CAA: Genetic Exchange Between Bacillus Species

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The nature of species, and to what degree closely related species are demarcated by barriers to genetics exchange, are perhaps less clear for bacteria than for any other major group of organisms. Studies of genetic exchange between the closely related soil bacteria Bacillus subtilis and Bacillus licheniformis are being conducted by Dr. Kathleen Duncan in order to test hypotheses about possible mechanisms opposing free gene exchange among bacteria. Knowledge of mechanisms operating in nature that might prevent the free interchange of genes among soil bacteria would greatly aid in making decisions about the release of genetically engineered microorganisms. Investigations will focus on: (1) spontaneous, natural exchange between spores germinated in sterilized soil; (2) protoplast fusion; and (3) transformation of competent B. subtilis with purified DNA. The hybrids produced will be analyzed to determine the extent of DNA transfer using methods of sequencing, restriction-enzyme digests, allozyme electrophoresis, and growth tests on selective media to identify the origin of specific genes. The fitness of hybrid strains will be evaluated during growth in soil in order to estimate the likelihood of success in nature. %%% New methods in molecular genetics make possible the monitoring of gene exchange among soil bacteria, a phenomenon critical to concerns about genetically engineered organisms. Dr. Kathleen Duncan employs sophisticated DNA analyses to evaluate the extent and fate of gene transfer among Bacillus soil bacteria, including the role of hybrid strains carrying blocks of DNA from closely related species.