Natronobacterium vacuolata sp. nov., a Haloalkaliphilic Archaeon Isolated from Lake Magadi, Kenya

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Abstract
A novel haloalkaliphilic archaeon was isolated from Lake Magadi, a Kenyan alkaline soda lake. Cells of the organism contain large gas vacuoles in the stationary phase of growth, and colonies produced by these archaea are bright pink in appearance. The major polar lipids of these organisms are C2,C2, and C20C2s derivatives of phosphatidylglycerol phosphate and phosphatidylglycerol, and the organisms contain an unidentified phospholipid as a minor component. The G+C content of the DNA is 62.7 mol%. The name Natronobucterium vacuofutu sp. nov. is proposed. The type strain is designated NCIMB 13189. The haloalkaliphilic members of the Archaea (15) make up a distinct physiological group within the halobacterial (ar- chaeal halophile) lineage (5, 9) in that they are confined to soda lakes and are obligately alkaliphilic. These archaea have been isolated from Lake Magadi, Kenya (13); Wadi Natrun, Egypt (12); Owens Lake, California (7); and Chinese and Russian soda lakes (16, 17). Like other halobacteria, these organisms may produce a red coloration in brines (in this case, alkaline brines) due to the synthesis of C,, carotenoids. Lake Magadi is an exam le of a red soda m1-l. The haloalkaliphiles comprise rod-shaped and coccoid isolates that are classified into the genera Natronobacterium and Natronococcus, respectively. Representatives of the genus Natronobacterium are readily distinguishable from other rod-shaped halobacteria by virtue of their alkaliphily and low Mg2+ requirement (3). Natronococci have coccoid morphologies like Halococcus s p. but are distinguished from them by alkaliphily, low Mg' requirement, and partial lysis of cells in distilled water (4). Three species of natronobacteria are currently recognized: Natronobacterium pharaonis, N. magadii, and N. gregoryi (14). They are identified on morphological and biochemical grounds and by DNA-DNA homology studies. In addition, slight differences in polar lipid composition have been shown to distinguish these species (7). Here we report the isolation of a new rod-shaped haloal- kaliphilic archaeon from Lake Magadi and its assignment as a new species of the genus Natronobacterium. lake, parts of which harbor lo7 to 10 P haloalkaliphiles

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