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Streptococcus mutans strain GS-5 was grown under a variety of environmental conditions in order to achieve different balanced growth rates. A range of growth rates could be obtained using limitations in the concentrations of glutamate/glutamine, leucine, or valine. Different balanced growth rates were also obtained when cells were grown in a variety of carbon sources. Using glucose, cellobiose, amygdalin, maltose, mannitol, and galactose, reproducible doubling times were obtained ranging from 61 to 226 min. [ABSTRACT FROM AUTHOR]

A reliable scheme for the differentiation of certain species of oral streptococci has been developed. It employs a commercial biochemical test system (API SOL) modified to accommodate some of the oral streptococci. The scheme relies primarily on eight biochemical reactions, which demonstrate consistent results. Compared to Shklair and Keene's very useful biochemical scheme, our scheme employs additional definitive tests, is a much simpler system technically, and can differentiate a proposed new species, S. ferus. [ABSTRACT FROM AUTHOR]

Stable fluoride-resistant mutants of Streptococcus mutans GS-5 were isolated on Todd-Hewitt agar by a step-wise selection procedure. Resistance is defined here as the ability to form colonies in 48 hr. First-step mutants demonstrated six different levels of resistance, ranging from 400 to 1000 µg /mL sodium fluoride. Second-step mutants demonstrated two levels of resistance, one at 1600 and the highest at 3000 µg/mL sodium fluoride. All mutants (originally isolated at pH 7.2) were tested for fluoride resistance at pH 5 and 6. At these lower pH values, all of the mutants demonstrated resistance to fluoride when compared with the parent strain, but at much-reduced levels. [ABSTRACT FROM AUTHOR]