Growth suppression of some wood-decay and other fungi by Bacillus subtilis

The antagonistic activity of an isolate of Bacillus subtilis was examined against five wood-decay fungi (Coriolus spp., Poria sp., Stereum sp., Hexagonia discopoda, and Schizophyllum commune) and five other fungi (Candida sp., Fusarium sp., Curvularia geniculata, Penicillium digitatum, and Trichoderma viride). The effect of the bacterium on the fungi was tested using aerated growth on potato dextrose agar, non-aerated (partially anaerobic) growth on potato dextrose agar, and growth in potato dextrose broth supplemented with cell-free filtrate of broth in which B. subtilis was previously cultured. All 10 fungal species were inhibited by water-soluble factors produced by the bacterium. Nine of the 10 species were adversely affected by volatiles synthesised by the bacterium. Varying degrees of inhibition were observed in the fungi in response to the presence of cell-free filtrate of B. subtilis in broth medium. The results of this study confirm the dual nature (production of antifungal volatile compounds in addition to water-soluble agents) of antagonism manifested by B. subtilis and the thermostable property of the antifungal factors it synthesises. It also broadens the range of fungi proven to be inhibited by the bacterium.