An alkaliphilic and halotolerant Gram-stain-positive bacterium, which was isolated from sediment samples from the South China Sea, was subjected to a taxonomic study. The isolate, strain L1T, grew well at a wide range of temperatures and pH values, 10.0-45.0 °C and pH 6-11, with optima at 30 °C and pH 9.0, respectively. The growth of strain L1T occurred at total salt concentrations of 0-10% (w/v) with an optimum at 2% (w/v). Phylogenetic analysis based on 16S rRNA sequence comparison indicated that the isolate represented a member of the genus Bacillus. The strains most closely related to strain L1T were Bacillus nanhaiisediminis JCM 16507T, Bacillus halodurans DSM 497T and Bacillus pseudofirmus DSM 8715T, with 16S rRNA similarities of 96.5%, 95.9% and 95.7%, respectively. DNA-DNA hybridization of strain L1T with the type strains of the most closely related species, B. nanhaiisediminis JCM 16507T, B. halodurans DSM 497T and B. pseudofirmus DSM 8715T, showed reassociation values of about 21.7%, 14.3% and 13.9%, respectively. The DNA G+C content of strain L1T was 40.76 mol%. The predominant isoprenoid quinone was menaquinone 7 (MK-7). The cell-wall peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. The predominant cellular fatty acids of strain L1T were iso-C14 : 0 and anteiso-C15:0. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. Based on the phenotypic and phylogenetic characteristics, it is proposed that strain L1T (=JCM 18543T=DSM 26145T) should be classified as the type strain of Bacillus ligniniphilus sp. nov.