Strain JW/YJL-B18 T , a spore-forming, sulfate-reducing bacterium, was isolated from constructed wetland sediment. Cells were curved rods, 0.7-1.2 mm in diameter and 3-7 mm long. Despite being phylogenetically a member of the Gram-type-positive phylum Firmicutes, cells stained Gram-negative at all growth phases. Strain JW/YJL-B18 T grew at 8-39 6C, with an optimum at 32-35 6C and no growth at 4 6C or below or at 42 6C or above. The pH 25 6C range for growth was 5.7-8.2, with an optimum at pH 25 6C 7.0-7.3, and no growth was detected at or below pH 5.2 or at or above pH 8.4. The salinity range for growth was 0-3 % (NaCl/KCl 9 : 1). Strain JW/YJL-B18 T utilized as carbon and energy sources beef extract, yeast extract, formate, succinate, lactate, pyruvate, ethanol and toluene. Fumarate, sulfate, sulfite and thiosulfate were reduced in the presence of lactate. Arsenate (V) was not used as an electron acceptor. Strain JW/YJL-B18 T showed no indication of growth under autotrophic conditions. The predominant cellular fatty acids were C 16 : 1 and C 16 : 0 . The genomic DNA G+C content was 36.6 mol% (HPLC). 16S rRNA gene sequence analysis indicated that strain JW/YJL-B18 T fell into the genus Desulfosporosinus, with Desulfosporosinus auripigmenti OREX-4 T as its closest neighbour with a validly published name (97.9 % similarity). Based on molecular genetic evidence and physiological and biochemical characters including differences in the DNA G+C content, we propose to place strain JW/YJL-B18 T (5DSM 17734 T 5ATCC BAA-1261 T ) as the type strain of a novel species, Desulfosporosinus youngiae sp. nov.Sulfate-reducing bacteria (SRB) are responsible for a variety of biogeochemical processes. For example, SRB reduce sulfate to dissolved sulfide (S 22 ), which may react with metals to form metal sulfides; thus, they are considered to play a major role in metal removal and alkalinity generation in treating acid mine drainage. The SRB are an ecologically and metabolically diverse group of anaerobes which include members of the phylum Firmicutes (formerly the phylogenetically Gram-type-positive bacteria; Wiegel, 1981) residing within the family Peptococcaceae in the order Clostridiales. Among them, the genus Desulfosporosinus currently consists of five species of obligately anaerobic, spore-forming bacteria (http:// www.bacterio.cict.fr/d/desulfosporosinus.html). Stackebrandt et al. (1997) distinguished this group from the genus Desulfotomaculum on the basis of phylogenetic evidence and their ability to grow under autotrophic conditions. However, the property of autotrophic growth (i.e. 50 % of the biomass is derived from inorganic carbon) has not been demonstrated unequivocally for all species. Vatsurina et al. (2008) recently reported Desulfosporosinus orientis 343 as the type strain of a novel species in the same genus, Desulfosporosinus hippei, which does not oxidize H 2 with CO 2 or acetate. Here, we report another novel Desulfosporosinus species that is not capable of growing lithotrophically, isolated from a construc...