Primary research by Bo Hu, William Margolin, Ian J. Molineux and Jun Liu. PNAS 112(35), E4919–E4928 (2015), DOI 10.1073/pnas.1501064112. Abstract and Figures 2–3 report cryo-electron tomographic observations of T4–E. coli complexes, with distinct tail and DNA-retention states. The counting example in the article is constructed, not a reported sample distribution.