Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): Vibrio anguillarum strains growing on a siderophore indicator plate, demonstrating two autonomous anguibactin biosynthetic activities encoded within the single angBG open reading frame (ORF). Bacteria in the top colony contain the 5' end of the angBG ORF, conferring the ability to produce dihydroxybenzoic acid (DHBA). DHBA diffuses to the bottom colony, which contains bacteria that are isogenic with those in the top colony, except that they harbor just the 3' end of the angBG ORF. The function encoded in this region is used to assemble DHBA into an anguibactin molecule. Notice the directional nature of the zone of anguibactin production and bacterial growth from the bottom towards the top colony. (Photograph by T. Welch and J. H. Crosa.) (See related article on page 6762.)