**4.3 Electroporation of BAC DNA into bacteria**

Electroporation of bacteria is usually performed with an exponential decay electroporation instrument, although square wave instruments can be adapted for bacterial electroporation. We found that for the initial electroporation of BAC DNA into recombineering bacterial strains, a "dirty" prep of BAC DNA containing genomic DNA prepared by alkaline lysis alcohol precipitation was sufficient.

With "Quick Prep" BAC DNA (described above), electroporation can be performed at 1.8KV with a time constant of 5µs. Cells are then resuspended in 1ml LB media and incubated for 1hr at 30C. As with standard practice, 100ul cells are streaked on selection plates and incubated at 30C overnight. To the remaining electroporated cells, 4ml LB medium are added and incubated overnight at 30C. The following day, cells were plated on selection plates and transformed cells are obtained from this selection.
