Transcriptomic analysis of iron transport mutants reveals serovar-specific adaptations in Salmonella enterica

Iron is an essential mineral for almost all pathogenic bacteria, including Salmonella enterica serovar Typhimurium and Enteritidis. We have investigated the effect of the deletion of iroN, fepA, and fhu genes on the transcriptomic profiles of S. Typhimurium and S. Enteritidis strains with double (ΔiroNΔfepA) and triple (ΔfhuΔiroNΔfepA) gene deletions and grown under iron-deficient conditions. Significant changes were observed in the expression of genes involved in virulence, stress-response, and energy metabolism in both Salmonella serovars. The pathways most affected were the tricarboxylic acid cycle, electron transport chain, and stress responses all of which were downregulated while cysteine biosynthesis was upregulated. In general, common and/or related genes were affected in the double and triple mutant strains which indicated that the additional deletion of the fhu gene affected a limited number of genes, although S. Typhimurium showed more differences than S. Enteritidis. Nevertheless, the main difference observed between the mutants of the two serovars grown under iron-depleted conditions is the enhanced upregulation of the flagellum genes in S. Enteritidis. This study reveals evidence of novel interactions between metabolic pathways and virulence under iron limitation, providing insights into adaptive strategies that may contribute to the enhanced virulence of these Salmonella serovars.