FIG 4 .

Growth of B. diazoefficiens strains under various stress conditions. (A to D) Growth of the WT (circles), the ΔhpnP mutant (squares), and the ΔhpnH mutant (triangles) was monitored as optical density at 600 nm (OD₆₀₀) in PSY at 30°C (A), PSY at 37°C (B), microaerobic PSY with 0.5% O₂ at 30°C (C), and PSY at pH 6 and 30°C (D). Each curve represents the average of at least three biological replicates, except the microaerobic growth curves, for which a representative data set out of four trials is shown. (E and F) Growth of B. diazoefficiens strains under stress as measured in stressor gradient plates with 50 mM NaCl, 500 mM inositol, 0.4% bile salts, or 1 mM EDTA (E) or by disc diffusion assays with 10% SDS, 5.5 M H₂O₂, and 2 M HCl (F). Error bars represent standard errors (n = 9). *, P < 0.05, and **, P < 0.01, by Tukey’s honestly significant difference test. (G) NCR335 sensitivity of B. diazoefficiens strains.