Nucleotide sequence of the Escherichia coli K12 histidine operon revisited.

We report on a significant difference between the published nucleotide sequence of the Escherichia coli K12 histidine operon and our sequencing results repeatedly obtained from a number of different E. coli K12 strains. The discrepancies include 39 base-pair changes and one addition located predominantly in the proximal portion of the operon. Our data also suggest that neutral and near-neutral mutations do not accumulate to a significant extent in the histidine operon of E. coli strains harbouring strong mutator alleles.