Browsing tag: aktywność antymikrobiologiczna


Characteristics and potential applications of circular bacteriocins
Urszula Błaszczyk, Kamila Dąbrowska

1. Charakterystyka i klasyfikacja bakteriocyn cyklicznych. 2. Genetyka bakteriocyn cyklicznych. 3. Biosynteza bakteriocyn cyklicznych. 4. Struktura bakteriocyn cyklicznych. 5. Mechanizmy działania bakteriocyn cyklicznych. 6. Enterocyna AS-48. 7. Potencjalne zastosowanie bakteriocyn cyklicznych. 8. Podsumowanie

Abstract: Bacteriocins are ribosomally synthesized peptides or proteins exerting anatagonistic activity toward organisms which are closely related to the producer strain. Circular bacteriocins are produced by Gram-positive bacteria, mainly lactic acid bacteria, and to a lesser extent by Bacillus, Clostridium and Staphylococcus genera. These bacteriocins are characterized by the head-to-tail cyclization of their backbone. The circular nature of these peptides makes them resistant to many proteolytic enzymes and provides great thermal and pH stability. Circular bacteriocins are divided into 2 subgroups based on their physicochemical properties and sequence identity. These bacteriocins are synthesized as linear precursors with a leader sequence which is cleaved off during maturation. The mature circular peptides are composed of 58–70 amino acid residues. Biosynthesis of circular bacteriocins requires three stages: cleavage of the leader sequence, circularization and export out of the cell. Circular bacteriocins have broad antimicrobial activity spectrum, including many food spoilage bacteria and pathogens, such as Listeria, Staphylococcus and Clostridum spp. Circular bacteriocins permeabilize the membrane of sensitive bacteria, causing loss of ions and dissipation of the membrane potential, and finally cell death. Enterocin AS-48 was the first identified circular bacteriocin and is best characterized so far. Circular bacteriocins or bacteriocin-producing lactic acid bacteria have great potential in food preservation, and possibly in pharmaceutical and cosmetic industries. Thanks to their properties, circular bacteriocins could be an alternative not only to preservatives and methods used to provide microbial food safety presently, but also to less stable, linear bacteriocins.

1. Characteristics and classification of circular bacteriocins. 2. Genetics of circular bacteriocins. 3. Biosynthesis of circular bacteriocins. 4. Structure of circular bacteriocins. 5. Modes of action of circular bacteriocins. 6. Enterocin AS-48. 7. Potential applications of circular bacteriocins. 8. Summary

Bakteriocyny bakterii Gram-ujemnych – struktura, mechanizm działania i zastosowanie

Bacteriocins of Gram-negative bacteria – structure, mode of action and potential applications
U. Błaszczyk, J. Moczarny

1. Wprowadzenie. 2. Klasyfikacja bakteriocyn bakterii Gram-ujemnych. 3. Produkcja kolicyn przez bakterie kolicynogenne. 3.1. Synteza kolicyn. 3.2. Eksport kolicyn z komórek producenta. 4. Mechanizmy działania kolicyn. 4.1. Translokacja. 4.2. Efekt letalny kolicyn. 5. Charakterystyka i podział mikrocyn. 5.1. Struktura i genetyka wybranych mikrocyn. 5.1.1. MccE492. 5.1.2. MccJ25. 5.1.3. MccC7-C51. 5.2. Mechanizmy działania mikrocyn. 5.2.1. MccE492. 5.2.2. MccJ25. 5.2.3. MccC7-C51. 6. Potencjalne zastosowanie kolicyn i mikrocyn. 7. Podsumowanie

Abstract: Bacteriocins are a diverse group of ribosomally synthesized peptides or proteins secreted by bacteria, which help them to compete in their local environments for the limited nutritional resources. Bacteriocins kill or inhibit the growth of other bacteria. Generally, these molecules have a narrow spectrum of antibacterial activity, but some of them demonstrate a broad spectrum of action. Bacteriocins from Gram-negative bacteria are divided into two main groups: high molecular mass proteins (30–80 kDa) known as colicins, and low molecular mass peptides (between 1–10 kDa) termed microcins. Colicins are produced by Escherichia coli strains harbouring a colicinogenic plasmid. Such colicinogenic strains are widespread in nature and are especially abundant in the gut of animals. The biosynthesis of colicins is mediated by the SOS regulon, which becomes activated in the response to DNA damage. The colicin synthesis is lethal for the producing cells as a consequence of the concomitant biosynthesis of the colicin lysis protein. Microcins are usually highly stable molecules, which are resistant to proteases, extreme pH values and temperatures. They are produced by enteric bacteria under stress conditions, particularly nutrient depletion. Microcins are encoded by gene clusters carried by plasmids or in certain cases by the chromosome. In this review, we have summarized the most important information about structure and properties of bacteriocins from Gram-negative bacteria, their diverse mechanisms of action and potential application as food preservatives and in livestock industry.

1. Introduction. 2. Classification of bacteriocins from Gram-negative bacteria. 3. Production of colicins by colicinogenic bacteria. 3.1. Colicin synthesis. 3.2.  Export of colicins from bacteriocin-producing cells. 4. Modes of colicin action. 4.1. Translocation. 4.2. Lethal effect of colicins. 5. Characteristics and classification of microcins. 5.1. Structure and genetics of selected microcins. 5.1.1. MccE492. 5.1.2. MccJ25. 5.1.3. MccC7-C51. 5.2. Mechanisms of action of microcins. 5.2.1. MccE492. 5.2.2. MccJ25. 5.2.3. MccC7-C51. 6. Potential applications of colicins and microcins. 7. Summary