Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Confocal laser scanning micrograph of a Beggiatoa filament from a hypersaline microbial mat (Lake Chiprana, Spain). The micrograph presents a series of 27 sections at 0.5-&mgr;m intervals through a filament after being stained with fluorescein isothiocyanate. The image was recorded in dual-channel mode, showing a reflection of sulfur granules (white) and vacuole staining (green). Due to the imaging mode, the filaments appear skeletonized, as only cell-internal structures are shown. The unfiltered data set was projected as an isosurface by using Imaris version 5.71. Images were printed using Photoshop CS without any adjustments. (See related article in November 2007: volume 73, issue 21, page 7013.)