The Repair Mechanism of Sublethal Salmonella by Intense Pulsed Light Treatment

Abstract

Salmonella is one of the most common foodborne pathogens that can survive broadly in food processing environments. In recent years, intense pulsed light (IPL) technology, as a novel non-thermal sterilization method, has been increasingly applied to the inactivation of microorganisms in food processing industry. In this study, IPL (only 0.98J/cm2/pulse luminous flux) showed different bactericidal capacity for Salmonella in water, LB broth, and on the surface of chicken, respectively reducing by approximately 5, 2.11 and 1.77 log CFU/mL after one application performed at a 3cm distance. The differences were speculated that sublethal injury to Salmonella was induced by IPL treatment and could be repaired in a nutrient environment such as foods or broths. To elucidate the repair mechanism, several intracellular oxidative damage enzymes were measured in sublethal Salmonella with IPL treatment, and then the differentially expressed genes of the sublethal cells were examined by RNA-seq. According to the results, Salmonella mainly depended on two ways to repair the damage caused by IPL. First and foremost, Salmonella repair the membrane protein structure by reducing the diameter of porin, increasing the synthesis of fimbria, and releasing disulfide bonds damaged by reactive oxygen species through TrxR protein. Besides, Salmonella repaired the DNA at the damaged site by interrupting DNA replication, activating the SOS system and the DNA double-strand break repair system. In conclusion, this study systematically analyzed the repair mechanism of Salmonella under IPL stimulus, and provides a new idea for reducing and controlling pathogenic bacteria in the food industry.

Keywords: Salmonella Enteritidis, RNA-seq, IPL, DNA repair, membrane repair, food processing industry