An anaerobic, Gram-stain-positive, spore-forming bacterium, designated strain PYR-10T, was isolated from a mesophilic methanogenic consortium. Cells were 0.7–1.2×6.0–6.3 µm, straight or slightly curved rods, with flagellar motility. Growth was observed in PYG (peptone-yeast glucose) medium at pH 5.5–8.0 (optimum, pH 6.5), 30–55 °C (45 °C) and in NaCl concentrations of 0–15 g l−1 (0 g l−1). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain PYR-10T belongs to the genus
Clostridium
. The strain showed 95.4, 93.7, 93.5 and 93.0 % 16S rRNA gene sequence similarity to
Clostridium swellfunianum
DSM 27788T,
Clostridium pascui
DSM 10365T,
Clostridium pasteurianum
DSM 525T and
Clostridium punense
DSM 28650T, respectively. The genomic DNA G+C content was 27.7 mol%. The major cellular fatty acids of strain PYR-10T were iso-C15 : 0, C16 : 0, C16 : 0 DMA, anteiso-C15 : 0 and C14 : 0. The main polar lipids were glycolipid, phosphoaminoglycolipid, diphosphatidylglycerol, phosphatidylglycerol, phospholipids, phosphatidylethanolamine and lipids. An unknown menaquinone was detected. 2,6-Diaminopimelic acid was not detected. The whole-cell sugars contained ribose and lower amounts of glucose. Based on the results of phylogenetic, chemotaxonomic and phenotypic analyses, strain PYR-10T represents a novel species of the genus
Clostridium
, for which the name
Clostridium
prolinivorans sp. nov. is proposed. The type strain is strain PYR-10T (=JCM 33161T=CCAM 531T=CGMCC 1.5286T).
