REU: Ecological Interactions of Genetically-Engineered Microorganisms in Root-Soil Systems

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Drs. Peter Hartel and colleagues at the University of Georgia, Athens propose to conduct research on several critical, ecological questions concerning genetically engineered microorganisms. The ability of a microorganism to survive, grow, and interact in a ever changing soil environment persists because microorganisms actively exchange genes horizontally for these traits. By asking a series of questions, the investigators will assess the ecological worth of specific genes to a microorganism in a root/soil system. They have used genetic engineering to clone and manipulate the genes which encode for endoglucanase and polygalacturonase in the bacterium Pseudomonas solanacearum. They will use the same techniques for the genes encoding for extracellular polysaccharide, protease, and lipase. The loss of expression of these specific genes will be tested singly and in combination for their effect on the ability of P. solanacearum to survive, grow, and transfer these cloned genes in soil and in the rhizosphere to tomato (Lycopersicon esculentum). The cloned genes will also be placed in Pseudomonas putida, Pseudomonas aeruginosa, and Escherichia coli. Rhizosphere interactions will be assessed by use of a rhizosphere cell employing membranes of varying porosities. In this manner, the microbial competitiveness of the genetically-engineered bacteria will be assessed. The research is expected to yield fundamental knowledge on the ecological value of a specific gene to a microorganism in the environment. Preliminary work on the genes for endoglucanase and polygalacturonase in P. solanacearum has shown that genetic engineering has a profound influence on the performance of this organism in a plant. These data will be of immediate value to microbial ecologists and to regulatory agencies concerned about accidental release of genetically engineered microorganisms.