Halobacterium NRC-1

Cell structure and metabolism

Halobacterium species are obligately halophilic microorganisms that have adapted to optimal growth under conditions of extremely high salinity—10 times that of sea water. They contain a correspondingly high concentration of salts internally and exhibit a variety of unusual and unique molecular characteristics. Halobacterium NRC-1 is an aerobic chemoorganotroph, growing on the degradation products of less halophilic organisms as the salinity reaches near saturation. In the laboratory, cells are cultured best in a complex medium. A minimal medium described for Halobacterium includes all but 5 of the 20 amino acids for growth. Several amino acids may be used as a source of energy, including arginine and aspartate, which are passed to the citric acid cycle via 2-oxoglutarate and oxaloacetate, respectively. Under aerobic conditions, arginine is presumably converted to glutamate via the arginine deiminase pathway, and this amino acid then enters the cycle via glutamate dehydrogenase. The arginine deiminase pathway is coded by the arcRACB genes, which are found on pNRC200.