The Effect of Hydrogen Peroxide on the Growth of Microscopic Mycelial Fungi Isolated from Habitats with Different Levels of Radioactive Contamination

The effect of hydrogen peroxide (10^?9–10^?1 M) on the mycelial growth of the fungi Alternaria alternata, Cladosporium cladosporioides, Mucor hiemalis, and Paecilomyces lilacinus has been studied. The growth of fungi isolated from habitats with a background level of radioactive contamination was stopped by H₂O₂ concentrations equal to 10^?3 and 10^?2 M, whereas the growth of fungi that were isolated from habitats with high levels of radioactive contamination was only arrested by 10^?1 M H₂O₂. The response of the different fungi to hydrogen peroxide was of three types: (1) a constant growth rate of fungal hyphae at H₂O₂ concentrations between 10^?9 and 10^?4 M and a decrease in this rate at 10^?3 M H₂O₂, (2) a gradual decrease in the growth rate as the H₂O₂ concentration was increased, and (3) an increase in the growth rate as the H₂O₂ concentration was increased from 10^?6 to 10^?5 M. The melanin-containing species A. alternata and C. cladosporioides exhibited all three types of growth response to hydrogen peroxide, whereas the light-pigmented species M. hiemalis and P. lilacinus showed only the first type of growth response. A concentration of hydrogen peroxide equal to 10^?1 M was found to be lethal to all of the fungi studied. The most resistant to hydrogen peroxide was found to be the strain A. alternata 56, isolated from the exclusion zone of the Chernobyl Nuclear Power Plant.