Fatty acid metabolism governed by FadR is essential for Cronobacter sakazakii survival in dry food matrices and neonatal infection

Cronobacter sakazakii poses significant neonatal health risks due to its exceptional desiccation tolerance and virulence, yet the molecular mechanisms linking membrane lipid regulation to these traits remain poorly defined. This study characterizes the global regulator FadR (ESA_01467) as a key modulator of fatty acid metabolism, membrane fluidity, and pathogenicity. Deletion of fadR resulted in a 52 % decrease in adhesion and 61 % reduction in invasion of intestinal epithelial cells, alongside attenuated virulence and reduced bacterial loads in a neonatal rat model. Proteomic and lipidomic analyses revealed downregulation of FabA and FabB, upregulation of beta-oxidation enzymes, and a 25 % increase in membrane rigidity associated with decreased levels of palmitoleic and oleic acids. The Δ fadR mutant showed a 3.2-log reduction in viability following 14 days of desiccation in phosphate-buffered saline, while survival in milk powder remained unaffected. Supplementation with milk-derived long-chain fatty acids restored both membrane fluidity and desiccation survival to wild-type levels. These findings establish FadR as a central regulator linking lipid homeostasis to environmental adaptation and virulence in C. sakazakii , providing mechanistic insight into its persistence in dry food environments and infection risk.