FIG. 4.
Expression analysis of the M. smegmatis cyd gene cluster. (A) Genetic organization at the cyd locus of the reporter strain, mc2155::pBK4. The hatched arrow denotes the putative cyd promoter, Pcyd. The genotype of this site-specific single recombinant was confirmed by Southern blotting (not shown). (B) Dependence of β-galactosidase reporter activity on pO2. The specific activity of a reporter gene product (β-galactosidase) was studied at 21, 5, 1, and 0.5% air saturation as described in Materials and Methods. The data shown are an average of three independent experiments for each air saturation level. A statistical pairwise comparison showed that the data followed a significant second-order relationship, as represented in the figure (P < 0.05).