FIG 4.

MtlB3 is required for ampicillin resistance in A. tumefaciens. (A) Phase-contrast microscopy of exponentially growing strains treated with ampicillin at 25 μg/mL (AMP 25) for 2 h. (B) Quantitative analysis of phase-contrast microscopy of exponentially growing strains treated with ampicillin at 25 μg/mL (AMP 25) for 2 h. The percent phenotype was calculated by counting the number of cells displaying one of the phenotypes indicated (1 cell = 1 phenotype) and dividing it by the total number of cells for each strain. (C) Growth of A. tumefaciens WT and ΔmltB3 in the absence (No AMP) and presence of ampicillin at 25 μg/mL (AMP 25) for 24 h (n = 1; 2 replicates). (D) Determination of β-lactamase production was performed by a nitrocefin assay using cell lysates. No AMP or AMP 25 indicates cells untreated or treated with ampicillin at 25 μg/mL, respectively, for 2 h before the generation of cell lysates. Data shown represent one of two biological replicates.