Inactivation of Cronobacter sakazakii by Blue Light and the Mechanism
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Abstract:
Blue light (BL) had been employed in medicine recently to inactivate bacteria, while its mechanism needed to be investigated. Thus, this work conducted herein examined the bactericidal effect of BL on the food borne pathogen Cronobacter sakazakii, and the underlying mechanism. The results showed that BL above 30 J/cm2 exhibited an efficient bactericidal effect against C. sakazakii, and an inactivation rate above 8 log10 CFU was achieved under 240 J/cm2. Under the sublethal BL dose, singlet oxygen (1O2) and reactive oxygen species (ROS) were rapidly produced and gradually increased, followed by the emergence of malondialdehyde (MDA), indicating lipid oxidation in cells. Moreover, the permeability of the outer membrane of cell increased by 48.96% at 30 J/cm2, indicating injury to cell membranes. Results of fatty acid spectra showed that the contents of unsaturated fatty acids C18:2, C16:1 and C18:1 decreased and disappeared. This work confirmed at the first time the dynamic change of intracellular 1O2、ROS and MDA, and especially, revealed that damage on cell outer membrane was one the inactivation means of BL, because bacterial lipids, especially unsaturated fatty acids, are important targets for BL. These results will contribute to the study of the mechanism of blue-light sterilization.
