FIG 11.

Differential H₂O₂ production of S. oralis J22, S. gordonii DL1, S. sanguinis SK36 (laboratory strains), and several clinical isolates. Shown is the relative H₂O₂ release. Cells were grown aerobically on H₂O₂ indicator agar plates with 0.3% and 2% glucose (glc). Presented are averages and standard deviations from at least three independent experiments. Significant differences are indicated by asterisks (two-tailed t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001). The species of clinical isolates were determined by sequencing of the 16S rRNA gene and recA. Species were grouped by their amount of H₂O₂ release and their response to the presence of glucose (H₂O₂ release under catabolite control). Group I shows large amounts of H₂O₂ and no or weak response to the presence of glucose. Members of group II release less H₂O₂ and show no or weak response to the presence of glucose. H₂O₂ release follows classical catabolite repression in strains of group III. S. paras., S. parasanguinis.