1. Microbiology and Molecular Genetics, 6120 Biomedical and Physical Sciences, Michigan State University, East Lansing, Michigan 48824, Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455, Centre for Water Science Cranfield University, Cranfield, Bedfordshire, MK43 OAL, U.K., and Department of Environmental Engineering, The Pennsylvania State University-Harrisburg, Middletown, Pennsylvania 17057