Biofilm genes expression of Listeria monocytogenes exposed to Latilactobacillus curvatus bacteriocins at 10 °C

Abstract

Listeria monocytogenes is a foodborne pathogen able to survive in a wide range of conditions, including low temperatures, being highly persistent in the food-processing environments. Anti-listerial bacteriocins produced by Latilactobacillus curvatus CRL705 and CRL1579 were used to prevent/control biofilm formation of L. monocytogenes FBUNT, Scott A and CECT 4031T strains at 10 °C and genes transcription was evaluated. Sub-inhibitory concentrations of bacteriocins were able to reduce biofilm after six days at 10 °C, which was confirmed by crystal violet staining, motility assay and confocal laser scanning microscopy. When a set of thirty genes related to adhesion, virulence and stress response were investigated by using RT-qPCR, adaptation of L. monocytogenes to the concurrence of cold and bacteriocin stresses induced the expression of luxS, agrA, agrB, cspB and cell surface proteins related to biofilm formation genes for the three Listeria strains, whereas actA gene decreased and sigB gene increased its transcription, showing changes in the relative expression (log2) between −2 and 4-fold for Scott A and CECT 4031T strains in presence of lactocin AL705. Results showed that bacteriocin treatment affected the expression levels of most genes, while a lack of transcription of the virulence regulatory prfA was observed in the assayed strains. In addition, some genes related to energy production and sugar transport were up-regulated, exhibiting up to 1.8-fold changes in the presence of the bacteriocins. A better understanding of bacteriocins, particularly of lactocin AL705, to control biofilm formation of L. monocytogenes strains on abiotic surfaces at 10 °C, was achieved. Bacteriocins represent a successful intervention strategy to mitigate post-processing contamination.