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Two extremely halophilic archaea, isolates SYSU A00711T and SYSU A00630, were isolated from a sediment soil sample collected from the Aiding lake, China. Cells of these isolates were cocci, non-motile and stained Gram-negative. They grew optimally at 37 °C, with 20–22% NaCl (w/v) and at pH 7.5–8.0. Cells lysed in distilled water. Major polar lipids were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, mannosyl glucosyl diether, sulfated mannosyl glucosyl diether, and two unidentified glycolipids. Pairwise sequence comparison revealed that isolates SYSU A00711T and SYSU A00630 were closely related to Halegenticoccus soli SYSU A9-0T (94.1 and 94.0% 16S rRNA gene sequence similarities; 94.0 and 94.2% rpoB' gene similarities, respectively). The overall genomic relatedness indices values between the two isolates and Halegenticocus soli SYSU A9-0 T were: AAI, both 79.6%; ANI, 84.6 and 84.5%; dDDH, 32.5 and 26.3%, respectively. Phylogenetic trees based on the 16S rRNA gene, rpoB' gene, and genome sequences demonstrated a robust clade of these two isolates with Halegenticoccus soli SYSU A9-0T. The DNA G + C contents of these two isolates are both 64.7% (genome method). Based on the differences in phenotypic, chemotaxonomic, and phylogenetic properties, isolates SYSU A00711T and SYSU A00630 are characterized to represent a novel species in the genus Halegenticoccus, for which the name Halegenticoccus tardaugens sp. nov. is proposed. The type strain of the species Halegenticoccus tardaugens is SYSU A00711T (= KCTC 4245T = CGMCC 1.15768T). [ABSTRACT FROM AUTHOR]

Two extreme halophilic archaeal strains, SYSUA9-0T and SYSUA9-1, were isolated from Ebi lake of Xinjiang, China. The colonies were Gram-negative, coccoid, and non-motile. Strains were aerobic and grew at 25–50 °C (optimum at 37 °C), in the presence of 10–35% (w/v) NaCl (optimum at 20–22%), and pH 6.0–8.0 (optimum at 7.0). The 16S rRNA gene sequence result revealed that the two strains were closely related to Haloprofundus marisrubri SB9T (92.7% similarity). The DNA–DNA hybridization value (97% ± 1%) suggested that SYSUA9-0T and SYSUA9-1 were similar; however, their sequence similarities with other archaeal members suggested that they were novel candidates. The genomic G + C content of SYSUA9-0T was 66.9%. The average nucleotide identity value between SYSU A9-0T and Haloprofundus marisrubri SB9T was 69.1%, which was far below the cutoff value (95–96%) proposed to define the species boundary. The polar lipids were phosphatidylglycerol (PG), phosphatidylglycerolphosphate methylester (PGP-Me), sulfated mannosyl glucosyl diether, mannosyl glucosyldiether, and four unidentified glycolipids. Phenotypic, chemotaxonomic and comparative genome analysis suggested that SYSU A9-0T and SYSU A9-1 represent a novel species of a new genus within the family Haloferacaceae, for which the name Halegenticoccus soli gen. nov., sp. nov., is proposed. The type strain is SYAUA9-0T (= KCTC4241T = CGMCC 1.15765T). [ABSTRACT FROM AUTHOR]

It has been suggested that archaea carrying the accA gene, encoding the alpha subunit of the acetyl CoA carboxylase, autotrophically fix CO using the 3-hydroxypropionate/4-hydroxybutyrate pathway in low-temperature environments (e.g., soils, oceans). However, little new information has come to light regarding the occurrence of archaeal accA genes in high-temperature ecosystems. In this study, we investigated the abundance and diversity of archaeal accA gene in hot springs in Yunnan Province, China, using DNA- and RNA-based phylogenetic analyses and quantitative polymerase chain reaction. The results showed that archaeal accA genes were present and expressed in the investigated Yunnan hot springs with a wide range of temperatures (66-96 °C) and pH (4.3-9.0). The majority of the amplified archaeal accA gene sequences were affiliated with the ThAOA/HWCG III [thermophilic ammonia-oxidizing archaea (AOA)/hot water crenarchaeotic group III]. The archaeal accA gene abundance was very close to that of AOA amoA gene, encoding the alpha subunit of ammonia monooxygenase. These data suggest that AOA in terrestrial hot springs might acquire energy from ammonia oxidation coupled with CO fixation using the 3-hydroxypropionate/4-hydroxybutyrate pathway. [ABSTRACT FROM AUTHOR]