Halobacterium, not a bacteria at all, this cellular prokaryotic salt-loving organism, and also an archaea, inhabits hypersaline environments. This halophile grows best at high salinity levels of (3.4-5 mol L) and also needs slightly elevated temperatures of (38-45 Celsius) for optimal growth. Halobacterium flourishes under intense solar radiation. Most Halobacterium have distinctive features such as gas vesicles, purple membrane and red-orange carotenoids. Under anaerobic conditions, when oxygen isn't available for ATP generation, Halobacterium forms a purple membrane. The main component of the purple membrane, Bacteriorhodopsin, keeps Halobacterium sp.'s life cycle going in this time of famine by functioning as an energy transducer. .
Bacteriorhodopsin (BR) is a light-driven ion pump which converts light energy into electrochemistry energy. BR, the main component of Halobacterium's purple membrane, is a seven-helical transmembrane protein with a retinal co-factor. In the presence of sunlight, BR moves protons out of the Halobacterium cell, creating a proton gradient. This proton gradient, in turn, is used by ATP synthase, a second membrane protein, to generate chemical energy in the form of ATP.
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