The ecology and taxonomy of halobacteria

Archaebacterial halophiles dominate naturally occurring brines as the concentration of salts approaches saturation. Although only 4 genera of these bacteria have been recognised ( Halobacterium, Halococcus, Natronobacterium, Natronococcus ), chemotaxonomic studies indicate that there are 4 or 5 additional distinct groups. Archaebacterial halophiles are extremely physiologically versatile, some examples being capable of an anaerobic fermentative mode of growth, others of growth linked to the reduction of sulphur compounds. Many strains contain retinal‐based pigments producing light‐mediated movements of ions across the cell membrane, that in some cases can be harnessed for energy generation. However, it is likely that under normal conditions, an aerobic, chemoorganotrophic mode of nutrition is adopted.