Streptococcus hohhotensis sp. nov., isolated from the breast milk of a healthy woman.

Human breast milk contains lactic acid bacteria (LAB), which have an important influence on the composition of the intestinal microbia of infants. In this study, one strain of an α-hemolytic species of the genus Streptococcus , IMAU99199 ^T , isolated from the breast milk of a healthy nursing mother in Hohhot city PR China, was studied to characterise its taxonomic status using phenotypic and molecular taxonomic methods. The results indicated that it represented a member of the mitis-suis clade, pneumoniae subclade of the genus Streptococcus . It is a Gram-stain-positive, catalase-negative and oxidase-negative bacterium, and the cells are globular, paired or arranged in short chains. The results of a phylogenetic analysis of its 16S rRNA gene and two housekeeping genes ( gyrB and rpoB ) placed it in the genus Streptococcus . A phylogenetic tree based on 135 single-copy genes sequences indicated that IMAU99199 ^T formed a closely related branch well separated from ' Streptococcus humanilactis ' IMAU99125, ' Streptococcus bouchesdurhonensis ' Marseille Q6994, Streptococcus mitis NCTC 12261 ^T , ' Streptococcus vulneris ' DM3B3, Streptococcus toyakuensis TP1632 ^T , Streptococcus pseudopneumoniae ATCC BAA-960 ^T and Streptococcus pneumoniae NCTC 7465 ^T . IMAU99199 ^T and ' S. humanilactis ' IMAU99125 had the highest average nucleotide identity (93.7 %) and digital DNA-DNA hybridisation (55.3 %) values, which were below the accepted thresholds for novel species. The DNA G+C content of the draft genome of IMAU99199 ^T was 39.8 %. The main cellular fatty acids components of IMAU99199 ^T were C _16 : 0 and C _16 : 1 ω7. It grew at a temperature range of 25-45 °C (the optimum growth temperature was 37 °C) and a pH range of 5.0-8.0 (the optimum growth pH was 7.0). These data indicate that strain IMAU99199 ^T represents a novel species in the genus Streptococcus , for which the name Streptococcus hohhotensis sp. nov. is proposed. The type strain is IMAU99199 ^T (=GDMCC 1.1874 ^T =KCTC 21155 ^T ).