Branching order of members of the salivarius group as inferred from ML and MP analyses of secA gene sequences (2484 positions; 1261 variable, 1169 phylogenetically informative). The best ML tree computed with PHYML 3.0 under the GTR+Γ4+I model of nucleotide substitution is shown here. Bootstrap support for the major nodes is indicated over the corresponding nodes: ML values left, MP values right. Asterisks denote nodes that were retrieved in all the bootstrap replicates. Dashes indicate nodes that were retrieved in fewer than 50% of the bootstrap replicates. Streptococcal species belonging to the salivarius group are shown in orange (S. salivarius), blue (S. vestibularis), or green (S. thermophilus). Strains CCUG 7215 and CCUG 27306, which are categorized as Streptococcus vestibularis in the CCUG culture collection, are capable of using raffinose as the sole carbon source. This contradicts Whiley and Hardie's  canonical S. vestibularis species definition. This metabolic trait is more a hallmark of the closely related Streptococcus salivarius species, to which the two strains belong. Other streptococcal species shown in black were outgroups. Branch lengths are drawn to scale.