Functional characterization of iucC and iucD in iron acquisition and virulence of Cronobacter sakazakii

Cronobacter is a group of opportunistic pathogens frequently associated with food contamination, particularly in powdered infant formula, posing a serious health risk to neonates and young children. Iron acquisition systems are critical for bacterial survival and virulence, with the iucABCD-iutA operon encoding the aerobactin siderophore synthesis pathway playing a central role.

Transcriptomic analysis comparing iron-limited and iron-replete conditions was performed to identify iron-responsive genes in Cronobacter. Single-, double-knockout, and corresponding complementation strains targeting iucC and iucD were constructed and systematically evaluated for siderophore production, intracellular iron accumulation, and host cell interaction.

Transcriptomic analysis revealed global changes in gene expression under iron-limited conditions, particularly in iron acquisition-related pathways, with iucC and iucD significantly upregulated. Deletion of iucC and iucD markedly reduced siderophore production and total intracellular iron content, and significantly impaired bacterial adhesion to and invasion of Caco-2 cells.

These findings highlight the essential roles of iucC and iucD in Cronobacter iron acquisition and pathogenicity and suggest that the aerobactin synthesis pathway may represent a potential target for future anti-infective strategies.