Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): A colorized scanning electron micrograph of cells that surround and are part of a “dumpling” speleothem from a geothermal mine adit near Glenwood Springs, CO. Several cell morphologies are evident along with extracellular polymeric substances which coat the gypsum crystals of the floating “dumpling.” These “dumplings” are one of two kinds of speleothems examined for microbial community composition. The other, a hollow, leather-like stalactite, was composed of a diverse assemblage of Bacteria and Archaea, which included a large number of sequences representative of putative ammonia-oxidizing archaea in this 50°C geothermal environment. Photo courtesy of Karl Hagglund and Brad Lubbers. (See related article in October 2007: volume 73, issue 19, page 6172.)