EFFECTS OF CRYPTOCOCCUS-HUMICOLA KILLER TOXIN UPON CRYPTOCOCCUS-TERREUS ENVELOPE - COMBINED FLUOROMETRIC AND MICROSCOPIC STUDIES

Killer toxin (microcin) produced by Cryptococcus humicola 9-6 induced interaction of the fluorogenic dyes, ethidium bromide, propidium iodid e, and hemimagnesium 8-anilino-1-naphtalenesulfonate, with the sensiti ve strain of Cryptococcus terreus VKM Y-2253. The toxin also made the cells susceptible to cetyltrimethylammonium bromide and leaky for K+. When excited at 360 nm, cell-bound ethidium (propidium) fluorescence w as enhanced by 8-anilino-1-naphtalensulfonate, and cell-bound 8-anilin o-1-naphtalensulfonate fluorescence was quenched by ethidium (propidiu m), indicating energy transfer from 8-anilino-1-naphtalensulfonate to ethidium (propidium). These results suggest that at least a portion of the probe molecules had the same binding site, possibly the cytoplasm ic membrane. The parameters of kinetics of microcin action were evalua ted fluorometrically. They were found to be identical for all probes a nd depended on microcin concentration. The fluorescence increment of e thidium and 8-anilino-1-naphtalensulfonate upon binding to microcin-tr eated cells correlated with the fraction of stainable cells and viabil ity. (C) 1998 Elsevier Science B.V. All rights reserved.