Role of the mar-sox-rob Regulon in Regulating Outer Membrane Porin Expression

Multiple factors control the expression of the outer membrane porins OmpF and OmpC inEscherichia coli . In this work, we investigated the role of themar-sox-rob regulon in regulating outer membrane porin expression in response to salicylate. We provide both genetic and physiological evidence that MarA and Rob can independently activatemicF transcription in response to salicylate, leading to reduced OmpF expression. MarA was also found to repress OmpF expression through a MicF-independent pathway. In the case of OmpC, we found that its transcription was moderately increased in response to salicylate. However, this increase was independent of MarA and Rob. Finally, we found that the reduction in OmpF expression in atolC mutant is due primarily to Rob. Collectively, this work further clarifies the coordinated role of MarA and Rob in regulating the expression of the outer membrane porins.