P22 Bacteriophages are double stranded DNA viruses (family Podoviridae) that attack salmonella bacteria. They are encased in an icosahedral protein capsid which contains the coiled genome (shown here as concentric reddish shells just visible through the translucent sepia capsid). At the bottom is the tail assembly that can penetrate bacteria and inject the viral genome. This tail also acts as a plug to keep the genome inside. With thanks to Ed Rybicki.