Research

Soil Microbiology with emphasis on biodegradation/bioremediation of synthetic chlorinated compounds in the environment, molecular ecology and genetics of plant-microbe interactions, and tracking sources fecal contaminants in surface waters.

One of the major research efforts of my laboratory is directed towards the identification and characterization of bacterial genes and metabolic pathways involved in the biodegradation of chlorinated herbicides. My laboratory (in collaboration with Dr. Larry Wackett, Department of Biochemistry. Biophysics, and Molecular Biology) is using recombinant DNA methodologies to examine the genes and enzymes involved in the mineralization of the broadleaf herbicide atrazine by a Pseudomonas sp. strain. We have cloned and sequenced the first three genes in the atrazine biodegradation pathway; and isolated, purified, and characterized the first two proteins involved in the dechlorination of atrazine. Using PCR, combinatorial DNA methodologies, and other recombinant DNA techniques, we are examining the ecology of atrazine-degrading microorganisms in soil, examining the evolution of the atrazine chlorohydrolase gene, and investigating the role that plasmid gene transfer and catabolic transposons play in the dissemination of atrazine degradation genes in soil microbial communities. Moreover, we are investigating the use of purified enzymes, and transgenic bacteria and plants, to bioremediate atrazine-contaminated soils and water.

Research in my laboratory is also directed towards the identification and characterization of bacterial genes involved in the early periods of legume-microbe symbioses. We are specifically interested in studying Rhizobium and Bradyrhizobium genes which play a prominent role in host/microbe recognition and in the establishment of symbiotic, nitrogen-fixing nodules on the roots of soybean. Molecular biological and immunological techniques are being used to elucidate mechanisms whereby the host plant restricts nodulation by specific B. japonicum strains. Using recombinant DNA and promoter probe techniques, we are also examining how host plant and soil environmental variables regulate the expression of bacterial nodulation, survival, and persistence genes.

Lastly, my laboratory is using DNA fingerprinting methodologies, REP-PCR and ARDRA, to track sources of E. coli contaminants in surface water and to understand the ecophysiology of E. coli in human and animal hosts.