FIG 1.

pH-dependent H₂O₂ production in S. sanguinis and S. gordonii. (A) Images of S. sanguinis and S. gordonii on H₂O₂ indicator plates adjusted to pH 7 and pH 6; representative images are shown. (B) Quantitative analysis of H₂O₂ production on indicator plates; production was determined by measuring the distance between the border of the colony and the border of the halo formed by the Prussian blue precipitate. (C) Quantitative analysis of H₂O₂ production in liquid cultures; production was determined enzymatically and normalized to CFU. All data were obtained in triplicate at separate times. *, significant difference (P < 0.05).