Aquabacterium tepidiphilum sp. nov., a moderately thermophilic bacterium isolated from a hot spring

A Gram-stain-negative, aerobic, non-spore-forming and rod-shaped bacterium, designated YIM 730274(T), was isolated from a sediment sample collected from a hot spring located in Tibet, PR China, and was characterized by using a polyphasic taxonomy approach. Cells were motile by means of a polar flagellum. The strain was oxidase- and catalase-positive, and contained polyalkanoates and polyphosphate as storage polymers. Growth occurred at 25-50 degrees C, at pH 6.0-8.5 and with 0.5-1.0 % NaCl. The major fatty acids (>10 %) were summed feature 3 (C-16:1 omega 6c and/or C-16:1 omega 7c), summed feature 8 (C-18:1 omega 6c and/or C-18:1 omega 6c) and C-16:0. The known polar lipids comprised of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylserine. The isoprenoid quinone was Q-8. The G+C content of genomic DNA was 70.7 mol%. The results of phylogenetic analyses based on 16S rRNA gene sequences indicated that the strain forms a monophyletic branch at the periphery of the evolutionary radiation occupied by the genus Aquabacterium in the class Betaproteobacteria. The most closely related phylogenetic neighbours were Aquabacterium limnoticum ABP-4(T) (97.8 % 16S rRNA gene sequence identity) and Aquabacterium commune B8(T) (97.2 % 16SrRNA gene sequence identity). DNA-DNA relatedness values between YIM 730274(T) and A. limnoticum KCTC 23306(T) (46.4 +/- 0.4%) and A. commune DSM 11901(T) (42.2 +/- 1.2 %) were well below the 70 % limit for species identification. YIM 730274(T) was distinguishable from other members of the genus Aquabacterium by the differences in phenotypic, chemotaxonomic and genotypic characteristics. YIM 730274(T) merits recognition as a representative of a novel species of the genus Aquabacterium. It is proposed that the isolate should be classified in the genus Aquabacterium as representing a novel species, Aquabacterium tepidiphilum sp. nov. The type strain is YIM 730274(T) (=KCTC 52716(T) =CCTCC AB 2016295(T)).