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 degrees C, with optimum growth at 37 degrees C. The major cellular fatty acids were anteiso-C15:0, C16:0, iso-C15:0, C16:1 omega11c and anteiso-C(17:0). 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 NN T (sequence similarity 95.5%), G. dipsosauri DD1T (96.1%), G. orientalis XH-63T (96.8%) and G. boraciitolerans T-16X(T) (99.1%). The DNA-DNA relatedness between strain YIM-C229(T) and G. boraciitolerans DSM 17256(T) 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.