EnvZ is Not Essential for the Upregulation of OmpC Following Treatment with Sublethal Kanamycin in Escherichia coli

Abstract

Increased OmpC expression and kanamycin resistance has been observed in Escherichia coli exposed to sublethal concentrations of kanamycin. However, the regulatory pathway through which kanamycin induces OmpC upregulation has not been elucidated. It is known that Escherichia coli detects increased environmental osmolarity via a membrane-bound sensor, EnvZ, and modulates OmpC and OmpF porin expression to limit permeability of the outer membrane. This study investigated the necessity of EnvZ in the induction of OmpC upregulation following high salt or kanamycin treatment. Our results showed that pre-treatment with either salt or kanamycin led to an increase in OmpC expression in the Δ env Z strain but not the wild type strain. Overall, the results suggest that EnvZ is not an essential protein for the upregulation of OmpC in response to high salt or kanamycin, and that other mechanisms may compensate for the loss of EnvZ. Furthermore, OmpC upregulation is not crucial in the conferred resistance to lethal concentrations of kanamycin following salt or sublethal treatment.