The PmrA/PmrB regulatory system controls the expression of the wzzfepE 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 wzzs t and wzzfepE genes. In the present study we investigated the role of the PmrA/PmrB regulatory system in wzzfepE transcription. We report that the direct binding of the PmrA regulator to a specific promoter site induces the expression of the wzzfepE 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 WzzfepE and Wzzst, although the genes for both proteins are regulated in a PmrA-dependent way.

Defensive remodeling: How bacterial surface properties and biofilm formation promote resistance to antimicrobial peptides

“…Some claim that S. enterica Typhimurium mutants in FepE showed higher susceptibility to PmB [119], while others showed no change in susceptibility [122] .…”

“…O-antigen length in these bacteria is defined by WZZst and fepE (WZZfepE) genes regulated by PmrAB TCS [119]. WZZst and fepE code for a long O-antigen and a very long O-antigen, respectively [120,121].…”

S. Typhimurium strategies to resist killing by cationic antimicrobial peptides

“…The biosynthesis of the short, long and very long O-antigen species is controlled by the length regulators: PbgE 2,3 , Wzz ST and FepE, respectively. The expression of these proteins is under the direct control of the PmrAB regulatory system [27, 28]. The presence of O-antigen has been shown to be important to resistance to Polymyxin B since a S. Typhimurium mutant devoid of O-antigen shows high susceptibility to this antimicrobial peptide [29].…”

“…The presence of O-antigen has been shown to be important to resistance to Polymyxin B since a S. Typhimurium mutant devoid of O-antigen shows high susceptibility to this antimicrobial peptide [29]. However, S. Typhimurium mutants devoid of long and/or very long O-antigen species show only a mild increase in susceptibility to Polymyxin B [27, 29] and the LPS of PhoP constitutive strains present shorter O-antigen chains [30, 31]. Together this suggests that short O-antigen chains are sufficient in providing a barrier against Polymyxin B and possibly other antimicrobial peptides.…”

Molecular Mechanisms Used by Salmonella to Evade the Immune System

“…1 Regulation of O-antigen length by the PmrA/PmrB system (Farizano et al, 2012;Pescaretti et al, 2011). 2 Modification of the anionic phosphate groups in the core and lipid A regions of the LPS by addition of aminoarabinose and phosphoethanolamine.…”