Abstract
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.