Background: Salmonella Typhimurium LPS structure is regulated by the PmrAB, PhoPQ, and RcsCDB systems. Results: Wzz st is required for lipid A modifications. PbgE 2 and PbgE 3 control formation of short O-antigen region. Conclusion: PmrAB system is the master regulator of LPS remodeling, modulating genes that modify lipid A, core, and O-antigen. Significance: Salmonella exhibits complex mechanisms to modulate its LPS, which influences host interaction.

Dps, the most abundant protein during the stationary growth phase, in Salmonella enterica is required for resistance to reactive oxygen species produced by the host during infection. It has been reported that in Salmonella dps expression is controlled by RpoS and Fur proteins. However, the regulation and function of Dps remain to be resolved. In the present work we demonstrate that activation of the complex RcsCDB regulatory system increases dps expression during exponential growth of Salmonella. In addition, we show that such dps upregulation produces high levels of H2O2 resistance. This phenotype allows the bacteria to avoid reactive oxygen species killing at early stages of growth, thus protecting its genetic material.