Cover photograph (Copyright © 2011, American Society for Microbiology. All Rights Reserved.): Bistable expression of the type I pilus genes in Streptococcus pneumoniae. Shown are cells of a strain of S. pneumoniae carrying the green fluorescent protein (GFP) gene in place of the rrgC pilus gene that have been stained with the membrane dye FM 4-64FX (Invitrogen). GFP reporter fluorescence is shown in yellow pseudocolor, and membrane dye fluorescence is shown in cyan pseudocolor. (See related article on p. 2974.)