Abstract
A novel Gram-negative, spore forming, obligately anaerobic, thermophilic, chitin-degrading bacterium, designated UUS1-1(T), was isolated from compost on Ishigaki Island, Japan by enrichment culturing using chitin powder as the carbon source. The strain has unique, long, hair-like rod morphological features and exhibits strong degradation activity toward crystalline chitin under thermophilic conditions. Growth of the novel strain was observed at 45-65 °C (optimum, 55 °C) and pH 6.5-7.5 (optimum, pH 7.0). In addition to chitin, the strain utilized several other carbon sources, including N-acetylglucosamine, glucose, galactose, mannose, maltose, cellobiose, fructose and sucrose. The end products of chitin degradation were acetate, lactate, H(2) and CO(2). Phylogenetic tree analysis based on 16S rRNA gene sequences revealed a clear affiliation of the proposed bacterium to the phylum Firmicutes; the most closely related species were Hydrogenispora ethanolica LX-B(T) and Desulfotomaculum thermobenzoicum DSM6193(T) with similarities of 90.4 and 87.8 %, respectively. The G+C content of the genomic DNA was 52.1 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between the genomes of UUS1-1(T) and H. ethanolica LX-B(T) were 65.5 and 21.0 %, respectively. The cellular fatty acid composition of the strain was C(16 : 0), anteiso-C(15 : 0), C(14 : 0), C(12 : 0) 3-OH and dimethyl acetal-C(13 : 0). Based on phenotypic, chemotaxonomic and genotypic analysis, strain UUS1-1(T) represents a novel genus and species, for which the name Capillibacterium thermochitinicola gen. nov., sp. nov. is proposed. The type strain is UUS1-1(T) (=JCM 33882(T)=DSM 111537(T)).