ABSTRACT
A variety of halophilic anaerobes were enriched from hypersaline environments by selecting for bacterial strains that grew readily on inexpensive nutrients and that made either exopolysaccharides or organic acid salts and alcohols as catabolic end products during the hydrolysis of complex organic matter. This chapter describes the physiology of halophilic anaerobes in relation to understanding how anaerobes adapt to extreme salt stress while faced with limited chemical thermodynamic energy. Since the mid-nineteenth century, it has been recognized that halophilic microorganisms could be isolated from different sources (i.e., hides, salt-preserved food, and saline aquatic sediments). Halophiles were presumably noticed to be a causative agent for color changes of salts and hence were considered of economic importance. Physiological studies on halophilic microorganisms have emphasized the eucaryotic green algae, Dunaliella; the purple bacterium, Halobacterium; and the phototrophic bacterium, Ectothiorhodospira. Halophilic eubacteria, on the other hand, produce high intracellular concentrations of betaine for osmoregulation.
