Description of Sporanaerobium hydrogeniformans gen. nov., sp. nov., an obligately anaerobic, hydrogen producing bacterium of Lachnospiraceae family isolated from Aravali hot spring in India

Abstract

Abstract An obligately anaerobic bacterium XHS1971T, capable of degrading cellulose and xylan, was isolated from the sediment sample of a hot spring located in Aravali, Ratnagiri, India. Cells of strain XHS1971T were Gram-stain-negative, spore-forming, motile, long rods. Growth of strain XHS1971T was observed at temperatures 30–50°C (optimum 40–45°C), pH 5.0–10.0 (optimum pH 8.0) and NaCl concentrations 0–0.5% (optimum 0%). The generation time of strain XHS1971T was 5 h under the optimized growth conditions. The strain XHS1971T showed the ability to metabolize different complex and simple sugars constituting lignocellulosic biomass. The strain fermented glucose, majorly into hydrogen, formic acid, acetic acid, and ethanol, whereas carbon dioxide, butyric acid, lactic acid and succinic acid were produced in traces. The major cellular fatty acids (> 5%) were C14:0, C16:0, C18:0, and C16:1 ω7c. The 16S rRNA gene analysis of the strain XHS1971T revealed the highest homology of < 94.5% with Cellulosilyticum lentocellum DSM 5427T followed by Cellulosilyticum ruminicola JCM 14822T, identifying it as a distinct member of family Lachnospiraceae. The genome size of the strain was 3.74 Mb with a G + C content of 35.3 mol% and predicted to have 3828 protein-coding genes. Of these, 357 genes were annotated to carbohydrate metabolism, including genes involved in the degradation of cellulose and xylan and the production of hydrogen, ethanol and acetate. The results indicate the potential use of strain XHS1971T in biomass-derived biofuel production. The uniqueness of our strain was further validated by digital DNA-DNA hybridization (dDDH), Average Nucleotide Identity (ANI), and Average Amino Acid Identity (AAI) values of 22%, 80%, and 63%, respectively, with nearest phylogenetic affiliates. Based on the detailed analyses, we propose a new genus and species, Sporanaerobium hydrogeniformans gen. nov., sp. nov., for strain XHS1971T (= MCC 3498T = KCTC 15729T = JCM 32657T) within the family Lachnospiraceae.