Natronobacterium nitratireducens sp nov., a haloalkaliphilic archaeon isolated from a soda lake in China

Two novel haloalkaliphilic archaea, strains C231(T) and C42, were isolated from a soda lake in China. Cells of the two strains were rod-shaped and Gramnegative and colonies were bright red. They required at least 2.5 M NaCl for growth, with an optimum at 3.5 M NaCl, and grew over a pH range from 8.0 to 10.5, with an optimum at pH 8.5. Hypotonic treatment with less than 1.5 M NaCl caused cell lysis. They had similar polar lipid compositions, possessing the diphytanyl (C20: C20) and phytanyl-sesterterpanyl (C20:C25) diether derivatives of phosphatidylglycerol and phosphatidylglycerophosphate methyl ester and a minor phospholipid, PL1. No glycolipids were detected. Comparison of 16S rDNA sequences and morphological features placed them in the genus Natronobacterium. Detailed phenotypic characterization and DNA-DNA hybridization studies revealed that the two strains belong to a new species in the genus Natronobacterium, for which the name Natronobacterium nitratireducens sp. nov. is proposed. The type strain is C231(T) (= AS 1.1980(T) = JCM 10879(T)).