1. Center for Microbial Ecology, Department of Microbiology, and Department of Civil and Environmental Engineering, Michigan State University, East Lansing, Michigan 48824, Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan 48109, Biologische Bundesanstalt für Land- und Forstwirtschaft, Institut für Biochemie und Pflanzenvirologie, Braunschweig, Germany, and Golder Associates, Inc., Lansing, Michigan 48906