Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights Reserved.): Three-dimensional structure of the marine algal virus PpV01 (cyan) calculated from images of vitrified virions. The 220-nm-diameter PpV01 is 390 times larger in volume than the 30-nm human rhinovirus, shown for comparison (light blue and white). The capsid shell of PpV01 contains 2,192 capsomers, which are arranged with T=219 quasisymmetry. These capsomers are grouped into 20 trisymmetrons (two are highlighted in dark blue) and 12 pentasymmetrons (one is highlighted in green and pink). Each trisymmetron consists of 91 similarly oriented trimers, three of which have an additional cap structure (red). Each pentasymmetron consists of 30 trimers plus one central pentamer (pink). A diagrammatic representation of the trimer packing in two adjacent trisymmetrons and part of one pentasymmetron appears above a micrograph of PpV01. (See related article in July 2005: vol. 79, no. 14, page 9236.)