Molecular mechanisms of colicin evolution.

This review explores features of the origin and evolution of colicins in Escherichia coli. First, the evolutionary relationships of 16 colicin and colicin-related proteins are inferred from amino acid and DNA sequence comparisons. These comparisons are employed to detail the evolutionary mechanisms involved in the origin and diversification of colicin clusters. Such mechanisms include movement of colicin plasmids between strains of E. coli and subsequent plasmid cointegration, transposition- and recombination-mediated transfer of colicin and related sequences, and rapid diversification of colicin and immunity proteins through the action of positive selection. The wealth of information contained in colicin sequence comparisons makes this an ideal system with which to explore molecular mechanisms of evolutionary change.