Fig 4.

Species specificity of McB action. (A) Two-microliter drops of solutions containing 200 μM Ec-McB, Ps-McB1, and Ps-McB2 were deposited onto lawns of E. coli BL21(DE3) or P. aeruginosa PAO1. After overnight growth at room temperature, diameters of growth inhibition zones were determined. Mean values and standard deviations obtained from three independent experiments are shown. (B) Genetic constructs expressing the chimeric microcins shown on the left were prepared by swapping elements marked I, II, and III of E. coli and P. syringae microcins. Compounds containing the entire complement of heterocycles (molecular masses of compounds determined by MALDI-MS are shown in the middle and correspond to compounds with a full complement of heterocycles) were purified, and 2-μl drops of solutions containing 200 μM each compound were deposited onto lawns of E. coli MG1655 or P. aeruginosa PAO1. After overnight growth at room temperature, diameters of growth inhibition zones were determined. Mean values and standard deviations obtained from three independent experiments are shown on the right.