Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Scanning electron micrograph of rosettes formed by Roseobacter sp. strain 27-4, a marine bacterium associated with fish larva rearing units. Roseobacter sp. strain 27-4 inhibits the fish-pathogenic bacteria Vibrio anguillarum and Vibrio splendidus, and the inhibitory compound is produced under culture conditions that facilitate rosette formation. SEM by José Bresciani and Michael Hansen. (See related article on p. 7263.)