FIG 5.

Manganese transport contributes to H₂O₂ tolerance. (A and B) Growth of S. mutans UA159, ΔsloC, ΔmntH, and ΔsloC ΔmntH strains in the presence of 0.2 mM H₂O₂ in (A) plain BHI agar or (B) BHI agar supplemented with 10 μM Mn. (C) A peroxigenic strain (S. gordonii DL-1 or S. sanguinis) SK150 was spotted at the center of a BHI agar plate (supplemented with 2 μM Mn) and grown for 24 h (37°C, 5% CO₂). S. mutans cultures were then spotted proximal to the peroxigenic strain and grown for an additional 24 h. The center spot of each grouping shown here is the H₂O₂-producing strain, while the S. mutans strains are labeled in the figure (ΔΔ corresponds to the ΔsloC ΔmntH double mutant). As a control, duplicate spotting was performed in which H₂O₂ produced by the peroxigenic strains was neutralized by overlaying the inoculum spot with a catalase solution prior to spotting of S. mutans. The images shown are representative of results from three independent experiments.