Differential regulation of OmpC and OmpF by AtpB in Escherichia coli exposed to nalidixic acid and chlortetracycline.

Little is known about mechanisms through which OmpR/EnvZ and CpxA/CpxR regulate the expression of OmpC and OmpF, and thereby regulate bacterial responses to antibiotics exposure. In this study we investigated the relationships among OmpC, OmpF and TCSs using Escherichia coli strains with the deletion of ompR, envZ, cpxA and cpxR genes and antibiotics nalidixic acid and chlortetracycline. Significant changes at expression levels of OmpC and OmpF were detected in the strains exposed to the antibiotics. Outer membrane proteins that were altered in response to the changes of OmpC and OmpF expression levels were identified using proteomics approaches and the networks involved in the regulation of protein changes in response to the antibiotic exposure were constructed. It was found that AtpB was upregulated and downregulated in parallel with the reduced and elevated expression of OmpC in response to chlortetracycline and nalidixic acid exposure, respectively and the change of AtpB was regulated by CpxR. These findings were validated by the detection of OmpC, OmpF and CpxR changes in ΔatpD and ΔphoE. Therefore, this study provides novel insight into the regulation network of TCSs and OM proteins involved in the differential responses of bacteria to different classes of antibiotics.