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

An obligately anaerobic bacterium XHS1971T, capable of degrading cellulose and xylan, was isolated from a sediment sample of Aravali hot spring, Ratnagiri, India. Cells of strain XHS1971T were Gram-stain-negative, spore-forming, motile, long-rods. Growth 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%). Generation time of strain XHS1971T was 5 h under optimised growth conditions. Strain XHS1971T showed the ability to metabolise different complex and simple sugars constituting lignocellulosic biomass. Glucose was fermented majorly into hydrogen, formic acid, acetic acid, and ethanol, whereas carbon dioxide, butyric acid, lactic acid and succinic acid were produced in traces. 16S rRNA gene analysis of strain XHS1971T revealed < 94.5% homology with Cellulosilyticum lentocellum DSM5427T followed by Cellulosilyticum ruminicola JCM14822T, identifying strain as a distinct member of family Lachnospiraceae. The major cellular fatty acids (> 5%) were C14:0, C16:0, C18:0, and C16:1 ω7c. The genome size of the strain was 3.74 Mb with 35.3 mol% G + C content, and 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 uniqueness of strain was further validated by digital DNA-DNA hybridisation (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 (= MCC3498T = KCTC15729T = JCM32657T) within family Lachnospiraceae.

Actinomyces ruminis sp. nov., an obligately anaerobic bacterium isolated from the rumen of cattle.

An obligately anaerobic, rod-shaped, Gram-stain-positive, non-spore-forming, non-motile bacterial strain; designated as CtC72T was isolated from the rumen of cattle. The 16S rRNA gene sequence similarity of less than 98.65% revealed the strain as a member of the genus Actinomyces, nearest to but distinct from Actinomyces qiguomingii DSM 106201T, Actinomyces ruminicola DSM 27982T, Actinomyces procaprae JCM 33484T, Actinomyces succiniciruminis TISTR 2317, Actinomyces glycerinitolerans TISTR 2318. The low values of digital DNA-DNA hybridization (< 70%) and average nucleotide identity (< 95%) further highlighted the distinctive nature of strain CtC72T from its closest relatives. The strain CtC72T could grow at temperatures between 30 and 50 °C (optimum 40 °C), pH between 6.0 and 9.0 (optimum 7.5-8.0), and NaCl between 0 and 1.5% (optimum 0%). The strain hydrolysed cellulose and xylan and utilised a range of mono-, di-, and oligo-saccharides as a source of carbon and energy. Glucose fermentation resulted in acetic acid and formic acid as major metabolic products, while propionic acid, lactic acid, and ethanol as minor products along with CO2 production. The DNA G + C content of strain CtC72T was 68.40 (mol%, Tm) and 68.05 (%, digital). Major cellular fatty acids (> 10%) were C16:0, C18:1 ω9c, and C18:1 ω9c DMA. Based on these data, we propose that strain CtC72T be classified as a novel species, Actinomyces ruminis sp. nov., under the genus Actinomyces. The type strain is CtC72T (= KCTC 15726T = JCM 32641T = MCC 3500T).

Genomic architecture of three newly isolated unclassified Butyrivibrio species elucidate their potential role in the rumen ecosystem.

One cellulose-degrading strain CB08 and two xylan-degrading strains XB500-5 and X503 were isolated from buffalo rumen. All the strains were designated as putative novel species of Butyrivibrio based on phylogeny, phylogenomy, digital DNA-DNA hybridization, and average nucleotide identity with their closest type strains. The draft genome length of CB08 was ~3.54 Mb, while X503 and XB500-5 genome sizes were ~3.24 Mb and ~3.27 Mb, respectively. Only 68.28% of total orthologous clusters were shared among three genomes, and 40-44% of genes were identified as hypothetical proteins. The presence of genes encoding diverse carbohydrate-active enzymes (CAZymes) exhibited the lignocellulolytic potential of these strains. Further, the genome annotations revealed the metabolic pathways for monosaccharide fermentation to acetate, butyrate, lactate, ethanol, and hydrogen. The presence of genes for chemotaxis, antibiotic resistance, antimicrobial activity, synthesis of vitamins, and essential fatty acid suggested the versatile metabolic nature of these Butyrivibrio strains in the rumen environment.