Lactococcal bacteriocins - mode of action and immunity
TL;DR: The lactococcal bacteriocins are hydrophobic cationic peptides, which form pores in the cytoplasmic membrane of sensitive cells.
Abstract: Bacteriocins are antimicrobial peptides produced by bacteria. Some of those synthesized by Lactococcus lactis have been characterized in great detail recently. The lactococcal bacteriocins are hydrophobic cationic peptides, which form pores in the cytoplasmic membrane of sensitive cells.
Summary (2 min read)
Jump to: [Lactococcal bacteriocins: mode of action and immunitv] – [Mode of action of lantlbiotics: nisin] – [REVIEWS] – [Mode of action of non-Iantibiotics Diplococcin] – [Lactostrepcin 5] – [Lactococcins A and B] – [Nisin immunity and resistance] and [Conclusions and perspectives]
Lactococcal bacteriocins: mode of action and immunitv
- It is tempting to assume that different strains of a species produce these substances to enable them to compete for the same ecological niche.
- Class I bacteriocins, or lantibiotics, are small membrane-active peptides that contain the unusual amino acids lanthionine, P-methyllanthionine, dehydroalanine and dehydrobutyrine.
- All the lactococcal bacteriocins that have been thoroughly characterized so far belong to class I or II.
Mode of action of lantlbiotics: nisin
- Nisin is the only lantibiotic produced by L. luctis for which the mode of action has been studied.
- It is active against a broad spectrum of Gram-positive bacteria; Escherichia coli and other Gram-negative bacteria are only affected when their outer membranes are weakened or disrupted by treatment with EDTA or osmotic shock21,22, which makes their inner membrane accessible to the lantibiotic.
REVIEWS
- Nisin has a dual activity against spore-forming bacteria: it inhibits the outgrowth of spores and kills cells in the vegetative state.
- The 2,3_didehydroamino acid residues in nisin are thought to act against spores by interacting with the membrane sulfhydryl groups of germinating spores 23.
- It dissipates the membrane potential of whole cells, cytoplasmic membrane vesicles and artificial membrane vesicles ( liposomes)24125, indicating that the peptide does not require a specific receptor protein for activity or for membrane insertion.
- Membrane disruption is believed to result from the incorporation of nisin into the cytoplasmic membrane to form an ion channel or pore.
- This may account for the differences in sensitivity seen be-tween bacterial species or strains, as permeabilization only occurs in liposomes that contain zwitterionic phospholipids28T2p.
Mode of action of non-Iantibiotics Diplococcin
- The effect of purified diplococcin from L. lactis subsp.
- The addition of 8 arbitrary units of diplococcin to sensitive cells completely abolishes DNA and RNA synthesis within 2 min, which may partially interrupt protein synthesis.
- Small pores allow leakage of protons and other small ions only, whereas amino acids leak through larger pores.
- No receptor is required for nisin activity.
Lactostrepcin 5
- Lactostrepcin 5 (Las.5) and other lactostrepcins have a strong and rapid bactericidal effect on sensitive cells33; only Las5 has been characterized in detail.
- It inhibits uridine uptake and causes leakage of K+ ions and ATP from cells.
- Like diplococcin, Las5 inhibits DNA, RNA and protein synthesis, probably by the inhibition of transport of precursors required for macromolecular synthesis, energy depletion of the cell and/or leakage from the cell of small solutes that are required for various metabolic activities.
- Las5 is equally active against energized and energy-depleted cells33.
Lactococcins A and B
- They belong to a group of small, cationic hydrophobic peptides (including several lantibiotics) that permeabilize membranes28934"6.
- The mode of action of purified lactococcin A has been studied using whole cells of sensitive lactococcal strains and membrane vesicles made from such cells, and also using liposomes obtained from lactococcal phospholipids3'.
- Similar studies on whole cells have also been done using partially purified lactococcin B (Ref. 38) .
- These results indicate that both lactococcins form pores in the cytoplasmic membrane in a voltage-independent manner.
- Low concentrations of lactococcin B allow leakage of protons and ions, whereas ISO-fold more bacteriocin is needed for leakage of glutamate to occur38, which indicates that pores of different sizes can exist.
Nisin immunity and resistance
- There are several mechanisms by which bacteria protect themselves against nisin.
- Nisin resistance (Nis') is not genetically linked to nisin production.
- These results have been united in a model for LciA topology (Fig. 3b ).
- Residues 29-47 are considered to span the cytoplasmic membrane as an amphiphilic a helix by interacting with another transmembrane protein, possibly the lactococcin A receptor.
Conclusions and perspectives
- The past few years have seen significant progress in their understanding of nisin and the lactococcins.
- The structural and immunity genes and the genes encoding the secretion and post-translational modification machinery have been cloned, and the authors are now beginning to understand the modes of action of nisin and the lactococcins A and B, and the way in which the lactococcin A immunity protein LciA works.
- This knowledge, combined with structure-function studies of the bacteriocins, should allow the construction of molecules with enhanced or altered activities and broader specificities for use as, for example, food preservatives.
- A tropism for the mucous membranes of the human respiratory tract; indeed, the upper respiratory tract of humans is virtually the sole reservoir for this organism.
- Infection by H. in/kenzae illustrates the complex interplay that can occur between the host and the pathogen, in a relationship that does not always culminate in disease4.
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Citations
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TL;DR: Toxicity data exist for only a few bacteriocins, but research and their long-time intentional use strongly suggest that bacteriOCins can be safely used.
Abstract: Bacteriocins are antibacterial proteins produced by bacteria that kill or inhibit the growth of other bacteria. Many lactic acid bacteria (LAB) produce a high diversity of different bacteriocins. Though these bacteriocins are produced by LAB found in numerous fermented and non-fermented foods, nisin is currently the only bacteriocin widely used as a food preservative. Many bacteriocins have been characterized biochemically and genetically, and though there is a basic understanding of their structure-function, biosynthesis, and mode of action, many aspects of these compounds are still unknown. This article gives an overview of bacteriocin applications, and differentiates bacteriocins from antibiotics. A comparison of the synthesis. mode of action, resistance and safety of the two types of molecules is covered. Toxicity data exist for only a few bacteriocins, but research and their long-time intentional use strongly suggest that bacteriocins can be safely used.
1,782 citations
Cites background from "Lactococcal bacteriocins - mode of ..."
...The Ž .lactococcin A immunity protein LcnI is by far the most studied one, yet the basic mechanism behind Žthe immunity is still not understood Nissen-Meyer .et al., 1993; Venema et al., 1994, 1995 ....
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TL;DR: The role of lactic acid bacteria in many such fermentations and the mechanisms of antibiosis with particular reference to bacteriocins are outlined and a brief description of some important fermented foods from various countries are given.
Abstract: Preservation of foods by fermentation is a widely practiced and ancient technology. Fermentation ensures not only increased shelf life and microbiological safety of a food but also may also make some foods more digestible and in the case of cassava fermentation reduces toxicity of the substrate. Lactic acid bacteria because of their unique metabolic characteristics are involved in many fermentation processes of milk, meats, cereals and vegetables. Although many fermentations are traditionally dependent on inoculation from a previous batch starter cultures are available for many commercial processes such as cheese manufacture thus ensuring consistency of process and product quality. This review outlines the role of lactic acid bacteria in many such fermentations and the mechanisms of antibiosis with particular reference to bacteriocins and gives a brief description of some important fermented foods from various countries. It is anticipated that the contribution of the advances in lactic acid bacteria research towards improvement of strains for use in food fermentation will benefit both the consumer and the producer.
1,013 citations
TL;DR: The present review attempts to provide an insight into general knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances.
Abstract: In the last decade, a variety of ribosomally synthesized antimicrobial peptides or bacteriocins produced by lactic acid bacteria have been identified and characterized. As a result of these studies, insight has been gained into fundamental aspects of biology and biochemistry such as producer self protection, membrane-protein interactions, and protein modification and secretion. Moreover, it has become evident that these peptides may be developed into useful antimicrobial additives. Class IIa bacteriocins can be considered as the major subgroup of bacteriocins from lactic acid bacteria, not only because of their large number, but also because of their activities and potential applications. They have first attracted particular attention as listericidal compounds and are now believed to be the next in line if more bacteriocins are to be approved in the future. The present review attempts to provide an insight into general knowledge available for class IIa bacteriocins and discusses common features and recent findings concerning these substances.
611 citations
Cites background from "Lactococcal bacteriocins - mode of ..."
...Class IIa bacteriocins are generally opposed to nisin in the sense that they interact with the cytoplasmic membranes of sensitive cells regardless of their degree of prior energization, suggesting that the loss of permeability of the cytoplasmic membrane occurs in a voltage-independent manner [3,49,85,86], while nisin acts in a membrane-potential-dependent manner [5,92]....
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...The initial step of class-IIa-bacteriocin interaction with the membrane surface is generally believed to be an electrostatic binding mediated by a putative membrane-bound receptor-type molecule [28,49,86]....
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...The lethal activity of class IIa bacteriocins is thus mainly ascribed to the dissipation of the PMF [3,28,49]....
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TL;DR: This review article focuses primarily on class I and class IIa bacteriocins produced by lactic acid bacteria (LAB) given their development as food preservatives.
Abstract: Over the last 2 decades, a variety of bacteriocins, produced by bacteria that kill or inhibit the growth of other bacteria, have been identified and characterized biochemically and genetically. This review article focuses on the ecology of bacteriocins, determination of bacteriocin activity, biosynthesis of bacteriocins, and mode of action. Bacteriocin production and modeling are discussed in the article. Nisin is discussed in some detail in this article since it is currently the only purified bacteriocin approved for food use in the U.S. and has been successfully used for several decades as a food preservative in more than 50 countries. For activity spectra and food applications, the review article focuses primarily on class I and class IIa bacteriocins produced by lactic acid bacteria (LAB) given their development as food preservatives.
502 citations
TL;DR: Although today a lot is known about LAB bacteriocins and the regulation of their production, several fundamental questions remain to be solved, including questions regarding mechanisms of immunity and resistance, as well as the molecular basis of target-cell specificity.
Abstract: Lactic acid bacteria (LAB) fight competing Gram-positive microorganisms by secreting anti-microbial peptides called bacteriocins. Peptide bacteriocins are usually divided into lantibiotics (class I) and non-lantibiotics (class II), the latter being the main topic of this review. During the past decade many of these bacteriocins have been isolated and characterized, and elements of the genetic mechanisms behind bacteriocin production have been unravelled. Bacteriocins often have a narrow inhibitory spectrum, and are normally most active towards closely related bacteria likely to occur in the same ecological niche. Lactic acid bacteria seem to compensate for these narrow inhibitory spectra by producing several bacteriocins belonging to different classes and having different inhibitory spectra. The latter may also help in counteracting the possible development of resistance mechanisms in target organisms. In many strains, bacteriocin production is controlled in a cell-density dependent manner, using a secreted peptide-pheromone for quorum-sensing. The sensing of its own growth, which is likely to be comparable to that of related species, enables the producing organism to switch on bacteriocin production at times when competition for nutrients is likely to become more severe. Although today a lot is known about LAB bacteriocins and the regulation of their production, several fundamental questions remain to be solved. These include questions regarding mechanisms of immunity and resistance, as well as the molecular basis of target-cell specificity.
363 citations
Cites background from "Lactococcal bacteriocins - mode of ..."
...This may be taken to indicate that immunity proteins act via an effect on a (putative) bacteriocin receptor in the cytoplasmic membrane (e.g. Venema et al. 1995)....
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...Venema et al. (1995) showed that the C-terminal part of the lactococcin A immunity protein is exposed to the exterior of the cell....
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...This may be taken to indicate that immunity proteins act via an effect on a (putative) bacteriocin receptor in the cytoplasmic membrane (e.g. Venema et al. 1995 )....
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... Venema et al. (1995) showed that the C-terminal part of the lactococcin A immunity protein is exposed to the exterior of the cell....
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...…indicate that immunity proteins for class II bacteriocins are soluble and mainly located in the cytoplasm, although in some cases the presence of one transmembrane helix has been suggested (Nissen-Meyer et al. 1993; Quadri et al. 1995; Venema et al. 1995; Dayem et al. 1996; Eijsink et al. 1998)....
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References
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TL;DR: The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.
Abstract: Lactic acid bacteria produce a variety of bacteriocins that have recently come under detailed investigation. The biochemical and genetic characteristics of these antimicrobial proteins are reviewed and common elements are discussed between the different classes of bacteriocins produced by these Gram-positive bacteria.
2,013 citations
TL;DR: The range of inhibitory activity by bacteriocins of lactic acid bacteria can be either narrow, inhibiting only those strains that are closely related to the producer organism, or wide, inhibited a diverse group of Gram-positive microorganisms as mentioned in this paper.
Abstract: Lactic acid bacteria produce a variety of antagonistic factors that include metabolic end products, antibiotic-like substances and bactericidal proteins, termed bacteriocins. The range of inhibitory activity by bacteriocins of lactic acid bacteria can be either narrow, inhibiting only those strains that are closely related to the producer organism, or wide, inhibiting a diverse group of Gram-positive microorganisms. The following review will discuss biochemical and genetic aspects of bacteriocins that have been identified and characterized from lactic acid bacteria.
1,754 citations
TL;DR: It is demonstrated that nisin is bactericidal to Salmonella species and that the observed inactivation can be demonstrated in other gram-negative bacteria.
Abstract: Nisin, produced by Lactococcus lactis subsp. lactis, has a broad spectrum of activity against gram-positive bacteria and is generally recognized as safe in the United States for use in selected pasteurized cheese spreads to control the outgrowth and toxin production of Clostridium botulinum. This study evaluated the inhibitory activity of nisin in combination with a chelating agent, disodium EDTA, against several Salmonella species and other selected gram-negative bacteria. After a 1-h exposure to 50 micrograms of nisin per ml and 20 mM disodium EDTA at 37 degrees C, a 3.2- to 6.9-log-cycle reduction in population was observed with the species tested. Treatment with disodium EDTA or nisin alone produced no significant inhibition (less than 1-log-cycle reduction) of the Salmonella and other gram-negative species tested. These results demonstrated that nisin is bactericidal to Salmonella species and that the observed inactivation can be demonstrated in other gram-negative bacteria. Applications involving the simultaneous treatment with nisin and chelating agents that alter the outer membrane may be of value in controlling food-borne salmonellae and other gram-negative bacteria.
586 citations
TL;DR: Transcription analyses of several L. lactis strains indicated that an expression product of the nisA gene, together with NisR, is required for the activation of nisinA transcription, indicating that NisI plays a role in the immunity mechanism.
Abstract: The nisin gene cluster nisABTCIPR of Lactococcus lactis, located on a 10-kbp DNA fragment of the nisin-sucrose transposon Tn5276, was characterized. This fragment was previously shown to direct nisin-A biosynthesis and to contain the nisP and nisR genes, encoding a nisin leader peptidase and a positive regulator, respectively [van der Meer, J. R., Polman, J., Beerthuyzen, M. M., Siezen, R. J., Kuipers, O. P. & de Vos, W. M. (1993) J. Bacteriol. 175, 2578–2588]. Further sequence analysis revealed the presence of four open-reading frames, nisB, nisT, nisC and nisI, downstream of the structural gene nisA. The nisT, nisC and nisI genes were subcloned and expressed individually in Escherichia coli, using the T7-RNA-polymerase system. This resulted in the production of radio-labelled proteins with sizes of 45 kDa (NisC) and 32 kDa (NisI). The nisT gene product was not detected, possibly because of protein instability. The deduced amino acid sequence of NisI contained a consensus Iipoprotein signal sequence, suggesting that this protein is a lipid-modified extracellular membrane-anchored protein. Expression of nisI in L. Iactis provided the cells with a significant level of protection against exogeneously added nisin, indicating that NisI plays a role in the immunity mechanism. In EDTA-treated E. coli cells, expression of nisI conferred up to a 170-fold increase in immunity against nisin A compared to controls. Moreover, a lactococcal strain deficient in nisin-A production, designated NZ9800, was created by gene replacement of nisA by a truncated nisA gene and was 10-fold less resistant to nisin A than the wild-type strain. A wild-type immunity level to nisin and production of nisin was obtained in strain NZ9800 harboring complementing nisA and nisZ plasmids. Transcription analyses of several L. IIactis strains indicated that an expression product of the nisA gene, together with NisR, is required for the activation of nisA transcription.
564 citations
TL;DR: The data suggest that the cytoplasmic membrane is the primary target and that membrane disruption accounts for the bactericidal action of nisin.
Abstract: The peptide antibiotic nisin was shown to cause a rapid efflux of amino acids and Rb+ from the cytoplasm of gram-positive bacteria (Staphylococcus cohnii 22, Bacillus subtilis W 23, Micrococcus luteus ATCC 4698, and Streptococcus zymogenes 24). It strongly decreased the membrane potential of cells as judged by the distribution of the lipophilic tetraphenylphosphonium cation. Ascorbate-phenazine methosulfate-driven transport of L-proline by cytoplasmic membrane vesicles was blocked after addition of nisin, and accumulated amino acids were released from the vesicles. Soybean phospholipid (asolectin) vesicles were not affected by nisin. The data suggest that the cytoplasmic membrane is the primary target and that membrane disruption accounts for the bactericidal action of nisin.
379 citations