We show that an inducible
rpoSantisense RNA complementary to the rpoSmessage can inhibit expression of RpoS in both exponential and stationary phases and can attenuate expression of the rpoSregulon in Escherichia coli. Plasmids containing rpoSantisense DNA expressed under the control of the T7lacpromoter and T7 RNA polymerase were constructed, and expression of the rpoSantisense RNA was optimized in the pET expression system. rpoSantisense RNA levels could be manipulated to effectively control the expression of RpoS and RpoS-dependent genes. RpoS expression was inhibited by the expression of rpoSantisense RNA in both exponential and stationary phases in E. coli. RpoS-dependent catalase HPII was also downregulated, as determined by catalase activity assays and with native polyacrylamide gels stained for catalase. Induced RpoS antisense expression also reduced the level of RpoS-dependent glycogen synthesis. These results demonstrate that controlled expression of antisense RNA can be used to attenuate expression of a regulator required for the expression of host adaptation functions and may offer a basis for designing effective antimicrobial agents.