Enzyme IIANtr Is Associated with Both Regulation of Propionate Metabolism and the Ability of Invasion in Salmonella enterica serovar Typhimurium

Abstract

Salmonella Typhimurium is one of the major food-borne pathogens which can infect a wide range of animals and cause food-borne gastroenteritis in millions of people worldwide. The ability of Salmonella to cause disease depends on metabolic activities and various virulence factors. Many Gram-negative bacteria including Salmonella have two parallel phosphotransferase systems and these are also known to be associated with bacterial virulence as well as metabolic and regulatory mechanisms. One system is phosphoenolpyruvate:carbohydrate phosphotransferase system (carbohydrate PTS) and the other is nitrogen-related phosphotransferase system (nitrogen-related PTS

PTSNtr). Enzyme IIANtr (EIIANtr), one component of PTSNtr, has been reported to show varieties of regulations associated with metabolism of carbon and nitrogen, potassium homeostasis, and virulence of some pathogens. In order to understand roles of EIIANtr further, I selected many genes showing noticeable differences of expression levels from RNA-sequencing data of wild-type and a mutant strain lacking ptsN. The expression levels of targeted genes are verified by quantitative real-time PCR and β-galactosidase assay. Interestingly, one of the highly down-regulated genes in the ptsN mutant was the propionate catabolism operon (prpBCDE). Even though prpR encoding regulator protein and rpoN encoding sigma factor 54 (σ54) are required for the expression of the propionate operon, the transcriptional levels of prpR and rpoN were not down-regulated by the ptsN mutation. The hilA expression was increased but the invasion ability of Salmonella was reduced in the ptsN mutant under SPI-1 inducing conditions. These results suggest that EIIANtr is required for the virulence of Salmonella as well as metabolism of alternative carbon source.