Fig 1.

Effects of H₂O₂ on the survival of S. meliloti strains. (A) S. meliloti strains were tested for survival in 1 mM H₂O₂ at various time points. The arrow indicates the 30-min time point chosen for subsequent assays. (B) Survival of several S. meliloti strains expressing different levels of EPS-I after treatment with 1 mM H₂O₂. Survival was normalized to that of the wild-type strain Rm1021 (33% ± 7.4%) or to that of pRF771 (37% ± 11%). (C) Survival of S. meliloti strains expressing different levels of EPS-I or EPS-II after treatment with H₂O₂. Survival was normalized to the average survival of the wild type (23% ± 5.3%). Qualitative levels of EPS-I or EPS-II expression are denoted by −, +, ++, and +++. Error bars indicate standard deviations. Asterisks indicate significant differences (P, <0.05) from the wild type.