Description of Halomicrobium halophilum sp. nov., a halophilic archaeon producing exopolysaccharides

An extremely halophilic archaeal strain, YIM 93990ᵀ, was isolated from a soil sample collected from Aiding Salt Lake, China. The 16S rRNA gene sequence, together with phylogenetic and phylogenomic analyses, suggests that strain YIM 93990ᵀ belongs to the genus Halomicrobium and was closely related to the type species, Halomicrobium zhouii. It grew optimally at 37 ºC, pH 6.5-7.0 with 20–25% NaCl (w/v). Cells were lysed in distilled water. The major polar lipids were phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, mannosyl glucosyl diether, sulfated mannosyl glucosyl diether, and an unidentified glycolipid. Strain YIM 93990ᵀ showed high exopolysaccharide production and demonstrated metal ion removal at 15% NaCl (w/v), with efficiencies of 63.1% for lead, 45.3% for chromium, and 49.1% for copper. The genomic DNA G + C content was 65.8%. The average nucleotide identity (ANI) values between YIM 93990 ^T and the other species of the genus Halomicrobium were below the threshold value (95–96%) for species delineation. Based on the polyphasic analysis, strain YIM 93990 ^T represents a novel species of the genus Halomicrobium , for which the name Halomicrobium halophilum sp. nov., is proposed. The type strain is YIM 93990 ^T (= KCTC 4246 ^T  = CGMCC 1.15775 ^T ).