Cover photograph (Copyright © 1999, American Society for Microbiology. All rights reserved.): Immunoelectron micrograph showing intracellular distribution of the Escherichia coli methyl-accepting chemotaxis proteins (MCPs). The MCPs are localized by anti-Tsr antibodies and visualized by secondary antibodies conjugated to 12-nm-diameter colloidal gold particles (depicted in yellow). (Photograph by S. R. Lybarger, colorized using Adobe Photoshop). (See related article on page 5527.)