4 strains of E. coli are used in these studies: JM101 for M13 infection and isolation, XL1BMRF'for M13 or pUC-based DNA transformation, and ED8767 for cosmid DNA transformation. To maintain their respective F' episomes necessary for M13 viral infection, JM101 is streaked onto a M9 minimal media plate and XL1BMRF' is streaked onto an LB plate containing tetracycline. ED8767 is streaked onto an LB plate. These plates are incubated at 37degC overnight. For each strain, 3 ml. of appropriate liquid.. - [Read Bacterial Cell Maintenance Protocol]