Cover photograph (Copyright © 1999, American Society for Microbiology. All rights reserved.): Pink Lake, Rottnest Island, Western Australia, January 1998. A hypersaline lake (approximately 20% salts when this photograph was taken) on an island famous for its native animal, the quokka (a small kangaroo-like marsupial). The lake water had a light, almost irridescent pink hue due to the high concentration of halobacteria (Archaea) and halophilic red algae (e.g., Dunaliella spp.). (For a guest commentary in this issue dealing with Archaea, see page 3613.) This contrasted with the white, heavily salt-encrusted banks of the lake, where prevailing winds had formed pockets of concentrated algal cells at the water's edge. (Photograph by Mike Dyall-Smith, University of Melbourne.)