Mode of action of an antifungal bacteriocin produced by a marine Bacillus sp. Sh10

bacteriocins are antimicrobial peptides produced by different bacteria and can be applied as a therapeutic agent. The aim of this study was to investigate the mode of action of broad-spectrum bacteriocin produced by a marine Bacillus strain Sh10, on Candida albicans ATCC 10231.

Cell viability assay, determination of UV-absorbing materials, K+, inorganic phosphate, ATP, and LIVE/DEAD cell viability assay as well as scanned and transmission electron microscopy were used to investigate the mode of action of bacteriocin.

The addition of 1 × MIC of bacteriocin to a cell suspension of C. albicans decreased the number of viable cells by about 4 log units over a period of 10 h. It displayed a fungicidal mode of action with a massive leakage of K+ ions, inorganic phosphates, ATP, and UV-absorbance materials, leading to cell lysis. In addition, the permeability of C. albicans treated cells to propidium iodide was also observed. The microscopic observations of treated cells indicated several modifications in cell morphology such as wrinkled surface, discontinuous and ruptured cell wall with concomitant lysis.

The data obtained in the current study demonstrated that the present bacteriocin interacted with the cytoplasmic membrane of C. albicans cells, resulting in pore formation, which allowed for the efflux of intracellular materials, ultimately leading to cell death.