Possible heterogeneity of Streptococcus milleri determined by DNA mol % (guanine plus cytosine) measurement and physiological characterization.
DNA base pair ratios (mol % guanine + cytosine) were calculated, for eighteen strains of Streptococcus milleri, from measurements of DNA melting temperature (Tm). Strains of vaginal origin which were also 'atypical' physiologically had a value of 40.3. The two culture collection of 'minute' beta-haemolytic strains of Lancefield groups G and F had values of 36.8 and 38.8 mol%, respectively. Three other reference strains had a DNA guanine plus cytosine content ranging from 40.4 to 43.0 mol%, including Streptococcus sp MG which had a value of 42.0 mol%. Strain 7H of oral origin had a value of 40.9 mol%. The remaining physiologically typical strains, of medical origin, had guanine plus cytosine contents ranging from 36.6 to 42.1 mol%. It therefore seems possible that genetic heterogeneity may exist among representatives of Streptococcus milleri.
D003596:Cytosine / Q000032:analysis; D004269:DNA, Bacterial / Q000032:analysis*; D006147:Guanine / Q000032:analysis; D013291:Streptococcus / Q000145:classification / Q000235:genetics* / Q000502:physiology
D004269:DNA, Bacterial; D006147:Guanine; D003596:Cytosine