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Halobacterium salinarum
''Halobacterium salinarum'' is an extremely halophilic marine Gram-negative obligate aerobic archaeon. Despite its name, this microorganism is not a bacterium, but rather a member of the domain Archaea.〔DasSarma, S., Extreme Microbes, Am Sci, 2007, 95(3):224–231.〕 It is found in salted fish, hides, hypersaline lakes, and salterns. As these salterns reach the minimum salinity limits for extreme halophiles, their waters become purple or reddish color due to the high densities of halophilic Archaea.〔 ''H. salinarum'' has also been found in high-salt food such as salt pork, marine fish, and sausages. The ability of ''H. salinarum'' to survive at such high salt concentrations has led to its classification as an extremophile.
== Cell morphology and metabolism ==
Halobacteria are single-celled, rod-shaped microorganisms that are among the most ancient forms of life and appeared on Earth billions of years ago. . The membrane consists of a single lipid bilayer surrounded by an S-layer.〔Ng, W.V., et al., Genome sequence of ''Halobacterium'' species NRC-1, Proc Natl Acad Sci USA, 2000, 97(22):12176–12181.〕 The S-layer is made of a cell-surface glycoprotein, which accounts for approximately 50% of the cell surface proteins.〔Mescher, M.F., Strominger, J.L., Purification and characterization of a prokaryotic glucoprotein from the cell envelope of ''Halobacterium salinarium'', J Biol Chem, 1976, 251(7):2005–2014.〕 These proteins form a lattice in the membrane. Sulfate residues are abundant on the glycan chains of the glycoprotein, giving it a negative charge. The negative charge is believed to stabilize the lattice in high-salt conditions.〔Sara, M., Sleytr, U.B., S-layer proteins. J Bacteriol. 2000, 182(4):859–68.〕
Amino acids are the main source of chemical energy for ''H. salinarum'', particularly arginine and aspartate, though they are able to metabolize other amino acids, as well.〔 ''H. salinarum'' have been reported to not be able to grow on sugars, and therefore need to encode enzymes capable of performing gluconeogenesis to create sugars. Although "H. salinarum" is unable to catabolize glucose, the transcription factor TrmB has been proven to regulate the gluconeogenic production of sugars found on the S-layer glycoprotein.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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