The PmrA/PmrB regulatory system controls the expression of the wzz fepE gene involved in the O-antigen synthesis of Salmonella enterica serovar Typhimurium

Abstract

The degree of polymerization of O-antigen from Salmonella enterica serovar Typhimurium is controlled by the products of the wzz st and wzz fepE genes. In the present study we investigated the role of the PmrA/PmrB regulatory system in wzz fepE transcription. We report that the direct binding of the PmrA regulator to a specific promoter site induces the expression of the wzz fepE gene. This effect increases the amount of very long (VL) O-antigen, which is required for the resistance of Salmonella to serum human complement and polymyxin B, and for the replication of the bacteria within macrophages. The results obtained here highlight functional differences between Wzz fepE and Wzz st, although the genes for both proteins are regulated in a PmrA-dependent way.