Cover photograph (Copyright © 2010, American Society for Microbiology. All Rights Reserved.): Transmission electron micrograph of a single Proteus mirabilis swarmer cell. When cultured on a solid rich medium, P. mirabilis differentiates into long (>50 μm), multinucleate, hyperflagellated forms and swarms rapidly over the surface. Numerous flagella are visible, many of which are bundled together into a wave-like pattern on the top side of this swarmer cell. This image was captured using a Philips CM-100 transmission electron microscope at the University of Michigan Microscopy and Image Analysis Laboratory. (See related articles on p. 2823 and 2834.)