How to be moderately halophilic with a broad salt tolerance: Cluesfrom the genome of chromohalobacter salexigens
There are two strategies that enable microorganisms to grow at high salt concentrations. Some groups balance the high osmolality of their environment with high intracellular concentrations of KCl1-4. Adaptation of all intracellular proteins is then necessary, and this is reflected in a large excess of acidic over basic residues and a low content of hydrophobic amino acids 2,5-7. Other halophilic and halotolerant microorganisms keep their intracellular ion concentrations low and synthesize or accumulate organic osmotic solutes 8. While halotolerance enables organisms to colonize highly saline environments,the ecological advantage for a salt-requirement is less obvious. We analyzed the amino acid composition of different categories of proteins of the moderately halophilic bacterium Chromohalobacter salexigens, as deduced from its genome sequence. Comparison with non-halophilic bacteria shows only a slight excess of acidic residues in the cytoplasmic proteins, no significant differences in membrane-bound components, but a distinctive halophilic signature of predicted periplasmic proteins, such as the substrate binding proteins of ABC-type transport systems. The salt requirement of proteins located external to the cytoplasmic membrane may thus determine salt requirement and salt tolerance of prokaryotes.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Biological andEnvironmental Research
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 861553
- Report Number(s):
- LBNL-56595; R&D Project: 626882; BnR: KP1103010; TRN: US200601%%184
- Journal Information:
- Nature, Vol. 9, Issue 4; Related Information: Journal Publication Date: 08/2005
- Country of Publication:
- United States
- Language:
- English
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