The longterm goal of this work is to elucidate the mechanistic basis and regulation of an antagonistic interaction between Oomycete fungi and a strain of Bacillus cereus. A strain of B. cereus has been identified that prevents infection of seedlings by a variety of Oomycete fungi. The ability to prevent infection is associated with a low molecular weight, extracellular peptide. The objectives of the proposed research are to purify the antifungal peptide, determine its structure, begin to determine its mode of action on the fungus, and to identify the genes required for its biosynthesis. The genetic analysis will involve identification of transposon mutants that lack antifungal activity, and cloning of the wild-type genes that restore activity to the mutants. An alternative approach to identify the appropriate genetic sequence will be to shot-gun clone DNA from the antifungal strain of B. cereus into either E. coli or B. subtilis, and identify the desired recipients by screening for antifungal activity. Identification of the genes involved in production of the antifungal agent will provide the basis for elucidating the pathway and regulation of its biosynthesis. The results of this research will provide important basic information about biochemical mechanisms involved in plant- microbe interactions. This fundamental information may, in the future, be useful in developing ecologically sound methods for protection of plants from fungal pathogens.
