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 single scan through a filament after staining with SyproOrange and fluorescein isothiocyanate (FITC). The image, recorded in threechannel mode, shows reflection of sulfur granules (white), protein staining of the cell surface and cytoplasm (red), and vacuole staining (green). Details of confocal laser scanning microscopy are as follows: TCS SP1; upright microscope; 63× 1.2 NA water immersion lens; sample mounting on slide with cover slip; excitation, 488 nm; emission, 480 to 500 nm (reflection)/500 to 550 nm (FITC)/590 to 655 nm (SyproOrange); pixel resolution, 512 × 512; pinhole − Airy = 1; zoom 2; average 2. The data set was subjected to a median filter (3 × 3 × 1) and projected as an isosurface by using Imaris version 5.71. (Related paper is S. Hinck, T. R. Neu, G. Lavik, M. Mu&bgr;mann, D. de Beer, and H. M. Jonkers, submitted for publication.)