Figure 2.

A new RND system involved in copper resistance. A, Northern-blot analysis of the expression of copB. Total RNA was isolated from wild-type cells grown in BG11C-Cu medium and exposed for 90 min to 3 μm of the indicated metal ions. Control cells were not exposed to added metals (−).The filter was hybridized with a copB probe and subsequently stripped and rehybridized with an rnpB probe as a control. B, Loss of copB induction in the COPR strain. Total RNA was isolated from wild-type and COPR strains grown in BG11C-Cu medium after addition of 3 μm of copper. Samples were taken at the indicated times. The filter was hybridized with a copB probe subsequently stripped and rehybridized with an rnpB probe as a control. C, Phenotypic characterization of copBAC mutants. Tolerance of wild-type, COPB, COPA, and COPC strains to copper was examined. Ten-fold serial dilutions of a 1 μg chlorophyll mL⁻¹ cells suspension were spotted onto BG11C-Cu supplemented with the indicated copper concentrations. Plates were photographed after 5 d of growth. [See online article for color version of this figure.]