Academic Service
- Assistant Professor to Professor of Biochemistry, University of Kentucky Medical Center, 1962-1972
- Professor, Department of Biological Sciences, Florida State University, 1973-1985
- Associate Director Program in Medical Sciences, FSU, 1973-1984
- University of Tennessee/Oak Ridge National Laboratory Distinguished Scientist 1986-2006
- Professor of Microbiology/Ecology and Environmental Toxicology, University of Tennessee, Knoxville 1986-2006
- Research Scientist and Oak Ridge National Laboratory, 1986-2006
- Founder and Director, Institute of Applied Microbiology, University of Tennessee/Oak ridge National Laboratory, Knoxville, 1986-1991
- Executive Director, Center for Environmental Biotechnology, University of Tennessee, 1991-1999
- Visiting Distinguished Scientist, The Jet Propulsion Laboratory, Pasadena, CA 1998-2000
- Founder and Director Center for Biomarker Analysis, 2001-2006
Adjunct Professorships
- Professor of Community Medicine and Family Medicine, University of Florida Medical Center, 1975-1984
- Professor of Biological Sciences 1972-1986, Professor of Oceanography, Professor of Chemistry, FSU, 1981-1986
- Professor Institute of Food and Agricultural Sciences, University of Florida, 1981-1986
- Professor Interdepartmental Toxicology Program, University of Arkansas Medical Center, and the National Center for Toxicological Research, 1981-1988
- Founder and Co-director Center for Biomedical and Toxicological Research, Florida State University, 1982-1985