The First report on Acyl Homoserine Lactone (AHL) enhanced expression of virulence factor, hemolysin in Gram positive, Listeria monocytogenes strain BN3 isolated from dairy industry

Abstract

Gram-positive, Listeria monocytogenes (Lm) are well-known bacterial pathogens causing listeriosis in humans. Lm is known to control its gene expression encoding virulence factors via agr peptide based quorum sensing (QS). In our previous study we had reported Lm strain BN3 isolated from milk collecting utensils in dairy industry, do not produce AHL molecule which is typical autoinducers in Gram-negative bacteria but respond to AHL molecules by enhanced biofilm formation in concentration dependent manner. In the present study response of Lm strain BN3 to N-hexanoyl-homoserine lactone (C6-HSL) by production of virulence factor, hemolysin was investigated using sheep blood agar well diffusion assay. Increased hemolysin production was observed in response to increasing concentration of AHL molecules (100 nM, 250 nM and 500 nM) as seen by blood hemolysis on blood agar plate. This is the first report on expression of virulence factor (hemolysin production) by Lm in response to AHL molecules which are usually produced by Gram negative bacteria. This study will help to further investigate cross-talk between Gram positive and Gram-negative bacteria, which share common econiche in the dairy industry.