Halobacterium

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Halobacterium

Scientific classification

Domain:	Archaea
Phylum:	Euryarchaeota
Class:	Halobacteria
Order:	Halobacteriales
Family:	Halobacteriaceae
Genus:	Halobacterium Elazari-Volcani, 1957

Species

See article

Note: The word "halobacterium" is also the singular form of the word "halobacteria".

The genus Halobacterium consists of several species of archaea with an obligate aerobic metabolism which require an environment with a high concentration of salt; many of their proteins will not function in low-salt environments. They grow on amino acids in their aerobic conditions. Their cell walls are also quite different from those of bacteria, as ordinary lipoprotein membranes fail in high salt concentrations. In shape, they may be either rods or cocci, and in color, either red or purple. They reproduce using binary fission (by constriction), and are motile. Halobacterium grows best in a 42 degree Celsius environment. The genome of an unspecified Halobacterium species has been sequenced and comprises 2,571,010 bp (base pairs) of DNA compiled into three circular strands: one large chromosome with 2,014,239 bp, and two smaller ones with 191,346 and 365,425 bp. This species, called Halobacterium sp. NRC-1, has been extensively used for post-genomic analysis. Halobacterium species can be found in the Great Salt Lake, the Dead Sea, Lake Magadi, and any other waters with high salt concentration. Purple Halobacterium species owe their color to bacteriorhodopsin, a light-sensitive protein which provides chemical energy for the cell by using sunlight to pump protons out of the cell. The resulting proton gradient across the cell membrane is used to drive the synthesis of the energy carrier ATP. Thus, when these protons flow back in, they are used in the synthesis of ATP. The bacteriorhodopsin protein is chemically very similar to the light-detecting pigment rhodopsin, found in the vertebrate retina.

Genus Halobacterium:

Halobacterium cutirubrum
Halobacterium denitrificans
Halobacterium distributum
Halobacterium halobium
Halobacterium lacusprofundi
Halobacterium mediterranei
Halobacterium noricense
Halobacterium pharaonis
Halobacterium saccharovorum
Halobacterium salinarium
Halobacterium sodomense
Halobacterium trapanicum
Halobacterium vallismortis
Halobacterium volcanii

[edit] Further reading

DasSarma, S., B.R. Berquist, J.A. Coker, P. DasSarma, J.A. Müller. 2006. Post-genomics of the model haloarchaeon Halobacterium sp. NRC-1. Saline Systems 2:3.

DasSarma, S. 2004. Genome sequence of an extremely halophilic archaeon, in Microbial Genomes, pp. 383-399, C.M. Fraser, T. Read, and K.E. Nelson (eds.), Humana Press, Inc, Totowa, NJ.

Lynn Margulis, Karlene V.Schwartz, Five Kingdoms. An Illustrated Guide to the Phyla of Life on Earth (W.H.Freeman, San Francisco, 1982) pp. 36-37