Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Image symbolizing the 2nd ASM Conference on Cell-Cell Communication in Bacteria, held in Banff, Canada, 2004. Colored shapes represent signaling functions. Chattering microbes are (clockwise from top) a Streptomyces coelicolor hypersporulating mutant (scanning electron micrograph; M. Eccleston and J. R. Nodwell), a dual-species biofilm of Pseudomonas aeruginosa (green) and Agrobacterium tumefaciens (red) (epifluorescence micrograph; D. An and M. R. Parsek), Streptococcus pneumoniae labeled with fluorescent vancomycin (epifluorescence micrograph; W.-L. Ng and M. E. Winkler), and the edge of a Myxococcus xanthus swarm (phase contrast micrograph; D. Kaiser). The central photograph is the Bow River below Sulphur Mountain in the town of Banff (C. Fuqua). (See related article on page 5507.)