OBSOLETE. Plasmid-encoded bacteriocins which are produced by enteric bacteria. Exert a lethal effect on other bacteria including E. coli strains that lack the Col plasmid. Bind to a cell surface receptor and are transported into the periplasm via an energy-dependent process involving a TonB- or TolA-dependent hetero-oligomeric protein complex. Some colicins kill their target cell by inserting into the cytoplasmic membrane where they form voltage-sensitive (trans-negative) channels that depolarize and deenergize the cell, and thereby kill it.