Undecaprenyl Pyrophosphate Phosphatase ( <scp>UppP</scp> ) is a Pivotal Element in <i>Salmonella</i> Intramacrophage Survival

To establish infection, Salmonella confronts a dynamic barrage of host-induced stresses. The peptidoglycan layer is essential for maintaining bacterial cell integrity and counteracting these environmental stress. Its synthesis relies on the lipid carrier undecaprenyl phosphate, which is generated by the enzyme undecaprenyl pyrophosphate phosphatase (UppP). While UppP is linked to virulence in other pathogens, its role in Salmonella remains unclear. We show that an uppP mutant in S. Typhimurium exhibits altered cell morphology, reduced stiffness, and impaired survival in RAW 264.7 macrophages. The mutant is also attenuated in systemic infection in C57BL/6 mice. These defects are associated with increased sensitivity to nitrosative stress. Notably, iNOS inhibition or deficiency restores intracellular survival of the uppP mutant in both RAW 264.7 macrophages and the mouse model, implicating UppP in resistance to nitrosative stress. Our findings reveal a critical role for UppP in promoting Salmonella survival within macrophages and contributing to systemic pathogenesis.