A low rate of nucleotide changes in Escherichia coli K-12 estimated from a comparison of the genome sequences between two different substrains

Two genome sequences of Escherichia coli K-12 substrains, one partial W3110 and one complete MG1655, have been determined by Japanese and American genome projects, respectively. In order to estimate the rate of nucleotide changes, we directly compared 2 Mb of the nucleotide sequences from these closely-related E. coli substrains. Given that the two substrains separated about 40 years ago, the rate of nucleotide changes was estimated to be less than 10^-7 per site per year. This rate was supported by a further comparison between partial genome sequences of E. coli and Shigella flexneri. Copyright (C) 1999 Federation of European Biochemical Societies.