The ecological role of bacteriocins in

TRENDS IN MICROBIOLOGY 129 VOL. 7 NO. 3 MARCH 1999 Bacteriocins are one of the most abundant and diverse classes of antimicrobial molecules, having been detected in all major lineages of Eubacteria and in Archaebacteria1–3. They are potent, often highly specific toxins that are usually produced during stressful conditions and result in the rapid elimination of neighboring cells that are not immune or resistant to their effect1,4. Given their often narrow range of activity, it has been proposed that the primary role of bacteriocins is to mediate intraspecific, or population-level, interactions5. One class of bacteriocins, the colicins produced by Escherichia coli, has been the focus of numerous ecological studies6–10. Mathematical models and empirical studies suggest that colicins play a key role in mediating E. coli population dynamics5. In this review, we describe what these studies reveal about the interactions between colicin producers and non-producers in E. coli populations.