Pulsed-field gel electrophoretic analysis of MG1655 deletion derivatives after 20 rounds of transposition and deletion. Transpositional deletion of chromosomal DNA was performed recursively for a total of 20 cycles. After these 20 cycles, chromosomal DNA was prepared from 4 deletion strains as well as the initial strain MG1655. The chromosomal DNA was digested to completion with NotI restriction endonuclease and analyzed by pulsed-field gel electrophoresis. Visualization by ethidium bromide staining and UV irradiation revealed the pattern of DNA bands. The pattern for MG1655 matches that reported previously (Heath et al. 1992), and the identification letter for each fragment is shown at right. For each of the deletion strains, the pattern is altered and indicates a loss of DNA. The size of each new band in the four deletion strains was estimated by comparison with DNA markers. The estimation for total amount of deleted DNA in each of the strains is shown atbottom.
