Four extremely halophilic archaeal strains, LYG-108T, LYG-24, DT1T and YSSS71, were isolated from salted Laminaria produced in Lianyungang and saline soil from the coastal beach at Jiangsu, PR China. The four strains were found to be related to the current species of Halomicroarcula (showing 88.1–98.5% and 89.3–93.6% similarities, respectively) as revealed by phylogenetic analysis based on 16S rRNA and rpoB′ genes. These phylogenies were fully supported by the phylogenomic analysis, and the overall genome-related indexes (average nucleotide identity, DNA–DNA hybridization and average amino acid identity) among these four strains and the Halomicroarcula species were 77–84 %, 23–30 % and 71–83 %, respectively, clearly below the threshold values for species demarcation. Additionally, the phylogenomic and comparative genomic analyses revealed that Halomicroarcula salina YGH18T is related to the current species of Haloarcula rather than those of Halomicroarcula , Haloarcula salaria Namwong et al. 2011 is a later heterotypic synonym of Haloarcula argentinensis Ihara et al. 1997, and Haloarcula quadrata Oren et al. 1999 is a later heterotypic synonym of Haloarcula marismortui Oren et al. 1990. The major polar lipids of strains LYG-108T, LYG-24, DT1T and YSSS71 were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulphate, sulphated mannosyl glucosyl diether and additional glycosyl-cardiolipins. All these results showed that strains LYG-108T (=CGMCC 1.13607T=JCM 32950T) and LYG-24 (=CGMCC 1.13605=JCM 32949) represent a new species of the genus Halomicroarcula , for which the name Halomicroarcula laminariae sp. nov. is proposed; strains DT1T (=CGMCC 1.18928T=JCM 35414T) and YSSS71 (=CGMCC 1.18783=JCM 34915) also represent a new species of the genus Halomicroarcula , for which the name Halomicroarcula marina sp. nov. is proposed.

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Two extremely halophilic archaeal strains, PSR5T and PSR8T, were isolated from a saline soil sample collected from the Tarim Basin, Xinjiang, PR China. Both strains had two copies of the 16S rRNA genes rrn1 and rrn2, showing 2.6 and 3.9% divergence, respectively. The rrn1 gene of PSR5T showed 98.4 and 95.3% similarity to the rrn1 and rrn2 genes of strain PSR8T; the rrn2 gene of PSR5T displayed 97.4 and 96.7% similarity to those of strain PSR8T, respectively. Phylogenetic analyses based on the 16S rRNA and rpoB′ genes revealed that strains PSR5T and PSR8T formed a single cluster, and then tightly clustered with the current four Haladaptatus species (93.5–97.1% similarities for the 16S rRNA gene and 89.3–90.9% similarities for the rpoB′ gene, respectively). Several phenotypic characteristics differentiate strains PSR5T and PSR8T from current Haladaptatus members. The polar lipids of the two strains are phosphatidic acid, phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester phosphatidylglycerol sulphate and three glycolipids. One of the glycolipids is sulphated mannosyl glucosyl diether, and the remaining two glycolipids are unidentified. The average nucleotide identity, in silico DNA–DNA hybridization, amino acid identity and percentage of conserved proteins values between the two strains were 88.5, 39.1, 89.3 and 72.8 %, respectively, much lower than the threshold values proposed as a species boundary. These values among the two strains and Haladaptatus members were 77.9–79.2, 22.0–23.5, 75.1–78.2 and 56.8–69.9 %, respectively, much lower than the recommended threshold values for species delimitation. These results suggested that strains PSR5T and PSR8T represent two novel species of Haladaptatus . Based on phenotypic, chemotaxonomic, genomic and phylogenetic properties, strains PSR5T (=CGMCC 1.16851T=JCM 34141T) and PSR8T (=CGMCC 1.17025T=JCM 34142T) represent two novel species of the genus Haladaptatus , for which the names Haladaptatus halobius sp. nov. and Haladaptatus salinisoli sp. nov. are proposed.

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