Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): This micrograph of microbial assemblages found on the surfaces of submerged aquatic macrophytes serves to illustrate the heterogeneous distributions of cells that can occur in microbial communities. In recent years, there has been increased interest in reaching a better understanding of inter- and intraspecies cell-cell communications in nature. In a study described in this issue of Applied and Environmental Microbiology, the kinetics of acyl-homoserine lactone biodegradation in natural samples were examined. The results suggest that signal decay may serve to insulate spatially separated bacterial microcolonies, indicating that this activity may be a key variable impacting quorum-sensing bacteria in the environment. (See related article on page 1291.)