Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Three-dimensional rendering of the central part of a dividing Caulobacter crescentus cell at an early stage of the cell division process, obtained from a cryoelectron tomography reconstruction. The cell is preserved in a near-native state by rapid freezing, without contrast enhancement by staining. The inner membrane is shown in yellow, the outer membrane in orange. Part of the cytoplasm is shown in a volume-rendered representation in green, along with the S-layer, which is faintly visible outside the outer membrane. (See related article on page 6874.)