gen. nov., sp. nov., a thermophilic chain-elongating bacterium, producing -caproate from polymeric carbohydrates.

Strain MDTJ8 is a chain-elongating thermophilic bacterium isolated from a thermophilic acidogenic anaerobic digestor treating human waste while producing the high commodity chemical -caproate. The strain grows and produces formate, acetate, -butyrate, -caproate and lactate from mono-, di- and polymeric saccharides at 37-60 °C (optimum, 50-55 °C) and at pH 5.0-7.0 (optimum, pH 6.5). The organism is an obligate anaerobe, is motile and its cells form rods (0.3-0.5×1.0-3.0 µm) that stain Gram-positive and occur primarily as chains. Phylogenetic analysis of both the 16S rRNA gene and full genome sequence shows that strain MDTJ8 belongs to a group that consists of mesophylic chain-elongating bacteria within the family , being nearest to EA1 (94.8 %) and BS-1 (93.7 %). Its genome (1.96 Mbp) with a G+C content of 49.6 mol% is remarkably smaller than those of other chain-elongating bacteria of the family . Pairwise average nucleotide identity and DNA-DNA hybridization values between strain MDJT8 and its mesophilic family members are less than 70 and 35 %, respectively, while pairwise average amino acid identity values are less than 68 %. In addition, strain MDJT8 uses far less carbohydrate and non-carbohydrate substrates compared to its nearest family members. The predominant cellular fatty acids of strain MDTJ8 are C, C DMA (dimethyl acetal) and C, while its polar lipid profile shows three unidentified glycophospholipids, 11 glycolipids, 13 phospholipids and six unidentified lipids. No respiratory quinones and polyamines are detected. Based on its phylogenetic, genotypic, morphological, physiological, biochemical and chemotaxonomic characteristics, strain MDTJ8 represents a novel species and novel genus of the family and gen. nov., sp. nov. is proposed as its name. The type strain is MDTJ8 (=DSM 114174=LMG 32615=NCCB 100883).