminated, using dedicated sensors on the surface of its body. It
then adjusts an iris-like "shutter" to release the correct amount of
light from his bacterial colony. The squid replaces the hosted vibrios
daily.
Still, bacteria multiply ceaselessly. How is a constant level of
luminescence maintained as time passes?
Woody Hastings, a microbiologist at the University of Illinois,
noticed in the early 1960s that though the bacterial population
doubles every 20 minutes - the quantity of luciferase (the light
producing enzyme) remains constant for up to five hours. luciferase
production resumes only when a certain "critical mass" (quantitative
threshold) is attained. This is called "quorum sensing".
http://www.lifesci.ucsb.edu/~biolum/
http://www.
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