Clostridium muellerianum sp. nov., a carbon monoxide-oxidizing acetogen isolated from old hay

An acid/alcohol-producing, Gram-stain-positive, obligately anaerobic, rod-shaped, non-motile, non-spore forming acetogen, designated as strain P21T, was isolated from old hay after enrichment with CO as the substrate. Spores not observed even after prolonged incubation (30 days). Phylogenetic analysis of the 16S rRNA gene sequence of strain P21T showed it was closely related to Clostridium carboxidivorans DSM 15243T (97.9%), Clostridium scatologenes DSM 757T (97.7 %) and Clostridium drakei DSM 12750T (97.7 %). The genome is 5.6 Mb and the G+C content is 29.4 mol%. Average nucleotide identity between strain P21T, C. carboxidivorans, C. scatologenes and C. drakei was 87.1, 86.4, 86.4 %, respectively. Strain P21T grew on CO:CO2, H2:CO2, l-arabinose, ribose, xylose, fructose, galactose, glucose, lactose, mannose, cellobiose, sucrose, cellulose, starch, pyruvate, choline, glutamate, histidine, serine, threonine and casamino acids. End products of metabolism were acetate, butyrate, caproate, ethanol and hexanol. Dominant cellular fatty acids (>10 %) were C16 : 0 (41.5 %), C16 : 1 ω7c/C16 : 1 ω6c (10.0 %), and a summed feature containing cyclo C17 : 1/C18 : 0 (17.3 %). Based on the phenotypic, chemotaxonomic, phylogenetic and phylogenomic analyses, strain P21T represents a new species in the genus Clostridium, for which the name Clostridium muellerianum sp. nov. is proposed. The type strain is P21T (=DSM 111390T=NCIMB 15261T).