Abstract
Clostridium is an important microbial component in pit mud due to its ability to produce alcohol and short-chain fatty acids. This study presents the characterization and taxonomy of two Gram-stain-positive, strictly anaerobic, rod-shaped mesophilic bacterial strains, designated MT-113T and MT-5T, isolated from pit mud in a fermentation cellar used for producing sauce-flavour Chinese baijiu. Phylogenetic analysis based on genome and 16S rRNA gene sequences of strains MT-113T and MT-5T indicates their affiliation with the genus Clostridium sensu stricto (Cluster I of the Clostridia), with C. luticellarii FW431T and C. aromativorans WLY-B-L2T as the closest related species. The major cellular fatty acids (>10.0%) of both strains are C14 : 0 and summed feature 1 (iso-C15 : 1 h and/or C13 : 0 3-OH). The G+C molar contents of the complete genomes for strains MT-113T and MT-5T are 35.84 and 32.74 mol%, respectively. The average nucleotide identity and average amino acid identity values between strains MT-113T, MT-5T, C. aromativorans WLY-B-L2T and C. luticellarii FW431T range from 79 to 85%. The primary products of glucose fermentation by MT-113T are acetic, butyric and isovaleric acids, while those of MT-5T are acetic, isobutyric, butyric and isovaleric acids. Based on their phenotypic, chemotaxonomic and phylogenetic characteristics, strains MT-113T (=CGMCC 1.18018T = JCM 36532T) and MT-5T (=CGMCC 1.18016T = JCM 36530T) are proposed as the type strains of two novel species of the genus Clostridium, namely Clostridium lapidicellarium sp. nov. and Clostridium moutaii sp. nov., respectively.