The regulatory effect of CsrA on cstA, glgCAP and flhDC in an RNase P ts mutant Escherichia coli

CsrA is a global post-transcriptional regulatory protein that has a great impact on many physiological pathways in a cell. It regulates central carbon metabolism, motility and biofilm formation as well as virulence, pathogenesis, quorum sensing and the oxidative stress response. However, CsrA is in turn also regulated by CsrB and CsrC sRNAs, among other factors. In this study, we explore its regulatory effect on three different genes/operons, cstA, glgCAP and flhDC. We performed beta-galactosidase assays on wild type (wt) and RNase P temperature sensitive (ts) cells to determine the dependence on RNaseP for the CsrA, CsrB and CsrC regulatory cascade on these three genes. Our results showed a clear decrease in cstA and glgCAP activity during CsrA activation, suggesting a regulatory cascade in which inhibition of RNase P leads to an inactivation of CsrB and CsrC. This in turn leads to an activation of CsrA and an inhibition of cstA and glgCAP. The effect on flhDC, however, was not as clear and needs further investigation