The role of RpoS, H-NS and AcP on the pH-dependent OmpC and OmpF porin expressions of <i>Escherichia coli</i> at different pH

Abstract

It is generally accepted that OmpC and OmpF porin proteins have important roles to play in the survival of Escherichia coli under different environmental conditions. However, the influence of different
environmental conditions on porin expression is not as well known. This work was carried out to find out the effect of envZ, ompR, rpoS, pta and hns mutations on the pH-dependent ompC and ompF expression in E. coli in minimal medium at different pH. The expression of ompF was higher in cells grown in an alkaline pH, and the expression of ompC increased at the acidic pH value. There was lowlevel expression of ompC and ompF in envZ mutants. The expression of ompC was increased in the presence of NaCl at three tested pH values while that was reduced in the case of OmpF. The level of expression of ompF in the strain with the rpoS mutation was greatly increased at all pH values and in the presence and absence of NaCl. The expression of ompC in the pta mutant was greatly increased compared to the wild type E. coli at all pH values in the presence and absence of NaCl. There was no expression of ompC and ompF in the ompR mutants. Mutations in hns and pta had variable effects on the expression of ompC and ompF in the presence and absence of NaCl. Overall, this work shows that although OmpC and OmpF porin protein synthesis was affected according to pH, it was not a direct role of RpoS, HNS, EnvZ and Acp at pH-depending porin expression.