Natrinema caseinilyticum sp. nov., Natrinema gelatinilyticum sp. nov., Natrinema marinum sp. nov., Natrinema zhouii sp. nov., extremely halophilic archaea isolated from marine environments and a salt mine.

Four extremely halophilic archaeal strains (ZJ2^T, BND6^T, DT87^T, and YPL30^T) were isolated from marine environments and a salt mine in China. The 16S rRNA and rpoB' gene sequence similarities among strains ZJ2^T, BND6^T, DT87^T, YPL30^T and the current species of Natrinema were 93.2-99.3% and 89.2-95.8%, respectively. Both phylogenetic and phylogenomic analyses revealed that strains ZJ2^T, BND6^T, DT87^T, and YPL30^T cluster with the Natrinema members. The overall genome-related indexes (ANI, isDDH, and AAI) among these four strains and the current species of genus Natrinema were 70-88%, 22-43% and 75-89%, respectively, clearly below the threshold values for species boundary. Strains ZJ2^T, BND6^T, DT87^T, and YPL30^T could be distinguished from the related species according to differential phenotypic characteristics. The major polar lipids of the four strains were phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylglycerol phosphate methyl ester (PGP-Me), sulfated mannosyl glucosyl diether (S-DGD-1), and disulfated mannosyl glucosyl diether (S₂-DGD). The phenotypic, chemotaxonomic, phylogenetic and phylogenomic features indicated that strains ZJ2^T (= CGMCC 1.18786 ^T = JCM 34918 ^T), BND6^T (= CGMCC 1.18777 ^T = JCM 34909 ^T), DT87^T (= CGMCC 1.18921 ^T = JCM 35420 ^T), and YPL30^T (= CGMCC 1.15337 ^T = JCM 31113 ^T) represent four novel species of the genus Natrinema, for which the names, Natrinema caseinilyticum sp. nov., Natrinema gelatinilyticum sp. nov., Natrinema marinum sp. nov., and Natrinema zhouii sp. nov., are proposed.