Mechanism by Which Laser Irradiation Combined with Spirulina platensis Enhances FeSO₄-Induced Ferroptosis in Salmonella Typhimurium and Listeria monocytogenes

To explore the mechanism by which laser (L) irradiation combined with Spirulina platensis (SP) enhances ferroptosis induced by FeSO₄ (Fe) in Salmonella enterica serovar Typhimurium (ST) and Listeria monocytogenes (LM), this study measured lipid peroxidation, reactive oxygen species (ROS), glutathione (GSH), morphological characteristics, cell membrane damage, and expression levels of key genes in the two foodborne pathogens after different treatments. The results showed that the L + SP treatment significantly enhanced the bactericidal effect of FeSO₄. The 4 mmol/L Fe + SP + L treatment reduced the counts of both ST and LM to less than 1.4 (lg(CFU/mL)). Additionally, the Fe + SP + L treatment led to increased lipid peroxidation and ROS production and decreased proportion of GSH, thereby damaging the integrity of the cell membrane, increasing the permeability of the cell membrane, decreasing the membrane potential, increasing the leakage of intracellular nucleic acids and proteins, and ultimately resulting in the death of bacteria. In addition, the biofilm inhibition and inactivation experiments showed that the 4 mmol/L Fe + SP + L treatment had an excellent antibiofilm capacity. Finally, the counts of ST and LM on lettuce were significantly decreased to 4.63 and 4.60 (lg(CFU/g)), respectively, after the 4 mmol/L Fe + SP + L treatment. In conclusion, the Fe + SP + L treatment could effectively reduce the counts of ST and LM in both planktonic and biological states, indicating its good potential for controlling foodborne pathogens on the surface of lettuce and other foods.