The mode of action of bacteriocin CHQS, a high antibacterial activity bacteriocin produced by Enterococcus faecalis TG2

This study aims to examine the inhibitory effects of the bacteriocin CHQS, produced by Enterococcus faecalis TG2, and its mode of action against Listeria ivanovii DSMZ 20750T, which is one of the pathogens sensitive to CHQS. The minimum inhibitory concentration, minimum bactericide concentration and time-inhibition curves were measured to confirm the strong effects of CHQS on L. ivanovii DSMZ 20750T, and its antibacterial mode of action was studied by observing the changes in cell membrane permeability, integrity, and proton motive force. The minimum inhibitory concentration and minimum bactericide concentration of CHQS were 26.74 ng/mL and 107.30 ng/mL, respectively, demonstrating that CHQS exhibited significantly strong and rapid antibacterial efficacy towards L. ivanovii DSMZ 20750T. The results showed that CHQS led to the leakage of K+ and electrolytes, the massive release of ATP and UV-absorbing materials, and the collapse of the proton motive force. The micrographs of scanning electron and transmission electron microscopy demonstrate the severe cellular destruction and release of intracellular substances induced by bacteriocin CHQS. Collectively, this study reveals the antibacterial activity and mode of action of CHQS against L. ivanovii DSMZ 20750T and demonstrates the mode of action of the inhibition by bacteriocins.