3 Molecular Evolution of Bacteriocins in Gram-Negative Bacteria

The study of molecular evolution has become a valuable tool in understanding the origin of life and the speciation of organisms, with the focus on changes in DNA and protein sequence and their functions. Interest in studying the molecular evolution of bacteriocins, the narrow-spectrum peptide antimicrobials, was elicited due to the broad diversity and abundance of these proteins. The availability of a large amount of data on colicins, the bacteriocins produced by the Gram-negative bacterium, Escherichia coli, made it a model bacteriocin to study molecular evolution. Colicins have characteristic features which make them amenable resources in the investigation of the mechanisms employed in evolution. In this chapter, we have reviewed these features of colicins and we describe models proposed to explain how these antimicrobial proteins have evolved. Further, we have described how our current understanding of colicin evolution is important to the understanding of colicin-like bacteriocins produced by other Gram-negative bacteria.