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Andre Gratia was the first to uncover the inhibition property of bacteriocins in a compound he named colicin v, which was released by a virulent strain of E.coli bacteria. In 1954, Pierre Frederic uncovered the genetic determinates of colicin, as a conjugation transmissible element that is similar to the F factor. Since then a host of bacteriocins have been discovered, and our understanding of the usefulness of bacteriocins moves forward (Scienceray, 2012). Bacteriocins Bacteriocins are a constituent of the wide array of microbial defense systems.
All bacteria produce bacteriocins (Riley & Chavan, 2007). These bacteriocins are proteinaceous compounds, which are lethal to bacteria other than the releasing strain. The spectrum of antibacterial activity can vary from narrow spectrum, with confined inhibition of closely related bacterial species or broad to include several of the other bacterial species (Joerger, 2003). Bacteriocins from gram positive bacteria are associated with the broader range of antibacterial range of activity. While initial studies were focused on colicins from E-coli and the bacteriocins from other gram negative bacteria, the current focus of studies on bacteriocins is on the bacteriocins from the gram positive bacteria, as they are assumed to have more application in humans and in foods and other products (Chen & Hoover, 2003).
At first glance there may be a tendency to classify the bacteriocins as an extension of the traditional peptide antibiotics, because they are synthesized peptides. Yet, they are different, and it is in the essence of this difference that their utility lies. Unlike peptide antibiotics, which are synthesized by enzymes bacteriocins are ribosomally synthesized peptides. In addition, while typical antibiotics are active against a broad range of bacteria, bacteriocins have a narrow range of activity within its own bacteria species or closely related bacteria species.
Furthermore, there is an important and unique difference in the potency. Within its narrow range of antibacterial activity it is potent in nanomolar concentrations, while in the case of antibiotics a much higher concentration is required for potent antibiotic activity. Though the initial origins and studies on bacteriocins pertain to those produced by gram negative bacteria, the current research on bacteriocins focuses more on the bacteriocins produced by gram positive bacteria, because of the greater potential utility seen in them.
Any evaluation of bacteriocins produced by gram positive bacteria is best undertaken by studying them as two groups, namely the heat-stable lantibiotics and the nonmodified heat-stable bacteriocins (Nes, 2011). Bacteriocins from the gram positive lactobacillus are the most investigated group of bacteriocins. Class – I of these bacteriocins consist of the lantibiotics, which are heat stable. They comprise of post-transitionally modified peptides, having multiple rings, bridged by lanthiones or methyllanthionine residues (Zendo & Sonomoto, 2011).
Class I bacteriocins are further
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