FIG. 4.

Effects of crp, cyaA, and hns on adaptation of MarA-mediated MDR to environmental stimuli. The percentage of MarA-mediated MDR was calculated as explained in Table 3, footnote a. The results are presented as the average ± the standard error of the mean (n = 3). When different conditions for the same strains were compared, addition of 0.4% glucose or 300 mM NaCl was found to produce statistically significant differences in MarA-mediated MDR in the parental strain (P was <0.01 for all antibiotics except for cefoxitin, in which case P was <0.05 for NaCl and P was <0.1 for glucose; these statistical significances are shown in the figure as “**,” “*,” and “+,” respectively), whereas these additions produced no differences in the mutants studied. Levels of MarA-mediated MDR were significantly different between the parental strain and the mutants in the absence of glucose and NaCl (P < 0.01 [see Table 3]; these statistical significances are not indicated in this figure), but no significant differences between them were found in the presence of glucose or NaCl.