FIG. 3.

(A) Disk diffusion susceptibility assays. Four-millimeter paper disks soaked with 15 μl of 125 mM GSNO were placed on RCV-malate plates on which a lawn of bacteria had been spread in order to examine the effect of NO on growth of R. capsulatus strains. The photograph shows R. capsulatus PAS100 (top), MC101 (lower left), and MC111 (lower right) demonstrating the greater degree of susceptibility of the cycP mutant strains to the NO releaser. (B) Growth of R. capsulatus strains under an NO headspace. NO gas (100 μl) was injected into the headspace of tubes containing R. capsulatus strains suspended in 0.3% agar which were subsequently incubated in the light for 24 h. Depth above which growth is not observed toward the top of the agar is shallower in PAS100 (tube 1) than in MC101 and MC111 (tubes 2 and 3, respectively), indicative of the greater capacity of PAS100 to withstand the toxic effects of NO than of either of the cycP mutants.