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Control of Toxic Endophytic Fungi with Bacterial Endophytes and Regulation of Bacterial Metabolites for Novel Uses in Food Safety

Riley, Ronald; Hinton, Jr., Arthur; Gold, Scott; Glenn, Anthony (Tony); Bacon, Charles
USDA - Agricultural Research Service
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1. Determine the potential and genetic mechanisms involved in horizontal gene transfer from Gram-negative pathogenic bacteria to a plant friendly Gram-positive bacterial endophyte Bacillus mojavensis affecting its use as a desirable biocontrol potential.

2. Determine the diversity, evolution, and function of bacterial endophytes in cornfield environments and their impact on the metabolic activity of Fusarium verticillioides, including the production of mycotoxins as well as the detoxification/inactivation of xenobiotic compounds.

3. Determine how the biocontrol organisms can be effectively utilized to prevent the accumulation of the fumonisins; specifically the enhancement of plant defense strategies and production of the antifungal agent surfactin by Bacillus mojavensis.

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Objective 1: We will test to determine if pathogenic Gram-negative bacteria can transfer genetic information via conjugation to Gram-positive endophytic bacteria that could potentially alter an otherwise nontoxic plant friendly bacterium to a potential virulent human pathogen while maintaining its stable endophytic host relationship.
Objective 2: A multilevel approach using molecular genetics, bioinformatics, and in planta analyses will be used to provide data on variation among mycotoxin-producing Fusarium species. Emphasis will be on genes encoding diverse metabolic activities, including xenobiotic detoxification. The hypothesis that such genes were acquired via horizontal gene transfer will be addressed. The approach will evaluate the contribution of these metabolic activities to the general fitness and competitiveness of the fungi.
Objective 3: The same bank of strains of B. mojavensis used in the experimental procedures of Objective 1 will be used here as needed (see Appendix, Table 1), as will the seedling bioassay (Appendix, Figure 6) developed for rating the in planta control of B. mojavensis strains under control conditions. Two cultivars of corn will be used, one rated resistant to Fusarium and the other susceptible. Most of the techniques, inoculations, measurements of disease expressions, endophytism, surface disinfections, microscopic and visual interpretation of diseases have been practiced or created in our laboratory over the years of studying this and other endophytic associations. All analytical analyses for surfactin and fumonisins will be determined as we have done over the past research accomplishments.
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Agricultural Research Service
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Natural Toxins
Bacterial Pathogens