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Bacteriocin is a small molecule, produced by bacteria, that inhibits closely related strains. It is usually a peptide or a protein—varying sized chains of amino acids. These compounds are of interest both in studies of basic microbiology, and for the preservation of food and enhancement of human health.
These toxins are produced by a wide range of bacteria. The first to be studied was that from escherichia coli, a bacterium that lives in human intestines and is frequently used in laboratory work. It produces a number of bacteriocins, with the most well-studied being the colicins.
There are several ways in which bacteriocins can affect human health. Our intestines are teeming with a whole microbial world that helps digestion and affects our immune system. Many of these bacteria produce a bacteriocin to help them gain a foothold amongst the competition for resources. When one takes antibiotics, that can kill the beneficial bacteria, allowing pathogenic organisms to take over.
One way to prevent this from happening is to take food with probiotics, such as enhanced yogurt. Probiotics are beneficial microorganisms introduced into food so that they can re-colonize our intestinal tract. Frequently these bacteria are in a group known as lactic acid bacteria, particularly species of Lactobaccillus. Lactic acid bacteria convert sugars to lactic acid and other compounds in the absence of oxygen.
Lactic acid bacteria produce a number of different bacteriocin types, known as lantibiotics. Some of these have been shown to inhibit the growth of bacteria that can cause disease. Another type of lactic acid bacterium that lives in our intestines is Enterococcus faecalis. Although this bacterium can be a human pathogen, several strains produce a bacteriocin with activity against the pneumococcal bacteria that cause pneumonia. Research has been done using non-pathogenic strains that produce this bacteriocin to inoculate the noses of children, in order to protect them from getting pneumococcal pneumonia.
Fermented foods are another area in which bacteriocins contribute to efforts to keep pathogens out of humans. They are one of several reasons for the anti-microbial activity of lactic acid bacteria in these types of foods. Other reasons include the production of anti-fungal compounds and organic acids. Starter cultures that produce bacteriocin have been tested with fermented sausage and cheese, and found to protect against the potentially deadly pathogens listeria in both cases, and clostridium in the latter.
As research continues into the industrial potential of bacteriocins, there is likely to be greater use of them in the food industry. The use of probiotics is a greatly expanding market as of 2010. Microbiological research is likely to continue to identify new bacteriocins with novel specificities that can be used to protect human health.