Mechanism of Antagonism of Oomycete Fungi by Bacillus cereu

这项工作的长期目标是阐明卵菌和蜡状芽孢杆菌之间拮抗相互作用的机制基础和调节。已鉴定出一种蜡状芽孢杆菌菌株，可防止各种卵菌真菌对幼苗的感染。预防感染的能力与一种低分子的胞外肽有关。这项研究的目的是提纯抗真菌多肽，确定其结构，开始确定其对真菌的作用方式，并鉴定其生物合成所需的基因。遗传分析将包括鉴定缺乏抗真菌活性的转座子突变体，以及克隆恢复突变体活性的野生型基因。另一种确定适当遗传序列的方法是将蜡状芽孢杆菌抗真菌菌株的DNA枪击克隆到大肠杆菌或枯草杆菌中，并通过筛选抗真菌活性来识别所需的接受者。鉴定参与抗真菌药物产生的基因将为阐明其生物合成的途径和调控提供基础。这一研究结果将为了解植物-微生物相互作用的生化机制提供重要的基础信息。这些基本信息在未来可能有助于开发保护植物免受真菌病原体侵袭的生态无害方法。

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.