Gordon Churchward, PhD

Assistant Dean
Medical Education & Student Affairs

Professor
Microbiology and Immunology

We are currently studying the mechanism of transposition of a group of genetic elements called conjugative transposons. These unusual elements, which generally confer antibiotic resistance on the host, are found in a wide variety of bacteria. Unlike other bacterial transposons, they are not only able to move from one place to another in the genome of an individual bacterium, but can transfer themselves from one bacterial host to another. The different hosts can belong to different species and genera. To understand how these elements can function in such a wide variety of hosts, we are analyzing the recombination reactions that occur during transposition. We have purified and characterized two transposon-encoded proteins that are involved in conjugative transposition, and have established an in vitro assay for excision of a conjugative transposon from the donor chromosome. In the course of these experiments we have found that conjugative transposons use a mechanism of transposition that is different from other bacterial transposons, retrotransposons and retroviruses, and is reminiscent of certain site-specific recombination reactions observed in bacteria, yeast and other eukaryotes. We are now investigating the role of bacterial host factors in conjugative transposition, determining the biochemical requirements for integration into the donor chromosome, and studying how the process of conjugative transposition is regulated.