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  • Title: [Unequal crossing over in Escherichia coli: genetic and physical mapping of duplications isolated in conjugational matings].
    Author: Sukhodolets VV, Dukhiĭ DE.
    Journal: Genetika; 1996 Jan; 32(1):42-52. PubMed ID: 8647423.
    Abstract:
    We previously demonstrated that stable heterozygous duplications deoA deoB :: Tn5/deoC deoD can be isolated among Deo+ recombinants obtained in conjugational matings between Escherichia coli strains HfrH deoA deoB :: Tn5 and HfrH deoC deoD. In this work, 30 duplications were tested by transduction for the inclusion of a set of genetic markers adjoining the deo operon (99.5 min) at the genetic map of E. coli: cycA :: Tn10 (96 min), zji :: Tn10 (98.2 min), thr :: Tn9 (100/0 min), car :: Tn10 (1 min), leu :: Tn9 (2 min), and proAB :: Tn10 (6 min). The results obtained indicate that only three out of 30 duplications could have originated from unequal crossing over between the rrn operons. In eight strains, duplications were chosen for physical mapping by the use of Not I restriction, pulsed-field electrophoresis, and Southern blot hybridization with DNA of the deo operon. In all these strains, the presence of duplications (once a triplication) was confirmed by corresponding changes in the set of Not I digests, although some strains had additional genetic rearrangements. The order of operon copies in a tandem was determined, and the length of a duplicated chromosomal segment was calculated as equal to 25, 46, 80, 150.5, and 175 kb in duplication D49, D4, D5, D9, and D18, respectively. Thus, the use of the conjugational Hfr x Hfr system allows the generation of unique rearrangements of the E. coli genetic material.
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