Periodic distribution of homologous genes or gene segments on the Escherichia coli K12 genome.

A computer search for homologous relationships among Escherichia coli proteins has been carried out with the use of databases. Homologous genes or gene segments thus identified at the amino acid sequence level have a tendency to lie on the genome separated by distances of multiples of 7 min. This relatively regular pattern of gene distribution on the E. coli genome is interpreted as reflecting the early history of multiple genome doublings. Evolutionary advantages of duplications of the total genome are discussed in relation to the acquisition of new multistep pathways such as the Krebs cycle and to the generation of a variety of proteins in existence today.