Halophilic archaea

Three groups of Archaea are known to inhabit hypersaline environments in which salt concentrations exceed 150-200 g _-1. The halophilic Archaea of the class Halobacteria are often found in high numbers in natural salt lakes and in solar saltern crystallizer ponds. Due to their pink-red pigmentation caused mainly by carotenoid pigments, their presence is visible by the coloration of the brines. These Archaea generally lead an aerobic chemoorganotrophic life style, but some species are capable of anaerobic photoheterotrophic life driven by light energy absorbed by retinal proteins. Recently the possibility of anaerobic lithoheterotrophic life was identified in a member of the group. Halophilic methanogenic Archaea are known, and these mainly use methylated amines as energy source. Application of cultivation-independent molecular methods has recently resulted in the recognition of a third group of halophilic Euryarchaeota: the Nanohaloarchaea. No members of this group have yet been brought into culture.