English: Bicaudaviridae. Electron micrographs of different forms of Acidianus two-tailed virus. a, Virions in the infected cell culture at the late stage of tail development. b, extrusion of virions from an Acidianus convivator cell; c, virions in growing culture of infected A. convivator, two days post-infection; d, as for c, but purified by CsCl gradient centrifugation; e-h, as for d, but after incubation at 75° C for 2, 5, 6, and 7 days, respectively. Samples were negatively-stained with 3% uranyl acetate, except for b, which was platinum- shadowed. Bars: a-c, 0.5 µm; d-h, 0.1 µm (first published in Häring et al., 2005).