Cover photograph (Copyright © 2011, American Society for Microbiology. All Rights Reserved.): The background of this image is an electron micrograph of Clostridium difficile. As for several other pathogens, it is possible that lipoproteins of C. difficile may play a role in adherence of this bacterium. The consensus sequence depicted at the bottom is a WebLogo consensus generated from the ClustalW alignment of the lipobox from 25 C. difficile lipoproteins. The consensus depicts the invariant nature of a cysteine within this motif. The background is also overlaid with a ribbon image of LolA from Escherichia coli generated from the Protein Data Bank structure file 1IWL using the PyMOL molecular graphics system. (See related article on page 548.)