FIG 3.

The ΔrgpF mutant has heightened sensitivity to stress. Cultures of S. mutans UA159, ΔrgpF, and rgpF⁺ strains were grown in continuous culture to steady state at pH values of 7 and 5 and challenged with either 0.1 M glycine (pH 2.5) (A) or 0.05% H₂O₂ (B). Surviving organisms were enumerated after a 60-min exposure, and data are expressed as mean log survival (versus starting inoculum) ± SD. Data were derived from three independent chemostat cultures, each performed in duplicate. Statistical significance (P ≤ 0.02) was determined by pairwise comparison using Student's t test and is indicated by comparison of like symbols.