1. Dental Research Institute, University of Toronto, 124 Edward Street, Toronto, Ontario M51G6, Canada
2. Institute for Oral Biology, Section for Oral Microbiology and General Immunology, Center for Dental, Oral Medicine and Maxillofacial Surgery, University of Zurich, Zurich, Switzerland
3. Department of Biology, Middlebury College, 276 Bicentennial Way, BIH354, Middlebury, Vermont 05753
4. Division of Diagnostic Science, Norris School of Dentistry, University of Southern California, 925 West 34th, Los Angeles, California 90089