Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Fluorescence microscopy of Leptospira biflexa cells stained with DAPI (4`,6`-diamidino-2-phenylindole). Leptospira spp. belong to the spirochete phylum and possess a helical cell body ranging in length from about 10 to 20 μm, with a diameter of 0.15 μm. (See related article on page 469.)