Halalkalirubrum salinum gen. nov., sp. nov., a halophilic archaeon isolated from a saline lake.

A novel extremely halophilic archaeon, strain N1521, was isolated from a saline lake in Tibet, China. Cells of the strain were pleomorphic and Gram-stain-negative. It produced red pigments. Growth was observed at 4-42 °C (optimum, 37 °C), pH 7.0-10.5 (optimum, 8.0-9.5), NaCl 11%-25% (optimum, 15%) and in the presence of 0-0.1 M MgCl (optimum, 0.05 M) in aerobic conditions. The minimum NaCl concentration that prevented cell lysis was 2% (w/v). The major polar lipids of strain N1521 were phosphatidylglycerol sulfate, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol and an unidentified glycolipid. The DNA G + C content was 58.37 mol%. According to 16S rRNA gene sequence comparisons, strain N1521 revealed the highest sequence similarity to Haloprofundus halophilus NK23 (91.38%) and Halogranum amylolyticum TNN58 (91.00%), and low sequence similarities (< 91%) with other genera in the order Haloferacales. Phylogenetic analysis based on the 16S rRNA gene and rpoB' gene sequence showed that strain N1521 was distinct from the members of the order Haloferacales. The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values calculated from whole genome-sequence comparison between strain N1521 and the members of the order Haloferacales were in the ranges of 15.1-18.2%, 68.8-73.0%, and 58.4-63.9%, respectively. Phylogenetic tree reconstructions based on the whole-genome sequences revealed that strain N1521 was closer to the members of the family Halorubraceae. Based on the data obtained, strain N1521 is thus considered to represent a novel species of a new genus within the family Halorubraceae, for which the name Halalkalirubrum salinum gen. nov., sp. nov. is proposed. The type strain is N1521 (= CGMCC 1.16693 = JCM 33785).