Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): A wrinkled-colony phenotype is a general property of Escherichia coli strains with nonlethal cell division defects. Wrinkled colonies are readily distinguished from smooth wild-type colonies, and thus, the wrinkled morphology provides a useful tool in the genetic analysis of the cell division process. fts123(Ts) is a lethal allele of the cell division gene ftsI and renders a strain unable to divide at the restrictive temperature of 42°C. When grown at 30°C, however, the same fts123(Ts)-containing strain shows only moderate impairment of division and forms a distinctly wrinkled colony, shown here juxtaposed with a smooth colony of the isogenic wild-type strain. (See related articles on pages 633 and 646.)