Natronococcus roseus sp. nov., a haloalkaliphilic archaeon from a hypersaline lake.

A novel halophilic archaeon, strain CG-1(T), belonging to the genus Natronococcus was isolated from sediment of the soda lake Chagannor in Inner Mongolia, China. The colonies of this strain were pink pigmented, the intensity of the colour decreased when the cells grew at salt saturation levels. The cells were non-motile cocci and strictly aerobic. Hypotonic treatment did not cause cell lysis, even in distilled water. Strain CG-1(T) grew at 15-30.0 % (w/v) NaCl and at 30-50 °C and pH 8.0-11.0, with optimal growth occurring at 25-30 % (w/v) NaCl, 37-45 °C and pH 9-9.5. MgCl(2) was not required for growth. Strain CG-1(T) was most closely related to the type strains of Natronococcus amylolyticus Ah-36(T), Natronococcus jeotgali B1(T) and Natronococcus occultus SP4(T), with which it shared 98.4 %, 96.2 and 95.7 % 16S rRNA gene sequence similarity, respectively. The polar lipids consisted of C(20)C(20) and C(20)C(25) derivatives of phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me) and minor phospholipid components. No glycolipids were detected. The DNA G+C content of strain CG-1(T) was 62.1 mol%. DNA-DNA hybridization with N. amylolyticus DSM 10524(T), phylogenetically the most closely related species, was 39 %; this value showed that strain CG-1(T) constituted a different genospecies. The comparison of 16S rRNA gene sequences, detailed phenotypic characterization, polar lipid profile and DNA-DNA hybridization studies revealed that strain CG-1(T) belongs to the genus Natronococcus and constitutes a novel species for which the name Natronococcus roseus sp. nov. is proposed. The type strain is CG-1(T) (=CECT 7984(T)=IBRC-M 10656(T)=JCM 17958(T)).