DESCRIPTION OF THE PHYLUM HALOBACTERIA

DESCRIPTION OF THE PHYLUM HALOBACTERIA (GRANT ET AL. 2001)

ARCHAEA> EURYARCHAEOTA> HALOBACTERIA

PHYLUM HALOBACTERIA LINKS

Halobacteria (ha-lo-bak-TE-re-a) is derived from two Greek words that mean “salty” (halos -αλοσ) and “little stick” (bakterion -βακτήριον).

INTRODUCTION TO THE HALOBACTERIA

The halophilic bacteria are unicellular cocci or rods (Figure 1) that inhabit environments where the solute concentrations can be much higher than the concentrations in sea water. For example, the Great Salt Lake (Utah) has a solute concentration that is about 10X the concentration of seawater in the same relative proportions. Other saline sites like the Dead Sea (Israel and Jordan) have chloride concentrations that are >10X that of sea water, but the dominant cation is magnesium. Thus, the relative proportions of ions can vary quite a lot. Still, the hypersaline environments, though simple, can be quite productive, and the extreme halophils can form the productive basis of that ecosystem (Figure 2). All of them are chemoorganotrophs and most are aerobic . Halobacteria have special lipids in the membranes to prevent them from falling apart at high salt concentrations. They employ K+ as an inorganic compatible solute inside the cell.

Of all the higher taxa in the Archaea, the extreme halophiles are most likely to be a natural group. Garrity et al. (2001, 2003) and Gao and Gupta (2007) place halophiles together as a class called Halobacteria within their phylum Euryarchaeota. Margulis and Schwartz (1998) lump the halobacteria with the methanobacteria into a taxon called Euryarcheota which we treat as a kingdom.

FIGURE 3. The relative position of the phylum Halobacteria in the context of the other phyla in the Euryarchaeota. They occupy a clade called Neobacteria, which also includes the Methanobacteria, both of which have growth maxima at non-extreme temperatures.

C = CRENARCHAEOTA

E = EURYARCHAEOTA

Eu = EURYTHERMEA CLADE

Ne = NEOBACTERIA

FURTHER READING:

DISCOVERY OF THE DOMAINS OF LIFE

LITERATURE CITED

Black, J. G. 2002. Microbiology, Principles and Explorations. 5th ed. John Wiley and Sons, Inc. New York.

Gao, B. and R. S. Gupta. 2007. Phylogenetic analysis of proteins that are distinctive of Archaea and its main subgroups and the origin of methanogenesis. BMC Genomics. 8:86. http://www.biomedcentral.com/1471-2164/8/86.

Garrity, G. M., M. Winters, and D. Searles. 2001. Bergey’s manual of systematic bacteriology. 2nd ed. Springer-Verlag. New York.

Garrity, G. M., J. A. Bell, and T. G. Lilburn. 2003. Taxonomic Outline of the Prokaryotes. Bergey’s Manual of Systematic Bacteriology. 2nd edition. Release 4.0. Springer-Verlag. New York. pp. 1-397.

Grant,W. D., M. Kamekura, T. J. McGenity, and A. Ventosa. 2001. Class III. Halobacteria class. nov. In: D. R. Boone and R. W. Castenholz, eds. Bergey’s Manual of Systematic Bacteriology. 2nd ed, vol. 1, pp. 294-301. Springer-Verlag. New York, Berlin and Heidelberg.

Margulis, L. and K. Schwartz. 1988. Five kingdoms, an illustrated guide to the phyla of life on earth. 2nd Edition. W. H. Freeman and Co. New York.

Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Co. New York.

Woese, C. R. and G. E. Fox. 1977. Phylogenetic structure of the prokaryotic domain: the primary kingdoms. Proceedings of the National Academy of Sciences USA. 74:5088-5090.

Woese, C. R., O. Kandler, and M. L. Wheelis. 1990. Towards a natural system of organisms: Proposal for the domains Archaea, Bacteria, and Eucarya. Proc. Natl. Acad. Sci. USA. 87: 4576-4579.

By Jack R. Holt. Last revised: 02/05/2013


FIGURE 1. Halobacterium taken with an SEM. Image from NASA, in the Public Domain	FIGURE 2. Halobacterium colors the water in this salt evaporation pond near the Great Salt Lake. Image from http://biology.kenyon.edu/Microbial_Biorealm/archaea/halobacterium/halobacterium.html

DESCRIPTION OF THE PHYLUM HALOBACTERIA (GRANT ET AL. 2001)

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