Abstract:Objective Cronobacter sakazakii (C. sakazakii), a milk-borne pathogen leading to high mortality, is hard to be controlled in dairy processing due to its special cell characteristics and strong environmental stress resistance. C. sakazakii produces carotenoids which are located in the cell membrane, while there are few studies on the physiological role of C. sakazakii carotenoids. This study aims to explore the effects of β-carotene hydroxylase gene (crtZ) deletion and complementation on cell characteristics and stress resistance and decipher the potential mechanisms.Method Using Red homologous recombination, the BAA-894ΔcrtZ (ΔcrtZ) mutant was constructed from C. sakazakii BAA-894 (BAA-894), and crtZ was complemented with pWSK29 to generate BAA-894ΔcrtZ/pWSK29-crtZ (ΔcrtZ/pWSK29-crtZ). The cellular characteristics and fatty acid profiles of these strains were then analyzed.Result Compared with BAA-894, ΔcrtZ exhibited enhanced outer membrane permeability, reduced membrane fluidity and biofilm formation, and attenuated resistance to various environmental stresses, whereas these changes were diminished in ΔcrtZ/pWSK29-crtZ. In addition, the number and mass fraction of unsaturated fatty acids increased significantly in ΔcrtZ, while they showed no notable changes in ΔcrtZ/pWSK29-crtZ.Conclusion Deletion of crtZ may be a critical factor influencing the cellular characteristics and environmental stress resistance of C. sakazakii. This study contributes to the theoretical understanding of stress resistance mechanisms in C. sakazakii and provides insights for food safety control strategies.
