Propionate reduces the viability of Salmonella enterica Serovar Typhi in macrophages by propionylation of PhoP K102.

Propionate, a major constituent of short chain fatty acids, has recently been reported to be involved in both prokaryotic and eukaryotic lysine propionylation (Kpr). However, the propionylation characteristics of the enteric pathogen Salmonella enterica serovar Typhi (S. Typhi) following invasion of the human gut under the influence of propionate, whether virulence is affected, and the underlying mechanisms are not yet known. In the present study, we report that propionate significantly reduces the viability of S. Typhi in macrophages through intra-macrophage survival assays. We also demonstrate that the concentration of propionate and the propionate metabolic intermediate propionyl coenzyme A can affect the level of modification of PhoP by propionylation, which is tightly linked to intracellular survival. By expressing and purifying PhoP protein in vitro and performing EMSA and protein phosphorylation analyses, We provide evidence that K102 of PhoP is modified by Kpr propionate, which regulates S. Typhi viability in macrophages by decreasing the phosphorylation and DNA-binding ability of PhoP. In conclusion, our study reveals a potential molecular mechanism by which propionate reduces the viability of S. Typhi in macrophages via Kpr.