[Changes in growth patterns and intracellular calcium concentrations in aspergillus awamori treated with amphotericin...

Growth patterns and intracellular Ca2+ concentrations in the mutant strain Aspergillus awamori 66A, containing a recombinant aequorin gene were studied in the presence of a permeabilizing fungicidal agent amphotericin B. The cell response, i.e., changes in the growth and development of the fungus (initiation of spore germination, mycelial growth, and intensity ofsporulation) was dose-dependent. Low concentrations of amphotericin B (2.5 microM) stimulated spore germination: the number of germinating spores was 2-3 times higher than in the control (without the fungicide). At higher amphotericin concentrations (20 microM) spore germination was inhibited. Amphotericin B had a dose-dependent effect on mycelial growth and sporulation intensity on solid Vogel medium. Intracellular Ca2+ concentrations in the presence of amphotericin B were investigated using the luminescence of the photoprotein aequorin. High concentrations of amphotericin B (10 and 20 microM) were shown to cause an instantaneous increase in Ca2+ concentrations, compared to the control and lower amphotericin concentration (2.5 microM). Ca2+ concentrations remained elevated throughout the experiment and correlated with the inhibition of mycelial growth and development.