Twenty alkaliphilic bacterial strains from industrial applications or enzyme studies were subjected to a polyphasic taxonomic investigation, including 16S rRNA gene sequencing, determination of genomic DNA G+C content, DNA-DNA hybridization, fatty acid analysis and standard bacteriological characterization. By comparing the groupings obtained based on the genomic DNA G+C content and the construction of a phylogenetic tree based on the 16S rRNA gene sequence, 12 clusters of similar strains were recognized. DNA-DNA hybridization revealed that these clusters represented five novel genospecies. Further analysis supported the proposal of five novel species in the genus Bacillus: Bacillus wakoensis sp. nov. (type strain N-1T=JCM 9140T=DSM 2521T), Bacillus hemicellulosilyticus sp. nov. (type strain C-11T=JCM 9152T=DSM 16731T), Bacillus cellulosilyticus sp. nov. (type strain N-4T=JCM 9156T=DSM 2522T), Bacillus akibai sp. nov. (type strain 1139T=JCM 9157T=ATCC 43226T) and Bacillus mannanilyticus sp. nov. (type strain AM-001T=JCM 10596T=DSM 16130T).