Revealing the inhibitory mechanism of carvacrol on physiological function and virulence expression of L. monocytogenes by transcriptome analysis

Foods in our daily life are susceptible to contaminate by L. monocytogenes due to its high stress resistance and wide distribution, which poses great risks to food safety. Carvacrol is the natural compound that has been recognized as the safe additives and can be utilized safely by food industry. The current study aimed to study the inhibitory effect and mechanism of carvacrol against L. monocytogenes. The results showed that carvacrol treatment resulted in disruption of cell integrity of L. monocytogenes, further led to leakage of intracellular substances. In addition, carvacrol treatment inhibited the activity of topoisomerase and β-galactosidase, which in turn affected the gene duplication and energy utilization of L. monocytogenes. Based on transcriptome analysis, it was found that 126 differential expression genes (DEGs) were existed between carvacrol treated groups and control groups, which were highly enriched in transmembrane transporter activity and transporter activity. In addition, those DEGs were enriched in 4 metabolic pathways with obvious enrichment including phosphotransferase system, starch and sucrose metabolism, quorum sensing, alanine, aspartic acid and glutamic acid metabolism. Finally, carvacrol treatment can inhibit the secretion or activity of hemolysin in L. monocytogenes, which was consistent with the result in transcriptome analysis. In conclusion, carvacrol could be a potential antimicrobial substance to inhibit the contamination of L. monocytogenes in foods.