Completion of the detailed restriction map of theE.coligenome by the isolation of overlapping cosmid clones

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Abstract
Ordered sets of cosmids derived from E.coli K-12 803 overlap the 6 remaining gaps left in the physical map of strain W3110 (1,2). We present detailed restriction maps of the gaps and surrounding regions, thus providing a comparison of about 30% of the genome of the two E.coli strains. Our analysis shows that there is a high degree of homology between the strains, with only occasional restriction fragment differences. However, the large inversion occurring between rrnD (72.1') and rrnE (90.4') in strain W3110 is absent in strain 803. Instead, a new inversion and adjacent deletion near argF is present in strain 803. The distribution of cosmid clones at, and adjacent to, the gaps shows that all gaps except one were difficult to clone in both λ and cosmid clones. A low copy number cosmid vector, pOU61cos, developed previously (2), was essential for cloning 3 of the 8 gaps.