Objectives. To determine the mechanism of antimicrobial action of lactocin 160, a bacteriocin produced by the healthy vaginal strain of Lactobacillus rhamnosus , using an established model, with Micrococcus luteus ATCC 10420 as a test organism. Methods. Sensitivity of M. luteus to lactocin 160 was determined by the diffusion assay. Loss of cellular ATP in the lactocintreated cells was elucidated using a commercially available ATP determination kit (luciferin-luciferase bioluminescence assay). Luminescence intensity as a reflection of ATP quantity was determined using a luminometer. Dissipation of membrane potential (Δψ) was studied using fluorophoreDiSC3(5) with the fluorescence spectrum sensitive to changes in Δψ. Results. Lactocin 160 inhibited growth of M. luteus ATCC 10420 at a concentration of 5 μg/ml. There were no significant changes in the intracellular ATP level of M. luteus upon the addition of 20 μg/ml of lactocin 160. However, the extracellular ATP level increased significantly. This means that the treatment of cells with lactocin 160 resulted in an efflux of ATP from inside the cells. Therefore, a partially purified lactocin 160 preparation (16 μg /ml of the bacteriocin in the sample) killed sensitive cells and dissipated 3.12±0.36% of Δψ. Conclusion. Lactocin 160 has a mode of action typical for bacteriocins. It disturbs the cellular membrane (Δψ dissipation) and induces ATP efflux, most likely because of the pore formation, which is a common mechanism of action for many bacteriocins.
Li, J., Aroutcheva, A. A., Faro, S., & Chikindas, M. L. (2005). Mode of Action of Lactocin 160, a Bacteriocin From Vaginal Lactobacillus rhamnosus . Infectious Diseases in Obstetrics and Gynecology, 13(3), 135–140. https://doi.org/10.1080/10647440500148156