An anaerobic, spore-forming, ethanol-hydrogen-coproducing bacterium, designated LX-B-T, was isolated from an anaerobic sludge treating herbicide wastewater. Cells of strain LX-B-T were nonmotile rods (0.3-0.5x3.0-18.0 gm). Spores were terminal with a bulged sporangium. Growth occurred at 20-50 degrees C (optimum 37-45 degrees C), pH 5.0-8.0 (optimum pH 6.0-7.7) and 0-2.5% (w/v) NaCl. The strain could grow fermentatively on glucose, maltose, arabinose, fructose, xylose, ribose, galactose, mannose, raffinose, sucrose, pectin, starch, glycerol, fumarate, tryptone and yeast extract. The major end-products of glucose fermentation were acetate, ethanol and hydrogen. Yeast extract was not required but stimulated growth. Nitrate, sulfate, thiosulfate, elemental sulfur, sulfite, anthraquinone-2,6-disulfonate, fumarate and Fe (III) nitrilotriacetate were not used as terminal electron acceptors. The G+C content of the genomic DNA was 56.1 mol%. The major cellular fatty acids were anteiso-C-15:0, iso-C-14:0 and C-16:0. The most abundant polar lipids of strain LX-B-T were diphosphatidylglycerol and phosphatidylglycerol. 16S rRNA gene sequence analysis revealed that it belongs to an as-yet-unidentified taxon at the order- or class-level (OPB54) within the phylum Firmicutes, showing 86.5% sequence similarity to previously described species of the Desulfotomaculum cluster. The name Hydrogenispora ethanolica gen. nov., sp. nov. is proposed to accommodate strain LX-B-T (=DSM 25471(T)=JCM 18117(T)=CGMCC 1.5175(T)) as the type strain.