peptide and the flag epitope digested with the same two enzymes these dnas are ligated and transformed into e coli strain sure u03b4lamb a derivative of sure 11 that does not contain the lamb gene as a result this strain is lambda resistant and unable to grow in minimal media with maltose as the carbon source amp r transformants are pooled together and replated on m9 minimal plates with maltose as the carbon source as shown in fig1 the plamb plasmid contains the amp r gene this prescreening removes from the population any plasmid vectors that do not contain inserts and those that contain mutations that result in a nonfunctional or truncated lamb gene the cells able to grow on minimal mal amp plates will then be pooled subject to plasmid dna miniprep isolation qiagen and this dna will be the source for transfection into the cell line of interest the selection screen for the variants that express better and or are more easily infected by lambda will proceed as described above with the first method of mutagenesis it may be useful to optimize the efficiency of lambda infection of particular cell lines that transiently or stably express the lamb or mutant transgene the initial experiments to accomplish this will be to vary the growth conditions media of the cell line of interest our initial data with cho cells indicated that either quiescent or growing cells could be infected and that the cells did not have to be treated in any special manner however the same may not be true for other cell lines.