( t of untreated cells. In fact the redu...)Electrotransformation of E. coli With M13 DNA

t of untreated cells. In fact, the reduced volume causes some problems due to the increased difficulty of dispersing the small volume evenly throughout the plating agar (resulting in uneven distribution of blue plaques, or no blue plaques at all). Adding the X-Gal and IPTG to the bottom agar has proven to be a reasonable solution: the efficiency is reduced by only about 10-30%, and the blue color is distributed evenly across the plates. Note that allowing the transformed electroporated cells to recover for 20 minutes before adding the X-Gal and IPTG (sample 10) increases the transformation efficiency somewhat. However, longer incubations should be avoided as the transformed cells will begin to produce infectious virus after about 30 minutes.

We have not been routinely successful in generating conventional competent cells with transformation efficiencies greater than 5 x 10⁸/g. However, our electroporation competent cells in the efficiency range of 10⁹-10¹⁰/g are easily and reproducibly generated with the protocol described above. In addition, conventional competent XL1-Blue cells take up M13mp18 DNA at a significantly reduced efficiency from that of plasmid DNA (Table 2, samples 1 and 2) which can not be explained with the decreased molar concentration of M13 due to its larger size. This effect is not seen with electroporated XL1-Blue cells (Table 1, samples 4 and 11), or with conventional competent INV1αF' cells (Table 2, samples 3 and 4).

Discussion
While attempting to increase electro-transformation efficiencies with M13 DNA, we found several critical factors that influence the process: 1) cells should be started from a fresh streak from a
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