Transformation inEscherichia coli: studies on the nature of donor DNA after uptake and integration

Abstract

SUMMARYChromosomalE. coliDNA appears to be sensitive towardsin vivoDNA restriction when transformed to a restrictiveE. colirecipient. It is therefore concluded that transforming chromosomal donor DNA is present in a double-stranded form immediately after uptake.Genetic analysis ofE. colitransformants, obtained with UV-irradiated donor DNA under conditions that exclude photorepair, show, especially in auvrBrecipient, loss of donor DNA information compared with the situation where DNA was not subjected to UV-irradiation. Similar conclusions were arrived at after genetic analysis of transductants obtained with UV-irradiated particles of the generalized transducing phage P1. The processing inE. coliof DNA after P1 transduction is thus similar to that of transforming DNA. The observations are discussed and a possible explanation based on single-stranded DNA integration is presented in detail.