Three xylanase-producing alkaliphilic strains, SU1(T), 36AC4 and 36AC6, were isolated from the guts of larvae of the Japanese horned beetle (Trypoxylus dichotomus septentrionalis). The isolates stained Gram-positive and were aerobic, spore-forming, non-motile and rod-shaped and grew optimally at 30 degrees C and pH 9. They contained MK-7 as the major isoprenoid quinone and iso-C(15 : 0), anteiso-C(15 : 0), anteiso-C(17 : 0) and iso-C(17 : 0) as the major fatty acids. The DNA G+C contents of the strains were 37.4-37.7 mol%. On the basis of 16S rRNA gene sequence similarity, these strains were shown to belong to the genus Bacillus. Although their 16S rRNA gene sequence similarity to the type strains of the alkaliphilic species Bacillus pseudalcaliphilus and B. alcalophilus was 97 %, the novel isolates formed a distinct group in the phylogenetic trees and DNA-DNA relatedness values to the type strains of these species were less than 30 %. Results of physiological and biochemical tests, including salt preference, enabled these strains to be differentiated phenotypically from described Bacillus species. Therefore, strains SU1(T), 36AC4 and 36AC6 represent a novel species for which the name Bacillus trypoxylicola sp. nov. is proposed; the type strain is SU1(T) (=NBRC 102646(T) =KCTC 13244(T)).