DNA Base Sequence Homologies among Strains of Streptococcus sanguis

Summary: DNA was isolated from 19 strains and substrains of Streptococcus sanguis and analysed for guanine plus cytosine (GC) contents and base sequence homologies. Three groups could be discerned: group 1 strains had 40·8 to 42·8 mol% GC; group 2, 42·7 to 44·0 mol% GC; group 3, 43·8 to 46·4 mol% GC. DNA homologies between groups 1 and 3 were 40 to 60% at 67°C and 40% at 72°C. The homologies of group 2 towards groups 1 and 3 were much lower. Strains in groups 1 and 3 hydrolysed arginine and aesculin and fermented inulin; group 2 strains did not. Groups 1 and 3 could be considered subspecies of S. sanguis. Group 2 should not be considered S. sanguis.