A facultative anaerobic, Gram-positive staining, endospore-forming bacterium, isolated from the rhizosphere of cucumber (Cucumis sativus), was taxonomically investigated. Based on 16S rRNA gene sequence similarity comparisons, strain AP-6T clustered together with other species of the genus Bacillus and showed highest similarities with Bacillus drentensis LMG 21831T (99.1 %), Bacillus vireti LMG 21834T (98.7 %) and Bacillus soli LMG 21838T (98.5 %). The 16S rRNA gene sequence similarity to the sequences of the type strains of other species of the genus Bacillus was 98.5 % or less. Chemotaxonomic features supported the grouping of the strain in the genus Bacillus; for example, the major fatty acids were anteiso-C15 : 0, iso-C15 : 0 and C16 : 0, the polar lipid profile contained the major components diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified glycolipid, the major quinone was menaquinone MK-7 and the major compound in the polyamine pattern was spermidine. Additionally, DNA-DNA hybridization with B. drentensis LMG 21831T, B. vireti LMG 21834T and B. soli LMG 21838T resulted in relatedness values that were clearly below 70 %. Physiological and biochemical test results were also different from those of the most closely related species. As a consequence, AP-6T represents a novel species of the genus Bacillus, for which the name Bacillus cucumis sp. nov. is proposed, with AP-6T ( = CIP 110974T = CCM 8651T) as the type strain.