A novel method for increasing the transformation efficiency of Escherichiacoli - application for bacterial artificial chromosome library construction

Bacterial artificial chromosome (BAC) libraries play a pivotal role in geno mics studies. A crucial step in BAC library construction is the transformat ion of Escherichia coli by electroporation. Absolute efficiency (cfu/mu g D NA) is affected by a number of factors including the topological form and t reatment of DNA samples. Here we report a simple new protocol using tRNA as sisted precipitation that increased transformation efficiency by 70-fold fo r BAC ligations and up to 400-fold for plasmid ligations. The mechanism may involve altering or stabilizing the topographical form of the DNA molecule s.