Cover: Nematic arrangement of DNA confined in phage capsids favours formation of DNA torus knots. An artist view of three sequential stages of osmotic shock-caused phage burst during which the nature of formed DNA knot is revealed. The graphic is by Julien Dorier and Andrzej Stasiak (Center for Integrative Genomics, University of Lausanne, Switzerland), the coordinates of packed DNA were kindly provided by Luca Tubiana (International School for Advanced Studies, Trieste, Italy).

For further information, please see the article by D. Reith et al., Nucleic Acids Res., 2012, 40, 5129–5137.