Genomic and phenotypic characterization of Streptococcus intestinihominis sp. nov. from the human intestinal tract

A novel α -haemolytic bacterial strain, IMAU11619 ^T , belonging to the genus Streptococcus , was isolated from human intestinal tract samples collected in Hohhot City, Inner Mongolia Autonomous Region of China. Strain IMAU11619 ^T is characterized as Gram-positive, non-motile, non-spore-forming cocci. Optimal growth conditions were anaerobically determined at 37 °C and pH 6 in De Man–Rogosa–Sharpe medium. We sequenced the draft genome of strain IMAU11619 ^T and characterized its taxonomic status using phylogenetic and phenotypic analyses. Comparative analysis with the TYGS database indicated that strain IMAU11619 ^T represents a novel species within the genus Streptococcus that is phylogenetically distinct from all previously characterized species. Phylogenetic reconstruction based on 176 single-copy genes positioned this strain within the parasanguinis subclade of the Mitis–Suis clade and closely related to Streptococcus rubneri DSM 26920 ^T , Streptococcus australis ATCC 700641 ^T and Streptococcus ilei I-G2 ^T . The highest observed average nucleotide identity and digital DNA–DNA hybridization values with its closest relative, S. australis ATCC 700641 ^T , were 93.1–93.8 and 52.8%, respectively. The genomic DNA G+C content of strain IMAU11619 ^T was 42.2 mol%. The major fatty acid components identified included C _16:0 , C _14:1 , C _18:0 and summed feature 8 (C _18:1  ω7 c and/or C _18:1  ω6 c). The respiratory quinone type of strain IMAU11619 ^T was identified as menaquinone-9. Based on its distinctive phylogenetic position and phenotypic features, strain IMAU11619 ^T is proposed as a novel species, Streptococcus intestinihominis sp. nov., with type strain IMAU11619 ^T (=CGMCC 1.64731 ^T =GDMCC 1.4355 ^T =JCM 37062 ^T ).