Bacteriocins are the toxic proteins that are synthesized and released by the bacteria that are the part of the normal microbiota. These proteins have a molecular weight of 900 to 5800 Daltons. The bacterial species that release the bacteriocins are resistant against it.
Secretion of bacteriocins is an adaptive feature as these toxic proteins do not allow the growth of other strains of the same species or related species. One of the examples of bacteriocins are colicins that are released by <em>Escherichia coli</em>.
