LISTERIA MONOCYTOGENES STRAIN BN3 RESPONDS TO ACYL HOMOSERINE LACTONE (AHL) BY EXPRESSION OF VIRULENCE GENE (HLYA) AND GENE RESPONSIBLE FOR BIOFILM (SRTA)

Listeria monocytogenes, a foodborne pathogen and well known causative agent of listeriosis in humans that is also known to form biofilm on utensils used in the dairy industry is well studied for peptide-based Quorum sensing system (agr QS system). In the present study, we are reporting L. monocytogenes strain BN3 to respond to an acyl-homoserine lactone (AHL) by expression of virulence gene (hlyA) and the gene responsible for biofilm formation (srtA) using Real-Time PCR technology. It revealed that in L. monocytogenes, hlyA gene (encodes listeriolysin O) expression increased 0.7-fold in response to 500 nM AHL (C4-HSL treated) as compared to control. Also, in response to 500 nM AHL, (C4-HSL treated) strain BN3 showed 27-fold up-regulation of srtA gene (encodes enzyme sortase) as compared to control. Our study confirmed the cross-talk between Gram-positive and Gram-negative bacteria since L. monocytogenes strain BN3 responds to C4-HSL, which is normally produced by Gram-negative bacteria. Here, we suggest targeting both agr based QS and AHL based QS system together in L. monocytogenes to tackle biofilm formed on milk cans in dairy industries and when treating listeria infections.