1 Department of Biology, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada. Electronic address: barb.katzenback@uwaterloo.ca.
2 Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN, 37235, USA; Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA. Electronic address: louise.rollins-smith@vanderbilt.edu.