Southern blot showing resolution of DNA forms. Lanes loaded as the following: lanes 1 and 2, duplicate samples of 10⁸ cells S flexneri bacteria carrying ≈230-kb circular megaplasmid, loaded live in each lane; lanes 3 and 4, duplicate samples of EBV cell line B95-8 with 10⁶ cells loaded per lane; lane 5, 10⁶ CMV lytically infected cells. Southern blot was sectioned, and each section hybridized with probe specific for those particular samples. The blots were then realigned for figure. The (∗) symbol marks the lower edge of the proteinase K/SDS/agarose trough.