Down-regulation of RpoN-controlled genes protects Salmonella cells from killing by the cationic antimicrobial peptide polymyxin B

JULIETA BARCHIESI; MARTÍN ESPARIZ; SUSANA K. CHECA; FERNANDO C. SONCINI

FEMS MICROBIOLOGY LETTERS

Blackwell Publishing Ltd.

Año: 2009 vol. 291 p. 73 - 79

0378-1097

Salmonella enterica polymyxin B resistance is modulated mainly by substitutions of the acyl chains and the phosphate groups on the lipid A moiety of lipopolysaccharide. These modifications are mediated by genes under the control of the PmrA/PmrB and PhoP/PhoQ two-component regulatory systems. In this study, a deletion in the gene encoding the alternative ó54 factor, rpoN, was shown to increase polymyxin B resistance without affecting protamine sensitivity. The results presented here showed that the increased polymyxin resistance observed in the DrpoN mutant occurs through a PmrA/PhoP independent pathway. Down regulation of one or more genes belonging to the RpoN regulon may provide an additional mechanism of defence against membrane-permeabilizing antimicrobial peptides that helps the pathogen to survive in different environments.