Expression ofSTM4467-Encoded Arginine Deiminase Controlled by theSTM4463Regulator Contributes to Salmonella enterica Serovar Typhimurium Virulence
ABSTRACTArginine deiminase (ADI), carbamate kinase (CK), and ornithine transcarbamoylase (OTC) constitute the ADI system. In addition to metabolic functions, the ADI system has been implicated in the virulence of certain pathogens. The pathogenic intracellular bacteriumSalmonella entericaserovar Typhimurium possesses theSTM4467,STM4466, andSTM4465genes, which are predicted to encode ADI, CK, and OTC, respectively. Here we report that theSTM4467gene encodes an ADI and that ADI activity plays a role in the successful infection of a mammalian host byS. Typhimurium. AnSTM4467deletion mutant was defective for replication inside murine macrophages and was attenuated for virulence in mice. We determined that a regulatory protein encoded by theSTM4463gene functions as an activator forSTM4467expression. The expression of the ADI pathway genes was enhanced inside macrophages in a process that required STM4463. Lack of STM4463 impaired the ability ofS. Typhimurium to replicate within macrophages. A mutant defective inSTM4467-encoded ADI displayed normal production of nitric oxide by macrophages.