FIG. 1.

Initial rates of hydrogen peroxide and l-lactic acid formation by S. gordonii CH1 in selected concentrations of glucose or sucrose. Cultures were grown to mid-logarithmic phase in TSBY–10 U of catalase per ml with vigorous shaking in air to obtain highly peroxidogenic cells. Cells were washed by repeated centrifugation and resuspension in 25 mM KH₂PO₄-K₂HPO₄ (pH 7.0)–1 mM MgCl₂ containing the indicated concentration of glucose or sucrose. The accumulation of hydrogen peroxide or l-lactic acid was measured at 37°C over time to determine initial rates of hydrogen peroxide formation (A) and l-lactic acid formation (B). In assay buffer which contained no carbohydrate, the rate of peroxidogenesis was 1.1 ± 0.3 nmol/(min · 10⁹ cells). Results are means ± SD of three rate determinations at each concentration point.