Figure 6.

CopS responds to intracellular copper. A, Northern-blot analysis of the expression of copM, petE, and petJ in response to copper addition in wild-type, SAS, and PETE strains. Total RNA was isolated from wild-type, SAS, and PETE cells grown in BG11C-Cu medium after addition of copper 200 nm. Samples were taken at the indicated times. The filters were hybridized with copM, petE, and petJ probes and subsequently stripped and rehybridized with an rnpB probe as a control. B, Quantification of relative mRNA levels of copM in response to copper addition in wild-type, SAS, and PETE strains. Radioactive signals of three independent experiments for each strain were quantified and averaged. RNA levels were normalized with the rnpB signal in all strains. Plots of relative mRNA levels versus time were drawn; error bars represent se. Wild-type strain (triangles), SAS strain (circles), PETE strain (squares).