Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Fluorescence photomicrograph (artificially compiled) of the thecated dinoflagellate Alexandrium catenella. The internal cellulosic thecal plates were stained blue with the fluorescent brightener calcofluor white; DNA was stained green with SYTO 13. Red coloration corresponds to autofluorescence. A cell of A. catenella is approximately 40 μm. (See related article on page 563.)