Genome-based taxonomy of the family Haloarculaceae, proposal of Natronomonadaceae fam. nov., and description of four novel halophilic archaea from two saline lakes and a marine solar saltern.

A new family related to the family Haloarculaceae was proposed and the genus Actinarchaeum was merged into the genus Halocatena through phylogenetic, phylogenomic, and comparative genomic analyses. Four strains KK48, YCN56, SYNS191, and SYNS196 with new taxonomic status were isolated from inland saline lakes and a marine solar saltern. According to the comparison of 16S rRNA gene and rpoB' gene sequences, strains KK48, YCN56, SYNS191, and SYNS196 showed high sequence similarities to the genera Salinibaculum and Salinirubellus, respectively. The values of average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity between these strains and the species of Salinibaculum and Salinirubellus ranged from 75.3 to 77.7 %, 24.5-25.9 % and 66.3-73.4 %, respectively. These data were well below the threshold for species classification, supporting their placements in new taxa. The major polar lipids of these strains were phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, sulfated mannosyl glucosyl diether, mannosyl glucosyl diether, and disulfated mannosyl glucosyl diether. Based on the phenotypic, chemotaxonomic, phylogenetic, and phylogenomic properties, strains KK48 (= CGMCC 1.19060 = JCM 35607), YCN56 (= CGMCC 1.62603 = JCM 36493), SYNS191 (= CGMCC 1.62607 = JCM 36494), and SYNS196 (= CGMCC 1.62608 = JCM 36495) represent four novel species of the genera Salinibaculum and Salinirubellus. And Salinibaculum rarum sp. nov., Salinibaculum salinum sp. nov., Salinibaculum marinum sp. nov., and Salinirubellus litoreus sp. nov. are proposed to accommodate these strains.