A xylanolytic and cellulolytic anaerobic bacterium strain CtC72 was isolated from cattle rumen liquor. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain CtC72 shared only 97.78% homology with its nearest phylogenetic affiliate Actinomyces ruminicola, showing its novelty. The strain could grow on medium containing xylan, carboxymethyl cellulose and avicel producing CO 2 , acetate, and ethanol as major fermentation products. The whole genome analysis of the strain CtC72 exhibited a broad range of carbohydrate-active enzymes required for the breakdown and utilization of lignocellulosic biomass. Genes related to the production of ethanol and stress tolerance were also detected. Further there were several unique genes in CtC72 for chitin degradation, pectin utilization, sugar utilization, and stress response in comparison with Actinomyces ruminicola. The results show that the strain CtC72, a putative novel bacterium can be used for lignocellulosic biomass based biotechnological applications.These authors contributed equally to this work.

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An obligately anaerobic, rod-shaped, Gram-stain-positive, non-spore-forming, non-motile bacterial strain; designated as CtC72 T 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 106201 T , Actinomyces ruminicola DSM 27982 T , Actinomyces procaprae JCM 33484 T , 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 CtC72 T from its closest relatives. The strain CtC72 T could grow at temperatures between 30-50°C (optimum 40°C), pH between 6.0-9.0 (optimum 7.5-8.0), and NaCl between 0-1.5% (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 CO 2 production. The DNA G + C content of strain CtC72 T was 68.40 (mol%, wet lab), and 68.05 (%, digital). Major cellular fatty acids (> 10%) were C 16:0 , C 18:1 ω9c, and C 18:1 ω9c DMA. Based on this data, we propose that strain CtC72 T be classi ed as a novel species, Actinomyces ruminis sp. nov., under the genus Actinomyces. The type strain is CtC72 T (= KCTC 15726 T = JCM 32641 T = MCC 3500 T ).