Gracilibacillus quinghaiensis sp. nov., isolated from salt-lake sediment in the Qaidam Basin, north-west China

A motile, Gram-positive, slightly halophilic, endospore-forming, catalase- and oxidase-positive, obligately aerobic, slender rod-shaped bacterium, strain YIM-C229T was isolated from the sediment of a salt lake in the Qaidam Basin, north-west China. Filamentous forms were present throughout the growth cycle. Strain YIM-C229T grew in the presence of 0.5–8% NaCl and at pH 6.0–8.5, with optimum growth at 1–3% NaCl and pH 7.0–7.5. It grew at 4–45 °C, with optimum growth at 37 °C. The major cellular fatty acids were anteiso-C15:0, C16:0, iso-C15:0, C16:1ω11c and anteiso-C17:0. The predominant respiratory quinone was MK-7, and diphosphatidylglycerol and phosphatidylglycerol were the polar lipids, with meso-diaminopimelic acid occurring in the cell-wall peptidoglycan. The genomic DNA G+C content was 40.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM-C229T was closely related to the type strains of the four recognized species of the genus Gracilibacillus: G. halotolerans NNT (sequence similarity 95.5%), G. dipsosauri DD1T (96.1%), G. orientalis XH-63T (96.8%) and G. boraciitolerans T-16XT (99.1%). The DNA–DNA relatedness between strain YIM-C229T and G. boraciitolerans DSM 17256T was 30.8%. The combination of phylogenetic analysis, phenotypic characteristics, chemotaxonomic differences and DNA–DNA hybridization data supported the view that this strain represented a novel species of the genus Gracilibacillus, for which the name Gracilibacillus quinghaiensis sp. nov. is proposed, with YIM-C229T (=DSM 17858T=CGMCC 1.6304T) as the type strain.