The Effect of Size of Chromosomal DNA from Escherichia coli VC10 on Transformation of Escherichia coli HB101 by the Plasmid p328.5

This study investigated the effects of the size of chromosomal DNA fragments on transformation efficacy of a plasmid. In our experiment, each of three chromosomal fragment sizes were co-transformed with varying amounts of plasmid DNA and results show that the conditions, plasmid alone, plasmid with 10kb, and plasmid with 20kb fragments gave no significant differences. On the other hand, plasmid with 30kb and plasmid with undigested chromosomal DNA exhibited a significantly decreased number of transformants compared to the above three conditions. Furthermore, when observing numbers of transformants with varying amounts of plasmid, we see that the plasmid alone and plasmid with 10kb conditions result in more transformants with increasing amounts of DNA and plasmid, whereas plasmid with 20kb and plasmid with 30kb increases with more DNA and plasmid but then decreases. Thus, in general, among the three DNA fragment conditions, there seems to be a decrease or at least a leveling off in the number of transformants as plasmid concentration increased  a marked difference from the consistent upward trend of the plasmid alone condition. Conversely, when contaminated with undigested DNA, transformation efficiency remained suppressed regardless of plasmid concentration. Based on these results, larger contaminating fragments exhibit lower transformation efficiencies then do smaller chromosomal fragments.