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Bacteriocin



Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). They are phenomenologically analogous to yeast and paramecium killing factors, and are structurally, functionally, and ecologically diverse. Bacteriocins were first discovered by A. Gratia in 1925.[1][2] He was involved in the process of searching for ways to kill bacteria, which also resulted in the development of antibiotics and the discovery of bacteriophage, all within a span of a few years. He called his first discovery a colicine because it killed E. coli.

Additional recommended knowledge

Contents

Classification of bacteriocins

Bacteriocins are categorized in several ways, including producing strain, common resistance mechanisms, and mechanism of killing. There are several large categories of bacteriocin which are only phenomenologically related. These include the bacteriocins from gram-positive bacteria, the colicins [3], the microcins, and the bacteriocins from Archaea. The bacteriocins from E. coli are called colicins (formerly called 'colicines'). They are the longest studied bacteriocins. They are a diverse group of bacteriocins and do not include all the bacteriocins produced by E. coli. In fact, one of the oldest known so-called colicins was called colicin V and is now know as microcin V. It is much smaller and produced and secreted in a different manner than the classic colicins. The bacteriocins of lactic acid-fermenting bacteria are called lantibiotics.

Class II bacteriocins

The action of Class IIa bacteriocins seems to involve disruption of mannose transport into target cells. Class IIb bacteriocins form pores in the membranes of target cells and disrupt the proton gradient of target cells. Other bacteriocins can be grouped together as Class IIc. These have a wide range of effects on membrane permeability, cell wall formation and pheromone actions of target cells.

Database

A database of bacteriocins is available (see link below) [4].

Medical significance

Bacteriocins are of interest in medicine because they are made by non-pathogenic bacteria that normally colonize the human body. Loss of these harmless bacteria following antibiotic use may allow oportunistic pathogenic bacteria to invade the human body.

Production

There are many ways to demonstrate bacteriocin production, depending on the sensitivity and labor intensiveness desired. To demonstrate their production, technicians stab inoculate multiple strains on separate multiple nutrient agar Petri dishes, incubate at 30 °C for 24 h., overlay each plate with one of the strains (in soft agar), incubate again at 30 °C for 24 h. After this process, the presence of bacteriocins can be inferred if there are zones of growth inhibition around stabs. This is the simplest and least sensitive way. It will often mistake phage for bacteriocins. Some methods prompt production with UV radiation, Mitomycin C, or heat shock. UV radiation and Mitomycin C are used because the DNA damage they produce stimulates the SOS response. Cross streaking may be substituted for lawns. Similarly, production in broth may be followed by dripping the broth on a nascent bacterial lawn, or even filtering it. Precipitation (ammonium sulfate) and some purification (e.g. column or HPLC) may help exclude lysogenic and lytic phage from the assay.

Bacteriocins by Class

  • Class I
  • Class IIa
  • Class IIb
  • Class IIc

Bacteriocins by Name

alveicin carnocin colicin curvacin divercin enterocin epidermin halocin lactococin lacticin leucoccin mesentericin nisin pediocin plantaricin sakacin subtilin sulfolobicin vibriocin

References

  1. ^ Gratia, A. (1925). Sur un remarquable example d'antagonisme entre deux souches de colibacille. Compt. Rend. Soc. Biol. 93, 1040-1042.
  2. ^ Gratia, J.P. (2000). Andre Gratia: a forerunner in microbial and viral genetics. Genetics. 156, 471-476. PMID 11014798 PDF
  3. ^ Cascales et al (2007). Colicin Biology. Microbio. and Mol. Bio. Rev. 71(1), 158-229. [1]
  4. ^ de Jong A, van Hijum S A F T, Bijlsma J J E, Kok J, Kuipers O P (2006). "BAGEL: a web-based bacteriocin genome mining tool". Nucleic Acids Research 34: W273–W279. PMID 1538908.

See also

Peripheral membrane proteins

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Bacteriocin". A list of authors is available in Wikipedia.
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