FIG 1.

Loss of MpfA alleviates Co(II) and Mn(II) intoxication in efflux-deficient mutants. (A) Map of suppressor mutants [Mn(II) and Co(II)] with transposon insertions in the yhdQ-mpfA operon. (B and C) The sensitivity of the wild type and its derived mutants to Mn (B) and Co (C) was monitored using a disk diffusion assay. The mutant strains tested in panel B were mpfA::mls, mntR::tet, mntR::tet mpfA::mls, mntR::tet ΔmntH, and mntR::tet ΔmntH mpfA::mls. The mutant strains tested in panel C were mpfA::mls, czcD::tet, and czcD::tet mpfA::mls. Ten microliters of 250 mM MnCl₂ or 250 mM CoCl₂ was applied to each disk. Data are expressed as the diameter of the zone of clearance (ZOC) (mean ± standard error [SE]; n = 3) and zone of sensitivity (mean ± SE; n = 3). * (P < 0.05) and ** (P < 0.01) indicate statistically significant differences between the indicated groups as judged using a paired Student t test.