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  ω7c and/or C_18:1  ω6c). 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).