Genomics of Streptococcus salivarius, a major human commensal.

•S. salivarius isolated from diverse human sites is a paradigm to study commensal lifestyle.•The S. salivarius species consists of two clusters of strains, having genomic and functional specificities.•Horizontal gene transfer between and within species has extensively contributed to species diversity.•Specific traits of S. salivarius involved in its adaptation to its environment were highlighted.•The phylogenetic, genomic or metabolic relationships between strains were independent of their origin.