1. Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA
2. Department of Natural Sciences, Clayton College and State University, Morrow, GA 30260-1250, USA
3. Center for Biomarker Analysis, University of Tennessee, Knoxville, TN 37932-2575, USA
4. Institute of Ecology, University of Georgia, Athens, GA 30602-2360, USA