Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Bioluminescence detected from a swarming colony of Pseudomonas aeruginosa PAO1 rendered luminescent by chromosomal integration of p16Slux. The image was acquired with a Xenogen IVIS 100 system. A black-and-white photograph of the sloppy agar plate is overlaid with a false color image of detected bioluminescence intensities on a blue-to-red scale. Photo courtesy of Heidi Mulcahy, Martin Riedel, and Christian U. Riedel. (See related article in November 2007: volume 73, issue 21, page 7092.)