An obligately anaerobic, Gram-positive, spore-forming bacterial strain, designated SL206(T), was isolated from pear orchard soils. Strain SL206(T) cells were straight or slightly curved rods, with motility by peritrichate flagella. Cell walls contained meso-diaminopimelic acid; wall sugars were glucose, rhamnose and mannose. The major fatty acids were C(16 : 0), C(18 : 1)omega9c and summed feature 10 (containing C(18 : 1)omega11c/9t/6t). API 20A reactions were negative for oxidase, catalase and acid production from l-rhamnose, sucrose, trehalose, d-xylose, melezitose, salicin and d-sorbitol, and positive for acid production from d-glucose, sucrose, maltose, d-mannose and raffinose. Glucose was fermented to acetate, butyrate, CO(2), H(2) and ethanol in culture. The G+C content of the genomic DNA was 31.1 mol%. Based on comparative 16S rRNA gene sequence analysis, the isolate belonged to the genus Clostridium and formed a clade with Clostridium pasteurianum. The species most closely related to strain SL206(T) were C. pasteurianum (98.6 % similarity) and Clostridium acidisoli (97.8 % similarity). In DNA-DNA relatedness studies, the isolate had 59.5 % relatedness with C. pasteurianum and thus represented a unique species. On the basis of these studies, strain SL206(T) (=KCTC 5449(T) =JCM 14858(T)) is proposed to represent the type strain of a novel species, Clostridium arbusti sp. nov.