Transcriptomic analysis of iron transport mutants reveals serovar-specific adaptations in <i>Salmonella enterica</i>

Iron is an essential mineral for almost all pathogenic bacteria, including <i>Salmonella enterica</i> serovar Typhimurium and Enteritidis. We have investigated the effect of the deletion of <i>iroN</i>, <i>fepA</i>, and <i>fhu</i> genes on the transcriptomic profiles of <i>S.</i> Typhimurium and <i>S.</i> Enteritidis strains with double (<i>Δ</i><i>iroN</i><i>Δ</i><i>fepA</i>) and triple (<i>Δ</i><i>fhu</i><i>Δ</i><i>iroN</i><i>Δ</i><i>fepA</i>) 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 <i>Salmonella</i> 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 <i>fhu</i> gene affected a limited number of genes, although <i>S.</i> Typhimurium showed more differences than <i>S</i>. 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 <i>S.</i> 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 <i>Salmonella</i> serovars.