Nukacin ISK-1, a bacteriostatic lantibiotic.

We determined the mode of action of nukacin ISK-1. It did not cause membrane potential dissipation or the efflux of ATP or K(+) ions from the cells of a sensitive bacterial strain; however, it blocked the membrane depolarization activity of nisin. Nukacin ISK-1-treated cells had single arrangements of cells without the formation of a complete septum. A remarkable reduction in cell wall width was also observed, but cytoplasmic content was unaffected. We concluded that nukacin ISK-1 is bacteriostatic.