Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Structure of the tetramer of Enterococcus faecalis agmatine deiminase, shown as a ribbon representation of the tetramer viewed along one of its twofold axes, with the covalently bound agmatine in a space-filling representation. Each subunit is colored differently. The image was generated using PyMOL. (See related article on page 1254.)