Toxic effects of Ag(I) and Hg(II) on Candida albicans and C-maltosa: a flow cytometric evaluation

The effects of Ag(I) and Hg(II) on membrane potential and integrity of cell s of Candida albicans and C. maltosa were determined with a flow cytometric procedure that employed an anionic membrane potential-sensitive dye, bis-( 1,3-dibutylbarbituric acid) trimethine oxonol, and a membrane integrity ind icator, propidium iodide. The membrane potentials of cells of both species were reduced rapidly within 15 min of exposure to Ag(I). No threshold dose for Hg(II) existed, and cells of both species lost membrane potential gradu ally in Hg(II) solutions. Cells of both species lost membrane integrity mor e rapidly in Ag(I) solutions than in Hg(II) solutions. In Ag(I) solutions, the decrease in the numbers of cells recoverable in culture occurred at a r ate similar to the rate of cell depolarization and membrane permeabilizatio n. In Hg(II) solutions, loss of cell recoverability preceded the loss of me mbrane potential and membrane integrity. C. albicans, in contrast to C. mal tosa, showed no loss of membrane integrity after exposure to Hg(II) solutio ns for I h. Different rates of binding of Ag(I) and Hg(II) between the two species suggest that the two ions target different primary sites.