Alcalilimnicola halodurans gen. nov., sp. nov., an alkaliphilic, moderately halophilic and extremely halotolerant bacterium, isolated from sediments of soda-depositing Lake Natron, East Africa Rift Valley

MM Yakimov, L Giuliano, TN Chernikova, G Gentile, WR Abraham, H Lunsdorf, KN Timmis and PN Golyshin Division of Microbiology, GBF--National Research Centre for Biotechnology, Mascheroder Weg 1, 38124 Braunschweig, Germany An alkaliphilic, halotolerant, Gram-negative, heterotrophic, aerobic and rod-shaped organism was isolated from drying soda and at a water-covered site of Lake Natron, Tanzania, by means of the most-probable-number technique developed for anoxygenic, phototrophic sulfur bacteria. It had an absolute requirement for alkalinity, but not for salinity; growth occurred at salt concentrations of 0--28% (w/v), with optimal growth at 3--8% (w/v) NaCl. The bacterium preferentially metabolized volatile fatty acids and required vitamins for growth. The name Alcalilimnicola halodurans gen. nov., sp. nov. is proposed for the novel isolate, placed in the gamma-Proteobacteria within the family Ectothiorhodospiraceae on the basis of analysis of the 16S rDNA sequence, polar lipids, fatty acids and DNA base composition. Although Alcalilimnicola halodurans is closely related to the extreme anoxygenic, phototrophic sulfur bacteria of the genus Halorhodospira, it is not phototrophic.