Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Type IV pili (Tfp) play important roles in the molecular and cell biology of eubacterial species. Shown here are Tfp elaborated by Neisseria gonorrhoeae expressing the PilA pilin subunit protein of Pseudomonas aeruginosa (immunofluorescence microscopy showing the Tfp [red] and diplococcal cells [green]). The relaxed specificity of the gonococcal Tfp biogenesis machinery made it possible to examine the direct contributions of pilin constitution to Tfp-associated phenotypes. (See related article on page 6676.)