Yanbo Wang,Feifei Wang,Xiaoshuang Zhang,Congnan Cen,Linglin Fu
Shewanella baltica is the specific spoilage microorganism of Pseudosciaena crocea during low-temperature storage. Exploring the correlation between cold adaptability and spoilage potential may provide a new perspective for prolonging shelf life of aquatic products. In the present study, we investigated the synthesis pathway of unsaturated fatty acid (UFA) responsible for regulating cold adaptability in Shewanella baltica and its effect on spoilage potential. FabR and FadR, as key regulators of membrane unsaturated fatty acids synthesis pathway, were identified in S. baltica . FabR was significantly down-regulated at 4 °C compared to at 30 °C, yet FadR displayed the opposite results. By overexpressing fabR and fadR genes at 4 °C, we found that FabR and FadR had negative and positive effects on UFA content and membrane fluidity as well as spoilage potential, respectively. These data indicated that FabR and FadR functioned collectively to increase the membrane fluidity for better cold adaptability at low temperature, resulting in the maintenance of spoilage potential of S. baltica .
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.
危险品化学品经营许可证（带存储）