Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Stream biofilms can form conspicuous filamentous streamers under turbulent flow, as seen by epifluorescence and dark-field microscopy. These garland-like streamers are composed of a bacterial backbone and diatoms and are a great adaptation to flow and low-nutrient environments. Photos by Gabriel Singer. (See related article in August 2007: volume 73, issue 15, page 4966.)