REGULATION OF SPVR, THE POSITIVE REGULATORY GENE OF SALMONELLA PLASMID VIRULENCE GENES

The regulation of the spvR promoter from the Salmonella dublin virulen ce plasmid was monitored using promoter-reporter gene fusion construct s. Activity was dependent upon the presence of the spv region and was affected by the number of copies of the spv region present within the cell. Activity remained constant throughout exponential growth, and in creased rapidly with the onset of stationary phase, under both aerobic and anaerobic conditions. Additionally, the level of spvR expression was controlled by the availability of iron, activity being greatest un der low iron conditions in stationary phase. The spvA gene product neg atively regulated spvR expression in a dose-dependent manner, indicati ng that SpvA provides a negative feedback mechanism far this operon.