Development of Class IIa Bacteriocins as Therapeutic Agents

OpenAIRE

Christopher T. Lohans; John C. Vederas

2012-01-01

Class IIa bacteriocins have been primarily explored as natural food preservatives, but there is much interest in exploring the application of these peptides as therapeutic antimicrobial agents. Bacteriocins of this class possess antimicrobial activity against several important human pathogens. Therefore, the therapeutic development of these bacteriocins will be reviewed. Biological and chemical modifications to both stabilize and increase the potency of bacteriocins are discussed, as well as ...

Discovering the bacterial circular proteins : bacteriocins, cyanobactins, and pilins

NARCIS (Netherlands)

Montalban-Lopez, Manuel; Sanchez-Hidalgo, Marina; Cebrian, Ruben; Maqueda, Mercedes

2012-01-01

Over recent years, several examples of natural ribosomally synthesized circular proteins and peptides from diverse organisms have been described. They are a group of proteins for which the precursors must be post-translationally modified to join the N and C termini with a peptide bond. This feature

Bacteriocins as food preservatives: Challenges and emerging horizons.

Science.gov (United States)

Johnson, Eldin Maliyakkal; Jung, Dr Yong-Gyun; Jin, Dr Ying-Yu; Jayabalan, Dr Rasu; Yang, Dr Seung Hwan; Suh, Joo Won

2017-09-07

The increasing demand for fresh-like food products and the potential health hazards of chemically preserved and processed food products have led to the advent of alternative technologies for the preservation and maintenance of the freshness of the food products. One such preservation strategy is the usage of bacteriocins or bacteriocins producing starter cultures for the preservation of the intended food matrixes. Bacteriocins are ribosomally synthesized smaller polypeptide molecules that exert antagonistic activity against closely related and unrelated group of bacteria. This review is aimed at bringing to lime light the various class of bacteriocins mainly from gram positive bacteria. The desirable characteristics of the bacteriocins which earn them a place in food preservation technology, the success story of the same in various food systems, the various challenges and the strategies employed to put them to work efficiently in various food systems has been discussed in this review. From the industrial point of view various aspects like the improvement of the producer strains, downstream processing and purification of the bacteriocins and recent trends in engineered bacteriocins has also been briefly discussed in this review.

LAB Bacteriocins Controlling the Food Isolated (Drug-Resistant Staphylococci

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Jesús Perales-Adán

2018-06-01

Full Text Available Staphylococci are a group of microorganisms that can be often found in processed food and they might pose a risk for human health. In this study we have determined the content of staphylococci in 7 different fresh goat-milk cheeses. These bacteria were present in all of them, ranging from 103 to 106 CFU/g based on growth on selective media. Thus, a set of 97 colonies was randomly picked for phenotypic and genotypic identification. They could be clustered by RAPD-PCR in 10 genotypes, which were assigned by 16S rDNA sequencing to four Staphylococcus species: Staphylococcus aureus, Staphylococcus chromogenes, S. simulans, and S. xylosus. Representative strains of these species (n = 25 were tested for antibiotic sensitivity, and 11 of them were resistant to at least one of the antibiotics tested, including erythromycin, amoxicillin-clavulanic acid and oxacillin. We also tested two bacteriocins produced by lactic acid bacteria (LAB, namely the circular bacteriocin AS-48 and the lantibiotic nisin. These peptides have different mechanism of action at the membrane level. Nevertheless, both were able to inhibit staphylococci growth at low concentrations ranging between 0.16–0.73 μM for AS-48 and 0.02–0.23 μM for nisin, including the strains that displayed antibiotic resistance. The combined effect of these bacteriocins were tested and the fractional inhibitory concentration index (FICI was calculated. Remarkably, upon combination, they were active at the low micromolar range with a significant reduction of the minimal inhibitory concentration. Our data confirms synergistic effect, either total or partial, between AS-48 and nisin for the control of staphylococci and including antibiotic resistant strains. Collectively, these results indicate that the combined use of AS-48 and nisin could help controlling (pathogenic staphylococci in food processing and preventing antibiotic-resistant strains reaching the consumer in the final products.

Application of Bacteriocins and Protective Cultures in Dairy Food Preservation

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Célia C. G. Silva

2018-04-01

Full Text Available In the last years, consumers are becoming increasingly aware of the human health risk posed by the use of chemical preservatives in foods. In contrast, the increasing demand by the dairy industry to extend shelf-life and prevent spoilage of dairy products has appeal for new preservatives and new methods of conservation. Bacteriocins are antimicrobial peptides, which can be considered as safe since they can be easily degraded by proteolytic enzymes of the mammalian gastrointestinal tract. Also, most bacteriocin producers belong to lactic acid bacteria (LAB, a group that occurs naturally in foods and have a long history of safe use in dairy industry. Since they pose no health risk concerns, bacteriocins, either purified or excreted by bacteriocin producing strains, are a great alternative to the use of chemical preservatives in dairy products. Bacteriocins can be applied to dairy foods on a purified/crude form or as a bacteriocin-producing LAB as a part of fermentation process or as adjuvant culture. A number of applications of bacteriocins and bacteriocin-producing LAB have been reported to successful control pathogens in milk, yogurt, and cheeses. One of the more recent trends consists in the incorporation of bacteriocins, directly as purified or semi-purified form or in incorporation of bacteriocin-producing LAB into bioactive films and coatings, applied directly onto the food surfaces and packaging. This review is focused on recent developments and applications of bacteriocins and bacteriocin-producing LAB for reducing the microbiological spoilage and improve safety of dairy products.

Bacteriocins: Novel Solutions to Age Old Spore-Related Problems?

OpenAIRE

Kevin eEgan; Des eField; Mary Clare Rea; Mary Clare Rea; R Paul Ross; R Paul Ross; Colin eHill; Colin eHill; Paul David Cotter; Paul David Cotter

2016-01-01

Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, which have the ability to kill or inhibit other bacteria. Many bacteriocins are produced by food grade lactic acid bacteria (LAB). Indeed, the prototypic bacteriocin, nisin, is produced by Lactococcus lactis, and is licensed in over 50 countries. With consumers becoming more concerned about the levels of chemical preservatives present in food, bacteriocins offer an alternative, more natural, approach, while ...

Bacteriocins: Novel Solutions to Age Old Spore-Related Problems?

OpenAIRE

Egan, Kevin; Field, Des; Rea, Mary C.; Ross, R. Paul; Hill, Colin; Cotter, Paul D.

2016-01-01

Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, which have the ability to kill or inhibit other bacteria. Many bacteriocins are produced by food grade lactic acid bacteria (LAB). Indeed, the prototypic bacteriocin, nisin, is produced by Lactococcus lactis, and is licensed in over 50 countries. With consumers becoming more concerned about the levels of chemical preservatives present in food, bacteriocins offer an alternative, more natural approach, while e...

Structure-activity relationships of an antimicrobial peptide plantaricin s from two-peptide class IIb bacteriocins.

Science.gov (United States)

Soliman, Wael; Wang, Liru; Bhattacharjee, Subir; Kaur, Kamaljit

2011-04-14

Class IIb bacteriocins are ribosomally synthesized antimicrobial peptides comprising two different peptides synergistically acting in equal amounts for optimal potency. In this study, we demonstrate for the first time potent (nanomolar) antimicrobial activity of a representative class IIb bacteriocin, plantaricin S (Pls), against four pathogenic gram-positive bacteria, including Listeria monocytogenes. The structure-activity relationships for Pls were studied using activity assays, circular dichroism (CD), and molecular dynamics (MD) simulations. The two Pls peptides and five Pls derived fragments were synthesized. The CD spectra of the Pls and selected fragments revealed helical conformations in aqueous 2,2,2-trifluoroethanol. The MD simulations showed that when the two Pls peptides are in antiparallel orientation, the helical regions interact and align, mediated by strong attraction between conserved GxxxG/AxxxA motifs. The results strongly correlate with the antimicrobial activity suggesting that helix-helix alignment of the two Pls peptides and interaction between the conserved motifs are crucial for interaction with the target cell membrane.

Bacteriocins from lactic acid bacteria as an alternative to antibiotics

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Aleksandra Ołdak

2017-05-01

Full Text Available Bacteriocins are ribosomally synthesized, proteinaceous substances that inhibit the growth of closely related species through numerous mechanisms. The classification system used in this review divided bacteriocins into four sub-groups based on their size. Currently, there is extensive research focused on bacteriocins and their usage as a food preservative.The increasing incidence of multidrug resistant bacterial pathogens is one of the most pressing medical problems in recent years. Recently, the potential clinical application of LAB (Lactic Acid Bacteria bacteriocin has been the subject of investigations by many scientists.Bacteriocins can be considered in a sense as antibiotic, although they differ from conventional antibiotics in numerous aspects. The gene-encoded nature of bacteriocins makes them easily amenable through bioengineering to either increase their activity or specify target microorganism. Owing to this feature of bacteriocins, antibiotic therapy would become less damaging to the natural gut microflora, which is a common drawback of conventional antibiotic use. Bacteriocins from lactic acid bacteria represent one of the most studied microbial defense systems and the idea of subjecting them to bioengineering to either increase antimicrobial activity or further specify their target microorganism is now a rapidly expanding field. This review aimed to present bacteriocins as a possible alternative to conventional antibiotics basic on latest scientific data.

Bacteriocins: Novel Solutions to Age Old Spore-Related Problems?

Directory of Open Access Journals (Sweden)

Kevin eEgan

2016-04-01

Full Text Available Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, which have the ability to kill or inhibit other bacteria. Many bacteriocins are produced by food grade lactic acid bacteria (LAB. Indeed, the prototypic bacteriocin, nisin, is produced by Lactococcus lactis, and is licensed in over 50 countries. With consumers becoming more concerned about the levels of chemical preservatives present in food, bacteriocins offer an alternative, more natural, approach, while ensuring both food safety and product shelf life. Bacteriocins also show additive/synergistic effects when used in combination with other treatments, such as heating, high pressure, organic compounds, and as part of food packaging. These features are particularly attractive from the perspective of controlling sporeforming bacteria. Bacterial spores are common contaminants of food products, and their outgrowth may cause food spoilage or food-borne illness. They are of particular concern to the food industry due to their thermal and chemical resistance in their dormant state. However, when spores germinate they lose the majority of their resistance traits, making them susceptible to a variety of food processing treatments. Bacteriocins represent one potential treatment as they may inhibit spores in the post-germination/outgrowth phase of the spore cycle. Spore eradication and control in food is critical, as they are able to spoil and in certain cases compromise the safety of food by producing dangerous toxins. Thus, understanding the mechanisms by which bacteriocins exert their sporostatic/sporicidal activity against bacterial spores will ultimately facilitate their optimal use in food. This review will focus on the use of bacteriocins alone, or in combination with other innovative processing methods to control spores in food, the current knowledge and gaps therein with regard to bacteriocin-spore interactions and discuss future research approaches to enable

Therapeutic enhancement of newly derived bacteriocins against Giardia lamblia.

Science.gov (United States)

Amer, Eglal I; Mossallam, Shereen F; Mahrous, Hoda

2014-11-01

Trials for identifying efficient anti-giardial agents are still ongoing. Nowadays, bacteriocins have attracted the attention as potential antimicrobial compounds. For the first time, the current study evaluated the therapeutic efficacy of bacteriocins derived from newly isolated Egyptian strains of probiotics Lactobacilli; L. acidophilus (P106) and L. plantarum (P164) against Giardia lamblia. Bacteriocins' efficacy was evaluated both in vitro; by growth inhibition and adherence assays, and in vivo; through estimation of parasite density, intestinal histopathological examination and ultrastructural analysis of Giardia trophozoites. In vivo bacteriocins' clinical safety was assessed. In vitro results proved that 50 µg of L. acidophilus bacteriocin induced reduction of the mean Giardia lamblia trophozoites by 58.3 ± 4.04%, while at lower concentrations of 10 and 20 µg of both L. acidophilus and L. plantarum, non significant reduction of the mean parasite density was achieved. In vitro trophozoites adherence was susceptible to the tested bacteriocins at all studied concentrations with variable degrees, while the highest adherence reduction was demonstrated using 50 µg of L acidophilus bacteriocin. In vivo, oral inoculation of 50 µg/mouse L. acidophilus bacteriocin for 5 successive days resulted in a noteworthy decline of the intestinal parasite density, along with amelioration of intestinal pathology of infected mice. Ultrastructural examination proved thatfive doses of L. acidophilus bacteriocin showed marked changes in cellular architecture of the trophozoites with evident disorganization of the cell membrane, adhesive disc and cytoplasmic components. This is the first reported study of the safe anti-giardial efficacy of L. acidophilus (P106) derived bacteriocin, hence highlighting its great promise as a potential therapeutic safe alternative to existing commercial drugs. Copyright © 2014 Elsevier Inc. All rights reserved.

Bacteriocins: Novel Solutions to Age Old Spore-Related Problems?

Science.gov (United States)

Egan, Kevin; Field, Des; Rea, Mary C; Ross, R Paul; Hill, Colin; Cotter, Paul D

2016-01-01

Bacteriocins are ribosomally synthesized antimicrobial peptides produced by bacteria, which have the ability to kill or inhibit other bacteria. Many bacteriocins are produced by food grade lactic acid bacteria (LAB). Indeed, the prototypic bacteriocin, nisin, is produced by Lactococcus lactis, and is licensed in over 50 countries. With consumers becoming more concerned about the levels of chemical preservatives present in food, bacteriocins offer an alternative, more natural approach, while ensuring both food safety and product shelf life. Bacteriocins also show additive/synergistic effects when used in combination with other treatments, such as heating, high pressure, organic compounds, and as part of food packaging. These features are particularly attractive from the perspective of controlling sporeforming bacteria. Bacterial spores are common contaminants of food products, and their outgrowth may cause food spoilage or food-borne illness. They are of particular concern to the food industry due to their thermal and chemical resistance in their dormant state. However, when spores germinate they lose the majority of their resistance traits, making them susceptible to a variety of food processing treatments. Bacteriocins represent one potential treatment as they may inhibit spores in the post-germination/outgrowth phase of the spore cycle. Spore eradication and control in food is critical, as they are able to spoil and in certain cases compromise the safety of food by producing dangerous toxins. Thus, understanding the mechanisms by which bacteriocins exert their sporostatic/sporicidal activity against bacterial spores will ultimately facilitate their optimal use in food. This review will focus on the use of bacteriocins alone, or in combination with other innovative processing methods to control spores in food, the current knowledge and gaps therein with regard to bacteriocin-spore interactions and discuss future research approaches to enable spores to be more

Characterization of bacteriocin produced by Lactobacillus plantarum ...

African Journals Online (AJOL)

Characterization of bacteriocin produced by Lactobacillus plantarum F1 and ... brevis OG1 isolated from Nigerian fermented food products, produced bacteriocins ... interest for food safety and may have future applications as food preservative.

Utilization of bacteriocin-producing bacteria in dairy products

Directory of Open Access Journals (Sweden)

Matěj Patrovský

2016-07-01

Full Text Available Lactic acid bacteria have been used since ancient times for food preparation and for bio-conservation by fermentation. Selected strains are capable of producing antimicrobial peptides - bacteriocins, which can be natural preservatives, especially in products with short shelf lives. The present study is focused on inhibitory effects of the bacteriocin-producing bacteria strains Enterococcus faecium, Pediococccus acidilactici and Lactobacillus plantarum against Listeria innocua as an indicator microorganism. Freeze-dried preparations of bacterial strains producing particular bacteriocins were tested by agar well-diffusion assay and by the traditional spread plate method. Plantaricin exhibited the highest anti-listerial effect among the tested bacteriocins. Pediocin also demonstrated a distinct inhibitory effect, but enterocin appeared to be heat labile and its efficiency was also suppressed under cold storage conditions. Plantaricin reduced Listeria innocua counts by 1 log in dairy spread made from cheese and quark. The formation of bacteriocins by various Lactobacillus plantarum strains were substantially influenced by the cultivation conditions of the mother culture and by the microbial preparation process before freeze-drying. Bacteriocins introduced into foodstuffs via protective cultures in situ offer new perspectives on enhancing food quality and safety.

Competitive Dominance by a Bacteriocin-Producing Vibrio harveyi Strain.

Science.gov (United States)

Hoyt, P R; Sizemore, R K

1982-09-01

Vibrio (Beneckea) harveyi, a bioluminescent marine bacterium, has been shown to produce a bacteriocin-like substance the production of which is mediated by a plasmid. This substance is assumed to be proteinaceous because of its sensitivity to certain proteolytic enzymes. It is stable at low temperatures and can be concentrated by ammonium sulfate precipitation or negative-pressure dialysis. The molecular weight of the bacteriocin was determined to be 2.4 x 10 by molecular exclusion chromatography. Competition experiments indicated that bacteriocin-producing strains predominated over cured variants of the same strain in broth culture experiments. We studied several environmental parameters (pH, salinity, temperature, nutrient concentration) to determine their effects on the competitive advantage bestowed on a bacteriocin-producing strain. Under simulated free-living conditions, no competitive advantage attributable to bacteriocin production was observed. In a simulated enteric habitat, a bacteriocin-producing strain showed dramatic (>90%) inhibition of the sensitive strain within 24 h.

Novel Group of Leaderless Multipeptide Bacteriocins from Gram-Positive Bacteria.

Science.gov (United States)

Ovchinnikov, Kirill V; Chi, Hai; Mehmeti, Ibrahim; Holo, Helge; Nes, Ingolf F; Diep, Dzung B

2016-09-01

From raw milk we found 10 Lactococcus garvieae isolates that produce a new broad-spectrum bacteriocin. Though the isolates were obtained from different farms, they turned out to possess identical inhibitory spectra, fermentation profiles of sugars, and repetitive sequence-based PCR (rep-PCR) DNA patterns, indicating that they produce the same bacteriocin. One of the isolates (L. garvieae KS1546) was chosen for further assessment. Purification and peptide sequencing combined with genome sequencing revealed that the antimicrobial activity was due to a bacteriocin unit composed of three similar peptides of 32 to 34 amino acids. The three peptides are produced without leader sequences, and their genes are located next to each other in an operon-like structure, adjacent to the genes normally involved in bacteriocin transport (ABC transporter) and self-immunity. The bacteriocin, termed garvicin KS (GarKS), showed sequence homology to four multipeptide bacteriocins in databases: the known staphylococcal aureocin A70, consisting of four peptides, and three unannotated putative multipeptide bacteriocins produced by Bacillus cereus All these multipeptide bacteriocin loci show conserved genetic organization, including being located adjacent to conserved genetic determinants (Cro/cI and integrase) which are normally associated with mobile genetic elements or genome rearrangements. The antimicrobial activity of all multipeptide bacteriocins was confirmed with synthetic peptides, and all were shown to have broad antimicrobial spectra, with GarKS being the most active of them. The inhibitory spectrum of GarKS includes important pathogens belonging to the genera Staphylococcus, Bacillus, Listeria, and Enterococcus Bacterial resistance to antibiotics is a very serious global problem. There are no new antibiotics with novel antimicrobial mechanisms in clinical trials. Bacteriocins use antimicrobial mechanisms different from those of antibiotics and can kill antibiotic

Potency Of Bacteriocin For Animal Health And Food Safety

Directory of Open Access Journals (Sweden)

Siti Chotiah

2013-06-01

Full Text Available The emergence of antibiotic resistance in many bacteria related to animal and public health stresses the importance of decreasing the use of antibiotics in animal production. The reduction of antibiotic application in livestock can only be achieved if alternative antimicrobial strategies are available. A number of strategies have been explored to control microbial pathogens and to improve growth and feed efficiency in livestock without the use of antibiotics. Bacteriocins have been more extensively studied and proposed as potential alternatives to conventional antibiotics in animal husbandry. Bacteriocins are antimicrobial peptides ribosomally synthesized by many species of Bacteria and some strains of Archaea. In general, bacteriocins just exhibited bactericidal or bacteriostatic activity against other bacteria that are closely related to the producing strain. The main mechanisms of bacteriocin activity vary from pore formation in cytoplasmic membranes to the inhibition of cell wall biosynthesis and enzyme activities (RNAse or DNAse in target cells. The use of bacteriocins in probiotic applications, as preservatives, and most excitingly as alternatives to conventional antibiotics is being broadly explored and studied. This review will describe the bacteriocins potency for animal health and food safety, as well as the results of bacteriocin study that had been conducted in Indonesia.

Antibacterial Activities of Bacteriocins: Application in Foods and Pharmaceuticals

Directory of Open Access Journals (Sweden)

Shih-Chun eYang

2014-05-01

Full Text Available Bacteriocins are a kind of ribosomal synthesized antimicrobial peptides produced by bacteria, which can kill or inhibit bacterial strains closely-related or non-related to produced bacteria, but will not harm the bacteria themselves by specific immunity proteins. Bacteriocins become one of the weapons against microorganisms due to the specific characteristics of large diversity of structure and function, natural resource, and being stable to heat. Many recent studies have purified and identified bacteriocins for application in food technology, which aims to extend food preservation time, treat pathogen disease and cancer therapy, and maintain human health. Therefore, bacteriocins may become a potential drug candidate for replacing antibiotics in order to treat multiple drugs resistance pathogens in the future. This review article summarizes different types of bacteriocins from bacteria. The latter half of this review focuses on the potential applications applications in food science and pharmaceutical industry.

Genetic identification of the bacteriocins produced by Enterococcus faecium IT62 and evidence that bacteriocin 32 is identical to enterocin IT.

Science.gov (United States)

Izquierdo, Esther; Cai, Yimin; Marchioni, Eric; Ennahar, Saïd

2009-05-01

Enterococcus faecium IT62, a strain isolated from ryegrass in Japan, produces three bacteriocins (enterocins L50A, L50B, and IT) that have been previously purified and the primary structures of which have been determined by amino acid sequencing (E. Izquierdo, A. Bednarczyk, C. Schaeffer, Y. Cai, E. Marchioni, A. Van Dorsselaer, and S. Ennahar, Antimicrob. Agents Chemother., 52:1917-1923, 2008). Genetic analysis showed that the bacteriocins of E. faecium IT62 are plasmid encoded, but with the structural genes specifying enterocin L50A and enterocin L50B being carried by a plasmid (pTAB1) that is separate from the one (pTIT1) carrying the structural gene of enterocin IT. Sequencing analysis of a 1,475-bp region from pTAB1 identified two consecutive open reading frames corresponding, with the exception of 2 bp, to the genes entL50A and entL50B, encoding EntL50A and EntL50B, respectively. Both bacteriocins are synthesized without N-terminal leader sequences. Genetic analysis of a sequenced 1,380-bp pTIT1 fragment showed that the genes entIT and entIM, encoding enterocin IT and its immunity protein, respectively, were both found in E. faecium VRE200 for bacteriocin 32. Enterocin IT, a 6,390-Da peptide made up of 54 amino acids, has been previously shown to be identical to the C-terminal part of bacteriocin 32, a 7,998-Da bacteriocin produced by E. faecium VRE200 whose structure was deduced from its structural gene (T. Inoue, H. Tomita, and Y. Ike, Antimicrob. Agents Chemother., 50:1202-1212, 2006). By combining the biochemical and genetic data on enterocin IT, it was concluded that bacteriocin 32 is in fact identical to enterocin IT, both being encoded by the same plasmid-borne gene, and that the N-terminal leader peptide for this bacteriocin is 35 amino acids long and not 19 amino acids long as previously reported.

Bacteriocins of Non-aureus Staphylococci Isolated from Bovine Milk

Science.gov (United States)

Carson, Domonique A.; Barkema, Herman W.; Naushad, Sohail

2017-01-01

ABSTRACT Non-aureus staphylococci (NAS), the bacteria most commonly isolated from the bovine udder, potentially protect the udder against infection by major mastitis pathogens due to bacteriocin production. In this study, we determined the inhibitory capability of 441 bovine NAS isolates (comprising 26 species) against bovine Staphylococcus aureus. Furthermore, inhibiting isolates were tested against a human methicillin-resistant S. aureus (MRSA) isolate using a cross-streaking method. We determined the presence of bacteriocin clusters in NAS whole genomes using genome mining tools, BLAST, and comparison of genomes of closely related inhibiting and noninhibiting isolates and determined the genetic organization of any identified bacteriocin biosynthetic gene clusters. Forty isolates from 9 species (S. capitis, S. chromogenes, S. epidermidis, S. pasteuri, S. saprophyticus, S. sciuri, S. simulans, S. warneri, and S. xylosus) inhibited growth of S. aureus in vitro, 23 isolates of which, from S. capitis, S. chromogenes, S. epidermidis, S. pasteuri, S. simulans, and S. xylosus, also inhibited MRSA. One hundred five putative bacteriocin gene clusters encompassing 6 different classes (lanthipeptides, sactipeptides, lasso peptides, class IIa, class IIc, and class IId) in 95 whole genomes from 16 species were identified. A total of 25 novel bacteriocin precursors were described. In conclusion, NAS from bovine mammary glands are a source of potential bacteriocins, with >21% being possible producers, representing potential for future characterization and prospective clinical applications. IMPORTANCE Mastitis (particularly infections caused by Staphylococcus aureus) costs Canadian dairy producers $400 million/year and is the leading cause of antibiotic use on dairy farms. With increasing antibiotic resistance and regulations regarding use, there is impetus to explore bacteriocins (bacterially produced antimicrobial peptides) for treatment and prevention of bacterial infections

Bacteriocin-mediated competition in cystic fibrosis lung infections

DEFF Research Database (Denmark)

Ghoul, Melanie; West, Stuart A.; Johansen, Helle Krogh

2015-01-01

Bacteriocins are toxins produced by bacteria to kill competitors of the same species. Theory and laboratory experiments suggest that bacteriocin production and immunity play a key role in the competitive dynamics of bacterial strains. The extent to which this is the case in natural populations......, especially human pathogens, remains to be tested. We examined the role of bacteriocins in competition using Pseudomonas aeruginosa strains infecting lungs of humans with cystic fibrosis (CF). We assessed the ability of different strains to kill each other using phenotypic assays, and sequenced their genomes...

Bacteriocin-producing Enterococci from Rabbit Meat

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Szabóová, R.

2012-01-01

Full Text Available Aims: Enterococci are lactic acid bacteria belonging to the division Firmicutes. They occur in different ecosystems, rabbits including. Enterococci can possess probiotic properties and produce antimicrobial substances-bacteriocins. Rabbit meat as nutritionally healthy food offers novel source to study bacteriocin-producing and/or probiotic enterococci. Methodology and results: Enterococci were detected from rabbit meat samples (42. Most of the isolates were allotted to the species Enterococcus faecium by PCR method. The isolates have possessed the structural genes for enterocins A, P, B production. The inhibitory substances produced by the isolated enterococci inhibited the growth of 12 indicators. Of 34 isolates, 15 strains have shown the antimicrobial activity against L. monocytogenes CCM 4699, 12 strains against S. aureus 3A3, 10 strains against S. aureus 5A2 as well as Salmonella enterica serovar Enteritidis PT4. Moreover, enterococci have tolerated 5 % bile, low pH; they have produced lactid acid in the amount from 0.740 ± 0.091 to 1.720 ± 0.095 mmol/l. The isolates were mostly sensitive to antibiotics. Conclusion, significance and impact of study: Bacteriocin-producing strain E. faecium M3a has been selected for more detail characterization of its bacteriocin and probiotic properties with the aim for its further application as an additive.

Partial Purification Characterization and Application of Bacteriocin from Bacteria Isolated Parkia biglobosa Seeds

OpenAIRE

Olorunjuwon, O. Bello; Olubukola, O. Babalola; Mobolaji, Adegboye; Muibat, O. Fashola; Temitope, K. Bello

2018-01-01

Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strains. Fermented Parkia biglobosa seeds (African locust bean) were screened for bacteriocin-producing lactic acid bacteria (LAB) with the characterization of putative bacteriocins. Bacteriocin-producing lactic acid bacteria (LAB) were identified by 16s rDNA sequencing. Molecular sizes of the bacteriocins were determined using the tricine-sodium dodecyl sulphate-polyacryla...

Current state of purification, isolation and analysis of bacteriocins produced by lactic acid bacteria.

Science.gov (United States)

Kaškonienė, Vilma; Stankevičius, Mantas; Bimbiraitė-Survilienė, Kristina; Naujokaitytė, Gintarė; Šernienė, Loreta; Mulkytė, Kristina; Malakauskas, Mindaugas; Maruška, Audrius

2017-02-01

The scientific interest for the search of natural means of microbial inhibitors has not faded for several years. A search of natural antibiotics, so-called bacteriocins which are produced by lactic acid bacteria (LAB), gains a huge attention of the scientists in the last century, in order to reduce the usage of synthetic food additives. Pure bacteriocins with wide spectra of antibacterial activity are promising among the natural biopreservatives. The usage of bacteriocin(s) producing LAB as starter culture for the fermentation of some food products, in order to increase their shelf-life, when synthetic preservatives are not allowable, is also possible. There are a lot of studies focusing on the isolation of new bacteriocins from traditional fermented food, dairy products and other foods or sometimes even from unusual non-food matrices. Bacteriocins producing bacteria have been isolated from different sources with the different antibacterial activity against food-borne microorganisms. This review covers the classification of bacteriocins, diversity of sources of bacteriocin(s) producing LAB, antibacterial spectra of isolated bacteriocins and analytical methods for the bacteriocin purification and analysis within the last 15 years.

Bacteriocins of Non-aureus Staphylococci Isolated from Bovine Milk.

Science.gov (United States)

Carson, Domonique A; Barkema, Herman W; Naushad, Sohail; De Buck, Jeroen

2017-09-01

Non- aureus staphylococci (NAS), the bacteria most commonly isolated from the bovine udder, potentially protect the udder against infection by major mastitis pathogens due to bacteriocin production. In this study, we determined the inhibitory capability of 441 bovine NAS isolates (comprising 26 species) against bovine Staphylococcus aureus Furthermore, inhibiting isolates were tested against a human methicillin-resistant S. aureus (MRSA) isolate using a cross-streaking method. We determined the presence of bacteriocin clusters in NAS whole genomes using genome mining tools, BLAST, and comparison of genomes of closely related inhibiting and noninhibiting isolates and determined the genetic organization of any identified bacteriocin biosynthetic gene clusters. Forty isolates from 9 species ( S. capitis , S. chromogenes , S. epidermidis , S. pasteuri , S. saprophyticus , S. sciuri , S. simulans , S. warneri , and S. xylosus ) inhibited growth of S. aureus in vitro , 23 isolates of which, from S. capitis , S. chromogenes , S. epidermidis , S. pasteuri , S. simulans , and S. xylosus , also inhibited MRSA. One hundred five putative bacteriocin gene clusters encompassing 6 different classes (lanthipeptides, sactipeptides, lasso peptides, class IIa, class IIc, and class IId) in 95 whole genomes from 16 species were identified. A total of 25 novel bacteriocin precursors were described. In conclusion, NAS from bovine mammary glands are a source of potential bacteriocins, with >21% being possible producers, representing potential for future characterization and prospective clinical applications. IMPORTANCE Mastitis (particularly infections caused by Staphylococcus aureus ) costs Canadian dairy producers $400 million/year and is the leading cause of antibiotic use on dairy farms. With increasing antibiotic resistance and regulations regarding use, there is impetus to explore bacteriocins (bacterially produced antimicrobial peptides) for treatment and prevention of bacterial

Enterocin TW21, a novel bacteriocin from dochi-isolated Enterococcus faecium D081821.

Science.gov (United States)

Chang, S-Y; Chen, Y-S; Pan, S-F; Lee, Y-S; Chang, C-H; Chang, C-H; Yu, B; Wu, H-C

2013-09-01

Purification and characterization of a novel bacteriocin produced by strain Enterococcus faecium D081821. Enterococcus faecium D081821, isolated from the traditional Taiwanese fermented food dochi (fermented black beans), was previously found to produce a bacteriocin against Listeria monocytogenes and some Gram-positive bacteria. This bacteriocin, termed enterocin TW21, was purified from culture supernatant by ammonium sulfate precipitation, Sep-Pak C18 cartridge, ion-exchange and gel filtration chromatography. Mass spectrometry analysis showed the mass of the peptide to be approximately 5300·6 Da. The N-terminal amino acid sequencing yielded a partial sequence NH2 -ATYYGNGVYxNTQK by Edman degradation, and it contains the consensus class IIa bacteriocin motif YGNGV in the N-terminal region. The open reading frame (ORF) encoding the bacteriocin was identified from the draft genome sequence of Enterococcus faecium D081821, and sequence analysis of this peptide indicated that enterocin TW21 is a novel bacteriocin. Enterococcus faecium D081821 produced a bacteriocin named enterocin TW21, the molecular weight and amino acid sequence both revealed it to be a novel bacteriocin. A new member of class IIa bacteriocin was identified. This bacteriocin shows great inhibitory ability against L. monocytogenes and could be applied as a natural food preservative. © 2013 The Society for Applied Microbiology.

Purification of bacteriocins produced by lactic acid bacteria.

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Saavedra, Lucila; Castellano, Patricia; Sesma, Fernando

2004-01-01

Bacteriocins are antibacterial substances of a proteinaceous nature that are produced by different bacterial species. Lactic acid bacteria (LAB) produce biologically active peptides or protein complexes that display a bactericidal mode of action almost exclusively toward Gram-positive bacteria and particularly toward closely related species. Generally they are active against food spoilage and foodborne pathogenic microorganisms including Bacillus cereus, Clostridium perfringens, Staphylococcus aureus, and Listeria monocytogenes. There is an increased tendency to use natural occurring metabolites to prevent the growth of undesirable flora in foodstuffs. These metabolites could replace the use of chemical additives such as sorbic acid, sulfur dioxide, nitrite, nitrate, and others. For instance, bacteriocins produced by LAB may be promising for use as bio-preservaties. Bacteriocins of lactic acid bacteria are typically cationic, hydrophobic peptides and differ widely in many characteristics including molecular weight, presence of particular groups of amino acids, pI, net positive charge, and post-translational modifications of certain amino acids. This heterogeneity within the LAB bacteriocins may explain the different procedures for isolation and purification developed so far. The methods most frequently used for isolation, concentration, and purification involve salt precipitation of bacteriocins from culture supernatants, followed by various combinations of gel filtration, ion-exchange chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). In this chapter, a protocol is described that combines several methods used in our laboratory for the purification of two cationic bacteriocins, Lactocin 705AL and Enterocin CRL10, produced by Lactobacillus casei CRL705 and Enterococcus mundtii CRL10, respectively.

Antagonistic activity expressed by Shigella sonnei: identification of a putative new bacteriocin

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Mireille Angela Bernardes Sousa

2013-09-01

Full Text Available Bacteriocins are antibacterial, proteinaceous substances that mediate microbial dynamics. Bacteriocin production is a highly disseminated property among all major lineages of bacteria, including Shigella. In this paper, we addressed the purification and characterisation of a bacteriocin produced by a Shigella sonnei strain (SS9 isolated from a child with acute diarrhoea. The substance was purified through ammonium-sulphate precipitation and sequential steps of chromatography. The intracellular fraction obtained at 75% ammonium sulphate maintained activity following exposure to pH values from 1-11 and storage at -80ºC for more than two years and was inactivated by high temperatures and proteases. The molecular mass of the purified bacteriocin was determined by mass spectrometry to be 18.56 kDa. The N-terminal sequence of the bacteriocin did not match any other antibacterial proteins described. A putative new bacteriocin produced by S. sonnei has been detected. This bacteriocin may represent a newly described protein or a previously described protein with a newly detected function. Considering that SS9 expresses antagonism against other diarrhoeagenic bacteria, the bacteriocin may contribute to S. sonnei virulence and is potentially applicable to either preventing or controlling diarrhoeal disease.

Production and Characterization of Bacteriocin Produced by Lactobacillus Viridescence(NICM 2167

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Sure KP

Full Text Available The present study focused on the production optimization of bacteriocin by Lactobacillus viridescence NICM 2167 followed by its purification and characterization. The bacteriocins are antimicrobial peptides produced by many Gram positive and Gram negative bacteria.The bacteriocin produced by LAB (lactic acid bacteria received attention in recent years due to their potential application as natural preservatives in food. Bacteriocinproduced by Lactobacillus viridescence showed broad range of antimicrobial activity against food borne pathogens. Production parameters were optimized showing highest production of bacteriocinin MRS broth with pH= 7.0 incubated at 37°C for 48 h. Bacteriocin was purified in two steps involving ammonium sulphate precipitation followed by gel filtration using Sephadex G-100. Purified bacteriocin with single band on SDS-PAGE showed molecular weight of 8.3 kDa. This purified bacteriocin was stable over wide range of pH (4-10 as well as temperatures (4°C-121°C suggesting it as a potent candidate for preservation of various foods.

Novel bacteriocins from lactic acid bacteria (LAB): various structures and applications.

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Perez, Rodney H; Zendo, Takeshi; Sonomoto, Kenji

2014-08-29

Bacteriocins are heat-stable ribosomally synthesized antimicrobial peptides produced by various bacteria, including food-grade lactic acid bacteria (LAB). These antimicrobial peptides have huge potential as both food preservatives, and as next-generation antibiotics targeting the multiple-drug resistant pathogens. The increasing number of reports of new bacteriocins with unique properties indicates that there is still a lot to learn about this family of peptide antibiotics. In this review, we highlight our system of fast tracking the discovery of novel bacteriocins, belonging to different classes, and isolated from various sources. This system employs molecular mass analysis of supernatant from the candidate strain, coupled with a statistical analysis of their antimicrobial spectra that can even discriminate novel variants of known bacteriocins. This review also discusses current updates regarding the structural characterization, mode of antimicrobial action, and biosynthetic mechanisms of various novel bacteriocins. Future perspectives and potential applications of these novel bacteriocins are also discussed.

Partial Purification, Characterization and Application of Bacteriocin from Bacteria Isolated Parkia biglobosa Seeds

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Olorunjuwon O. Bello

2018-05-01

Full Text Available Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strains. Fermented Parkia biglobosa seeds (African locust bean were screened for bacteriocin-producing lactic acid bacteria (LAB with the characterization of putative bacteriocins. Bacteriocin-producing lactic acid bacteria (LAB were identified by 16s rDNA sequencing. Molecular sizes of the bacteriocins were determined using the tricine-sodium dodecyl sulphate-polyacrylamide gel electrophoresis (tricine-SDS–PAGE and effects of enzymes, pH, detergents and temperature on bacteriocin activity investigated, using standard procedures. Bacteriocins production and activities were measured by spectrophotometric analysis. Statistical analysis was carried out using student t-test and Analyses of Variance. Bacteriocigenic LAB isolated were Lactobacillus plantarum Z1116, Enterococcus faecium AU02 and Leuconostoc lactis PKT0003. They inhibited the growth of both Gram-positive and Gram-negative bacteria. The sizes of bacteriocins Z1116, AU02 and PKT0003 were 3.2 kDa, 10 kDa and 10 kDa, respectively. The synergistic effects of characterized bacteriocins and rifampicin tested on organisms showed significant differences (P < 0.05, as compared with the effects of only one of the two. The antimicrobial activity of the three bacteriocins was deactivated after treatment of the cell-free supernatants with proteinase K, papain, pepsin and trypsin. Parkia biglobosa seeds are, therefore, rich in LAB bacteriocins which could be explored. The biosynthetic mechanisms of LAB bacteriocins could be employed in food safety and security, preservation, peptide design, infection control and pharmacotherapy. This should help in the control of undesirable bacteria and in designing more potent and selective antimicrobial peptides.

Pentocin KCA1: a novel circular bacteriocin gene encoded in the ...

African Journals Online (AJOL)

C termini (Maqueda, et al., 2008; Heng & Tagg,. 2006). The circular structure appears to enhance the ... pentosus KCA1 (Anukam et al., 2013) isolated from the vagina of a ..... Montalba ́n-Lo ́pez M, Valdivia E, Mart ́ınez-Bueno. M (2008).

Enterocin T, a novel class IIa bacteriocin produced by Enterococcus sp. 812.

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Chen, Yi-Sheng; Yu, Chi-Rong; Ji, Si-Hua; Liou, Min-Shiuan; Leong, Kun-Hon; Pan, Shwu-Fen; Wu, Hui-Chung; Lin, Yu-Hsuan; Yu, Bi; Yanagida, Fujitoshi

2013-09-01

Enterococcus sp. 812, isolated from fresh broccoli, was previously found to produce a bacteriocin active against a number of Gram-positive bacteria, including Listeria monocytogenes. Bacteriocin activity decreased slightly after autoclaving (121 °C for 15 min), but was inactivated by protease K. Mass spectrometry analysis revealed the bacteriocin mass to be approximately 4,521.34 Da. N-terminal amino acid sequencing yielded a partial sequence, NH2-ATYYGNGVYXDKKKXWVEWGQA, by Edman degradation, which contained the consensus class IIa bacteriocin motif YGNGV in the N-terminal region. The obtained partial sequence showed high homology with some enterococcal bacteriocins; however, no identical peptide or protein was found. This peptide was therefore considered to be a novel bacteriocin produced by Enterococcus sp. 812 and was termed enterocin T.

Subspecies diversity in bacteriocin production by intestinal Lactobacillus salivarius strains.

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O' Shea, Eileen F; O' Connor, Paula M; Raftis, Emma J; O' Toole, Paul W; Stanton, Catherine; Cotter, Paul D; Ross, R Paul; Hill, Colin

2012-01-01

A recent comparative genomic hybridization study in our laboratory revealed considerable plasticity within the bacteriocin locus of gastrointestinal strains of Lactobacillus salivarius. Most notably, these analyses led to the identification of two novel unmodified bacteriocins, salivaricin L and salivaricin T, produced by the neonatal isolate L. salivarius DPC6488 with immunity, regulatory and export systems analogous to those of abp118, a two-component bacteriocin produced by the well characterized reference strain L. salivarius UCC118. In this addendum we discuss the intraspecific diversity of our seven bacteriocin-producing L. salivarius isolates on a genome-wide level, and more specifically, with respect to their salivaricin loci.

Pediocins: The bacteriocins of Pediococci. Sources, production, properties and applications

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Anastasiadou Sofia

2009-01-01

Full Text Available Abstract Class IIa bacteriocins from lactic acid bacteria are small, cationic proteins with antilisterial activity. Within this class, the pediocins are those bacteriocins that share a highly conserved hydrophilic and charged N-terminal part harboring the consensus sequence -YGNGV- and a more variable hydrophobic and/or amphiphilic C-terminal part. Several pediocins have been isolated and characterized. Despite the structural similarities, their molecular weight varies, as well as their spectrum of antimicrobial activity. They exhibit important technological properties, e.g. thermostability and retaining of activity at a wide pH range, which along with the bactericidal action against Gram-positive food spoilage and pathogenic bacteria, make them an important class of biopreservatives. Much new information regarding the pediocins has emerged during the last years. In this review, we summarize and discuss all the available information regarding the sources of pediocins, the characteristics of their biosynthesis and production in fermentation systems, the characteristics of the known pediocin molecules, and their antibacterial action. The advances made by genetic engineering in improving the features of pediocins are also discussed, as well as their perspectives for future applications.

LAB bacteriocin applications in the last decade

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Ma. del Rocío López-Cuellar

2016-11-01

Full Text Available In the early 2000s, the expectations about bacteriocins produced by lactic acid bacteria (LABs were aimed at food applications. However, the effectiveness of bacteriocins against undesirable micro-organisms opened endless possibilities for innovative research. In the present review, we collected a database including 429 published papers and 245 granted patents (from 2004 to 2015. Based on bibliometric analysis, the progress of bacteriocin research in the last 11 years was discussed in detail. It was found that 164 patents were granted in 2010–2015, which is equivalent to 60% in comparison with previous years (i.e. only 81 patents were granted in 2004–2009. Currently, the research on bacteriocins is still gaining importance. In the realm of therapeutic strategies, about a 37% of the published research was focused on biomedical applications in the last decade. This vein of research is currently seeking for alternative solutions to problems such as cancer, systemic infections, oral-care, vaginal infections, contraception and skincare. On the other hand, food preservation, bio-nanomaterial and veterinary applications represent 29%, 25% and 9%, respectively. All this technology is being applied and will surely grow in the future, since about 31% of the patents granted since 2004 are focused on the biomedical area, 29% on food preservation, 5% on veterinary use; whereas 13% and 16% correspond to patents granted on production–purification systems and recombinant proteins or molecular modifications in the producer strains. This review contributes to the analysis of recent LAB bacteriocin applications and their role in safety, quality and improvement of human health.

Purification and partial characterization of bacteriocin produced by Lactococcus lactis ssp. lactis LL171.

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Kumari, Archana; Akkoç, Nefise; Akçelik, Mustafa

2012-04-01

Lactic acid bacteria (LAB) are possessing ability to synthesize antimicrobial compounds (like bacteriocin) during their growth. In this regard, novel bacteriocin compound secreting capability of LAB isolated from Tulum Cheese in Turkey was demonstrated. The synthesized bacteriocin was purified by ammonium sulphate precipitation, dialysis and gel filtration. The molecular weight (≈3.4 kDa) of obtained bacteriocin was confirmed by SDS-PAGE, which revealed single peptide band. Molecular identification of LAB strain isolated from Tulum Cheese was conducted using 16S rDNA gene sequencing as Lactococcus lactis ssp. lactis LL171. The amino acid sequences (KKIDTRTGKTMEKTEKKIELSLKNMKTAT) of the bacteriocin from Lactococcus lactis ssp. lactis LL171 was found unique and novel than reported bacteriocins. Further, the bacteriocin was possessed the thermostable property and active at wide range of pH values from 1 to 11. Thus, bacteriocin reported in this study has the potential applications property as food preservative agent.

Bacteriocins produced by lactic acid bacteria: A review

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Vesković-Moračanin Slavica M.

2014-01-01

Full Text Available Lactic acid bacteria (LAB have an essential role in the production of fermented products. With their metabolic activity, they influence the ripening processes - leading to desired sensory qualities while at the same time inhibiting the growth of undesired microorganisms. Because of their dominant role during fermentation and because of a long tradition of utilization, Lhave been designated as “safe microbiota”. Biological protection of LAB, as a naturally present and/or selected and intentionally added microflora, is realized through the production of non-specific (lactic acid, acetic acid and other volatile organic acids, hydrogen peroxide, diacetyl, etc and specific metabolites, bacteriocins. Bacteriocins are extracellularly released proteins or peptides which possess certain antibacterial activity towards certain types of microorganisms, usually related to the producing bacteria. Today, bacteriocins represent a very interesting potential for their application in the food industry. Their application can reduce the use of synthetic preservatives and/or the intensity of thermal treatment during food production consumer’s need for safe, fresh and minimally-processed food. With the intention of realizing this potential to the fullest, it is necessary to understand the nature of bacteriocins, their production mechanisms, regulations and actions, as well as the influence of external factors on the their antimicrobial activity. The composition of food, i.e. its characteristics (pH, temperature, ingredients and additives, types and quantities of epiphytic microbiota and the actual technological process used in production, can all influence the stability and activity of the added bacteriocins. The future research in this field should also aim to clarify this unknown aspect of the application of bacteriocins, to provide the necessary knowledge about the optimization of the external conditions and open up the possibility of discovering their new

Identification and characterization of novel multiple bacteriocins produced by Leuconostoc pseudomesenteroides QU 15.

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Sawa, N; Okamura, K; Zendo, T; Himeno, K; Nakayama, J; Sonomoto, K

2010-07-01

To characterize novel multiple bacteriocins produced by Leuconostoc pseudomesenteroides QU 15. Leuconostoc pseudomesenteroides QU 15 isolated from Nukadoko (rice bran bed) produced novel bacteriocins. By using three purification steps, four antimicrobial peptides termed leucocin A (ΔC7), leucocin A-QU 15, leucocin Q and leucocin N were purified from the culture supernatant. The amino acid sequences of leucocin A (ΔC7) and leucocin A-QU 15 were identical to that of leucocin A-UAL 187 belonging to class IIa bacteriocins, but leucocin A (ΔC7) was deficient in seven C-terminal residues. Leucocin Q and leucocin N are novel class IId bacteriocins. Moreover, the DNA sequences encoding three bacteriocins, leucocin A-QU 15, leucocin Q and leucocin N were obtained. These bacteriocins including two novel bacteriocins were identified from Leuc. pseudomesenteroides QU 15. They showed similar antimicrobial spectra, but their intensities differed. The C-terminal region of leucocin A-QU 15 was important for its antimicrobial activity. Leucocins Q and N were encoded by adjacent open reading frames (ORFs) in the same operon, but leucocin A-QU 15 was not. These leucocins were produced concomitantly by the same strain. Although the two novel bacteriocins were encoded by adjacent ORFs, a characteristic of class IIb bacteriocins, they did not show synergistic activity. © 2010 The Authors. Journal compilation © 2010 The Society for Applied Microbiology.

Using the overlay assay to qualitatively measure bacterial production of and sensitivity to pneumococcal bacteriocins.

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Maricic, Natalie; Dawid, Suzanne

2014-09-30

Streptococcus pneumoniae colonizes the highly diverse polymicrobial community of the nasopharynx where it must compete with resident organisms. We have shown that bacterially produced antimicrobial peptides (bacteriocins) dictate the outcome of these competitive interactions. All fully-sequenced pneumococcal strains harbor a bacteriocin-like peptide (blp) locus. The blp locus encodes for a range of diverse bacteriocins and all of the highly conserved components needed for their regulation, processing, and secretion. The diversity of the bacteriocins found in the bacteriocin immunity region (BIR) of the locus is a major contributor of pneumococcal competition. Along with the bacteriocins, immunity genes are found in the BIR and are needed to protect the producer cell from the effects of its own bacteriocin. The overlay assay is a quick method for examining a large number of strains for competitive interactions mediated by bacteriocins. The overlay assay also allows for the characterization of bacteriocin-specific immunity, and detection of secreted quorum sensing peptides. The assay is performed by pre-inoculating an agar plate with a strain to be tested for bacteriocin production followed by application of a soft agar overlay containing a strain to be tested for bacteriocin sensitivity. A zone of clearance surrounding the stab indicates that the overlay strain is sensitive to the bacteriocins produced by the pre-inoculated strain. If no zone of clearance is observed, either the overlay strain is immune to the bacteriocins being produced or the pre-inoculated strain does not produce bacteriocins. To determine if the blp locus is functional in a given strain, the overlay assay can be adapted to evaluate for peptide pheromone secretion by the pre-inoculated strain. In this case, a series of four lacZ-reporter strains with different pheromone specificity are used in the overlay.

Thermostable Bacteriocin BL8 from Bacillus licheniformis isolated from marine sediment.

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Smitha, S; Bhat, S G

2013-03-01

To isolate and characterize bacteriocin, BL8, from the bacteria identified as Bacillus licheniformis from marine environment. One-hundred and twelve bacterial isolates from sediment and water samples collected off the coast of Cochin, India, were screened for antibacterial activity. Strain BTHT8, identified as Bacillus licheniformis, inhibited the growth of Gram-positive test organisms. The active component labelled as bacteriocin BL8 was partially purified by ammonium sulphate fractionation and was subjected to glycine SDS-PAGE. The band exhibiting antimicrobial activity was electroeluted and analysed using MALDI-TOF mass spectrometry, and the molecular mass was determined as 1.4 kDa. N-terminal amino acid sequencing of BL8 gave a 13 amino acid sequence stretch. Bacteriocin BL8 was stable even after boiling at 100 °C for 30 min and over a wide pH range of 1-12. A novel, pH-tolerant and thermostable bacteriocin BL8, active against the tested Gram-positive bacteria, was isolated from Bacillus licheniformis. This study reports a stable, low molecular weight bacteriocin from Bacillus licheniformis. This bacteriocin can be used to address two important applications: as a therapeutic agent and as a biopreservative in food processing industry. © 2012 The Society for Applied Microbiology.

Impact of Environmental Factors on Bacteriocin Promoter Activity in Gut-Derived Lactobacillus salivarius.

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Guinane, Caitriona M; Piper, Clare; Draper, Lorraine A; O'Connor, Paula M; Hill, Colin; Ross, R Paul; Cotter, Paul D

2015-11-01

Bacteriocin production is regarded as a desirable probiotic trait that aids in colonization and persistence in the gastrointestinal tract (GIT). Strains of Lactobacillus salivarius, a species associated with the GIT, are regarded as promising probiotic candidates and have a number of associated bacteriocins documented to date. These include multiple class IIb bacteriocins (salivaricin T, salivaricin P, and ABP-118) and the class IId bacteriocin bactofencin A, which show activity against medically important pathogens. However, the production of a bacteriocin in laboratory media does not ensure production under stressful environmental conditions, such as those encountered within the GIT. To allow this issue to be addressed, the promoter regions located upstream of the structural genes encoding the L. salivarius bacteriocins mentioned above were fused to a number of reporter proteins (green fluorescent protein [GFP], red fluorescent protein [RFP], and luciferase [Lux]). Of these, only transcriptional fusions to GFP generated signals of sufficient strength to enable the study of promoter activity in L. salivarius. While analysis of the class IIb bacteriocin promoter regions indicated relatively weak GFP expression, assessment of the promoter of the antistaphylococcal bacteriocin bactofencin A revealed a strong promoter that is most active in the absence of the antimicrobial peptide and is positively induced in the presence of mild environmental stresses, including simulated gastric fluid. Taken together, these data provide information on factors that influence bacteriocin production, which will assist in the development of strategies to optimize in vivo and in vitro production of these antimicrobials. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Characterization, production, and purification of carnocin H, a bacteriocin produced by Carnobacterium 377.

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Blom, H; Katla, T; Nissen, H; Holo, H

2001-10-01

Carnocin H, a bacteriocin produced by a Carnobacterium sp., inhibited lactic acid bacteria, clostridia, enterococci, and some Staphylococcus aureus strains. Some strains of Listeria and Pediococcus were also sensitive to carnocin H. The bacteriocin was produced during the late stationary growth phase. Carnocin H was purified by cation exchange chromatography and reverse phase chromatography. Amino acid sequence and composition indicate that carnocin H is a novel bacteriocin belonging to the class II bacteriocins. The bacteriocin consists of approximately 75 amino acid residues with a highly cationic N-terminal containing six succeeding lysines. Activity, as measured by agar diffusion zones, was reduced at increased pH values, levels of indicator bacteria, NaCl, agar, and soy oil.

Sec-mediated secretion of bacteriocin enterocin P by Lactococcus lactis

NARCIS (Netherlands)

Herranz, C; Driessen, AJM

Most lactic acid bacterium bacteriocins utilize specific leader peptides and dedicated machineries for secretion. In contrast, the enterococcal bacteriocin enterocin P (EntP) contains a typical signal peptide that directs its secretion when heterologously expressed in Lactococcus lactis. Signal

Fungicidal effect of bacteriocins harvested from Bacillus spp.

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Adetunji, V. O.

2013-01-01

Full Text Available Aims: This study investigated the ability of bacteriocins isolated from Bacillus spp. (Bacillus species to inhibit fourdifferent yeast isolates obtained from common food products (nono, yoghurt, ogi and cheese commonly consumed byNigerians with minimal heat treatment.Methodology and results: Forty-five Bacillus spp. was isolated and identified from common food products usingcultural, morphological, physiological and biochemical characteristics. These isolates were tested for antimicrobialactivity against Salmonella enteritidis (3, Micrococcus luteus (1 and Staphylococcus aureus (2. Eight bacteriocinproducing strains were identified from an over- night broth culture centrifugated at 3500 revolutions for five minutes.Fungicidal effects of these bacteriocins were tested against four yeast strains using the Agar Well Diffusion method. Thebacteriocins produced wide zones of inhibition ranging from 5.9±0.000 to 24.00±0.000 mm against the 4 yeast strainstested. There was a significant difference (at p<0.05 between the yeast organisms and the bacteriocins from theBacillus spp.Conclusion, significance and impact of study: The study reveals the antifungal property of bacteriocins from Bacillusspp. and serves therefore as a base for further studies in its use in the control of diseases and extension of shelf-life ofproducts prone to fungi contamination.

Interactions between oral bacteria: inhibition of Streptococcus mutans bacteriocin production by Streptococcus gordonii.

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Wang, Bing-Yan; Kuramitsu, Howard K

2005-01-01

Streptococcus mutans has been recognized as an important etiological agent in human dental caries. Some strains of S. mutans also produce bacteriocins. In this study, we sought to demonstrate that bacteriocin production by S. mutans strains GS5 and BM71 was mediated by quorum sensing, which is dependent on a competence-stimulating peptide (CSP) signaling system encoded by the com genes. We also demonstrated that interactions with some other oral streptococci interfered with S. mutans bacteriocin production both in broth and in biofilms. The inhibition of S. mutans bacteriocin production by oral bacteria was stronger in biofilms than in broth. Using transposon Tn916 mutagenesis, we identified a gene (sgc; named for Streptococcus gordonii challisin) responsible for the inhibition of S. mutans bacteriocin production by S. gordonii Challis. Interruption of the sgc gene in S. gordonii Challis resulted in attenuated inhibition of S. mutans bacteriocin production. The supernatant fluids from the sgc mutant did not inactivate the exogenous S. mutans CSP as did those from the parent strain Challis. S. gordonii Challis did not inactivate bacteriocin produced by S. mutans GS5. Because S. mutans uses quorum sensing to regulate virulence, strategies designed to interfere with these signaling systems may have broad applicability for biological control of this caries-causing organism.

Bacteriocin Isolated From Halomon sp.: A Bacterial Ding Protein?

International Nuclear Information System (INIS)

Atirah Azemin; Klappa, P.; Mohd Shahir Shamsir Omar

2015-01-01

A marine halophile, Halomonas sp. strain M3 was isolated from Straits of Johor, Malaysia and produce bacteriocin CC that acts as bacteriostatic agent. Characterisation of the bacterium showed that optimal growth and bacteriocin production is at ambient temperature, pH of 8-8.5 in nutrient broth medium supplemented with 2.9 % w/v NaCI to mimic saltwater conditions. The stability studies indicated that bacteriocin CC is heat-labile (35-50 degree Celsius) and was stable over 2 years when stored in 0.02 M Tris- HCI with 30-60 % glycerol at 4 degree Celsius. A loss of activity was detected after proteolytic enzymes treatment, indicating the proteinaceous nature of the antimicrobial compound. The amino acid sequence of bacteriocin CC was obtained by Edman degradation and MALDI-TOF analysis, showed the characteristic sequence of a DING protein (D-I-N-G-G-G-A-T-L-P-Q-A-LY- Q) in size 38.9-kDa at pI of 6.8. These proteins constitute a conserved and widely distributed set of proteins found in all kingdoms with ligand-binding activities and hydrolytic enzyme, suggesting a possible role in cell signalling and bio mineralization in DING isolates. Intriguingly, DING proteins also have been involved as an anti-tumour agent in humans. Thus, bacteriocin CC as DING protein family members should be further studied to investigate its potential as a novel antimicrobial agent. (author)

Enterocin AS-48 as Evidence for the Use of Bacteriocins as New Leishmanicidal Agents.

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Abengózar, María Ángeles; Cebrián, Rubén; Saugar, José María; Gárate, Teresa; Valdivia, Eva; Martínez-Bueno, Manuel; Maqueda, Mercedes; Rivas, Luis

2017-04-01

We report the feasibility of enterocin AS-48, a circular cationic peptide produced by Enterococcus faecalis , as a new leishmanicidal agent. AS-48 is lethal to Leishmania promastigotes as well as to axenic and intracellular amastigotes at low micromolar concentrations, with scarce cytotoxicity to macrophages. AS-48 induced a fast bioenergetic collapse of L. donovani promastigotes but only a partial permeation of their plasma membrane with limited entrance of vital dyes, even at concentrations beyond its full lethality. Fluoresceinated AS-48 was visualized inside parasites by confocal microscopy and seen to cause mitochondrial depolarization and reactive oxygen species production. Altogether, AS-48 appeared to have a mixed leishmanicidal mechanism that includes both plasma membrane permeabilization and additional intracellular targets, with mitochondrial dysfunctionality being of special relevance. This complex leishmanicidal mechanism of AS-48 persisted even for the killing of intracellular amastigotes, as evidenced by transmission electron microscopy. We demonstrated the potentiality of AS-48 as a new and safe leishmanicidal agent, expanding the growing repertoire of eukaryotic targets for bacteriocins, and our results provide a proof of mechanism for the search of new leishmanicidal bacteriocins, whose diversity constitutes an almost endless source for new structures at moderate production cost and whose safe use on food preservation is well established. Copyright © 2017 American Society for Microbiology.

Influence of cultural conditions on the production of bacteriocin by ...

African Journals Online (AJOL)

Bacteriocin produced by Lactobacillus brevis OG1 has large spectrum of inhibition against pathogenic, food spoilage microorganisms and various Lactic acid bacteria employed as test strains. The bacteriocin inhibited E coli NCTC 10418 and Enterococcus faecalis, but did not inhibit Candida albicans ATCC 10231 and ...

PHYSICHOCHEMICAL CHACTERIZATION OF BACTERIOCIN PRODUCING ENTEROCOCCUS DURANS ISOLATED FROM COLON’S BALI CATTLE

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I Wayan Suardana

2017-08-01

Full Text Available Lactic acid bacteria can excrete antimicrobial compounds like bacteriocins. The study  aimed  to  find  out  the  characteristic  of  physic-chemical  of  bacteriocin  producing Enterococcus durans          isolate 18A isolated from  colon’s bali cattle. The study initiated by Gram staining and catalase test, followed by isolation and purification  of bacteriocin.       The result of the research showed  that bacteriocins of    Enterococcus durans    isolate 18A as a protein with it’s concentrationis  0,272?g/ml  and  it  does  not  contain  carbohydrate.  On  the  other  hand,  the bacteriocins was not showed a band while tested on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE. The result showed, the bacteriocin producing            Enterococcus durans isolate 18A has antimicrobial activity to Bacillus cereus  as 23,88%.

Importance in dairy technology of bacteriocins produced by dairy starter cultures

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Bedia Şimşek

2002-03-01

Full Text Available Bacteriocins produced by Lactic acid bacteria (LAB and propionic acid bacteria (PAB are heterogeneous group of peptide inhibitors which include lantibiotics (class I, e. g. nisin, small heat-stable peptides (class II, e. g. pediocin PA-1 and large heat-labile proteins (class III, e. g. helveticin J. Many bacteriocins belonging to the first two groups can be successfully used to inhibit undesirable microorganisms in foods, but only nisin is produced industrially and is used as a food preservative. LAB and PAB develops easily in milk and milk products. LAB and PAB growth in dairy products can cause microbial interference to spoilage and pathogenic bacteria through several metabolits, specially bacteriocins. The review deals with the description of milk-borne bacteriocins and their application in milk and milk products either to extend the shelf life or to inhibit milk pathogens.

Bacteriocins from the rhizosphere microbiome – from an agriculture perspective

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Sowmyalakshmi eSubramanian

2015-10-01

Full Text Available Bacteria produce and excrete a versatile and dynamic suit of compounds to defend against microbial competitors and mediate local population dynamics. These include a wide range of broad-spectrum non-ribosomally synthesized antibiotics, lytic enzymes, metabolic by-products, proteinaceous exotoxins and ribosomally produced antimicrobial peptides (bacteriocins. Most bacteria produce at least one bacteriocin. Bacteriocins are of interest in the food industry as natural preservatives and in the probiotics industry, leading to extensive studies on lactic acid bacteria (colicin produced by Escherichia coli is a model bacteriocin. Recent studies have projected use of bacteriocins in veterinary medicine and in agriculture, as a biostimulants of plant growth and development and as biocontrol agents. For example, bacteriocins such as Cerein 8A, Bac-GM17, putidacin, Bac 14B, amylocyclicin have been studied for their mechanisms of anti-microbial activity. Bac IH7 promotes tomato and musk melon plant growth. Thuricin 17 (Th17 is the only bacteriocin studied extensively for plant growth promotion and at the molecular level. Th17 functions as a bacterial signal compound, promoting plant growth in legumes and non-legumes. In Arabidopsis thaliana and Glycine max Th17 increased phytohormones IAA and SA at 24 h post treatment. At the proteome level Th17 treatment of 3-week-old A. thaliana rosettes led to > 2-fold changes in activation of the carbon and energy metabolism pathway proteins, 24 h post treatment. At 250 mM NaCl stress, the control plants under osmotic-shock shut down most of carbon-metabolism and activated energy-metabolism and antioxidant pathways. Th17 treated plants, at 250 mM NaCl, retained meaningful levels of the light harvesting complex, photosystem I and II proteins and energy and antioxidant pathways were activated, so that rosettes could better withstand the salt stress. In Glycine max, Th17 helped seeds germinate in the presence of Na

Lactococcus lactis LMG2081 Produces Two Bacteriocins, a Nonlantibiotic and a Novel Lantibiotic.

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Mirkovic, Nemanja; Polovic, Natalija; Vukotic, Goran; Jovcic, Branko; Miljkovic, Marija; Radulovic, Zorica; Diep, Dzung B; Kojic, Milan

2016-04-01

Bacteriocin producers normally possess dedicated immunity systems to protect themselves from their own bacteriocins.Lactococcus lactis strains LMG2081 and BGBM50 are known as lactococcin G producers. However, BGBM50 was sensitive to LMG2081, which indicated that LMG2081 might produce additional bacteriocins that are not present in BGBM50. Therefore, whole-genome sequencing of the two strains was performed, and a lantibiotic operon (called lctLMG) was identified in LMG2081 but not in BGBM50. The lctLMG operon contains six open reading frames; the first three genes,lmgA ,lmgM, and lmgT, are involved in the biosynthesis and export of bacteriocin, while the other three genes,lmgF,lmgE, and lmgG, are involved in lantibiotic immunity. Mutational analysis confirmed that the lctLMG operon is responsible for the additional antimicrobial activity. Specifically, site-directed mutation within this operon rendered LMG2081 inactive toward BGBM50. Subsequent purification and electrospray ionization-time of flight mass spectrometric analysis confirmed that the lantibiotic bacteriocin called lacticin LMG is exported as a 25-amino-acid peptide. Lacticin LMG is highly similar to the lacticin 481 group. It is interesting that a bacteriocin producer produces two different classes of bacteriocins, whose operons are located in the chromosome and a plasmid. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Antibacterial efficacy of nisin, pediocin 34 and enterocin FH99 against L. monocytogenes, E. faecium and E. faecalis and bacteriocin cross resistance and antibiotic susceptibility of their bacteriocin resistant variants.

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Kaur, Gurpreet; Singh, Tejinder Pal; Malik, Ravinder Kumar; Bhardwaj, Arun; De, Sachinandan

2014-02-01

The bacteriocin susceptibility of Listeria monocytogenes MTCC 657, Enterococcus faecium DSMZ 20477, E. faecium VRE, and E. faecalis ATCC 29212 and their corresponding bacteriocin resistant variants was assessed. The single and combined effect of nisin and pediocin 34 and enterocin FH99 bacteriocins produced by Pediococcus pentosaceus 34, and E. faecium FH99, respectively, was determined. Pediocin34 proved to be more effective in inhibiting L. monocytogenes MTCC 657. A greater antibacterial effect was observed against E. faecium DSMZ 20477 and E. faecium (VRE) when the a combination of nisin, pediocin 34 and enterocin FH99 were used whereas in case of L. monocytogenes MTCC 657 a combination of pediocin 34 and enterocin FH99 was more effective in reducing the survival of pathogen. Bacteriocin cross-resistance and the antibiotic susceptibility of wild type and their corresponding resistant variants were assessed and results showed that resistance to a bacteriocin may extend to other bacteriocins within the same class and also the acquired resistance to bacteriocins can modify the antibiotic susceptibility/resistance profile of the bacterial species used in the study. According to the hydrophobicity nisin resistant variant of L. monocytogenes was more hydrophobic (p enterocin FH99 resistant variants were less hydrophobic than the wild type strain. Nisin, pediocin 34 and enterocin FH99 resistant variants of E. faecium DSMZ 20477 and E. faecium VRE were less hydrophobic than their wild type counterparts. Nisin resistant E. faecalis ATCC 29212 was less hydrophobic than its wild type counterpart.

Antilisterial Activity of Bacteriocin Isolated from Leuconostoc mesenteroides ssp. mesenteroides IMAU:10231 in the Production of Sremska Sausages: Lactic Acid Bacteria Isolation, Bacteriocin Identification and Meat Application Experiments

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Marija Škrinjar

2013-01-01

Full Text Available Lactic acid bacteria (LAB have an essential role in the production of fermented meat products. The metabolic activity of LAB affects the ripening process, leading to the formation of the desired sensory characteristics of the products, while inhibiting the growth of undesirable microorganisms. Bacteriocins are extracellular peptides or protein molecules, produced by some LAB, which possess bactericidal properties against specific species or genera of microorganisms, usually related bacteria. Bacteriocin production by LAB can act in a selective and competitive way against the surrounding microbiota, which may contain spoilage bacteria or pathogenic microorganisms including Listeria monocytogenes. This pathogen is widely distributed in raw products, it survives in different production areas, and human infections have a high mortality rate, all of which makes the control of this microorganism important in food production. The aim of this work is to determine the possibilities of utilizing a novel bacteriocin isolated from Leuconostoc mesenteroides ssp. mesenteroides IMAU:10231 in order to prevent the survival of Listeria monocytogenes in the production of traditional Serbian Sremska sausages. The bacteriocin-producing strain of Leuconostoc originated from the same sausage, which had been produced in the traditional manner. Bacteriocin was isolated using precipitation procedures with ammonium sulphate, and then its properties (strength and range of activities, relationship to high temperatures and proteolytic enzymes were determined under laboratory conditions. Also, based on the obtained laboratory results, the antilisterial effect of bacteriocin, included as an additive, was examined in the production of traditional Sremska sausages. Expressed antilisterial activity of bacteriocin has an interesting food safety potential which can be used in the meat industry in the production of fermented sausages. Further research will contribute to a better

Recent Progress in the Chemical Synthesis of Class II and S-Glycosylated Bacteriocins

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François Bédard

2018-05-01

Full Text Available A wide variety of antimicrobial peptides produced by lactic acid bacteria (LAB have been identified and studied in the last decades. Known as bacteriocins, these ribosomally synthesized peptides inhibit the growth of a wide range of bacterial species through numerous mechanisms and show a great variety of spectrum of activity. With their great potential as antimicrobial additives and alternatives to traditional antibiotics in food preservation and handling, animal production and in veterinary and medical medicine, the demand for bacteriocins is rapidly increasing. Bacteriocins are most often produced by fermentation but, in several cases, the low isolated yields and difficulties associated with their purification seriously limit their use on a large scale. Chemical synthesis has been proposed for their production and recent advances in peptide synthesis methodologies have allowed the preparation of several bacteriocins. Moreover, the significant cost reduction for peptide synthesis reagents and building blocks has made chemical synthesis of bacteriocins more attractive and competitive. From a protein engineering point of view, the chemical approach offers many advantages such as the possibility to rapidly perform amino acid substitution, use unnatural or modified residues, and make backbone and side chain modifications to improve potency, modify the activity spectrum or increase the stability of the targeted bacteriocin. This review summarized synthetic approaches that have been developed and used in recent years to allow the preparation of class IIa bacteriocins and S-linked glycopeptides from LAB. Synthetic strategies such as the use of pseudoprolines, backbone protecting groups, microwave irradiations, selective disulfide bridge formation and chemical ligations to prepare class II and S-glycosylsated bacteriocins are discussed.

Bacteriocin Production with Lactobacillus amylovorus DCE 471 Is Improved and Stabilized by Fed-Batch Fermentation

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Callewaert, Raf; De Vuyst, Luc

2000-01-01

Amylovorin L471 is a small, heat-stable, and hydrophobic bacteriocin produced by Lactobacillus amylovorus DCE 471. The nutritional requirements for amylovorin L471 production were studied with fed-batch fermentations. A twofold increase in bacteriocin titer was obtained when substrate addition was controlled by the acidification rate of the culture, compared with the titers reached with constant substrate addition or pH-controlled batch cultures carried out under the same conditions. An interesting feature of fed-batch cultures observed under certain culture conditions (constant feed rate) is the apparent stabilization of bacteriocin activity after obtaining maximum production. Finally, a mathematical model was set up to simulate cell growth, glucose and complex nitrogen source consumption, and lactic acid and bacteriocin production kinetics. The model showed that bacterial growth was dependent on both the energy and the complex nitrogen source. Bacteriocin production was growth associated, with a simultaneous bacteriocin adsorption on the producer cells dependent on the lactic acid accumulated and hence the viability of the cells. Both bacteriocin production and adsorption were inhibited by high concentrations of the complex nitrogen source. PMID:10653724

Bacteriocins from lactic acid bacteria: production, purification, and food applications.

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De Vuyst, Luc; Leroy, Frédéric

2007-01-01

In fermented foods, lactic acid bacteria (LAB) display numerous antimicrobial activities. This is mainly due to the production of organic acids, but also of other compounds, such as bacteriocins and antifungal peptides. Several bacteriocins with industrial potential have been purified and characterized. The kinetics of bacteriocin production by LAB in relation to process factors have been studied in detail through mathematical modeling and positive predictive microbiology. Application of bacteriocin-producing starter cultures in sourdough (to increase competitiveness), in fermented sausage (anti-listerial effect), and in cheese (anti-listerial and anti-clostridial effects), have been studied during in vitro laboratory fermentations as well as on pilot-scale level. The highly promising results of these studies underline the important role that functional, bacteriocinogenic LAB strains may play in the food industry as starter cultures, co-cultures, or bioprotective cultures, to improve food quality and safety. In addition, antimicrobial production by probiotic LAB might play a role during in vivo interactions occurring in the human gastrointestinal tract, hence contributing to gut health.

Bacteriocins from lactic acid bacteria: purification, properties and use as biopreservatives

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José Luis Parada

2007-05-01

Full Text Available Biopreservation systems in foods are of increasing interest for industry and consumers. Bacteriocinogenic lactic acid bacteria and/or their isolated bacteriocins are considered safe additives (GRAS, useful to control the frequent development of pathogens and spoiling microorganisms in foods and feed. The spreading of bacterial antibiotic resistance and the demand for products with fewer chemicals create the necessity of exploring new alternatives, in order to reduce the abusive use of therapeutic antibiotics. In this context, bacteriocins are indicated to prevent the growth of undesirable bacteria in a food-grade and more natural way, which is convenient for health and accepted by the community. According to their properties, structure, molecular weight (MW, and antimicrobial spectrum, bacteriocins are classified in three different groups: lantibiotics and non-lantibiotics of low MW, and those of higher MW. Several strategies for isolation and purification of bacteriocins from complex cultivation broths to final products were described. Biotechnological procedures including salting-out, solvent extraction, ultrafiltration, adsorption-desortion, ion-exchange, and size exclusion chromatography are among the most usual methods. Peptide structure-function studies of bacteriocins and bacterial genetic advances will help to understand the molecular basis of their specificity and mode of action. Nisin is a good example of commercial success, and a good perspective is open to continue the study and development of new bacteriocins and their biotechnological applications. These substances in appropriate concentrations may be used in veterinary medicine and as animal growth promoter instead usual antibiotics, as well as an additional hurdle factor for increasing the shelf life of minimal processed foods.

Purification Techniques of Bacteriocins from Lactic Acid Bacteria and Other Gram-Positive Bacteria

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Saavedra, Lucila; Sesma, Fernando

The search for new antimicrobial peptides produced by lactic acid ­bacteria and other Gram-positive microorganisms has become an interesting field of research in the past decades. The fact that bacteriocins are active against numerous foodborne and human pathogens, are produced by generally regarded as safe (GRAS) microorganisms, and are readily degraded by proteolytic host systems makes them attractive candidates for biotechnological applications. However, before suggesting or choosing a new bacteriocin for future technology developments, it is necessary to elucidate its biochemical structure and its mode of action, which may be carried out once the bacteriocin is purified to homogeneity. This chapter focuses on describing the main strategies used for the purification of numerous bacteriocins.

Purification and characterization of plantaricin Y, a novel bacteriocin produced by Lactobacillus plantarum 510.

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Chen, Yi-sheng; Wang, Yan-chong; Chow, Yiou-shing; Yanagida, Fujitoshi; Liao, Chen-chung; Chiu, Chi-ming

2014-03-01

Lactobacillus plantarum 510, previously isolated from a koshu vineyard in Japan, was found to produce a bacteriocin-like inhibitory substance which was purified and characterized. Mass spectrometry analysis showed that the mass of this bacteriocin is 4,296.65 Da. A partial sequence, NH2- SSSLLNTAWRKFG, was obtained by N-terminal amino acid sequence analysis. A BLAST search revealed that this is a unique sequence; this peptide is thus a novel bacteriocin produced by Lactobacillus plantarum 510 and was termed plantaricin Y. Plantaricin Y shows strong inhibitory activity against Listeria monocytogenes BCRC 14845, but no activity against other pathogens tested. Bacteriocin activity decreased slightly after autoclaving (121 °C for 15 min), but was completely inactivated by protease K. Furthermore, trypsin-digested bacteriocin product fragments retained activity against L. monocytogenes BCRC 14845 and exhibited a different inhibitory spectrum.

Identification, purification and characterization of laterosporulin, a novel bacteriocin produced by Brevibacillus sp. strain GI-9.

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Pradip Kumar Singh

Full Text Available BACKGROUND: Bacteriocins are antimicrobial peptides that are produced by bacteria as a defense mechanism in complex environments. Identification and characterization of novel bacteriocins in novel strains of bacteria is one of the important fields in bacteriology. METHODOLOGY/FINDINGS: The strain GI-9 was identified as Brevibacillus sp. by 16 S rRNA gene sequence analysis. The bacteriocin produced by strain GI-9, namely, laterosporulin was purified from supernatant of the culture grown under optimal conditions using hydrophobic interaction chromatography and reverse-phase HPLC. The bacteriocin was active against a wide range of Gram-positive and Gram-negative bacteria. MALDI-TOF experiments determined the precise molecular mass of the peptide to be of 5.6 kDa and N-terminal sequencing of the thermo-stable peptide revealed low similarity with existing antimicrobial peptides. The putative open reading frame (ORF encoding laterosporulin and its surrounding genomic region was fished out from the draft genome sequence of GI-9. Sequence analysis of the putative bacteriocin gene did not show significant similarity to any reported bacteriocin producing genes in database. CONCLUSIONS: We have identified a bacteriocin producing strain GI-9, belonging to the genus Brevibacillus sp. Biochemical and genomic characterization of laterosporulin suggests it as a novel bacteriocin with broad spectrum antibacterial activity.

Identification, purification and characterization of laterosporulin, a novel bacteriocin produced by Brevibacillus sp. strain GI-9.

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Singh, Pradip Kumar; Chittpurna; Ashish; Sharma, Vikas; Patil, Prabhu B; Korpole, Suresh

2012-01-01

Bacteriocins are antimicrobial peptides that are produced by bacteria as a defense mechanism in complex environments. Identification and characterization of novel bacteriocins in novel strains of bacteria is one of the important fields in bacteriology. The strain GI-9 was identified as Brevibacillus sp. by 16 S rRNA gene sequence analysis. The bacteriocin produced by strain GI-9, namely, laterosporulin was purified from supernatant of the culture grown under optimal conditions using hydrophobic interaction chromatography and reverse-phase HPLC. The bacteriocin was active against a wide range of Gram-positive and Gram-negative bacteria. MALDI-TOF experiments determined the precise molecular mass of the peptide to be of 5.6 kDa and N-terminal sequencing of the thermo-stable peptide revealed low similarity with existing antimicrobial peptides. The putative open reading frame (ORF) encoding laterosporulin and its surrounding genomic region was fished out from the draft genome sequence of GI-9. Sequence analysis of the putative bacteriocin gene did not show significant similarity to any reported bacteriocin producing genes in database. We have identified a bacteriocin producing strain GI-9, belonging to the genus Brevibacillus sp. Biochemical and genomic characterization of laterosporulin suggests it as a novel bacteriocin with broad spectrum antibacterial activity.

Characterization, production, and purification of leucocin H, a two-peptide bacteriocin from Leuconostoc MF215B.

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Blom, H; Katla, T; Holck, A; Sletten, K; Axelsson, L; Holo, H

1999-07-01

Leuconostoc MF215B was found to produce a two-peptide bacteriocin referred to as leucocin H. The two peptides were termed leucocin Halpha and leucocin Hbeta. When acting together, they inhibit, among others, Listeria monocytogenes, Bacillus cereus, and Clostridium perfringens. Production of leucocin H in growth medium takes place at temperatures down to 6 degrees C and at pH below 7. The highest activity of leucocin H in growth medium was demonstrated in the late exponential growth phase. The bacteriocin was purified by precipitation with ammonium sulfate, ion-exchange (SP Sepharose) and reverse phase chromatography. Upon purification, specific activity increased 10(5)-fold, and the final specific activity was 2 x 10(7) BU/OD280. Amino acid composition analyses of leucocin Halpha and leucocin Hbeta indicated that both peptides consisted of around 40 amino acid residues. Their N-termini were blocked for Edman degradation, and the methionin residues of leucocin Hbeta did not respond to Cyanogen Bromide (CNBr) cleavage. Absorbance at 280 nm indicated the presence of tryptophan residues and tryptophan-fracturing opened for partial sequencing by Edman degradation. From leucocin Halpha, the sequence of 20 amino acids was obtained; from leucocin Hbeta the sequence of 28 amino acid residues was obtained. No sequence homology to other known bacteriocins could be demonstrated. It also appeared that the two peptides themselves shared little or no sequence homology. The presence of soy oil did not affect the activity of leucocin H in agar.

Optimization of Fermentation Conditions for the Production of Bacteriocin Fermentate

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2015-03-30

FERMENTATION CONDITIONS FOR THE PRODUCTION OF BACTERIOCIN “ FERMENTATE ” by Anthony Sikes Wayne Muller and Claire Lee March 2015...From - To) October 2010 – November 2013 4. TITLE AND SUBTITLE OPTIMIZATION OF FERMENTATION CONDITIONS FOR THE PRODUCTION OF BACTERIOCIN “ FERMENTATE ...nisin and pediocin. Whey + yeast extract was the best performing whey fermentation media. The nisin producer strain Lactococcus. lactis ssp. lactis was

Use of synthetic genes for cloning, production and functional expression of the bacteriocins enterocin A and bacteriocin E 50-52 by Pichia pastoris and Kluyveromyces lactis.

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Jiménez, Juan J; Borrero, Juan; Gútiez, Loreto; Arbulu, Sara; Herranz, Carmen; Cintas, Luis M; Hernández, Pablo E

2014-06-01

The use of synthetic genes may constitute a successful approach for the heterologous production and functional expression of bacterial antimicrobial peptides (bacteriocins) by recombinant yeasts. In this work, synthetic genes with adapted codon usage designed from the mature amino acid sequence of the bacteriocin enterocin A (EntA), produced by Enterococcus faecium T136, and the mature bacteriocin E 50-52 (BacE50-52), produced by E. faecium NRRL B-32746, were synthesized. The synthetic entA and bacE50-52 were cloned into the protein expression vectors pPICZαA and pKLAC2 for transformation of derived vectors into Pichia pastoris X-33 and Kluyveromyces lactis GG799, respectively. The recombinant vectors were linearized and transformed into competent cells selecting for P. pastoris X-33EAS (entA), P. pastoris X-33BE50-52S (bacE50-52), K. lactis GG799EAS (entA), and K. lactis GG799BE50-52S (bacE50-52). P. pastoris X-33EAS and K. lactis GG799EAS, but not P. pastoris X-33BE50-52S and K. lactis GG799BE50-52S, showed antimicrobial activity in their supernatants. However, purification of the supernatants of the producer yeasts permitted recovery of the bacteriocins EntA and BacE50-52. Both purified bacteriocins were active against Gram-positive bacteria such as Listeria monocytogenes but not against Gram-negative bacteria, including Campylobacter jejuni.

Semi-preparative scale purification of enterococcal bacteriocin enterocin EJ97, and evaluation of substrates for its production.

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López, Rosario Lucas; García, Ma Teresa; Abriouel, Hikmate; Ben Omar, Nabil; Grande, Ma José; Martínez-Cañamero, Magdalena; Gálvez, Antonio

2007-12-01

The influence of substrate composition on the production of enterocin EJ97 and the conditions for semi-preparative bacteriocin recovery have been studied. Final bacteriocin concentrations of 12.5 or 15.6 mg/l were obtained in the commercial media brain heart infusion broth (BHI) and tryptic soya broth, respectively. The bacteriocin was also produced in the complex medium CM (8.75 mg/l), in which the vitamin supplement was essential for production. Some combinations of meat peptone and yeast extract plus either soy peptone or BHI also supported bacteriocin production, at concentrations of 6.25-7.5 mg/l. In cow milk (whole, half-skimmed, and skimmed), the final bacteriocin concentrations obtained ranged from 7.5 to 11.25 mg/l. Highest bacteriocin activity was obtained by using pasteurised milk whey as growth substrate (up to 25 mg/l), suggesting that this bacteriocin can be obtained on a large scale by using this cheap food-grade industrial by-product. Highest bacteriocin titres were always obtained after 8 h of incubation at 37 degrees C. Semi-preparative concentration and purification of enterocin EJ97 produced in a complex medium was achieved by bulk cation exchange chromatography without previous cell separation, followed by reversed-phase chromatography. This two-step procedure allowed preparation of milligram quantities of purified bacteriocin, which is an improvement compared to purification procedures established for most other bacteriocins (35). The availability of purified enterocin EJ97 will facilitate other studies such as the elucidation of its molecular structure and its interaction with target bacteria.

Effects of Streptococcus sanguinis Bacteriocin on Cell Surface Hydrophobicity, Membrane Permeability, and Ultrastructure of Candida Thallus

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Shengli Ma

2015-01-01

Full Text Available Candida albicans (C.a and Candida tropicalis (C.t were treated with Streptococcus sanguinis bacteriocin (S.s bacteriocin, respectively; the bacteriostatic dynamics of S.s bacteriocin, their effects on cell surface hydrophobicity, leakage of inorganic phosphorus and macromolecular substance, cytosolic calcium concentration, and ultrastructure changes of Candida thallus were detected and analyzed. The results showed that inhibitory effect of S.s bacteriocin on C.a and C.t reached peak level at 24 h, the cell-surface hydrophobicity decreased significantly (P < 0.05 after S.s bacteriocin treatment, and there was leakage of cytoplasmic inorganic phosphorus and macromolecular substance from C.a and C.t; cytosolic calcium concentration decreased greatly. After 24 h treatment by S.s bacteriocin, depressive deformity and defect could be found in the cell surface of C.a and C.t; the thallus displayed irregular forms: C.a was shrunken, there was unclear margins abutting upon cell wall and cell membrane, nucleus disappeared, and cytoplasm was inhomogeneous; likewise, C.t was first plasmolysis, and then the cytoplasm was shrunk, the ultrastructure of cell wall and cell membrane was continuously damaged, and the nucleus was karyolysis. It was illustrated that S.s bacteriocin had similar antifungal effect on C.a and C.t; their cell surface hydrophobicity, membrane permeability, and ultrastructure were changed significantly on exposure to S.s bacteriocin.

Enterocin 96, a Novel Class II Bacteriocin Produced by Enterococcus faecalis WHE 96, Isolated from Munster Cheese▿

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Izquierdo, Esther; Wagner, Camille; Marchioni, Eric; Aoude-Werner, Dalal; Ennahar, Saïd

2009-01-01

Enterococcus faecalis WHE 96, a strain isolated from soft cheese based on its anti-Listeria activity, produced a 5,494-Da bacteriocin that was purified to homogeneity by ultrafiltration and cation-exchange and reversed-phase chromatographies. The amino acid sequence of this bacteriocin, named enterocin 96, was determined by Edman degradation, and its structural gene was sequenced, revealing a double-glycine leader peptide. After a comparison with other bacteriocins, it was shown that enterocin 96 was a new class II bacteriocin that showed very little similarity with known structures. Enterocin 96 was indeed a new bacteriocin belonging to class II bacteriocins. The activity spectrum of enterocin 96 covered a wide range of bacteria, with strong activity against most gram-positive strains but very little or no activity against gram-negative strains. PMID:19411428

Enterocin 96, a novel class II bacteriocin produced by Enterococcus faecalis WHE 96, isolated from Munster cheese.

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Izquierdo, Esther; Wagner, Camille; Marchioni, Eric; Aoude-Werner, Dalal; Ennahar, Saïd

2009-07-01

Enterococcus faecalis WHE 96, a strain isolated from soft cheese based on its anti-Listeria activity, produced a 5,494-Da bacteriocin that was purified to homogeneity by ultrafiltration and cation-exchange and reversed-phase chromatographies. The amino acid sequence of this bacteriocin, named enterocin 96, was determined by Edman degradation, and its structural gene was sequenced, revealing a double-glycine leader peptide. After a comparison with other bacteriocins, it was shown that enterocin 96 was a new class II bacteriocin that showed very little similarity with known structures. Enterocin 96 was indeed a new bacteriocin belonging to class II bacteriocins. The activity spectrum of enterocin 96 covered a wide range of bacteria, with strong activity against most gram-positive strains but very little or no activity against gram-negative strains.

A Natural Chimeric Pseudomonas Bacteriocin with Novel Pore-Forming Activity Parasitizes the Ferrichrome Transporter.

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Ghequire, Maarten G K; Kemland, Lieselore; Anoz-Carbonell, Ernesto; Buchanan, Susan K; De Mot, René

2017-02-21

Modular bacteriocins represent a major group of secreted protein toxins with a narrow spectrum of activity, involved in interference competition between Gram-negative bacteria. These antibacterial proteins include a domain for binding to the target cell and a toxin module at the carboxy terminus. Self-inhibition of producers is provided by coexpression of linked immunity genes that transiently inhibit the toxin's activity through formation of bacteriocin-immunity complexes or by insertion in the inner membrane, depending on the type of toxin module. We demonstrate strain-specific inhibitory activity for PmnH, a Pseudomonas bacteriocin with an unprecedented dual-toxin architecture, hosting both a colicin M domain, potentially interfering with peptidoglycan synthesis, and a novel colicin N-type domain, a pore-forming module distinct from the colicin Ia-type domain in Pseudomonas aeruginosa pyocin S5. A downstream-linked gene product confers PmnH immunity upon susceptible strains. This protein, ImnH, has a transmembrane topology similar to that of Pseudomonas colicin M-like and pore-forming immunity proteins, although homology with either of these is essentially absent. The enhanced killing activity of PmnH under iron-limited growth conditions reflects parasitism of the ferrichrome-type transporter for entry into target cells, a strategy shown here to be used as well by monodomain colicin M-like bacteriocins from pseudomonads. The integration of a second type of toxin module in a bacteriocin gene could offer a competitive advantage against bacteria displaying immunity against only one of both toxic activities. IMPORTANCE In their continuous struggle for ecological space, bacteria face a huge load of contenders, including phylogenetically related strains that compete for the same niche. One important group of secreted antibacterial proteins assisting in eliminating these rivals are modular bacteriocins of Gram-negative bacteria, comprising a domain for docking onto the

Mutations near the cleavage site of enterocin NKR-5-3B prepeptide reveal new insights into its biosynthesis.

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Perez, Rodney H; Sugino, Haruki; Ishibashi, Naoki; Zendo, Takeshi; Wilaipun, Pongtep; Leelawatcharamas, Vichien; Nakayama, Jiro; Sonomoto, Kenji

2017-04-01

Enterocin NKR-5-3B (Ent53B) is a 64-residue novel circular bacteriocin synthesized from an 87-residue prepeptide. Albeit through a still unknown mechanism, the EnkB1234 biosynthetic enzyme complex processes the prepeptide to yield its mature active, circular form. To gain insights into the key region/residue that plays a role in Ent53 maturation, several mutations near the cleavage site on the precursor peptide were generated. The interaction of the precursor peptide and EnkB1234 appeared to be hydrophobic in nature. At the Leu1 position, only mutations with helix structure-promoting hydrophobic residues (Ala, Ile, Val or Phe) were able to yield the mature Ent53B derivative. In this study, we also highlight the possible conformation-stabilizing role of the Ent53B leader peptide on the precursor peptide for its interaction with its biosynthetic enzyme complex. Any truncations of the leader peptide moiety interfered in the processing of the prepeptide. However, when propeptides of other circular bacteriocins (circularin A, leucocyclicin Q or lactocyclicin Q) were cloned at the C-terminus of the leader peptide, EnkB1234 could not process them to yield a mature bacteriocin. Taken together, these findings offer new perspectives in our understanding of the possible molecular mechanism of the biosynthesis of this circular bacteriocin. These new perspectives will help advance our current understanding to eventually elucidate circular bacteriocin biosynthesis. Understanding the biosynthetic mechanism of circular bacteriocins will materialize their application potential.

Isolation and purification of two bacteriocins 3D produced by Enterococcus faecium with inhibitory activity against Listeria monocytogenes.

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Bayoub, Kaoutar; Mardad, Ilham; Ammar, Emna; Serrano, Aurelio; Soukri, Abdelaziz

2011-02-01

Strain 3D, isolated from fermented traditional Moroccan dairy product, and identified as Enterococcus faecium, was studied for its capability to produce two bacteriocins acting against Listeria monocytogenes. Bacteriocins 3 Da and 3Db were heat stable inactivated by proteinase K, pepsin, and trypsin but not when treated with catalase. The evidenced bacteriocins were stable in a wide pH range from 2 to 11 and bactericidal activity was kept during storage at 4°C. However, the combination of temperature and pH exhibited a stability of the bacteriocins. RP-HPLC purification of the anti-microbial compounds shows two active fractions eluted at 16 and 30.5 min, respectively. Mass spectrometry analysis showed that E. faecium 3D produce two bacteriocins Enterocin 3 Da (3893.080 Da) and Enterocin 3Db (4203.350 Da). This strain is food-grade organism and its bacteriocins were heat-stable peptides at basic, neutral, and acid pH: such bacteriocins may be of interest as food preservatives.

Bacteriocins produced by L. fermentum and L .acidophilus can inhibit cephalosporin resistant E .coli.

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Saba Riaz

2010-10-01

Full Text Available Reemerging infections occur due to resistant bacteria. Such infections create restrictions for clinicians and microbiologists in drug selection. Such problems demand new strategies for solution. Use of bacteriocins for this purpose may be fruitful. In the present research work, the inhibitory effects of bactericins on cephalosporin resistant Escherichia coli are used as model system for the control of antibiotic resistant pathogenic bacteria. Cephalosporin resistant Escherichia coli strain was isolated from pus by using conventional methodology. For bacteriocin production, Lactobacilli strains were selected by using selective media. Out of seventy two strains isolated from yogurt, fecal materials of human, chick, parrot and cat, only two strains (strain 45 and strain 52 were found to produce bacteriocins having antimicrobial potential against cephalosporin resistant Escherichia coli. Biochemical characterization showed that strain 45 belonged to group of Lactobacillus fermentum and strain 52 to Lactobacillus acidophilus. Both strains showed maximum growth at 25°C and 35°C respectively. Suitable pH was 5.5 and 6.0 for Lactobacillus fermentum and Lactobacillus acidophilus respectively. Bacteriocins produced by both strains were found stable at 50, 75 and 100°C for 60min. Function of bacteriocin was also not disturbed due to change in pH. These findings suggest that bacteriocin produced by Lactobacillus fermentum and Lactobacillus acidophilus can be used for the infection control of cephalosporin resistant Escherichia coli.

Production of bacteriocin by Leuconostoc mesenteroides 406 isolated from Mongolian fermented mare's milk, airag.

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Wulijideligen; Asahina, Takayuki; Hara, Kazushi; Arakawa, Kensuke; Nakano, Hiroyuki; Miyamoto, Taku

2012-10-01

The purification and characterization of a bacteriocin produced by Leuconostoc mesenteroides strain 406 that was isolated from traditional Mongolian fermented mare's milk, airag, were carried out. Leuconostoc mesenteroides strain 406 was identified on the basis of its morphological and biochemical characteristics and carbohydrate fermentation profile and by API 50 CH kit and 16S ribosomal DNA analyses. The neutral-pH cell-free supernatant of this bacterium inhibited the growth of several lactic acid bacteria and food spoilage and pathogenic organisms, including Listeria monocytogenes and Clostridium botulinum. The bacteriocin was heat-stable and not sensitive to acid and alkaline conditions, but was sensitive to several proteolytic enzymes such as pepsin, pronase E, proteinase K, trypsin, and α-chymotrypsin, but not catalase. Optimum bacteriocin production (4000 activity units/mL) was achieved when the strain was cultured at 25°C for 24-36 h in Man Rogosa Sharpe medium. The bacteriocin was partially purified by ammonium sulfate precipitation (80% saturation), dialysis (cut-off MW: 1000), and gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the bacteriocin had a molecular weight of approximately 3.3 kDa. To our knowledge, this is the first report of the isolation of a bacteriocin-producing Leuconostoc strain from airag. An application to fermented milks would be desired. © 2012 The Authors. Animal Science Journal © 2012 Japanese Society of Animal Science.

A counterselection method for Lactococcus lactis genome editing based on class IIa bacteriocin sensitivity.

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Wan, Xing; Usvalampi, Anne M; Saris, Per E J; Takala, Timo M

2016-11-01

In this paper, we present a new counterselection method for deleting fragments from Lactococcus lactis chromosome. The method uses a non-replicating plasmid vector, which integrates into the chromosome and makes the cell sensitive to bacteriocins. The integration vector carries pUC ori functional in Escherichia coli but not in L. lactis, an erythromycin resistance gene for selecting single crossover integrants, and two fragments from L. lactis chromosome for homologous recombinations. In addition, the integration vector is equipped with the Listeria monocytogenes gene mptC encoding the mannose-phosphotransferase system component IIC, the receptor for class IIa bacteriocins. Expression of mptC from the integration vector renders the naturally resistant L. lactis sensitive to class IIa bacteriocins. This sensitivity is then used to select the double crossover colonies on bacteriocin agar. Only the cells which have regained the endogenous bacteriocin resistance through the loss of the mptC plasmid will survive. The colonies carrying the desired deletion can then be distinguished from the wild-type revertants by PCR. By using the class IIa bacteriocins leucocin A, leucocin C or pediocin AcH as the counterselective agents, we deleted 22- and 33-kb chromosomal fragments from the wild-type nisin producing L. lactis strain N8. In conclusion, this counterselection method presented here is a convenient, efficient and inexpensive technique to generate successive deletions in L. lactis chromosome.

Characterization of Partially Purified Bacteriocin Like Substance (BLIS Produced by Probiotic Lactobacillus Strains

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Saeed Ismail Khanian

2014-05-01

Full Text Available Background: There is an increasing interest in search for antimicrobial peptides (bacteriocins and bacteriocin-like compounds produced by lactic acid bacteria (LAB because of their potential to be used as antimicrobial agents for improving the safety of food products. Objectives: The main objective of study was to evaluate the antibacterial potential of locally isolated Lactic Acid bacteria (LAB and determine their bacteriocin producing ability in in-vitro conditions. Materials and Methods: The antibacterial activity of 77 isolated LAB strains was tested against a number of pathogens by well-diffusion method. The isolates demonstrating antimicrobial potential were selected and tested for the production of bacteriocin or bacteriocin like substance. The bacteriocin produced by two of the isolates were partially purified and characterized. Results: The results indicated the neutralized supernatant fluid of two of the isolates identified as L. brevis LB32 and L. pentosus LP05, were active against the growth of Listeria monocytogenes, Salmonella enteritidis, Shigella dysenteriae, Staphylococcus aureus and Streptococcus pneumoniae. Additionally, L. brevis LB32 was able to inhibit the growth of Salmonella typhi and Klebsiella pneumoniae, while, S. pnuemoniae and L. monocytogenes appeared to be the most sensitive strain as apparent by highest zone of inhibition against these pathogens, respectively. The antimicrobial activity in the supernatant fluids of the mentioned strains remained unaffected after treating with enzymes catalase, lipase and lysozyme, while were strongly sensitive to the action of proteolytic enzymes, suggesting the presence of bacteriocin like inhibitory substance (BLIS in the two isolates. The inhibitory substance produced by the two isolates appeared heat resistant and tolerated 100˚C and 121˚C for 55 minutes and 20 minutes, respectively. Partial purification of the concentrated culture supernatant fluids of L. brevis LB32 and L

Elimination of Listeria monocytogenes in sausage meat by combination treatment: Radiation and radiation-resistant bacteriocins

International Nuclear Information System (INIS)

Turgis, Mélanie; Stotz, Viviane; Dupont, Claude; Salmieri, Stéphane; Khan, Ruhul A.; Lacroix, Monique

2012-01-01

Two new bacteria were isolated from human feces and were designated MT 104 and MT 162. They were able to produce bacteriocins that are active against five strains of Listeria monocytogenes. Bacteriocins produced by these isolated strains had 100% and 82.35% residual activity when they were treated by gamma radiation at doses of 4 and 40 kGy, respectively. A reduction of 1.0, 1.5 and 3 log CFU/g of L. monocytogenes was observed in sausage meat when treated with bacteriocins from MT 104, MT 162, and nisin, respectively. For synergic effect, the D 10 value in presence of the bacteriocins produced by MT 104 showed a 1.08 fold increased relative sensitivity of L. monocytogenes as compared to control after 5 days. The highest synergic effect was observed in presence of nisin which led to 1.61 fold increased relative sensitivity. Combined treatments with nisin and γ-irradiation showed a synergic antimicrobial effect in meat after 24 h and 5 days of storage. A synergic effect was observed only after 5 days at 4 °C for the bacteriocin from MT 104, as compared to the bacteriocin produced by MT 162 that had only an additive antimicrobial effect in all conditions.

Elimination of Listeria monocytogenes in sausage meat by combination treatment: Radiation and radiation-resistant bacteriocins

Science.gov (United States)

Turgis, Mélanie; Stotz, Viviane; Dupont, Claude; Salmieri, Stéphane; Khan, Ruhul A.; Lacroix, Monique

2012-08-01

Two new bacteria were isolated from human feces and were designated MT 104 and MT 162. They were able to produce bacteriocins that are active against five strains of Listeria monocytogenes. Bacteriocins produced by these isolated strains had 100% and 82.35% residual activity when they were treated by gamma radiation at doses of 4 and 40 kGy, respectively. A reduction of 1.0, 1.5 and 3 log CFU/g of L. monocytogenes was observed in sausage meat when treated with bacteriocins from MT 104, MT 162, and nisin, respectively. For synergic effect, the D10 value in presence of the bacteriocins produced by MT 104 showed a 1.08 fold increased relative sensitivity of L. monocytogenes as compared to control after 5 days. The highest synergic effect was observed in presence of nisin which led to 1.61 fold increased relative sensitivity. Combined treatments with nisin and γ-irradiation showed a synergic antimicrobial effect in meat after 24 h and 5 days of storage. A synergic effect was observed only after 5 days at 4 °C for the bacteriocin from MT 104, as compared to the bacteriocin produced by MT 162 that had only an additive antimicrobial effect in all conditions.

Improving safety of salami by application of bacteriocins produced by an autochthonous Lactobacillus curvatus isolate.

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de Souza Barbosa, Matheus; Todorov, Svetoslav Dimitrov; Ivanova, Iskra; Chobert, Jean-Marc; Haertlé, Thomas; de Melo Franco, Bernadette Dora Gombossy

2015-04-01

The aims of this study were to isolate LAB with anti-Listeria activity from salami samples, characterize the bacteriocin/s produced by selected isolates, semi-purify them and evaluate their effectiveness for the control of Listeria monocytogenes during manufacturing of salami in a pilot scale. Two isolates (differentiated by RAPD-PCR) presented activity against 22 out of 23 L. monocytogenes strains for bacteriocin MBSa2, while the bacteriocin MBSa3 inhibited all 23 strains in addition to several other Gram-positive bacteria for both antimicrobials and were identified as Lactobacillus curvatus based on 16S rRNA sequencing. A three-step purification procedure indicated that both strains produced the same two active peptides (4457.9 Da and 4360.1 Da), homlogous to sakacins P and X, respectively. Addition of the semi-purified bacteriocins produced by Lb. curvatus MBSa2 to the batter for production of salami, experimentally contaminated with L. monocytogenes (10(4)-10(5) CFU/g), caused 2 log and 1.5 log reductions in the counts of the pathogen in the product after 10 and 20 days respectively, highlighting the interest for application of these bacteriocins to improve safety of salami during its manufacture. Copyright © 2014 Elsevier Ltd. All rights reserved.

The structure of pyogenecin immunity protein, a novel bacteriocin-like immunity protein from streptococcus pyogenes.

Energy Technology Data Exchange (ETDEWEB)

Chang, C.; Coggill, P.; Bateman, A.; Finn, R.; Cymborowski, M.; Otwinowski, Z.; Minor, W.; Volkart, L.; Joachimiak, A.; Wellcome Trust Sanger Inst.; Univ. of Virginia; UT Southwestern Medical Center

2009-12-17

Many Gram-positive lactic acid bacteria (LAB) produce anti-bacterial peptides and small proteins called bacteriocins, which enable them to compete against other bacteria in the environment. These peptides fall structurally into three different classes, I, II, III, with class IIa being pediocin-like single entities and class IIb being two-peptide bacteriocins. Self-protective cognate immunity proteins are usually co-transcribed with these toxins. Several examples of cognates for IIa have already been solved structurally. Streptococcus pyogenes, closely related to LAB, is one of the most common human pathogens, so knowledge of how it competes against other LAB species is likely to prove invaluable. We have solved the crystal structure of the gene-product of locus Spy-2152 from S. pyogenes, (PDB: 2fu2), and found it to comprise an anti-parallel four-helix bundle that is structurally similar to other bacteriocin immunity proteins. Sequence analyses indicate this protein to be a possible immunity protein protective against class IIa or IIb bacteriocins. However, given that S. pyogenes appears to lack any IIa pediocin-like proteins but does possess class IIb bacteriocins, we suggest this protein confers immunity to IIb-like peptides. Combined structural, genomic and proteomic analyses have allowed the identification and in silico characterization of a new putative immunity protein from S. pyogenes, possibly the first structure of an immunity protein protective against potential class IIb two-peptide bacteriocins. We have named the two pairs of putative bacteriocins found in S. pyogenes pyogenecin 1, 2, 3 and 4.

Novel bacteriocins from lactic acid bacteria (LAB): various structures and applications

OpenAIRE

Perez, Rodney H; Zendo, Takeshi; Sonomoto, Kenji

2014-01-01

Bacteriocins are heat-stable ribosomally synthesized antimicrobial peptides produced by various bacteria, including food-grade lactic acid bacteria (LAB). These antimicrobial peptides have huge potential as both food preservatives, and as next-generation antibiotics targeting the multiple-drug resistant pathogens. The increasing number of reports of new bacteriocins with unique properties indicates that there is still a lot to learn about this family of peptide antibiotics. In this review, we...

Screening and characterization of bacteriocins produced by some Strains of Lactobacillus spp isolated from Iranian Dairy products

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S Mirdamadi

2011-11-01

Full Text Available In this study, the inhibitory effects of bacteriocins of lactobacilli which were isolated from Iranian traditional dairy products was determined against known gram positive, gram negative and yeast by well diffusion technique. Among 8 isolates with higher capability of bacteriocin production, 2 isolates were selected for further investigations. The bacteriocins were purified by iso-propanol and ammonium sulfate precipitation following by dialysis and chromatography technique. The molecular weight of bacteriocins was determined as 45 to 66/2 KDa. by SDS-page electrophoresis. According to the results, the produced bacteriocins had more inhibition effect on Micrococcus luteus PTCC1169, Staphylococcus epidermidis PTCC1435 as well as Bacillus cereus PTCC1247 and with lesser degree of extent on Listeria monocytogenes PTCC 1301. Results also revealed that, Micrococcus luteus  was the most sensitive bacterium among indicator bacteria, while Candid albicans PTCC 5027 identified as the most resistance organism. This research showed that, bacteriocins produced by lactobacilli isolated from traditional dairy products have high potency to be used against microbial pathogens and could be applied as bio-preservative in food products.

Method for Rapid Purification of Class IIa Bacteriocins and Comparison of Their Activities

OpenAIRE

Guyonnet, D.; Fremaux, C.; Cenatiempo, Y.; Berjeaud, J. M.

2000-01-01

A three-step method was developed for the purification of mesentericin Y105 (60% yield) from the culture supernatant of Leuconostoc mesenteroides Y105. The same procedure was successfully applied to the purification of five other anti-Listeria bacteriocins identified by mass spectrometry. Specific activities of the purified bacteriocins were compared.

Optimization and partial characterization of bacteriocin produced by Lactobacillus bulgaricus -TLBFT06 isolated from Dahi.

Science.gov (United States)

Mahmood, Talat; Masud, Tariq; Ali, Sartaj; Abbasi, Kashif Sarfraz; Liaquat, Muhammad

2015-03-01

Lactobacillus bulgaricus is one of the predominant lactic acid bacteria of dahi, conferring technological and functional attributes. In the present study thirty dahi samples were investigated for bacteriocin producing L. bulgaricus. Fourteen different isolates were obtained and five were scrutinized for antibacterial activities against food born pathogens. Amongst, a strain TLB06FT was found to have a wide array of antibacterial activities against Gram positive and negative bacteria was selected for further characterization. Growth media optimization for this strain revealed maximum bacteriocin production on MRS media supplemented with glucose (2%), sodium chloride (1%), Tween-80 (0.5%) and yeast extract (1 %). In addition, optimization of growth conditions revealed maximum bacteriocin production at pH 5.5 and temperature of 30-37°C. Bacteriocin showed thermo stability at 90°C and remained highly active in the pH range of 3.5-7.5, inactive by protein catalyzing enzymes and showed no change in activity (800AumL(-1)) when treated with organic solvents and surfactants. The obtained bacteriocin was purified to 1600AU mL(-1) by ammonium sulfate precipitation (80%) by using dialyzing tubing. In the same way, a single peak was obtained by RP-HPLC having antibacterial activity of 6400AU mL(-1). Thus, wild strains of L. bulgaricus have great potential for the production new and novel type of bacteriocins.

Role of acetate in production of an autoinducible Class IIa Bacteriocin in Carnobacterium piscicola A9b

DEFF Research Database (Denmark)

Nilsson, Lilian; Nielsen, Michael Krogsgaard; Ng, Yin

2002-01-01

was to purify the compound and describe factors affecting its production, with particular emphasis on food-relevant factors. Amino acid sequencing showed that the compound is a class IIa bacteriocin with an N-terminal amino acid sequence identical to that of carnobacteriocin B2. The production....... The induction of bacteriocin production showed a dose-dependent relationship at acetate concentrations of up to 10 to 20 mM (depending on the growth medium) and at a concentration of 1.9 x 10(-8) M for the bacteriocin itself; a saturation level of bacteriocin specific activity was reached...

Gene Cluster Responsible for Secretion of and Immunity to Multiple Bacteriocins, the NKR-5-3 Enterocins

Science.gov (United States)

Ishibashi, Naoki; Himeno, Kohei; Masuda, Yoshimitsu; Perez, Rodney Honrada; Iwatani, Shun; Wilaipun, Pongtep; Leelawatcharamas, Vichien; Nakayama, Jiro; Sonomoto, Kenji

2014-01-01

Enterococcus faecium NKR-5-3, isolated from Thai fermented fish, is characterized by the unique ability to produce five bacteriocins, namely, enterocins NKR-5-3A, -B, -C, -D, and -Z (Ent53A, Ent53B, Ent53C, Ent53D, and Ent53Z). Genetic analysis with a genome library revealed that the bacteriocin structural genes (enkA [ent53A], enkC [ent53C], enkD [ent53D], and enkZ [ent53Z]) that encode these peptides (except for Ent53B) are located in close proximity to each other. This NKR-5-3ACDZ (Ent53ACDZ) enterocin gene cluster (approximately 13 kb long) includes certain bacteriocin biosynthetic genes such as an ABC transporter gene (enkT), two immunity genes (enkIaz and enkIc), a response regulator (enkR), and a histidine protein kinase (enkK). Heterologous-expression studies of enkT and ΔenkT mutant strains showed that enkT is responsible for the secretion of Ent53A, Ent53C, Ent53D, and Ent53Z, suggesting that EnkT is a wide-range ABC transporter that contributes to the effective production of these bacteriocins. In addition, EnkIaz and EnkIc were found to confer self-immunity to the respective bacteriocins. Furthermore, bacteriocin induction assays performed with the ΔenkRK mutant strain showed that EnkR and EnkK are regulatory proteins responsible for bacteriocin production and that, together with Ent53D, they constitute a three-component regulatory system. Thus, the Ent53ACDZ gene cluster is essential for the biosynthesis and regulation of NKR-5-3 enterocins, and this is, to our knowledge, the first report that demonstrates the secretion of multiple bacteriocins by an ABC transporter. PMID:25149515

ANTIMICROBIAL ACTIVITY OF BACTERIOCIN FROM INDIGENOUS Lactobacillus plantarum 2C12 AND ITS APPLICATION ON BEEF MEATBALL AS BIOPRESERVATIVE

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I.I. Arief

2014-10-01

Full Text Available One purpose of food preservation is to extend the shelf life of foods. Biological preservations canbe conducted by adding antimicrobial substances, such as bacteriocin produced by lactic acid bacteriaand has been characterized as biopreservatives. The aims of this research were to evaluate antimicrobialactivity of bacteriocin produced by indigenous lactic acid bacteria Lactobacillus plantarum 2C12isolated from local beef and to study the quality of beef meatball with 0.3% bacteriocin asbiopreservative at different storage times (0, 3, and 6 days in cold temperature (4oC, compared to 0.3%nitrite and control (without preservative. The results showed that bacteriocin from L. plantarum 2C12could inhibit pathogenic bacteria such as Escherichia coli, Staphylococcus aureus and SalmonellaTyphimurium. Bacteriocin was effective as well as nitrite as biopreservatives of meatballs by inhibitingthe growth of total microbes and E. coli. The addition of bacteriocin did not lead the physical andnutritional changes in the meatballs. The quality of meatball with bacteriocin treatment conformed withIndonesia National Standard of meatball.

ANTIMICROBIAL ACTIVITY OF BACTERIOCIN FROM INDIGENOUS Lactobacillus plantarum 2C12 AND ITS APPLICATION ON BEEF MEATBALL AS BIOPRESERVATIVE

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T. Suryati

2012-06-01

Full Text Available One purpose of food preservation is to extend the shelf life of foods. Biological preservations can be conducted by adding antimicrobial substances, such as bacteriocin produced by lactic acid bacteria and has been characterized as biopreservatives. The aims of this research were to evaluate antimicrobial activity of bacteriocin produced by indigenous lactic acid bacteria Lactobacillus plantarum 2C12 isolated from local beef and to study the quality of beef meatball with 0.3% bacteriocin as biopreservative at different storage times (0, 3, and 6 days in cold temperature (4oC, compared to 0.3% nitrite and control (without preservative. The results showed that bacteriocin from L. plantarum 2C12 could inhibit pathogenic bacteria such as Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. Bacteriocin was effective as well as nitrite as biopreservatives of meatballs by inhibiting the growth of total microbes and E. coli. The addition of bacteriocin did not lead the physical and nutritional changes in the meatballs. The quality of meatball with bacteriocin treatment conformed with Indonesia National Standard of meatball.

Method for Rapid Purification of Class IIa Bacteriocins and Comparison of Their Activities

Science.gov (United States)

Guyonnet, D.; Fremaux, C.; Cenatiempo, Y.; Berjeaud, J. M.

2000-01-01

A three-step method was developed for the purification of mesentericin Y105 (60% yield) from the culture supernatant of Leuconostoc mesenteroides Y105. The same procedure was successfully applied to the purification of five other anti-Listeria bacteriocins identified by mass spectrometry. Specific activities of the purified bacteriocins were compared. PMID:10742275

Coculture-inducible bacteriocin biosynthesis of different probiotic strains by dairy starter culture Lactococcus lactis

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Blaženka Kos

2011-12-01

Full Text Available Bacteriocins produced by probiotic strains effectively contribute to colonization ability of probiotic strains and facilitate their establishment in the competitive gut environment and also protect the gut from gastrointestinal pathogens. Moreover, bacteriocins have received considerable attention due to their potential application as biopreservatives, especially in dairy industry. Hence, the objective of this research was to investigate antimicrobial activity of probiotic strains Lactobacillus helveticus M92, Lactobacillus plantarum L4 and Enterococcus faecium L3, with special focus on their bacteriocinogenic activity directed towards representatives of the same or related bacterial species, and towards distant microorganisms including potential food contaminants or causative agents of gut infections. In order to induce bacteriocin production, probiotic cells were cocultivated with Lactococcus lactis subsp. lactis LMG 9450, one of the most important starter cultures in cheese production. The presence of bacteriocin coding genes was investigated by PCR amplification with sequence-specific primers for helveticin and was confirmed for probiotic strain L. helveticus M92. All examined probiotic strains have shown bacteriocinogenic activity against Staphylococcus aureus 3048, Staphylococcus aureus K-144, Escherichia coli 3014, Salmonella enterica serovar Typhimurium FP1, Bacillus subtilis ATCC 6633, Bacillus cereus TM2, which is an important functional treat of probiotic strains significant in competitive exclusion mechanism which provides selective advantage of probiotic strains against undesirable microorganisms in gastrointestinal tract of the host. According to obtained results, living cells of starter culture Lc. lactis subsp. lactis LMG 9450 induced bacteriocin production by examined probiotic strains but starter culture itself was not sensitive to bacteriocin activity.

Purification and Characterization of Bacteriocin Produced by Weissella confusa A3 of Dairy Origin.

Science.gov (United States)

Goh, Hweh Fen; Philip, Koshy

2015-01-01

A dramatic increase in bacterial resistance towards currently available antibiotics has raised worldwide concerns for public health. Therefore, antimicrobial peptides (AMPs) have emerged as a promisingly new group of therapeutic agents for managing infectious diseases. The present investigation focusses on the isolation and purification of a novel bacteriocin from an indigenous sample of cow milk and it's mode of action. The bacteriocin was isolated from Weissella confusa A3 that was isolated from the sample and was shown to have inhibitory activity towards pathogenic bacteria namely Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Micrococcus luteus. The bacteriocin was shown to be heat stable and functioned well at low pH (2 to 6). Reduction of activity was shown after treatment with proteinase K, trypsin and peptidase that confirmed the proteinaceous nature of the compound. MALDI-TOF analysis of the sample gave a mass approximating 2.7 kDa. The membrane of the bacteria was disrupted by the bacteriocin causing SYTOX® green dye to enter the cell and bind to the bacterial DNA giving fluorescence signal. Bacterial cell treated with the bacteriocin also showed significant morphological changes under transmission electron microscope. No virulence and disease related genes can be detected from the genome of the strain.

Purification and Characterization of Bacteriocin Produced by Weissella confusa A3 of Dairy Origin

Science.gov (United States)

Goh, Hweh Fen; Philip, Koshy

2015-01-01

A dramatic increase in bacterial resistance towards currently available antibiotics has raised worldwide concerns for public health. Therefore, antimicrobial peptides (AMPs) have emerged as a promisingly new group of therapeutic agents for managing infectious diseases. The present investigation focusses on the isolation and purification of a novel bacteriocin from an indigenous sample of cow milk and it’s mode of action. The bacteriocin was isolated from Weissella confusa A3 that was isolated from the sample and was shown to have inhibitory activity towards pathogenic bacteria namely Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Micrococcus luteus. The bacteriocin was shown to be heat stable and functioned well at low pH (2 to 6). Reduction of activity was shown after treatment with proteinase K, trypsin and peptidase that confirmed the proteinaceous nature of the compound. MALDI-TOF analysis of the sample gave a mass approximating 2.7 kDa. The membrane of the bacteria was disrupted by the bacteriocin causing SYTOX® green dye to enter the cell and bind to the bacterial DNA giving fluorescence signal. Bacterial cell treated with the bacteriocin also showed significant morphological changes under transmission electron microscope. No virulence and disease related genes can be detected from the genome of the strain. PMID:26474074

Coculture-inducible bacteriocin activity of Lactobacillus plantarum strain J23 isolated from grape must.

Science.gov (United States)

Rojo-Bezares, Beatriz; Sáenz, Yolanda; Navarro, Laura; Zarazaga, Myriam; Ruiz-Larrea, Fernanda; Torres, Carmen

2007-08-01

Detection and characterization of bacteriocin production by Lactobacillus plantarum strain J23, recovered from a grape must sample in Spain, have been carried out. Bacteriocin activity was degraded by proteolytic enzymes (trypsin, alfa-chymotrypsin, papaine, protease, proteinase K and acid proteases), and it was stable at high temperatures (121 degrees C, 20min), in a wide range of pH (1-12), and after treatment with organic solvents. L. plantarum J23 showed antimicrobial activity against Oenococcus oeni, and a range of Lactobacillus and Pediococcus species. Bacteriocin production was detected in liquid media only when J23 was cocultivated with some inducing bacteria, and induction took place when intact cells or 55 degrees C heated cells of the inducer were cocultivated with J23, but not with their autoclaved cells. Bacteriocin activity of J23 was not induced by high initial J23 inocula, and it was detected in cocultures during the exponential phase. The presence of ethanol or acidic pH in the media reduced bacteriocin production in the cocultures of J23 with the inducing bacteria. The presence of plantaricin-related plnEF and plnJ genes was detected by PCR and sequencing. Nevertheless, negative results were obtained for plnA, plnK, plNC8, plS and plW genes.

Antimicrobial Effect of Bacteriocin produced Pediococcus pentosaceus on some clinical isolates

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Nehad A. Taher

2017-07-01

Full Text Available About 10 isolates of Pediococcus sp were isolated from different cheese made in Iraq, These isolates were identified morphologically and biochemically and Api20 kit, thus there was only 6 isolate were identified as Pediococcus pentosaceus (60%.In this study, we investigate, the effect of crude Bacteriocin from Pediococcus pentosaceus on 30 clinical isolates (5 E.coli, 5 Klepsiella pneumoniae, 5 Staphylococcus aureus, 5 Pseudomonas aeroginosa, 5 Bacillus subtilis, 5 Candida albicans. The protein concentration of this Bacteriocin was measured 67mg\\ml by Bradford method and used as (1:2 by vol during the measuring the antimicrobial activity against the above clinical isolates by two methods wells and  agar plug assay. The results showed that  the inhibitory activity of this Bacteriocin was higher by wells method than agar pluq assay against Gram–positive bacteria or Gram-negative bacteria and yeast under this study.

EFFECT OF CULTURE MEDIUM ON BACTERIOCIN PRODUCTION BY LACTOBACILLUS RHAMNOSUS HN001 AND LACTOBACILLUS REUTERI ATCC 53608

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Aguilar-Uscanga B. R.

2013-06-01

Full Text Available The aim of this study was to evaluate the effect of media on bacteriocin production by Lactobacillus rhamnosus HN001 and Lactobacillus reuteri ATCC 53608 using three different media: YPM, YPF and MRS supplemented with glucose and K2HPO4. The optimum temperature was 37°C and initial pH 6.5. Bacteriocin-like substances produced by tested bacteria in MRS medium supplemented with glucose and K2HPO4 exhibited a broad antimicrobial spectrum determined by well diffusion assay against indicator bacteria Listeria monocytogenes, Lactobacillus sakei, Enterococcus faecium, Lactobacillus delbrueckii, Lactobacillus acidophilus, but no antimicrobial spectrum against E. coli O157:H7, Salmonella typhimurium, Staphylococcus aureus, Bacillus cereus was detected. Bacteriocin was sensitive to protease IV, trypsin, pepsin and -amylases, but resistant to lipase. It was also resistant to detergents such as Tween 80, Triton-X and SDS. This bacteriocin was thermo-stable (resistant at 60°C, 90°C and 100°C for 30 min. Tested bacteria showed the best antimicrobial (bacteriocin-like activity after growth in MRS medium. Bacteriocin substances produced by tested bacteria showed promising thermo-stable technological properties.

Interactions of meat-associated bacteriocin-producing Lactobacilli with Listeria innocua under stringent sausage fermentation conditions.

Science.gov (United States)

Leroy, Frédéric; Lievens, Kristoff; De Vuyst, Luc

2005-10-01

The kinetics of the antilisterial effect of meat-associated lactobacilli on Listeria innocua LMG 13568 were investigated during laboratory batch fermentations. During these fermentations, which were performed in a liquid meat simulation medium, a combination of process factors typical for European-style sausage fermentations was applied, such as a temperature of 20 degrees C and a representative pH and salting profile. Two bacteriocin-producing sausage isolates (Lactobacillus sakei CTC 494 and Lactobacillus curvatus LTH 1174), which have already proven efficacy in sausage trials, and one nonbacteriocinogenic, industrial strain (Lactobacillus sakei I), were evaluated. Staphylococcus carnosus 833 was included in the experiment because of its role in flavor and color development. When grown as a monoculture or upon cocultivation with L. sakei I and S. carnosus 833, L. innocua LMG 13568 developed slightly, despite the stress of low temperature, pH, lactic acid, salt, and nitrite. In contrast, when either of the bacteriocin producers was used, the L. innocua LMG 13568 population was rapidly inactivated with more than 3 log CFU ml(-1) after 2 days of fermentation. A bacteriocin-tolerant L. innocua LMG 13568 subpopulation (4 X 10(-4)) remained after bacteriocin inactivation. Thus, when the initial level of L. innocua LMG 13568 equaled 3 log CFU ml(-1), all cells were inactivated and no bacteriocin-tolerant cells were detected, even after 7 days of incubation. S. carnosus was not inactivated by the Lactobacillus bacteriocins and displayed slight growth.

Influence of Growth Medium on Hydrogen Peroxide and Bacteriocin Production of Lactobacillus Strains

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Edina Németh

2005-01-01

Full Text Available This study was conducted to investigate the inhibitory effect of bacteriocin and the production of hydrogen peroxide by four non-starter lactic acid bacteria, Lactobacillus plantarum 2142, Lactobacillus curvatus 2770, Lactobacillus curvatus 2775, Lactobacillus casei subsp. pseudoplantarum 2750 and the probiotic strain Lactobacillus casei Shirota, propagated in de Man Rogosa Sharpe (MRS and tomato juice (TJ broth. The methods were a commonly used agar diffusion technique and a microtiter assay method. The best peroxide-producing Lactobacillus strain was selected for screening the inhibitory activity against Listeria monocytogenes, Bacillus cereus, Escherichia coli and the activity of bacteriocins against Lactobacillus sakei and Candida glabrata. All of the investigated lactic acid bacteria (LAB strains grown in MRS broth produced the highest concentration of hydrogen peroxide ranging from 2–6 g/mL after 72 h of storage. L. plantarum 2142 produced enough hydrogen peroxide already after 24 h at 5 °C in phosphate buffer to inhibit the growth of L. monocytogenes and B. cereus. Crude bacteriocin suspension from the investigated LAB inhibited only slightly the growth of L. sakei, however, the same suspension from MRS completely inhibited the 6-fold diluted yeast suspension. The concentrated bacteriocin suspensions from the both broths inhibited the growth of L. sakei completely. Among the strains, L. plantarum 2142 seemed to be the best peroxide and bacteriocin producer, and the antimicrobial metabolite production was better in MRS than in TJ broth.

Cloning, overexpression, purification of bacteriocin enterocin-B and structural analysis, interaction determination of enterocin-A, B against pathogenic bacteria and human cancer cells.

Science.gov (United States)

Ankaiah, Dasari; Palanichamy, Esakkiraj; Antonyraj, Christian Bharathi; Ayyanna, Repally; Perumal, Venkatesh; Ahamed, Syed Ibrahim Basheer; Arul, Venkatesan

2018-05-02

In this present study, a gene (ent-B) encoding the bacteriocin enterocin-B was cloned, overexpressed and purified from Enterococcus faecium por1. The molecular weight of the bacteriocin enterocin-B was observed around 7.2 kDa and exhibited antimicrobial activity against several human pathogenic bacteria. The antimicrobial activity of cloned enterocin-B was increased effectively by combining with another bacteriocin enterocin-A from the same microorganism. Protein-protein docking and molecular dynamics simulation studies revealed that the bacteriocin enterocin-B is interacting with enterocin-A and formation of a heterodimer (enterocin A + B). The heterodimer of bacteriocin enterocin-A + B exhibited potential anti-bacterial, anti-biofilm activity against Staphylococcus aureus, Acinetobacter baumannii, Listeria monocytogenes and Escherichia coli. The bacteriocin enterocin-B, A and heterodimer of bacteriocin enterocin A + B showed no haemolysis on human RBC cells. This is the first report that the cell growth inhibitory activity of the bacteriocin enterocin B against HeLa, HT-29 and AGS human cancer cells and this cell growth inhibitory activity was significantly increased when cancer cells treated with the heterodimer of bacteriocins enterocin-A + B. The cell growth inhibitory activity of the bacteriocin enterocin-B and the heterodimer of bacteriocin enterocin-A + B were not observed in non-cancerous INT-407 cells (intestinal epithelial cells). Copyright © 2018. Published by Elsevier B.V.

Modeling Bacteriocin Resistance and Inactivation of Listeria innocua LMG 13568 by Lactobacillus sakei CTC 494 under Sausage Fermentation Conditions

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Leroy, Frédéric; Lievens, Kristoff; De Vuyst, Luc

2005-01-01

In mixed cultures, bacteriocin production by the sausage isolate Lactobacillus sakei CTC 494 rapidly inactivated sensitive Listeria innocua LMG 13568 cells, even at low bacteriocin activity levels. A small fraction of the listerial population was bacteriocin resistant. However, sausage fermentation conditions inhibited regrowth of resistant cells. PMID:16269805

Screening and characterization of bacteriocins produced by some Strains of Lactobacillus spp isolated from Iranian Dairy products

OpenAIRE

S Mirdamadi; M Tangestani

2011-01-01

In this study, the inhibitory effects of bacteriocins of lactobacilli which were isolated from Iranian traditional dairy products was determined against known gram positive, gram negative and yeast by well diffusion technique. Among 8 isolates with higher capability of bacteriocin production, 2 isolates were selected for further investigations. The bacteriocins were purified by iso-propanol and ammonium sulfate precipitation following by dialysis and chromatography technique. The molecular we...

Growing insights into the safety of bacteriocins: the case of enterocin S37.

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Belguesmia, Yanath; Madi, Amar; Sperandio, Daniel; Merieau, Annabelle; Feuilloley, Marc; Prévost, Hervé; Drider, Djamel; Connil, Nathalie

2011-01-01

Very few studies have been reported on the cytotoxicity and impact of bacteriocins, and especially enterocins, upon eukaryotic cells. In order to gain more information on the safety of bacteriocins, we focused this study on enterocin S37, a bacteriocin produced by Enterococcus faecalis S37. We observed dose-dependent cytotoxicity toward undifferentiated Caco-2/TC7 cells. Moreover, no significant effect on differentiated monolayer Caco-2/TC7 and no apoptotic features were observed when cells were treated with 10 μg/ml of enterocin S37. The results obtained indicate possible safe use of enterocin S37 in the gastrointestinal tract of animals to prevent pathogen invasion and/or infection. Copyright © 2010 Institut Pasteur. Published by Elsevier SAS. All rights reserved.

Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: characterization of the bacteriocin

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Danielle N. Furtado

2014-12-01

Full Text Available Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi was isolated from goat milk, and studied for its antimicrobial activity. The bacteriocin presented a broad spectrum of activity, was sensitive to proteolytic enzymes, resistant to heat and pH extremes, and not affected by the presence of SDS, Tween 20, Tween 80, EDTA or NaCl. Bacteriocin production was dependent on the components of the culture media, especially nitrogen source and salts. When tested by PCR, the bacteriocin gene presented 100% homology to nisin Z gene. These properties indicate that this L. lactis subsp. lactis DF4Mi can be used for enhancement of dairy foods safety and quality.

Bacteriocinogenic Lactococcus lactis subsp. lactis DF04Mi isolated from goat milk: Characterization of the bacteriocin

Science.gov (United States)

Furtado, Danielle N.; Todorov, Svetoslav D.; Landgraf, Mariza; Destro, Maria T.; Franco, Bernadette D.G.M.

2014-01-01

Lactic acid bacteria capable of producing bacteriocins and presenting probiotic potential open innovative technological applications in the dairy industry. In this study, a bacteriocinogenic strain (Lactococcus lactis subsp. lactis DF4Mi) was isolated from goat milk, and studied for its antimicrobial activity. The bacteriocin presented a broad spectrum of activity, was sensitive to proteolytic enzymes, resistant to heat and pH extremes, and not affected by the presence of SDS, Tween 20, Tween 80, EDTA or NaCl. Bacteriocin production was dependent on the components of the culture media, especially nitrogen source and salts. When tested by PCR, the bacteriocin gene presented 100% homology to nisin Z gene. These properties indicate that this L. lactis subsp. lactis DF4Mi can be used for enhancement of dairy foods safety and quality. PMID:25763065

Sensitivity to the two-peptide bacteriocin lactococcin G is dependent on UppP, an enzyme involved in cell-wall synthesis

NARCIS (Netherlands)

Kjos, Morten; Oppegård, Camilla; Diep, Dzung B; Nes, Ingolf F; Veening, Jan-Willem; Nissen-Meyer, Jon; Kristensen, Tom

Most bacterially produced antimicrobial peptides (bacteriocins) are thought to kill target cells by a receptor-mediated mechanism. However, for most bacteriocins the receptor is unknown. For instance, no target receptor has been identified for the two-peptide bacteriocins (class IIb), whose activity

Distinct colicin M-like bacteriocin-immunity pairs in Burkholderia.

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Ghequire, Maarten G K; De Mot, René

2015-11-27

The Escherichia coli bacteriocin colicin M (ColM) acts via degradation of the cell wall precursor lipid II in target cells. ColM producers avoid self-inhibition by a periplasmic immunity protein anchored in the inner membrane. In this study, we identified colM-like bacteriocin genes in genomes of several β-proteobacterial strains belonging to the Burkholderia cepacia complex (Bcc) and the Burkholderia pseudomallei group. Two selected Burkholderia ambifaria proteins, designated burkhocins M1 and M2, were produced recombinantly and showed antagonistic activity against Bcc strains. In their considerably sequence-diverged catalytic domain, a conserved aspartate residue equally proved pivotal for cytotoxicity. Immunity to M-type burkhocins is conferred upon susceptible strains by heterologous expression of a cognate gene located either upstream or downstream of the toxin gene. These genes lack homology with currently known ColM immunity genes and encode inner membrane-associated proteins of two distinct types, differing in predicted transmembrane topology and moiety exposed to the periplasm. The addition of burkhocins to the bacteriocin complement of Burkholderia reveals a wider phylogenetic distribution of ColM-like bacteriotoxins, beyond the γ-proteobacterial genera Escherichia, Pectobacterium and Pseudomonas, and illuminates the diversified nature of immunity-providing proteins.

A Microplate Growth Inhibition Assay for Screening Bacteriocins against Listeria monocytogenes to Differentiate Their Mode-of-Action

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Paul Priyesh Vijayakumar

2015-06-01

Full Text Available Lactic acid bacteria (LAB have historically been used in food fermentations to preserve foods and are generally-recognized-as-safe (GRAS by the FDA for use as food ingredients. In addition to lactic acid; some strains also produce bacteriocins that have been proposed for use as food preservatives. In this study we examined the inhibition of Listeria monocytogenes 39-2 by neutralized and non-neutralized bacteriocin preparations (Bac+ preps produced by Lactobacillus curvatus FS47; Lb. curvatus Beef3; Pediococcus acidilactici Bac3; Lactococcus lactis FLS1; Enterococcus faecium FS56-1; and Enterococcus thailandicus FS92. Activity differences between non-neutralized and neutralized Bac+ preps in agar spot assays could not readily be attributed to acid because a bacteriocin-negative control strain was not inhibitory to Listeria in these assays. When neutralized and non-neutralized Bac+ preps were used in microplate growth inhibition assays against L. monocytogenes 39-2 we observed some differences attributed to acid inhibition. A microplate growth inhibition assay was used to compare inhibitory reactions of wild-type and bacteriocin-resistant variants of L. monocytogenes to differentiate bacteriocins with different modes-of-action (MOA whereby curvaticins FS47 and Beef3, and pediocin Bac3 were categorized to be in MOA1; enterocins FS92 and FS56-1 in MOA2; and lacticin FLS1 in MOA3. The microplate bacteriocin MOA assay establishes a platform to evaluate the best combination of bacteriocin preparations for use in food applications as biopreservatives against L. monocytogenes.

A Microplate Growth Inhibition Assay for Screening Bacteriocins against Listeria monocytogenes to Differentiate Their Mode-of-Action.

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Vijayakumar, Paul Priyesh; Muriana, Peter M

2015-06-11

Lactic acid bacteria (LAB) have historically been used in food fermentations to preserve foods and are generally-recognized-as-safe (GRAS) by the FDA for use as food ingredients. In addition to lactic acid; some strains also produce bacteriocins that have been proposed for use as food preservatives. In this study we examined the inhibition of Listeria monocytogenes 39-2 by neutralized and non-neutralized bacteriocin preparations (Bac+ preps) produced by Lactobacillus curvatus FS47; Lb. curvatus Beef3; Pediococcus acidilactici Bac3; Lactococcus lactis FLS1; Enterococcus faecium FS56-1; and Enterococcus thailandicus FS92. Activity differences between non-neutralized and neutralized Bac+ preps in agar spot assays could not readily be attributed to acid because a bacteriocin-negative control strain was not inhibitory to Listeria in these assays. When neutralized and non-neutralized Bac+ preps were used in microplate growth inhibition assays against L. monocytogenes 39-2 we observed some differences attributed to acid inhibition. A microplate growth inhibition assay was used to compare inhibitory reactions of wild-type and bacteriocin-resistant variants of L. monocytogenes to differentiate bacteriocins with different modes-of-action (MOA) whereby curvaticins FS47 and Beef3, and pediocin Bac3 were categorized to be in MOA1; enterocins FS92 and FS56-1 in MOA2; and lacticin FLS1 in MOA3. The microplate bacteriocin MOA assay establishes a platform to evaluate the best combination of bacteriocin preparations for use in food applications as biopreservatives against L. monocytogenes.

Examination of Lactic Acid Bacteria to Secretion of Bacteriocins

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Maira Urazova

2014-01-01

Full Text Available Introduction: Bacteriocins produced by lactic acid bacteria (LAB have the potential to cover a very broad field of applications, including the food industry and the medical sector. In the food industry, bacteriocinogenic LAB strains can be used as starter cultures, co-cultures, and bioprotective cultures, which would be used to improve food quality and safety. In the medical sector, bacteriocins of probiotic LAB might play a role in interactions, which take place in human gastrointestinal tract, and contribute to gut health. The aim of this study was the examine the effect of LAB antimicrobial activity. Methods: LAB were isolated from different commercial and home made products, such as kazy and sour cream. To screen for bacteriocin producing LAB, we used an agar diffusion bioassay, described in a previous study by Dr. Yang, with three modifications in cell-free supernatant (CFS. First we had a clear supernatant, second we adjusted the CFS to pH 6.0 to eliminate acids antimicrobial effects, and third the CFS pH 6.0 was treated with catalase to exclude the action of H2O2 and confirm action of bacteriocin-like substances. Pathogenic S.marcescens, E. coli, S.aureus cultures were used as indicators. Results: Screening of 95 strains of LAB through deferred antagonism to six indicator cultures showed that all of the selected strains had a high value of antibacterial activity. However, CFS of only 50 strains retained their antimicrobial activity, and 10 of them lost this activity in the second modification of CFS with pH 6.0 to test culture S.marcescens, which confirmed the acidic nature of antimicrobial activity of CFS. Lb.rhamnosus (P-1, Lb.fermentum (N-6, and Lc.lactis (7M lost antibacterial activity in the presence of the catalase. All modifications of CFS of three strains: Lb.pentosus (16al, Lb.pentosus (P-2, and Pediococcusacidilactici (8 retained inhibitory activity to E.coli and S. aureus. Supernatants of only Lactococcusgarvieae (10a and

Effect of Lactobacillus salivarius bacteriocin Abp118 on the mouse and pig intestinal microbiota.

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Eliette Riboulet-Bisson

Full Text Available Lactobacilli are gram-positive bacteria that are a subdominant element in the human gastrointestinal microbiota, and which are commonly used in the food industry. Some lactobacilli are considered probiotic, and have been associated with health benefits. However, there is very little culture-independent information on how consumed probiotic microorganisms might affect the entire intestinal microbiota. We therefore studied the impact of the administration of Lactobacillus salivarius UCC118, a microorganism well characterized for its probiotic properties, on the composition of the intestinal microbiota in two model animals. UCC118 has anti-infective activity due to production of the bacteriocin Abp118, a broad-spectrum class IIb bacteriocin, which we hypothesized could impact the microbiota. Mice and pigs were administered wild-type (WT L. salivarius UCC118 cells, or a mutant lacking bacteriocin production. The microbiota composition was determined by pyrosequencing of 16S rRNA gene amplicons from faeces. The data show that L. salivarius UCC118 administration had no significant effect on proportions of major phyla comprising the mouse microbiota, whether the strain was producing bacteriocin or not. However, L. salivarius UCC118 WT administration led to a significant decrease in Spirochaetes levels, the third major phylum in the untreated pig microbiota. In both pigs and mice, L. salivarius UCC118 administration had an effect on Firmicutes genus members. This effect was not observed when the mutant strain was administered, and was thus associated with bacteriocin production. Surprisingly, in both models, L. salivarius UCC118 administration and production of Abp118 had an effect on gram-negative microorganisms, even though Abp118 is normally not active in vitro against this group of microorganisms. Thus L. salivarius UCC118 administration has a significant but subtle impact on mouse and pig microbiota, by a mechanism that seems at least partially

Inhibitory effect of bacteriocin-producing lactic acid bacteria against histamine-forming bacteria isolated from Myeolchi-jeot

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Eun-Seo Lim

2016-12-01

Full Text Available Abstract The objectives of this study were to identify the histamine-forming bacteria and bacteriocin- producing lactic acid bacteria (LAB isolated from Myeolchi-jeot according to sequence analysis of the 16S rRNA gene, to evaluate the inhibitory effects of the bacteriocin on the growth and histamine accumulation of histamine-forming bacteria, and to assess the physico-chemical properties of the bacteriocin. Based on 16S rRNA gene sequences, histamine-forming bacteria were identified as Bacillus licheniformis MCH01, Serratia marcescens MCH02, Staphylococcus xylosus MCH03, Aeromonas hydrophila MCH04, and Morganella morganii MCH05. The five LAB strains identified as Pediococcus acidilactici MCL11, Leuconostoc mesenteroides MCL12, Enterococcus faecium MCL13, Lactobacillus sakei MCL14, and Lactobacillus acidophilus MCL15 were found to produce an antibacterial compound with inhibitory activity against the tested histamine-producing bacteria. The inhibitory activity of these bacteriocins obtained from the five LAB remained stable after incubation at pH 4.0–8.0 and heating for 10 min at 80 °C; however, the bacteriocin activity was destroyed after treatment with papain, pepsin, proteinase K, α-chymotrypsin, or trypsin. Meanwhile, these bacteriocins produced by the tested LAB strains also exhibited histamine-degradation ability. Therefore, these antimicrobial substances may play a role in inhibiting histamine formation in the fermented fish products and preventing seafood-related food-borne disease caused by bacterially generated histamine.

A Novel High-Molecular-Mass Bacteriocin Produced by Enterococcus faecium: Biochemical Features and Mode of Action.

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Vasilchenko, A S; Vasilchenko, A V; Valyshev, A V; Rogozhin, E A

2018-02-08

Discovery of a novel bacteriocin is always an event in sciences, since cultivation of most bacterial species is a general problem in microbiology. This statement is reflected by the fact that number of bacteriocins is smaller for tenfold comparing to known antimicrobial peptides. We cultivated Enterococcus faecium on simplified medium to reduce amount of purification steps. This approach allows to purify the novel heavy weight bacteriocin produced by E. faecium ICIS 7. The novelty of this bacteriocin, named enterocin-7, was confirmed by N-terminal sequencing and by comparing the structural-functional properties with available data. Purified enterocin-7 is characterized by a sequence of amino acid residues having no homology in UniProt/SwissProt/TrEMBL databases: NH2 - Asp - Ala - His - Leu - Ser - Glu - Val - Ala - Glu - Arg - Phe - Glu - Asp - Leu - Gly. Isolated thermostable protein has a molecular mass of 65 kDa, which allows it to be classified into class III in bacteriocin classification schemes. Enterocin-7 displayed a broad spectrum of activity against some Gram-positive and Gram-negative microorganisms. Fluorescent microscopy and spectroscopy showed the permeabilizing mechanism of the action of enterocin-7, which is realized within a few minutes.

Improved adsorption-desorption extraction applied to the partial characterization of the antilisterial bacteriocin produced by Carnobacterium maltaromaticum C2

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F. L Tulini

2010-06-01

Full Text Available Bacteriocins are ribosomally produced peptides useful for food biopreservation. An improved adsorption-desorption process is proposed for the partial purification of the bacteriocin produced by the fish isolate Carnobacterium maltaromaticum C2. Analyzis of extract by SDS-PAGE indicated this method may offer an alternative to improve the yield of purification of bacteriocins.

Purification and antibacterial mechanism of fish-borne bacteriocin and its application in shrimp (Penaeus vannamei) for inhibiting Vibrio parahaemolyticus.

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Lv, Xinran; Du, Jingfang; Jie, Yu; Zhang, Bolin; Bai, Fengling; Zhao, Hongfei; Li, Jianrong

2017-08-01

Vibrio parahaemolyticus: is recognized as the main cause of gastroenteritis associated with consumption of seafood. Bacteriocin-producing Lactobacillus plantarum FGC-12 isolated from golden carp intestine had strong antibacterial activity toward V. parahaemolyticus. The fish-borne bacteriocin was purified by a three-step procedure consisting of ethyl acetate extraction, gel filtration chromatography and high performance liquid chromatography. Its molecular weight was estimated at 4.1 kDa using SDS-PAGE. The fish-borne bacteriocin reached the maximum production at stationary phase after 20 h. It was heat-stable (30 min at 121 °C) and remained active at pH range from 3.0 to 5.5, but was sensitive to nutrasin, papain and pepsin. Its minimum inhibitory concentration for V. parahaemolyticus was 6.0 mg/ml. Scanning electron microscopy analysis showed that the fish-borne bacteriocin disrupted cell wall of V. parahaemolyticus. The antibacterial mechanism of the fish-borne bacteriocin against V. parahaemolyticus might be described as action on membrane integrity in terms of the leakage of electrolytes, the losses of Na + K + -ATPase, AKP and proteins. The addition of the fish-borne bacteriocin to shrimps leaded V. parahaemolyticus to reduce 1.3 log units at 4 °C storage for 6 day. Moreover, a marked decline in total volatile base nitrogen and total viable counts was observed in bacteriocin treated samples than the control. It is clear that this fish-borne bacteriocin has promising potential as biopreservation for the control of V. parahaemolyticus in aquatic products.

Inhibitory activity of bacteriocin produced from Lactobacillus SCG 1223 toward L. monocytogenes, S. thypimurium and E. coli

Science.gov (United States)

Marwati, T.; Cahyaningrum, N.; Widodo, S.; Januarsyah, T.; Purwoko

2018-01-01

Bacteriocin is a protein compound which has bactericidal ability against pathogen bacteria. This research aims to study the inhibitory activity of bacteriocin produced from Lactobacillus SCG 1223 against Listeria monocytogenes, Salmonella thypimuruim and Escherchia coli. The bacteriocin produce from Lactobacillus SCG 1223 in the MRS broth media The experimental design used was Completely Randomized Design. The variations used in this design were percentage of inoculum (5%, 10%), medium pH (4, 6), incubation temperature (27°C, 40°C), and incubation time (4, 10, 14 hours). Result showed that bacteriocin from Lactobacillus SCG 1223 had wide spectrum toward L. monocytogenes, S. thypimuruim and E. coli. The highest bacteriocin activity toward L. monocytogenes produced by Lactobacillus SCG 1223 with 10% inoculum in media with initial pH 6, incubation temperature 27°C for 14 hour, toward S. thypimurium produced by Lactobacillus SCG 1223 with in media with initial pH 6, incubation temperature 40°C for 14 hour, and toward E. coli was 1085.81 AU/ml, produced by Lactobacillus SCG 1223 in MRS broth with initial pH 4, incubation temperature 40°C for 14 hour. This study is expected to find a new food preservative that can inhibit the growth of pathogenic bacteria and extend the shelf life of food. From the economic prospective of view, bacteriocin is very promising natural alternative biopreservatives.

Antimicrobial activities of the bacteriocin-like substances produced ...

African Journals Online (AJOL)

Administrator

2011-09-07

Sep 7, 2011 ... bacteriocins (subclass IIc); the large (>30 kDa) heat-labile non-lantibiotics (class III) and ... LAB from cow and goat milk and dairy products were ... (Oxoid, Hapshire, UK) was used to determine hydrolysis of esculin and growth ...

Simultaneous Production of Biosurfactants and Bacteriocins by Probiotic Lactobacillus casei MRTL3

Science.gov (United States)

Sharma, Deepansh; Singh Saharan, Baljeet

2014-01-01

Lactic acid bacteria (LAB) are ubiquitous and well-known commensal bacteria in the human and animal microflora. LAB are extensively studied and used in a variety of industrial and food fermentations. They are widely used for humans and animals as adjuvants, probiotic formulation, and dietary supplements and in other food fermentation applications. In the present investigation, LAB were isolated from raw milk samples collected from local dairy farms of Haryana, India. Further, the isolates were screened for simultaneous production of biosurfactants and bacteriocins. Biosurfactant produced was found to be a mixture of lipid and sugar similar to glycolipids. The bacteriocin obtained was found to be heat stable (5 min at 100°C). Further, DNA of the strain was extracted and amplified by the 16S rRNA sequencing using universal primers. The isolate Lactobacillus casei MRTL3 was found to be a potent biosurfactant and bacteriocin producer. It seems to have huge potential for food industry as a biopreservative and/or food ingredient. PMID:24669225

Selection of bacteriocin producer strains of lactic acid bacteria from a dairy environment.

Science.gov (United States)

Lasagno, M; Beoleito, V; Sesma, F; Raya, R; Font de Valdez, G; Eraso, A

2002-01-01

Two strains showing bacteriocin production were selected from a total of 206 lactic acid bacteria isolated from samples of milk, milk serum, whey and homemade cheeses in Southern Cordoba, Argentina. This property was detected by means of well diffusion assays. The strains were identified as Enterococcus hirae and Enterococcus durans. The protein nature of those substances was proved by showing their sensitivity to type IV and XXV proteases, papaine, trypsin, pepsin and K proteinase. The bacteriocins inhibited the growth of Listeria monocytogenes, Bacillus cereus, Clostridium perfringes and two strains of Staphylococcus aureus, an A-enterotoxin and a B-enterotoxin producers. All of these bacteria are common pathogens usually associated with food borne diseases (ETA). These lactic acid bacteria or their bacteriocins could be suitable candidates for food preservation and specially useful in the our regional dairy industry.

BAGEL2 : mining for bacteriocins in genomic data

NARCIS (Netherlands)

de Jong, Anne; van Heel, Auke J.; Kok, Jan; Kuipers, Oscar P.

Mining bacterial genomes for bacteriocins is a challenging task due to the substantial structure and sequence diversity, and generally small sizes, of these antimicrobial peptides. Major progress in the research of antimicrobial peptides and the ever-increasing quantities of genomic data, varying

Determination of bacteriocin activity with bioassays carried out on solid and liquid substrates: assessing the factor "indicator microorganism"

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Ambrosiadis Ioannis

2006-10-01

Full Text Available Abstract Background Successful application of growth inhibition techniques for quantitative determination of bacteriocins relies on the sensitivity of the applied indicator microorganism to the bacteriocin to which is exposed. However, information on indicator microorganisms' performance and comparisons in bacteriocin determination with bioassays is almost non-existing in the literature. The aim of the present work was to evaluate the parameter "indicator microorganism" in bioassays carried out on solid -agar diffusion assay- and liquid -turbidometric assay- substrates, applied in the quantification of the most studied bacteriocin nisin. Results The performance of characterized microorganisms of known sources, belonging to the genera of Lactobacillus, Pediococcus, Micrococcus and Leuconostoc, has been assessed in this work in the assays of plate agar diffusion and turbidometry. Dose responses and sensitivities were examined and compared over a range of assay variables in standard bacteriocin solutions, fermentation broth filtrates and processed food samples. Measurements on inhibition zones produced on agar plates were made by means of digital image analysis. The data produced were analyzed statistically using the ANOVA technique and pairwise comparisons tests. Sensitivity limits and linearity of responses to bacteriocin varied significantly among different test-microorganisms in both applied methods, the lower sensitivity limits depending on both the test-microorganism and the applied method. In both methods, however, only two of the nine tested microorganisms (Lactobacillus curvatus ATCC 51436 and Pediococcus acidilactici ATCC 25740 were sensitive to very low concentrations of the bacteriocin and produced a linear-type of response in all kinds of samples used in this work. In all cases, very low bacteriocin concentrations, e.g. 1 IU/ml nisin, were more accurately determined in the turbidometric assay. Conclusion The present work shows that in

Purification of bacteriocins using size-exclusion chromatography

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Vivek K. Bajpai

2016-06-01

Full Text Available The bacteriocin purification involves following main steps. a. Extraction of cell-free-supernatant of bacteria. b. Ammonium sulfate precipitation. c. Dialysis. d. Diafiltration using PVP and e. Size-exclusion chromatography. However, depending on the nature of work, the compound could be further analyzed by reverse-phase HPLC, NMR, mass spectrometry and sequencing.

Solution Structure of Enterocin HF, an Antilisterial Bacteriocin Produced by Enterococcus faecium M3K31.

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Arbulu, Sara; Lohans, Christopher T; van Belkum, Marco J; Cintas, Luis M; Herranz, Carmen; Vederas, John C; Hernández, Pablo E

2015-12-16

The solution structure of enterocin HF (EntHF), a class IIa bacteriocin of 43 amino acids produced by Enterococcus faecium M3K31, was evaluated by CD and NMR spectroscopy. Purified EntHF was unstructured in water, but CD analysis supports that EntHF adopts an α-helical conformation when exposed to increasing concentrations of trifluoroethanol. Furthermore, NMR spectroscopy indicates that this bacteriocin adopts an antiparallel β-sheet structure in the N-terminal region (residues 1-17), followed by a well-defined central α-helix (residues 19-30) and a more disordered C-terminal end (residues 31-43). EntHF could be structurally organized into three flexible regions that might act in a coordinated manner. This is in agreement with the absence of long-range nuclear Overhauser effect signals between the β-sheet domain and the C-terminal end of the bacteriocin. The 3D structure recorded for EntHF fits emerging facts regarding target recognition and mode of action of class IIa bacteriocins.

Detection of bacteriocins produced by plant pathogenic bacteria from the general Erwinia, Pseudomonas and Xanthomonas

International Nuclear Information System (INIS)

Biagi, C.M.R. de

1992-01-01

Detection of bacteriocin production was studied under distinct conditions using strains of plant pathogenic bacteria from the genera Erwinia, Pseudomonas and Xanthomonas. 58.06%, 79.31% and 40.00% of producing strains were found respectively in the three groups of bacteria using the 523 medium which was the best for the detection of bacteriocin production. Increasing agar concentrations added to the medium up to 1,5% improved the detection. The amount of medium added to the Petri dishes did not affect bacteriocin production. The longest incubation time (72 h.) improved the detection of haloes production. Ultra-violet irradiation in low dosages seems to improve the visualization of haloes production but this is dependent on the tested strains. (author)

Partial purification and characterization of bacteriocin produced by Enterococcus faecalis DU10 and its probiotic attributes.

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Perumal, Venkatesh; Repally, Ayyanna; Dasari, Ankaiah; Venkatesan, Arul

2016-10-02

A novel bacteriocin produced by avian duck isolated lactic acid bacterium Enterococcus faecalis DU10 was isolated. This bacteriocin showed a broad spectrum of antibacterial activity against important food-borne pathogens and was purified by size exclusion chromatography followed by reverse-phase high-performance liquid chromatography in a C-18 column. Tricine-SDS PAGE revealed the presence of a band with an estimated molecular mass of 6.3 kDa. The zymogram clearly linked the antimicrobial activity with this band. This result was further confirmed by mass-assisted laser desorption ionization time-of-flight mass spectrometry, since a sharp peak corresponding to 6.313 kDa was detected and the functional groups were revealed by Fourier transform infrared spectroscopy. Bacteriocin DU10 activity was found sensitive to proteinase-K and pepsin and partially affected by trypsin and α-chymotrypsin. The activity of bacteriocin DU10 was partially resistant to heat treatments ranging from 30 to 90°C for 30 min. It also withstood a treatment at 121°C for 10 min. Cytotoxicity of bacteriocin DU10 by methyl-thiazolyl-diphenyl-tetrazolium bromide assay showed that the viability of HT-29 and HeLa cells decreased 60 ± 0.7% and 43 ± 4.8%, respectively, in the presence of 3,200 AU/mL of bacteriocin. The strain withstood 0.3% w/v of bile oxgall and pH 2 affected the bacterial growth between 2 and 4 hr of incubation. Adhesion properties examined with HT-29 cell line showed 69.85% initial population of strain E. faecalis DU10, which was found to be strongly adhered to this cell line. These results conclude bacteriocin DU10 may be used as a potential biopreservative and E. faecalis DU10 may be used as a potential probiont to control Salmonella infections.

Purification and characteristics of a novel bacteriocin produced by Enterococcus faecalis L11 isolated from Chinese traditional fermented cucumber.

Science.gov (United States)

Gao, Yurong; Li, Benling; Li, Dapeng; Zhang, Liyuan

2016-05-01

To purify and characterize a novel bacteriocin with broad inhibitory spectrum produced by an isolate of Enterococcus faecalis from Chinese fermented cucumber. E. faecalis L11 produced a bacteriocin with antimicrobial activity against both Escherichia coli and Staphylococcus aureus. The amino acid sequence of the purified bacteriocin, enterocin L11, was assayed by Edman degradation method. It differs from other class II bacteriocins and exhibited a broad antimicrobial activity against not only Gram-positive bacteria, including Bacillus subtilis, S. aureus, Listeria monocytogenes, Sarcina flava, Lactobacillus acidophilus, L. plantarum, L. delbrueckii subsp. delbrueckii, L. delbrueckii subsp. bulgaricus and Streptococcus thermophilus, but also some Gram-negative bacteria including Salmonella typhimurium, E. coli and Shigella flexneri. Enterocin L11 retained 91 % of its activity after holding at 121 °C for 30 min. It was also resistant to acids and alkalis. Enterocin L11 is a novel broad-spectrum Class II bacteriocin produced by E. faecalis L11, and may have potential as a food biopreservative.

Partial characterization of bacteriocin induced by irradiated and non-irradiated strain of yersinia enterocolitical

International Nuclear Information System (INIS)

Awny, N.M.

1991-01-01

Twenty isolates of yersinia enterocolitica were tested for the inhibition of the growth of different strains of yersinia. The screening tests revealed three possible bacteriocinogenic strains. One of them was selected for additional studies after it was shown that its inhibitory substances differed in their activity spectra. The gamma irradiated strain lost the ability to produce bacteriocin at 0.6 kGy level. Crude preparation of bacteriocin obtained from the wild strain were not affected by chloroform or other organic solvents but inactivated by trypsin and heating at 80 C for 45 min. Bacteriocin induced by irradiated strain was easily inactivated by thermal treatment. Exposure of agar fragments containing the inhibitory active component to a pH value ranging between 2 to 11 did not affect bactericidal activity.4 tab

Interactions between Oral Bacteria: Inhibition of Streptococcus mutans Bacteriocin Production by Streptococcus gordonii

OpenAIRE

Wang, Bing-Yan; Kuramitsu, Howard K.

2005-01-01

Streptococcus mutans has been recognized as an important etiological agent in human dental caries. Some strains of S. mutans also produce bacteriocins. In this study, we sought to demonstrate that bacteriocin production by S. mutans strains GS5 and BM71 was mediated by quorum sensing, which is dependent on a competence-stimulating peptide (CSP) signaling system encoded by the com genes. We also demonstrated that interactions with some other oral streptococci interfered with S. mutans bacterio...

Variable characteristics of bacteriocin-producing Streptococcus salivarius strains isolated from Malaysian subjects.

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Abdelahhad Barbour

Full Text Available BACKGROUND: Salivaricins are bacteriocins produced by Streptococcus salivarius, some strains of which can have significant probiotic effects. S. salivarius strains were isolated from Malaysian subjects showing variable antimicrobial activity, metabolic profile, antibiotic susceptibility and lantibiotic production. METHODOLOGY/PRINCIPAL FINDINGS: In this study we report new S. salivarius strains isolated from Malaysian subjects with potential as probiotics. Safety assessment of these strains included their antibiotic susceptibility and metabolic profiles. Genome sequencing using Illumina's MiSeq system was performed for both strains NU10 and YU10 and demonstrating the absence of any known streptococcal virulence determinants indicating that these strains are safe for subsequent use as probiotics. Strain NU10 was found to harbour genes encoding salivaricins A and 9 while strain YU10 was shown to harbour genes encoding salivaricins A3, G32, streptin and slnA1 lantibiotic-like protein. Strain GT2 was shown to harbour genes encoding a large non-lantibiotic bacteriocin (salivaricin-MPS. A new medium for maximum biomass production buffered with 2-(N-morpholinoethanesulfonic acid (MES was developed and showed better biomass accumulation compared with other commercial media. Furthermore, we extracted and purified salivaricin 9 (by strain NU10 and salivaricin G32 (by strain YU10 from S. salivarius cells grown aerobically in this medium. In addition to bacteriocin production, S. salivarius strains produced levan-sucrase which was detected by a specific ESI-LC-MS/MS method which indicates additional health benefits from the developed strains. CONCLUSION: The current study established the bacteriocin, levan-sucrase production and basic safety features of S. salivarius strains isolated from healthy Malaysian subjects demonstrating their potential for use as probiotics. A new bacteriocin-production medium was developed with potential scale up application for

Cultivation, isolation and characterization of bacteriocin from fresh ...

African Journals Online (AJOL)

This study focus on cultivation, isolation and characterization of Bacteriocin from fresh cow milk (FCM) and fresh cow meat (FMS) samples obtained from Lapai Market in Niger State, Nigeria. Potential bacteriocinogenic bacteria were screened with agar diffusion method on culture plates seeded with Staphylococcus and ...

Lactobacillus pentosus B231 Isolated from a Portuguese PDO Cheese: Production and Partial Characterization of Its Bacteriocin.

Science.gov (United States)

Guerreiro, Joana; Monteiro, Vitor; Ramos, Carla; Franco, Bernadette Dora Gombossy de Melo; Martinez, Rafael Chacon Ruiz; Todorov, Svetoslav Dimitrov; Fernandes, Paulo

2014-06-01

Bacteriocin B231 produced by Lactobacillus pentosus, isolated from an artisanal raw cow's milk protected designation of origin Portuguese cheese, is a small protein with an apparent relative mass of about 5 kDa and active against a large number of Listeria monocytogenes wild-type strains, Listeria ivanovii and Listeria innocua. Bacteriocin B231 production is highly dependent on the type of the culture media used for growth of Lact. pentosus B231. Replacement of glucose with maltose yielded the highest bacteriocin production from eight different carbon sources. Similar results were recorded in the presence of combination of glucose and maltose or galactose. Production of bacteriocin B231 reached maximal levels of 800 AU/ml during the stationary phase of growth of Lact. pentosus B231 in MRS broth at 30 °C. Bacteriocin B231 (in cell-free supernatant) was sensitive to treatment with trypsin and proteinase K, but not affected by the thermal treatment in range of 55-121 °C, or freezing (-20 °C). Bacteriocin production and inhibitory spectrum were evaluated. Gene encoding plantaricin S has been detected in the genomic DNA. Virulence potential and safety of Lact. pentosus B231 were assessed by PCR targeted the genes gelE, hyl, asa1, esp, cylA, efaA, ace, vanA, vanB, hdc1, hdc2, tdc and odc. The Lact. pentosus B231 strains harbored plantaricin S gene, while the occurrence of virulence, antibiotic resistance and biogenic amine genes was limited to cytolysin, hyaluronidase, aggregation substance, adhesion of collagen protein, gelatinase, tyrosine decarboxylase and vancomycin B genes.

Maltaricin CPN, a new class IIa bacteriocin produced by Carnobacterium maltaromaticum CPN isolated from mould-ripened cheese.

Science.gov (United States)

Hammi, I; Delalande, F; Belkhou, R; Marchioni, E; Cianferani, S; Ennahar, S

2016-11-01

The purpose of this study was to isolate, characterize and determine the structure and the antibacterial activities of a bacteriocin produced by Carnobacterium maltaromaticum CPN, a strain isolated from unpasteurized milk Camembert cheese. This bacteriocin, termed maltaricin CPN, was produced at higher amounts in MRS broth at temperatures between 15°C and 25°C. It was purified to homogeneity from culture supernatant by using a simple method consisting of cation-exchange and reversed-phase chromatographies. Mass spectrometry showed that maltaricin was a 4427·29 Da bacteriocin. Its amino acid sequence was determined by Edman degradation which showed that it had close similarity with bacteriocins of the class IIa. Maltaricin CPN consisted in fact of 44 unmodified amino acids including two cysteine residues at positions 9 and 14 linked by a disulphide bond. The antimicrobial activity of maltaricin CPN covered a range of bacteria, with strong activity against many species of Gram-positive bacteria, especially the food-borne pathogen Listeria monocytogenes, but no activity against Gram-negative ones. In the studied conditions, C. maltaromaticum CPN produced a new class IIa bacteriocin with strong anti-Listeria activity. The study covers the purification and the structural characterization of a new bacteriocin produced by strain C. maltaromaticum CPN isolated from Camembert cheese. Its activity against strains of L. monocytogenes and higher production rates at relatively low temperatures show potential technological applications to improve the safety of refrigerated food. © 2016 The Society for Applied Microbiology.

Antimicrobial potential of bacteriocins in poultry and swine production.

Science.gov (United States)

Ben Lagha, Amel; Haas, Bruno; Gottschalk, Marcelo; Grenier, Daniel

2017-04-11

The routine use of antibiotics in agriculture has contributed to an increase in drug-resistant bacterial pathogens in animals that can potentially be transmitted to humans. In 2000, the World Health Organization identified resistance to antibiotics as one of the most significant global threats to public health and recommended that the use of antibiotics as additives in animal feed be phased out or terminated, particularly those used to treat human infections. Research is currently being carried out to identify alternative antimicrobial compounds for use in animal production. A number of studies, mostly in vitro, have provided evidence indicating that bacteriocins, which are antimicrobial peptides of bacterial origin, may be promising alternatives to conventional antibiotics in poultry and swine production. This review provides an update on bacteriocins and their potential for use in the poultry and swine industries.

Partial Diversity Generates Effector Immunity Specificity of the Bac41-Like Bacteriocins of Enterococcus faecalis Clinical Strains.

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Kurushima, Jun; Ike, Yasuyoshi; Tomita, Haruyoshi

2016-09-01

Bacteriocin 41 (Bac41) is the plasmid-encoded bacteriocin produced by the opportunistic pathogen Enterococcus faecalis Its genetic determinant consists of bacL1 (effector), bacL2 (regulator), bacA (effector), and bacI (immunity). The secreted effectors BacL1 and BacA coordinate to induce the lytic cell death of E. faecalis Meanwhile, the immunity factor BacI provides self-resistance to the Bac41 producer, E. faecalis, against the action of BacL1 and BacA. In this study, we demonstrated that more than half of the 327 clinical strains of E. faecalis screened had functional Bac41 genes. Analysis of the genetic structure of the Bac41 genes in the DNA sequences of the E. faecalis strains revealed that the Bac41-like genes consist of a relatively conserved region and a variable region located downstream from bacA Based on similarities in the variable region, the Bac41-like genes could be classified into type I, type IIa, and type IIb. Interestingly, the distinct Bac41 types had specific immunity factors for self-resistance, BacI1 or BacI2, and did not show cross-immunity to the other type of effector. We also demonstrated experimentally that the specificity of the immunity was determined by the combination of the C-terminal region of BacA and the presence of the unique BacI1 or BacI2 factor. These observations suggested that Bac41-like bacteriocin genes are extensively disseminated among E. faecalis strains in the clinical environment and can be grouped into at least three types. It was also indicated that the partial diversity results in specificity of self-resistance which may offer these strains a competitive advantage. Bacteriocins are antibacterial effectors produced by bacteria. In general, a bacteriocin-coding gene is accompanied by a cognate immunity gene that confers self-resistance on the bacteriocin-producing bacterium itself. We demonstrated that one of the bacteriocins, Bac41, is disseminated among E. faecalis clinical strains and the Bac41 subtypes with

Rapid Two-Step Procedure for Large-Scale Purification of Pediocin-Like Bacteriocins and Other Cationic Antimicrobial Peptides from Complex Culture Medium

Science.gov (United States)

Uteng, Marianne; Hauge, Håvard Hildeng; Brondz, Ilia; Nissen-Meyer, Jon; Fimland, Gunnar

2002-01-01

A rapid and simple two-step procedure suitable for both small- and large-scale purification of pediocin-like bacteriocins and other cationic peptides has been developed. In the first step, the bacterial culture was applied directly on a cation-exchange column (1-ml cation exchanger per 100-ml cell culture). Bacteria and anionic compounds passed through the column, and cationic bacteriocins were subsequently eluted with 1 M NaCl. In the second step, the bacteriocin fraction was applied on a low-pressure, reverse-phase column and the bacteriocins were detected as major optical density peaks upon elution with propanol. More than 80% of the activity that was initially in the culture supernatant was recovered in both purification steps, and the final bacteriocin preparation was more than 90% pure as judged by analytical reverse-phase chromatography and capillary electrophoresis. PMID:11823243

Isolation of a bacteriocin-producing Lactococcus lactis subsp. lactis and application to control Listeria monocytogenes in Moroccan jben.

Science.gov (United States)

Benkerroum, N; Oubel, H; Zahar, M; Dlia, S; Filali-Maltouf, A

2000-12-01

Use of a bacteriocin-producing lactococcal strain to control Listeria monocytogenes in jben. A Lactococcus lactis strain isolated from lben was shown, by the spot technique, to produce a bacteriocin different from nisin. Inhibitory activity of the bacteriocin-producing strain against Listeria monocytogenes was investigated in jben, made from cow's milk fermented with the producer organism and contaminated with 104 or 107 cfu ml-1. Listeria counts were monitored during manufacture, and during conservation at room and at refrigeration temperatures. Results showed that the pathogen was reduced by 2.7 logarithmic units after 30 h of jben processing when the initial inoculum of 107 cfu ml(-1) was used. For the initial inoculum of 104 cfu ml(-1), the bacterium was completely eliminated at 24 h. Furthermore, the use of the bacteriocin-producing starter culture extended the shelf-life of jben by 5 days. In situ production of the lactococcal bacteriocin is an efficient biological means of controlling L. monocytogenes in jben and of allowing shelf-life extension. The proposed technology will essentially benefit minimally processed dairy products and those made with raw milk.

Evaluation of leader peptides that affect the secretory ability of a multiple bacteriocin transporter, EnkT.

Science.gov (United States)

Sushida, Hirotoshi; Ishibashi, Naoki; Zendo, Takeshi; Wilaipun, Pongtep; Leelawatcharamas, Vichien; Nakayama, Jiro; Sonomoto, Kenji

2018-02-13

EnkT is a novel ATP-binding cassette (ABC) transporter responsible for secretion of four bacteriocins, enterocins NKR-5-3A, C, D, and Z (Ent53A, C, D, and Z), produced by Enterococcus faecium NKR-5-3. It is generally recognized that the secretion of a bacteriocin requires a dedicated ABC transporter, although molecular mechanisms of this secretion are yet to be revealed. In order to characterize the unique ability of EnkT to secrete multiple bacteriocins, the role of N-terminal leader peptides of bacteriocin precursors was evaluated using Ent53C precursor as a model. The 18-amino acid leader peptide of Ent53C (Lc) was modified by site-directed mutagenesis to generate various point mutations, truncations, or extensions, and substitutions with other leader peptides. The impact of these Lc mutations on Ent53C secretion was evaluated using a quantitative antimicrobial activity assay. We observed that Ent53C production increased with Ala substitution of the highly conserved C-terminal double glycine residues that are recognized as the cleavage site. In contrast, Ent53C antimicrobial activity decreased, with decrease in the length of the putative α-helix-forming region of Lc. Furthermore, EnkT recognized and transported Ent53C of the transformants possessing heterologous leader peptides of enterocin A, pediocin PA-1, brochocins A and B, and lactococcins Qα and Qβ. These results indicated that EnkT shows significant tolerance towards the sequence and length of leader peptides, to secrete multiple bacteriocins. This further demonstrates the functional diversity of bacteriocin ABC transporters and the importance of leader peptides as their recognition motif. Copyright © 2018 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

The effect of bacteriocin-producing Lactobacillus plantarum strains on the intracellular pH of sessile and planktonic Listeria monocytongenes single cells

DEFF Research Database (Denmark)

Nielsen, Dennis Sandris; Cho, Gyu-Sung; Hanak, Alexander

2010-01-01

and/or bacteriocin-producing LAB as “natural” food preservatives in foods such as cheese, meat and ready-to-eat products. Some strains of Lactobacillus plantarum produce bacteriocins termed plantaricins. Using a single-cell based approach, the effect on the intracellular pH as a measure......A wide range of lactic acid bacteria (LAB) produce bacteriocins mainly active against other closely related LAB, but some bacteriocins are also active against the food-borne pathogen Listeria monocytogenes. With the aim of increasing food safety it has thus been considered to utilise bacteriocins...

Effect of Bacteriocin-like Inhibitory Substances Produced by Vaginal ...

African Journals Online (AJOL)

Reduction of vaginal Lactobacillus population leads to overgrowth of opportunistic organisms such as Streptococcus agalactiae (Group B Streptococcus, GBS), which causes life threatening neonatal infections. The activities of bacteriocin-like inhibitory substances (BLIS) produced by Lactobacillus species isolated from the ...

Role of plnB gene in the regulation of bacteriocin production in Lactobacillus paraplantarum L-XM1.

Science.gov (United States)

Zhang, Xiangmei; Shang, Nan; Zhang, Xu; Gui, Meng; Li, Pinglan

2013-06-12

Homologues of plnB gene have been shown to participate in regulation of bacteriocin production through quorum sensing system in other organisms, to investigate the possible role of plnB gene in Lactobacillus paraplantarum L-XM1, we cloned and insertionally inactivated the plnB gene. The plnB knockout mutant ΔplnB21 showed loss of bacteriocin production, its Bac⁺ phenotype could not be restored even after the addition of PlnA. Furthermore, reverse transcription-PCR analysis from total RNA preparations showed that the bacteriocin structural genes of the plnEF and plnJK were not transcribed in the plnB knockout mutant compared with the wild-type strain. It was therefore concluded that plnB is invovled in a quorum sensing based bacteriocin production. This is the first demonstration of a role for plnB by gene knockout in L. paraplantarum. Copyright © 2012 Elsevier GmbH. All rights reserved.

[A comparison of the properties of bacteriocins formed by Lactococcus lactis subsp. lactis strains of diverse origin].

Science.gov (United States)

Stoianova, L G; Egorov, N S; Fedorova, G B; Katrukha, G S; Netrusov, A I

2007-01-01

Bacteriocins formed by four strains of Lactococcus lactis subsp. lactis have been studied and compared: 729 (a natural strain isolated from milk), 1605 (a mutant of strain 729), F-116 (a recombinant obtained by fusing of protoplasts of the two related strain 729 and 1605), and a nisin-forming strain obtained by adaptive selection at Moscow State University. Antimicrobial activity studies revealed differences between the strains in the effects on individual groups of microorganisms; the activities of the strains were also distinct from that of Nisaplin (a commercial preparation of the bacteriocin nisin). Methods for isolation and purification of bacteriocins have been developed, making it possible to obtain individual components of antibiotic complexes as chromatographically pure preparations. Bacteriocins formed by the strains of Lactococcus lactis subsp. lactis have been identified and differences in their biological and physicochemical properties, established. A novel potent broad-spectrum antibiotic substance distinct from nisin has been isolated from the recombinant strain F-116.

Improved antimicrobial activities of synthetic-hybrid bacteriocins designed from enterocin E50-52 and pediocin PA-1.

Science.gov (United States)

Tiwari, Santosh Kumar; Sutyak Noll, Katia; Cavera, Veronica L; Chikindas, Michael L

2015-03-01

Two hybrid bacteriocins, enterocin E50-52/pediocin PA-1 (EP) and pediocin PA-1/enterocin E50-52 (PE), were designed by combining the N terminus of enterocin E50-52 and the C terminus of pediocin PA-1 and by combining the C terminus of pediocin PA-1 and the N terminus of enterocin E50-52, respectively. Both hybrid bacteriocins showed reduced MICs compared to those of their natural counterparts. The MICs of hybrid PE and EP were 64- and 32-fold lower, respectively, than the MIC of pediocin PA-1 and 8- and 4-fold lower, respectively, than the MIC of enterocin E50-52. In this study, the effect of hybrid as well as wild-type (WT) bacteriocins on the transmembrane electrical potential (ΔΨ) and their ability to induce the efflux of intracellular ATP were investigated. Enterocin E50-52, pediocin PA-1, and hybrid bacteriocin PE were able to dissipate ΔΨ, but EP was unable to deplete this component. Both hybrid bacteriocins caused a loss of the intracellular concentration of ATP. EP, however, caused a faster efflux than PE and enterocin E50-52. Enterocin E50-52 and hybrids PE and EP were active against the Gram-positive and Gram-negative bacteria tested, such as Micrococcus luteus, Salmonella enterica serovar Enteritidis 20E1090, and Escherichia coli O157:H7. The hybrid bacteriocins designed and described herein are antimicrobial peptides with MICs lower those of their natural counterparts. Both hybrid peptides induce the loss of intracellular ATP and are capable of inhibiting Gram-negative bacteria, and PE dissipates the electrical potential. In this study, the MIC of hybrid bacteriocin PE decreased 64-fold compared to the MIC of its natural peptide counterpart, pediocin PA-1. Inhibition of Gram-negative pathogens confers an additional advantage for the application of these peptides in therapeutics. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Isolation and Characterization of a Broad Spectrum Bacteriocin from Bacillus amyloliquefaciens RX7

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Kong Boon Lim

2016-01-01

Full Text Available We isolated a Bacillus strain, RX7, with inhibitory activity against Listeria monocytogenes from soil and identified it as Bacillus amyloliquefaciens based on 16S rRNA gene sequencing. The inhibitory activity was stable over a wide range of pH and was fully retained after 30 min at 80°C, after which it decreased gradually at higher temperatures. The activity was sensitive to the proteolytic action of α-chymotrypsin, proteinase-K, and trypsin, indicating its proteinaceous nature. This bacteriocin was active against a broad spectrum of bacteria and the fungus Candida albicans. Direct detection of antimicrobial activity on a sodium dodecyl sulfate-polyacrylamide gel suggested an apparent molecular mass of approximately 5 kDa. Ammonium sulfate precipitation and anion-exchange and gel permeation chromatography integrated with reverse phase-high-performance liquid chromatography were used for bacteriocin purification. Automated N-terminal Edman degradation of the purified RX7 bacteriocin recognized the first 15 amino acids as NH2-X-Ala-Trp-Tyr-Asp-Ile-Arg-Lys-Leu-Gly-Asn-Lys-Gly-Ala, where the letter X in the sequence indicates an unknown or nonstandard amino acid. Based on BLAST similarity search and multiple alignment analysis, the obtained partial sequence showed high homology with the two-peptide lantibiotic haloduracin (HalA1 from Bacillus halodurans, although at least two amino acids differed between the sequences. A time-kill study demonstrated a bactericidal mode of action of RX7 bacteriocin.

Bacteriocin and cellulose production by lactic acid bacteria isolated ...

African Journals Online (AJOL)

SERVER

2007-11-19

after 20 and 25 min) and E. coli 0157:H7 (after 15, 20 and 25 ... in a coculture with various Lactobacillus mali strains showed that cell-cell .... were found to be capable of producing viable bacteriocin can be purified and charac-.

Identification of Structural and Immunity Genes of a Class IIb Bacteriocin Encoded in the Enterocin A Operon of Enterococcus faecium Strain MXVK29.

Science.gov (United States)

Escamilla-Martínez, E E; Cisneros, Y M Álvarez; Fernández, F J; Quirasco-Baruch, M; Ponce-Alquicira, E

2017-10-09

The Enterococcus faecium strain MXVK29, isolated from fermented sausages, produces a bacteriocin with a molecular mass of 3.5 kDa that belongs to the class of enterocins II.1, according to the terminal amino acid sequence, and has been identified as enterocin A. This bacteriocin is active against selected strains of Listeria, Staphylococcus, Pediococcus, and Enterococcus. In this study, we identified the genes adjacent to the structural gene for this bacteriocin, such as the immunity gene (entI) and the inducer gene (entF). Accessory genes for this bacteriocin, such as entK, entR, and entT, were identified as well, in addition to the orf2 and orf3, showing a high identity with class IIb peptides bacteriocins. The orf2 shows the consensus motif GxxxG, similar to those shown by bacteriocins such as PlnNC8α, EntCα, and Ent1071A, whereas orf3 shows a consensus motif SxxxS similar to that present in PlnNC8β (AxxxA). PlnNC8 is expressed only in bacterial cocultures, so there is the possibility that the expression of this two-peptide bacteriocin can be induced by a similar mechanism. So far, only the expression of enterocin A has been found in this strain; however, the presence of the genes ent29α and ent29β opens the possibility for further research on its induction, functionality, and origin. Although there are reports on this type of bacteriocin (EntX, EntC, and Ent1071) in other strains of E. faecium, no report exists yet on an Enterococcus strain producing two different classes of bacteriocin.

Eco-Innovation in Circular Agri-Business

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Dong-Her Shih

2018-04-01

Full Text Available This study constructs a theory of eco-innovation in circular agri-business. Although previous studies have discussed eco-innovation in circular agri-business, they did not address eco-innovation from the perspective of a closed-loop sustainable supply chain. Hence, this study applied the fuzzy TOPSIS method to conduct the analysis and determine the interrelationship between eco-innovation and the closed-loop concept. The results are consistent with the theory and a significant improvement in terms of the decisive attributes. The findings suggest that improving water management, relationships with suppliers, knowledge sharing, environmental management systems, and new product and service development are the most effective and efficient ways to build eco-innovation in circular agri-business. The managerial and theoretical implications are discussed.

Induction of bacteriocin production by coculture is widespread among plantaricin-producing Lactobacillus plantarum strains with different regulatory operons.

Science.gov (United States)

Maldonado-Barragán, Antonio; Caballero-Guerrero, Belén; Lucena-Padrós, Helena; Ruiz-Barba, José Luis

2013-02-01

We describe the bacteriocin-production phenotype in a group of eight singular bacteriocinogenic Lactobacillus plantarum strains with three distinct genotypes regarding the plantaricin locus. Genotyping of these strains revealed the existence of two different plantaricin-production regulatory operons, plNC8-plNC8HK-plnD or plnABCD, involving three-component systems controlled each of them by a specific autoinducer peptide (AIP), i.e. PLNC8IF or PlnA. While all of the strains produced antimicrobial activity when growing on solid medium, most of them halted this production when cultured in broth, thus reflecting the functionality of regulatory mechanisms. Antimicrobial activity in broth cultures was re-established or enhanced when the specific AIP was added to the culture or by coculturing with specific bacterial strains. The latter trait appeared to be widespread in bacteriocinogenic L. plantarum strains independently of the regulatory system used to regulate bacteriocin production or the specific bacteriocins produced. The induction spectrum through coculture, i.e. the pattern of bacterial strains able to induce bacteriocin production, was characteristic of each individual L. plantarum strain. Also, the ability of some bacteria to induce bacteriocin production in L. plantarum by coculture appeared to be strain specific. The fact that induction of bacteriocin production by coculturing appeared to be a common feature in L. plantarum can be exploited accordingly to enhance the viability of this species in food and feed fermentations, as well as to contribute to probiotic functionality when colonising the gastrointestinal tract. Copyright © 2012 Elsevier Ltd. All rights reserved.

Purification and amino acid sequence of a bacteriocins produced by Lactobacillus salivarius K7 isolated from chicken intestine

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Kenji Sonomoto

2006-03-01

Full Text Available A bacteriocin-producing strain, Lactobacillus K7, was isolated from a chicken intestine. The inhibitory activity was determined by spot-on-lawn technique. Identification of the strain was performed by morphological, biochemical (API 50 CH kit and molecular genetic (16S rDNA basis. Bacteriocin purification processes were carried out by amberlite adsorption, cation exchange and reverse-phase high perform- ance liquid chromatography. N-terminal amino acid sequences were performed by Edman degradation. Molecular mass was determined by electrospray-ionization (ESI mass spectrometry (MS. Lactobacillus K7 showed inhibitory activity against Lactobacillus sakei subsp. sakei JCM 1157T, Leuconostoc mesenteroides subsp. mesenteroides JCM 6124T and Bacillus coagulans JCM 2257T. This strain was identified as Lb. salivarius. The antimicrobial substance was destroyed by proteolytic enzymes, indicating its proteinaceous structure designated as a bacteriocin type. The purification of bacteriocin by amberlite adsorption, cation exchange, and reverse-phase chromatography resulted in only one single active peak, which was designated FK22. Molecular weight of this fraction was 4331.70 Da. By amino acid sequence, this peptide was homology to Abp 118 beta produced by Lb. salivarius UCC118. In addition, Lb. salivarius UCC118 produced 2-peptide bacteriocin, which was Abp 118 alpha and beta. Based on the partial amino acid sequences of Abp 118 beta, specific primers were designed from nucleotide sequences according to data from GenBank. The result showed that the deduced peptide was high homology to 2-peptide bacteriocin, Abp 118 alpha and beta.

Purification and partial characterization of bacillocin 490, a novel bacteriocin produced by a thermophilic strain of Bacillus licheniformis

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De Felice Maurilio

2002-04-01

Full Text Available Abstract Background Applications of bacteriocins as food preservatives have been so far limited, principally because of their low antimicrobial activity in foods. Nisin is the only bacteriocin of significant use, but applications are restricted principally because of its very low activity at neutral or alkaline pH. Thus the isolation of new bacteriocins active in foods is desirable. Results We isolated a Bacillus licheniformis thermophilic strain producing a bacteriocin with some novel features, named here bacillocin 490. This bacteriocin was inactivated by pronase E and proteinase K and was active against closely related Bacillus spp. both in aerobic and in anaerobic conditions. Bactericidal activity was kept during storage at 4°C and was remarkably stable in a wide pH range. The bacteriocin was partially purified by elution after adhesion to cells of the food-isolated strain Bacillus smithii and had a rather low mass (2 KDa. Antimicrobial activity against B. smithii was observed also when this organism was grown in water buffalo milk. Conclusions Bacillocin 490 is a novel candidate as a food anti-microbial agent since it displays its activity in milk, is stable to heat treatment and during storage, is active in a wide pH range and has bactericidal activity also at high temperature. These features may allow the use of bacillocin 490 during processes performed at high temperature and as a complementary antimicrobial agent of nisin against some Bacillus spp. in non-acidic foods. The small size suggests its use on solid foods.

Comparison of two methods for purification of enterocin B, a bacteriocin produced by Enterococcus faecium W3.

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Dündar, Halil; Atakay, Mehmet; Çelikbıçak, Ömür; Salih, Bekir; Bozoğlu, Faruk

2015-01-01

This study aimed to compare two different approaches for the purification of enterocin B from Enterococcus faecium strain W3 based on the observation that the bacteriocin was found both in cell associated form and in culture supernatant. The first approach employed ammonium sulfate precipitation, cation-exchange chromatography, and sequential reverse-phase high-performance liquid chromatography. The latter approach exploited a pH-mediated cell adsorption-desorption method to extract cell-bound bacteriocin, and one run of reverse-phase chromatography. The first method resulted in purification of enterocin B with a recovery of 4% of the initial bacteriocin activity found in culture supernatant. MALDI-TOF MS analysis and de novo peptide sequencing of the purified bacteriocin confirmed that the active peptide was enterocin B. The second method achieved the purification of enterocin B with a higher recovery (16%) and enabled us to achieve pure bacteriocin within a shorter period of time by avoiding time consuming purification protocols. The purity and identity of the active peptide were confirmed again by matrix-assisted laser desorption/ionization time-of flight (MALDI-TOF) mass spectrometry (MS) analysis. Although both approaches were satisfactory to obtain a sufficient amount of enterocin B for use in MS and amino acid sequence analysis, the latter was proved to be applicable in large-scale and rapid purification of enterocin B.

A strain-variable bacteriocin in Bacillus anthracis and Bacillus cereus with repeated Cys-Xaa-Xaa motifs

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Haft Daniel H

2009-04-01

Full Text Available Abstract Bacteriocins are peptide antibiotics from ribosomally translated precursors, produced by bacteria often through extensive post-translational modification. Minimal sequence conservation, short gene lengths, and low complexity sequence can hinder bacteriocin identification, even during gene calling, so they are often discovered by proximity to accessory genes encoding maturation, immunity, and export functions. This work reports a new subfamily of putative thiazole-containing heterocyclic bacteriocins. It appears universal in all strains of Bacillus anthracis and B. cereus, but has gone unrecognized because it is always encoded far from its maturation protein operon. Patterns of insertions and deletions among twenty-four variants suggest a repeating functional unit of Cys-Xaa-Xaa. Reviewers This article was reviewed by Andrei Osterman and Lakshminarayan Iyer.

Antimicrobial and Anti-Swarming Effects of Bacteriocins and Biosurfactants from Probiotic Bacterial Strains against Proteus spp.

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Laila Goudarzi

2017-02-01

Full Text Available Background:   Proteus spp. belongs to the family of Enterobacteriaceae. These bacteria are Gram-negative and motile microorganisms and known as the third most common causes of urinary tract infections. The aim of the current study was to investigate the effects of some secondary metabolites from probiotic strains of Lactobacillus spp. on swarming and growth of Proteus mirabilis and P. vulgaris. Methods:   After determination of optimal conditions for the growth and production of antimicrobials, bacteriocins and biosurfactants were partially purified from Lactobacillus culture supernatants. Then, effects of the purified compounds on growth and swarming migration of Proteus spp. were examined in the presence of various concentrations of semi-purified compounds. Results:  Results showed that the partially purified bacteriocins inhibited Proteus spp. swarming distance and had a significant reduction on the bacterial growth curves. Biosurfactants in a solvent form did not have any considerable effects on factors produced by Proteus spp. Conclusion:  According to the results, the secondary metabolites, especially bacteriocins or bacteriocin-like substances derived from Lactobacillus strains, can inhibit or reduce growth and swarming migration of Proteus spp. which are considered as the bacteria major virulence factors.

Bacteriocin and cellulose production by lactic acid bacteria isolated ...

African Journals Online (AJOL)

Sixteen colonies of lactic acid bacteria (LAB) were selected and screened for their ability to produce bacteriocin by agar well diffusion method using the supernatant of centrifuged test cultures. Four isolates inhibited the growth of Listeria monocytogenes and Escherichia coli. Lactobacillus plantarum (6) and Lactobacillus ...

Influence of culture media, pH and temperature on growth and bacteriocin production of bacteriocinogenic lactic acid bacteria.

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Yang, En; Fan, Lihua; Yan, Jinping; Jiang, Yueming; Doucette, Craig; Fillmore, Sherry; Walker, Bradley

2018-01-24

There has been continued interest in bacteriocins research from an applied perspective as bacteriocins have potential to be used as natural preservative. Four bacteriocinogenic lactic acid bacteria (LAB) strains of Lactobacillus curvatus (Arla-10), Enterococcus faecium (JFR-1), Lactobacillus paracasei subsp. paracasei (JFR-5) and Streptococcus thermophilus (TSB-8) were previously isolated and identified in our lab. The objective of this study was to determine the optimal growth conditions for both LAB growth and bacteriocins production. In this study, various growth conditions including culture media (MRS and BHI), initial pH of culture media (4.5, 5.5, 6.2, 7.4 and 8.5), and incubation temperatures (20, 37 and 44 °C) were investigated for LAB growth measured as optical density (OD), bacteriocin activity determined as arbitrary unit and viability of LAB expressed as log CFU ml -1 . Growth curves of the bacteriocinogenic LAB were generated using a Bioscreen C. Our results indicated that Arla-10, JFR-1, and JFR-5 strains grew well on both MRS and BHI media at growth temperature tested whereas TSB-8 strain, unable to grow at 20 °C. LAB growth was significantly affected by the initial pH of culture media (p < 0.001) and the optimal pH was found ranging from 6.2 to 8.5. Bacteriocin activity was significantly different in MRS versus BHI (p < 0.001), and the optimal condition for LAB to produce bacteriocins was determined in MRS broth, pH 6.2 at 37 °C. This study provides useful information on potential application of bacteriocinogenic LAB in food fermentation processes.

Isolation of Lactic Acid Bacteria That Produce Protease and Bacteriocin-Like Substance From Mud Crab (Scylla sp. Digestive Tract (Isolasi Bakteri Asam Laktat yang Menghasilkan Protease dan Senyawa Bacteriocin-Like dari Saluran Pencernaan Kepiting

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Heru Pramono

2015-03-01

Kata kunci: Bakteri Asam Laktat, Bakteriosin-like substance, Protease, Scylla  sp. Digestive tract is complex environment consist of large amount of bacteria’s species. Fish intestine bacteria consist of aerobic or facultative anaerob bacteria which can produce antibacterial and enzym. The objectives of this research were to isolated lactic acid bacteria that produce bacteriocin-like and protease from mud crab digestive tract. Isolation and characterization of isolates were conducted employing media MRS.  Neutralized cell free supernatant of isolates were tested using disc diffusion agar of against pathogenic and spoilage bacteria to indicate bacteriocin-like-producing lactic acid bacteria. Protease-producing isolate was tested using disc diffusion method in casein agar. Among a hundred isolates, 96 isolates were showed clear zone in MRS+CaCO3,, catalase negative, and Gram positive bacteria. Thirty four isolates produced protease and only four isolates (i.e. IKP29, IKP30, IKP52, and IKP94 showed strong inhibition against pathogenic and spoilage bacteria. There were three patterns of inhibition among three isolates against Bacillus subtilis, Staphylococcus aureus, Eschericia coli, and Salmonella sp. All three isolates showed potential uses for produce starter culture for fishery product fermentation purpose. This is the first report of isolation lactic acid bacteria that produced protease and bacteriocin-like from digestive tract of mud crab. Keywords: Lactic acid bacteria, Bacteriocin-like substance, Protease, Scylla  sp.

Growth of Enterococcus durans E204 producing bacteriocin-like ...

African Journals Online (AJOL)

Bacteriocin-like substance E204 is an antimicrobial compound produced by Enterococcus durans E204 isolated from camel milk of Morocco that shows a broad spectrum of inhibitory activity against taxonomically related microorganisms. It is sensitive to digestive proteases. In the first study, de Man, Regosa and Sharpe ...

Purification and characterization of two bacteriocins produced by lactic acid bacteria isolated from Mongolian airag.

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Batdorj, B; Dalgalarrondo, M; Choiset, Y; Pedroche, J; Métro, F; Prévost, H; Chobert, J-M; Haertlé, T

2006-10-01

The aim of this study was to isolate and identify bacteriocin-producing lactic acid bacteria (LAB) issued from Mongolian airag (traditional fermented mare's milk), and to purify and characterize bacteriocins produced by these LAB. Identification of the bacteria (Enterococcus durans) was carried out on the basis of its morphological, biochemical characteristics and carbohydrate fermentation profile and by API50CH kit and 16S rDNA analyses. The pH-neutral cell-free supernatant of this bacterium inhibited the growth of several Lactobacillus spp. and food-borne pathogens including Escherichia coli, Staphylococcus aureus and Listeria innocua. The antimicrobial agent (enterocin A5-11) was heat stable and was not sensitive to acid and alkaline conditions (pH 2-10), but was sensitive to several proteolytic enzymes. Its inhibitory activity was completely eliminated after treatment with proteinase K and alpha-chymotrypsin. The activity was however not completely inactivated by other proteases including trypsin and pepsin. Three-step purification procedure with high recovery yields was developed to separate two bacteriocins. The applied procedure allowed the recovery of 16% and 64% of enterocins A5-11A and A5-11B, respectively, present in the culture supernatant with purity higher than 99%. SDS-PAGE analyses revealed that enterocin A5-11 has a molecular mass of 5000 Da and mass spectrometry analyses demonstrates molecular masses of 5206 and 5218 Da for fractions A and B, respectively. Amino acid analyses of both enterocins indicated significant quantitative difference in their contents in threonine, alanine, isoleucine and leucine. Their N-termini were blocked hampering straightforward Edman degradation. Bacteriocins A5-11A and B from Ent. durans belong to the class II of bacteriocins. Judging from molecular masses, amino acid composition and spectrum of activities, bacteriocins A5-11A and B from Ent. durans show high degree of similarity with enterocins L50A and L50B

The Cyclic Antibacterial Peptide Enterocin AS-48: Isolation, Mode of Action, and Possible Food Applications

OpenAIRE

Grande Burgos, Mar?a Jos?; P?rez Pulido, Rub?n; L?pez Aguayo, Mar?a del Carmen; G?lvez, Antonio; Lucas, Rosario

2014-01-01

Enterocin AS-48 is a circular bacteriocin produced by Enterococcus. It contains a 70 amino acid-residue chain circularized by a head-to-tail peptide bond. The conformation of enterocin AS-48 is arranged into five alpha-helices with a compact globular structure. Enterocin AS-48 has a wide inhibitory spectrum on Gram-positive bacteria. Sensitivity of Gram-negative bacteria increases in combination with outer-membrane permeabilizing treatments. Eukaryotic cells are bacteriocin-resistant. This ...

Production, purification, and characterization of micrococcin GO5, a bacteriocin produced by Micrococcus sp. GO5 isolated from kimchi.

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Kim, Mi-Hee; Kong, Yoon-Jung; Baek, Hong; Hyun, Hyung-Hwan

2005-01-01

Strain GO5, a bacteriocin-producing bacterium, was isolated from green onion kimchi and identified as Micrococcus sp. The bacteriocin, micrococcin GO5, displayed a broad spectrum of inhibitory activity against a variety of pathogenic and nonpathogenic microorganisms, as tested by the spot-on-lawn method; its activity spectrum was almost identical to that of nisin. Micrococcin GO5 was inactivated by trypsin (whereas nisin was not) and was completely stable at 100 degrees C for 30 min and in the pH range of 2.0 to 7.0. Micrococcin GO5 exhibited a typical mode of bactericidal activity against Micrococcus flavus ATCC 10240. It was purified to homogeneity through ammonium sulfate precipitation, ultrafiltration, and CM-Sepharose column chromatography. The molecular mass of micrococcin GO5 was estimated to be about 5.0 kDa by tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in situ activity assay with the indicator organism. The amino acid sequence of micrococcin GO5 lacks lanthionine and beta-methyllanthionine and is rich in hydrophobic amino acids and glycine, providing the basis for the high heat stability of this bacteriocin. The N-terminal amino acid sequence of micrococcin GO5 is Lys-Lys-Ser-Phe-Cys-Gln-Lys, and no homology to bacteriocins reported previously was observed in the amino acid composition or N-terminal amino acid sequence. Based on the physicochemical properties, small molecular size, and inhibition of Listeria monocytogenes, micrococcin GO5 has been placed with the class II bacteriocins, but its broad spectrum of activity differs from that of other bacteriocins in this class.

Active polymers containing Lactobacillus curvatus CRL705 bacteriocins: effectiveness assessment in Wieners.

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Blanco Massani, M; Molina, V; Sanchez, M; Renaud, V; Eisenberg, P; Vignolo, G

2014-05-16

Bacteriocins from lactic acid bacteria have potential as natural food preservatives. In this study two active (synthetic and gluten) films were obtained by the incorporation of lactocin 705 and lactocin AL705, bacteriocins produced by Lactobacillus curvatus CRL705 with antimicrobial activity against spoilage lactic acid bacteria and Listeria. Antimicrobial film effectiveness was determined in Wieners inoculated with Lactobacillus plantarum CRL691 and Listeria innocua 7 (10(4)CFU/g) stored at 5°C during 45days. Active and control (absence of bacteriocins) packages were prepared and bacterial counts in selective media were carried out. Visual inspection and pH measurement of Wieners were also performed. Typical growth of both inoculated microorganisms was observed in control packages which reached 10(6)-10(7)CFU/g at the end of storage period. In the active packages, L. innocua 7 was effectively inhibited (2.5 log cycles reduction at day 45), while L. plantarum CRL691 was only slightly inhibited (0.5 log cycles) up to the second week of storage, then counts around 10(6)-10(7)CFU/g were reached. Changes in pH values from 6.3 to 5.8 were produced and gas formation was observed in active and control packages. The low inhibitory effectiveness against lactic acid bacteria is in correlation with the low activity observed for lactocin 705 in the presence of fat; Wieners fat content (20-30%) may adversely affect antimicrobial activity. This study supports the feasibility of using polymers activated with L. curvatus CRL705 bacteriocins to control Listeria on the surface of Wieners and highlights the importance of evaluating antimicrobial packaging systems for each particular food application. Copyright © 2014 Elsevier B.V. All rights reserved.

Purification and genetic characterisation of the novel bacteriocin LS2 produced by the human oral strain Lactobacillus salivarius BGHO1.

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Busarcevic, Milos; Dalgalarrondo, Michèle

2012-08-01

The aim of this study was to investigate the antimicrobial potential of Lactobacillus salivarius BGHO1, a human oral strain with probiotic characteristics and a broad inhibitory spectrum both against Gram-positive and Gram-negative pathogens. Here we present the bacteriocin LS2, an extremely pH- and heat-stable peptide with antilisterial activity. LS2 is a novel member of the class IId bacteriocins, unique among all currently characterised bacteriocins. It is somewhat similar to putative bacteriocins from several oral streptococci, including the cariogenic Streptococcus mutans. LS2 is a 41-amino-acid, highly hydrophobic cationic peptide of 4115.1Da that is sensitive to proteolytic enzymes. LS2 was purified from cells of strain BGHO1 by solvent extraction and reverse-phase chromatography. Mass spectrometry was used to determine the molecular mass of the purified peptide. N-terminal amino acid sequencing enabled identification of the LS2 structural gene bacls2 by a reverse genetics approach. Downstream of the bacls2 gene, two bacteriocin-like genes were found, named blp1a and blp1b, and one putative bacteriocin immunity gene named bimlp. We also present the identification of the 242-kb megaplasmid pMPHO1 by pulsed-field gel electrophoresis, which harbours the genes bacls2, blp1a, blp1b and bimlp. Two peptides with antimicrobial activity, whose approximate sizes corresponded to those of blp1a and blp1b, were identified only after culturing strain BGHO1 in a chemically defined medium. This study demonstrated the capacity of Lactobacillus salivarius BGHO1 to produce multiple bacteriocins and further established this strain as a promising probiotic candidate. Copyright © 2012 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

Description of durancin TW-49M, a novel enterocin B-homologous bacteriocin in carrot-isolated Enterococcus durans QU 49.

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Hu, C-B; Zendo, T; Nakayama, J; Sonomoto, K

2008-09-01

To characterize the novel bacteriocin produced by Enterococcus durans. Enterococcus durans QU 49 was isolated from carrot and expressed bactericidal activity over 20-43 degrees C. Bacteriocins were purified to homogeneity using the three-step purification method, one of which, termed durancin TW-49M, was an enterocin B-homologous peptide with most identical residues occurring in the N-terminus. Durancin TW-49M was more tolerant in acidic than in alkali. DNA sequencing analysis revealed durancin TW-49M was translated as a prepeptide of the double-glycine type. Durancin TW-49M and enterocin B expressed similar antimicrobial spectra, in which no significant variation due to the diversity in their C-termini was observed. Durancin TW-49M, a novel nonpediocin-like class II bacteriocin, was characterized to the amino acid and genetic levels. The diverse C-terminal parts of durancin TW-49M and enterocin B were hardly to be suggested as the place determining the target cell specificity. This is the first and comprehensive study of a novel bacteriocin produced by Ent. durans. The high homology at the N-terminal halves between durancin TW-49M and enterocin B makes them suitable to study the structure-function relationship of bacteriocins and their immunity proteins.

The study of Bacteriocin of Pseudomonas fluorescens and Citrus limon effects against Propionibacterium acnes and Staphylococcus epidermidis in acne patients

Science.gov (United States)

Ahmed, Mais E.

2018-05-01

Research was carried out on the antibacterial effect of (Citrus limon) juice on Acnevulgaris. Samples were obtained from individuals with pimples by swabbing their faces. Natural substances that derive from plants are promising to treat disease cause Acnevulgaris, the study in vitro biological activity of the juice, as well as bacterocin cultivated and fruits was investigated on two strains of bacteria (Propionibacterium acnes, Staphylococcus epidermidis). The new antimicrobial (bacteriocin and Citrus juice) is an ongoing search. This study used juice at different concentrations at (20%, 30%, 40%, 60%, 80% and 100%). The bacteriocin produced from local P. fluorescens isolates from wound infection and majority of isolates were found to produce crude bacteriocin were (P1 and P2) in Pseudomonas agar at 37°C for 24 hrs. Crude bacteriocin and Citrus limon juice against some pathogenic skin bacteria was find to be effective juice Citrus limon aganist S. epidermidis at 100% Concentrations with a range of inhibition zone (18) mm. The isolates of P. fluorescens (P2) was positive as producer of bacteriocin with a wide inhibition growth against gram positive pathogenic bacteria with a range between (10-12) mm.

Purification and Characterization of Bacteriocin Produced by Bacillus subtilis R75 Isolated from Fermented Chunks of Mung Bean (Phaseolus radiatus

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Riti Kapoor

2011-01-01

Full Text Available Food-grade bacteria capable of producing bacteriocin with desirable preservation attributes have been isolated from traditional Indian fermented food dal vari, which has not been investigated so far. Among different isolates, Bacillus subtilis R75, isolated on MRS agar, exhibited antagonism against a wide range of foodborne pathogens that cause serious spoilage. Extracellularly produced bacteriocin was purified by single step gel exclusion column chromatography. The purity rate and molecular mass of 12 kDa of this compound were determined using SDS-PAGE. Activity units (AU of bacteriocin were increased in each step of purification, reaching up to 5·10^6 AU/mL. The increase in the activity units directly affected the antimicrobial activity of purified bacteriocin, resulting in an increase up to 200, 333 and 175 % of the inhibition zones against indicator bacteria. Continuous decrease in the number of viable cells of microorganisms within 10 h after adding purified bacteriocin proved its bactericidal action. It withstood very high temperature, up to 121 °C, for 10 min, wider pH range, from 4.0 to 11.0, complete inactivation in the presence of proteolytic enzymes and storage stability up to 2.5 months.

Spatial attributes of the four-helix bundle group of bacteriocins – The high-resolution structure of BacSp222 in solution

KAUST Repository

Nowakowski, Michał

2017-11-01

BacSp222 is a multifunctional bacteriocin produced by Staphylococcus pseudintermedius strain 222, an opportunistic pathogen of domestic animals. At micromolar concentrations, BacSp222 kills Gram-positive bacteria and is cytotoxic toward mammalian cells, while at nanomolar doses, it acts as an immunomodulatory factor, enhancing nitric oxide release in macrophage-like cell lines. The bacteriocin is a cationic, N-terminally formylated, 50-amino-acid-long linear peptide that is rich in tryptophan residues.In this study, the solution structure of BacSp222 was determined and compared to the currently known structures of similar bacteriocins. BacSp222 was isolated from a liquid culture medium in a uniformly 13C- and 15N-labeled form, and NMR data were collected. The structure was calculated based on NMR-derived constraints and consists of a rigid and tightly packed globular bundle of four alpha-helices separated by three short turns.Although the amino acid sequence of BacSp222 has no significant similarity to any known peptide or protein, a 3D structure similarity search indicates a close relation to other four-helix bundle-motif bacteriocins, such as aureocin A53, lacticin Q and enterocins 7A/7B. Assuming similar functions, biology, structure and physicochemical properties, we propose to distinguish the four-helix bundle bacteriocins as a new Type A in subclass IId of bacteriocins, containing linear, non-pediocin-like peptides.

Purification and genetic characterization of gassericin E, a novel co-culture inducible bacteriocin from Lactobacillus gasseri EV1461 isolated from the vagina of a healthy woman.

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Maldonado-Barragán, Antonio; Caballero-Guerrero, Belén; Martín, Virginia; Ruiz-Barba, José Luis; Rodríguez, Juan Miguel

2016-03-12

Lactobacillus gasseri is one of the dominant Lactobacillus species in the vaginal ecosystem. Some strains of this species have a high potential for being used as probiotics in order to maintain vaginal homeostasis, since they may confer colonization resistance against pathogens in the vagina by direct inhibition through production of antimicrobial compounds, as bacteriocins. In this work we have studied bacteriocin production of gassericin E (GasE), a novel bacteriocin produced by L. gasseri EV1461, a strain isolated from the vagina of a healthy woman, and whose production was shown to be promoted by the presence of certain specific bacteria in co-culture. Biochemical and genetic characterization of this novel bacteriocin are addressed. We found that the inhibitory spectrum of L. gasseri EV1461 was broad, being directed to species both related and non-related to the producing strain. Interestingly, L. gasseri EV1461 inhibited the grown of pathogens usually associated with bacterial vaginosis (BV). The antimicrobial activity was due to the production of a novel bacteriocin, gassericin E (GasE). Production of this bacteriocin in broth medium only was achieved at high cell densities. At low cell densities, bacteriocin production ceased and only was restored after the addition of a supernatant from a previous bacteriocin-producing EV1461 culture (autoinduction), or through co-cultivation with several other Gram-positive strains (inducing bacteria). DNA sequence of the GasE locus revealed the presence of two putative operons which could be involved in biosynthesis and immunity of this bacteriocin (gaeAXI), and in regulation, transport and processing (gaePKRTC). The gaePKR encodes a putative three-component regulatory system, involving an autoinducer peptide (GaeP), a histidine protein kinase (GaeK) and a response regulator (GaeR), while the gaeTC encodes for an ABC transporter (GaeT) and their accessory protein (GaeC), involved in transport and processing of the

Quorum Sensing Regulation of Competence and Bacteriocins in Streptococcus pneumoniae and mutans

Science.gov (United States)

Shanker, Erin; Federle, Michael J.

2017-01-01

The human pathogens Streptococcus pneumoniae and Streptococcus mutans have both evolved complex quorum sensing (QS) systems that regulate the production of bacteriocins and the entry into the competent state, a requirement for natural transformation. Natural transformation provides bacteria with a mechanism to repair damaged genes or as a source of new advantageous traits. In S. pneumoniae, the competence pathway is controlled by the two-component signal transduction pathway ComCDE, which directly regulates SigX, the alternative sigma factor required for the initiation into competence. Over the past two decades, effectors of cellular killing (i.e., fratricides) have been recognized as important targets of the pneumococcal competence QS pathway. Recently, direct interactions between the ComCDE and the paralogous BlpRH pathway, regulating bacteriocin production, were identified, further strengthening the interconnections between these two QS systems. Interestingly, a similar theme is being revealed in S. mutans, the primary etiological agent of dental caries. This review compares the relationship between the bacteriocin and the competence QS pathways in both S. pneumoniae and S. mutans, and hopes to provide clues to regulatory pathways across the genus Streptococcus as a potential tool to efficiently investigate putative competence pathways in nontransformable streptococci. PMID:28067778

Cloning, purification, and functional characterization of Carocin S2, a ribonuclease bacteriocin produced by Pectobacterium carotovorum

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Tzeng Kuo-Ching

2011-05-01

Full Text Available Abstract Background Most isolates of Pectobacterium carotovorum subsp. carotovorum (Pcc produce bacteriocins. In this study, we have determined that Pcc strain F-rif-18 has a chromosomal gene encoding the low-molecular-weight bacteriocin, Carocin S2, and that this bacteriocin inhibits the growth of a closely related strain. Carocin S2 is inducible by ultraviolet radiation but not by mutagenic agents such as mitomycin C. Results A carocin S2-defective mutant, TF1-2, was obtained by Tn5 insertional mutagenesis using F-rif-18. A 5706-bp DNA fragment was detected by Southern blotting, selected from a genomic DNA library, and cloned to the vector, pMS2KI. Two adjacent complete open reading frames within pMS2KI were sequenced, characterized, and identified as caroS2K and caroS2I, which respectively encode the killing protein and immunity protein. Notably, carocin S2 could be expressed not only in the mutant TF1-2 but also in Escherichia coli DH5α after entry of the plasmid pMS2KI. Furthermore, the C-terminal domain of CaroS2K was homologous to the nuclease domains of colicin D and klebicin D. Moreover, SDS-PAGE analysis showed that the relative mass of CaroS2K was 85 kDa and that of CaroS2I was 10 kDa. Conclusion This study shown that another nuclease type of bacteriocin was found in Pectobacterium carotovorum. This new type of bacteriocin, Carocin S2, has the ribonuclease activity of CaroS2K and the immunity protein activity of CaroS2I.

Rapid Two-Step Procedure for Large-Scale Purification of Pediocin-Like Bacteriocins and Other Cationic Antimicrobial Peptides from Complex Culture Medium

OpenAIRE

Uteng, Marianne; Hauge, Håvard Hildeng; Brondz, Ilia; Nissen-Meyer, Jon; Fimland, Gunnar

2002-01-01

A rapid and simple two-step procedure suitable for both small- and large-scale purification of pediocin-like bacteriocins and other cationic peptides has been developed. In the first step, the bacterial culture was applied directly on a cation-exchange column (1-ml cation exchanger per 100-ml cell culture). Bacteria and anionic compounds passed through the column, and cationic bacteriocins were subsequently eluted with 1 M NaCl. In the second step, the bacteriocin fraction was applied on a lo...

PRODUCTION OF BACTERIOCIN EC2 AND ITS INTERFERENCE IN THE GROWTH OF SALMONELLA TYPHI IN A MILK MATRIX

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Yuri de Jesus Lopes de Abreu

2013-08-01

Full Text Available Bacterial interference can occur through various mechanisms, including the production of peroxides, acids, ammonia, bacteriolytic enzymes or bacteriocins. The strain Escherichia coli EC2 produces the antimicrobial substance (AMS EC2, able to inhibit different strains of Gram-negative bacteria isolated from food, as E. coli and Salmonella sp. The activity of AMS EC2 was lost after treatment with proteolytic enzymes, indicating the presence of an active proteinaceous compound, suggesting that it is a bacteriocin. The substance, renamed bacteriocin EC2, has its better production when the producer strain is grown on Casoy medium, at 37ºC and pH 6.0, without NaCl addition, but it is also able to be produced in milk. When co-cultivated in UHT milk with the producer strain E. coli EC2, the growth of the indicator strain Salmonella Typhi is totally inhibited within the first 4 hours of incubation, suggesting a potential application of bacteriocin EC2 in the control of Salmonella sp. e.g. in foods.

Class IIa bacteriocin resistance in Enterococcus faecalis V583: The mannose PTS operon mediates global transcriptional responses

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Opsata Mona

2010-08-01

Full Text Available Abstract Background The class IIa bacteriocin, pediocin PA-1, has clear potential as food preservative and in the medical field to be used against Gram negative pathogen species as Enterococcus faecalis and Listeria monocytogenes. Resistance towards class IIa bacteriocins appear in laboratory and characterization of these phenotypes is important for their application. To gain insight into bacteriocin resistance we studied mutants of E. faecalis V583 resistant to pediocin PA-1 by use of transcriptomic analyses. Results Mutants of E. faecalis V583 resistant to pediocin PA-1 were isolated, and their gene expression profiles were analyzed and compared to the wild type using whole-genome microarray. Significantly altered transcription was detected from about 200 genes; most of them encoding proteins involved in energy metabolism and transport. Glycolytic genes were down-regulated in the mutants, but most of the genes showing differential expression were up-regulated. The data indicate that the mutants were relieved from glucose repression and putative catabolic responsive elements (cre could be identified in the upstream regions of 70% of the differentially expressed genes. Bacteriocin resistance was caused by reduced expression of the mpt operon encoding the mannose-specific phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS, and the same transcriptional changes were seen in a mptD-inactivated mutant. This mutant also had decreased transcription of the whole mpt operon, showing that the PTS is involved in its own transcriptional regulation. Conclusion Our data confirm the important role of mannose PTS in class IIa bacteriocin sensitivity and we demonstrate its importance involving global carbon catabolite control.

Rapid and Efficient Purification Method for Small, Hydrophobic, Cationic Bacteriocins: Purification of Lactococcin B and Pediocin PA-1

OpenAIRE

Venema, K.; Chikindas, M. L.; Seegers, J.; Haandrikman, A. J.; Leenhouts, K. J.; Venema, G.; Kok, J.

1997-01-01

The bacteriocins lactococcin B and pediocin PA-1 were purified by ethanol precipitation, preparative isoelectric focusing, and ultrafiltration. The procedure reproducibly leads to high final yields in comparison to the generally low yields obtained by column chromatography. Specifically, during isoelectric focusing no loss of activity occurs. The method, in general, should be applicable to small, hydrophobic, cationic bacteriocins.

Identification of the Propionicin F Bacteriocin Immunity Gene (pcfI) and Development of a Food-Grade Cloning System for Propionibacterium freudenreichii▿ †

OpenAIRE

Brede, Dag Anders; Lothe, Sheba; Salehian, Zhian; Faye, Therese; Nes, Ingolf F.

2007-01-01

This report describes the first functional analysis of a bacteriocin immunity gene from Propionibacterium freudenreichii and its use as a selection marker for food-grade cloning. Cloning of the pcfI gene (previously orf5 [located as part of the pcfABC propionicin F operon]) rendered the sensitive host 1,000-fold more tolerant to the propionicin F bacteriocin. The physiochemical properties of the 127-residue large PcfI protein resemble those of membrane-bound immunity proteins from bacteriocin...

Alternatives for biosurfactants and bacteriocins extraction from Lactococcus lactis cultures produced under different pH conditions.

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Rodríguez, N; Salgado, J M; Cortés, S; Domínguez, J M

2010-08-01

Study of the potential of Lactococcus lactis CECT-4434 as a biosurfactants and nisin (the only bacteriocin allowed to be used in the food industry) producer for industrial applications, exploiting the possibility of recovering separately both metabolites, taking into account that L. lactis is an interesting micro-organism with several applications in the food industry because it is recognized as GRAS. The results showed the ability of this strain to produce cell-bound biosurfactants, under controlled pH, and cell-bound biosurfactants and bacteriocins, when pH was not controlled. Three extraction procedures were designed to separately recover these substances. The strain L. lactis CECT-4434 showed to be a cell-bound biosurfactants and bacterocins producer when fermentations were carried out under uncontrolled pH. Both products can be recovered separately. Development of a convenient tool for the extraction of cell-bound biosurfactants and bacteriocins from the fermentation broth.

Purification and Characterization of a Novel Cold Shock Protein-Like Bacteriocin Synthesized by Bacillus thuringiensis.

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Huang, Tianpei; Zhang, Xiaojuan; Pan, Jieru; Su, Xiaoyu; Jin, Xin; Guan, Xiong

2016-10-20

Bacillus thuringiensis (Bt), one of the most successful biopesticides, may expand its potential by producing bacteriocins (thuricins). The aim of this study was to investigate the antimicrobial potential of a novel Bt bacteriocin, thuricin BtCspB, produced by Bt BRC-ZYR2. The results showed that this bacteriocin has a high similarity with cold-shock protein B (CspB). BtCspB lost its activity after proteinase K treatment; however it was active at 60 °C for 30 min and was stable in the pH range 5-7. The partial loss of activity after the treatments of lipase II and catalase were likely due to the change in BtCspB structure and the partial degradation of BtCspB, respectively. The loss of activity at high temperatures and the activity variation at different pHs were not due to degradation or large conformational change. BtCspB did not inhibit four probiotics. It was only active against B. cereus strains 0938 and ATCC 10987 with MIC values of 3.125 μg/mL and 0.781 μg/mL, and MBC values of 12.5 μg/mL and 6.25 μg/mL, respectively. Taken together, these results provide new insights into a novel cold shock protein-like bacteriocin, BtCspB, which displayed promise for its use in food preservation and treatment of B. cereus-associated diseases.

Purification and characterization of plantaricin 163, a novel bacteriocin produced by Lactobacillus plantarum 163 isolated from traditional Chinese fermented vegetables.

Science.gov (United States)

Hu, Meizhong; Zhao, Haizhen; Zhang, Chong; Yu, Jiansheng; Lu, Zhaoxin

2013-11-27

Presumptive lactic acid bacteria (LAB) strains isolated from traditional Chinese fermented vegetables were screened for bacteriocin production. A novel bacteriocin-producing strain, Lactobacillus plantarum 163, was identified on the basis of its physiobiochemical characteristics and characterized by 16S rDNA sequencing. The novel bacteriocin, plantaricin 163, produced by Lb. plantarum 163 was purified by salt precipitation, gel filtration, and reverse-phase high-performance liquid chromatography (RP-HPLC). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of plantaricin 163 revealed the molecular weight to be 3553.2 Da. The complete amino acid sequence showed VFHAYSARGNYYGNCPANWPSCRNNYKSAGGK, and no similarity to known bacteriocins was found. Plantaricin 163 was highly thermostable (20 min, 121 °C), active in the presence of acidic pH (3-5), sensitive to protease, and exhibited broad-spectrum antimicrobial activity against LAB and other tested Gram-positive and Gram-negative bacteria. The results suggest that plantaricin 163 may be employed as a biopreservative in the food industry.

Antibacterial efficacy of Nisin, Pediocin 34 and Enterocin FH99 against Listeria monocytogenes and cross resistance of its bacteriocin resistant variants to common food preservatives.

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Kaur, G; Singh, T P; Malik, R K

2013-01-01

Antilisterial efficiency of three bacteriocins, viz, Nisin, Pediocin 34 and Enterocin FH99 was tested individually and in combination against Listeria mononcytogenes ATCC 53135. A greater antibacterial effect was observed when the bacteriocins were combined in pairs, indicating that the use of more than one LAB bacteriocin in combination have a higher antibacterial action than when used individually. Variants of Listeria monocytogenes ATCC 53135 resistant to Nisin, Pediocin 34 and Enterocin FH99 were developed. Bacteriocin cross-resistance of wild type and their corresponding resistant variants were assessed and results showed that resistance to a bacteriocin may extend to other bacteriocins within the same class. Resistance to Pediocin 34 conferred cross resistance to Enterocin FH 99 but not to Nisin. Similarly resistance to Enterocin FH99 conferred cross resistance to Pediocin 34 but not to Nisin. Also, the sensitivity of Nisin, Pediocin 34 and Enterocin FH99 resistant variants of Listeria monocytogenes to low pH, salt, sodium nitrite, and potassium sorbate was assayed in broth and compared to the parental wild-type strain. The Nisin, Pediocin 34 and Enterocin FH99 resistant variants did not have intrinsic resistance to low pH, sodium chloride, potassium sorbate, or sodium nitrite. In no case were the bacteriocin resistant Listeria monocytogenes variants examined were more resistant to inhibitors than the parental strains.

Antibacterial efficacy of Nisin, Pediocin 34 and Enterocin FH99 against Listeria monocytogenes and cross resistance of its bacteriocin resistant variants to common food preservatives

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G. Kaur

2013-01-01

Full Text Available Antilisterial efficiency of three bacteriocins, viz, Nisin, Pediocin 34 and Enterocin FH99 was tested individually and in combination against Listeria mononcytogenes ATCC 53135. A greater antibacterial effect was observed when the bacteriocins were combined in pairs, indicating that the use of more than one LAB bacteriocin in combination have a higher antibacterial action than when used individually. Variants of Listeria monocytogenes ATCC 53135 resistant to Nisin, Pediocin 34 and Enterocin FH99 were developed. Bacteriocin cross-resistance of wild type and their corresponding resistant variants were assessed and results showed that resistance to a bacteriocin may extend to other bacteriocins within the same class. Resistance to Pediocin 34 conferred cross resistance to Enterocin FH 99 but not to Nisin. Similarly resistance to Enterocin FH99 conferred cross resistance to Pediocin 34 but not to Nisin. Also, the sensitivity of Nisin, Pediocin 34 and Enterocin FH99 resistant variants of Listeria monocytogenes to low pH, salt, sodium nitrite, and potassium sorbate was assayed in broth and compared to the parental wild-type strain. The Nisin, Pediocin 34 and Enterocin FH99 resistant variants did not have intrinsic resistance to low pH, sodium chloride, potassium sorbate, or sodium nitrite. In no case were the bacteriocin resistant Listeria monocytogenes variants examined were more resistant to inhibitors than the parental strains.

Technological properties of bacteriocin-producing lactic acid bacteria isolated from Pico cheese an artisanal cow's milk cheese.

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Ribeiro, S C; Coelho, M C; Todorov, S D; Franco, B D G M; Dapkevicius, M L E; Silva, C C G

2014-03-01

Evaluate technologically relevant properties from bacteriocin-producing strains to use as starter/adjunct cultures in cheese making. Eight isolates obtained from Pico cheese produced in Azores (Portugal) were found to produce bacteriocins against Listeria monocytogenes and three isolates against Clostridium perfringens. They were identified as Lactococcus lactis and Enterococcus faecalis and submitted to technological tests: growth at different conditions of temperature and salt, acid production, proteolysis, lipolysis, coexistence, enzymatic profile and autolytic capacity. Safety evaluation was performed by evaluating haemolytic, gelatinase and DNase activity, resistance to antibiotics and the presence of virulence genes. Some isolates presented good technological features such as high autolytic activity, acid and diacetyl production. Lactococcus lactis was negative for all virulence genes tested and inhibit the growth of all Lactic acid bacteria (LAB) isolates. Enterococci were positive for the presence of some virulence genes, but none of the isolates were classified as resistant to important antibiotics. The bacteriocin-producing Lc. lactis present good potential for application in food as adjunct culture in cheese production. The study also reveals good technological features for some Enterococcus isolates. Bacteriocin-producing strains presented important technological properties to be exploited as new adjunct culture for the dairy industry, influencing flavour development and improve safety. © 2013 The Society for Applied Microbiology.

Characterization of Bacteriocin like inhibitory substance produced by a new Strain Brevibacillus borstelensis AG1 Isolated from 'Marcha'.

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Sharma, Nivedita; Gupta, Anupama; Gautam, Neha

2014-01-01

In the present study, a bacterium isolated from Marcha- a herbal cake used as traditional starter culture to ferment local wine in North East India, was evaluated for bacteriocin like inhibitory substance production and was tested against six food borne/spoilage causing pathogens viz. Listeria monocytogenes MTCC 839, Bacillus subtilis MTCC 121, Clostridium perfringens MTCC 450, Staphylococcus aureus, Lactobacillus plantarum and Leuconostoc mesenteroides MTCC 107 by using bit/disc method followed by well diffusion method. The bacterial isolate was identified as Brevibacillus borstelensis on the basis of phenotypic, biochemical and molecular characteristics using 16Sr RNA gene technique. Bacteriocin like inhibitory substance produced by Brevibacillus borstelensis AG1 was purified by gel exclusion chromatography. The molecular mass of the Brevibacillus borstelensis AG1 was found to be 12 kDa. Purified bacteriocin like inhibitory substance of Brevibacillus borstelensis was further characterized by studying the effect of temperature, pH, proteolytic enzyme and stability. Bacteriocin like inhibitory substance was found to be thermostable upto 100 °C, active at neutral pH, sensitive to trypsin, and partially stable till third week of storage thus showing a bright prospective to be used as a potential food biopreservative.

Partial purification and characterization of a bacteriocin produced by Enterococcus faecium 130 isolated from mozzarella cheese

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Fabrício Luiz Tulini

2011-03-01

Full Text Available Lactic acid bacteria are important in foods as potential probiotics and also due to the ability to produce antimicrobial compounds that can contribute for biopreservation. In this work, the bacteriocin produced by the food isolate Enterococcus faecium 130 was partially purified and characterized. The compound was active against Gram-positive bacteria, including Listeria monocytogenes. It was produced after 4 days of storage at a broad temperature range (4 to 37 °C; it was stable at pH ranging from 2 to 10 with no loss of activity after heating at 100 °C for 15 minutes. Bacteriocin was partially purified by the adsorption-desorption technique, and the analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE showed a molecular mass of 3.5 to 6.5 kDa. These data encourage studies on application of this bacteriocin in food systems as an additional hurdle to microbial growth.

Purification and characterization of a bacteriocin from an oenological strain of Leuconostoc mesenteroides subsp. cremoris.

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Dündar, Halil; Salih, Bekir; Bozoğlu, Faruk

2016-05-18

Malolactic fermentation (MLF), which improves organoleptic properties and biologic stability of some wines, may cause wine spoilage if uncontrolled. Bacteriocins were reported as efficient preservatives to control MLF through their bactericidal effect on malolactic bacteria. Leuconostoc mesenteroides subsp. cremoris W3 isolated from wine produces an inhibitory substance that is bactericidal against malolactic bacteria in model wine medium. Treatment of the culture supernatant of strain W3 with proteases eliminated the inhibitory activity, which proved that it is a true bacteriocin and we tentatively termed it mesentericin W3. The bacteriocin inhibited the growth of food-borne pathogenic bacteria such as Enterococcus faecalis, Listeria monocytogenes, and malolactic bacteria. It was active over a wide pH range and stable to organic solvents and heat. Mesentericin W3 was purified to homogeneity by a pH-mediated cell adsorption-desorption method, cation exchange, hydrophobic interaction, and reverse-phase chromatography. Matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy (MS) and partial amino acid sequence analysis revealed that mesentericin W3 was identical to mesentericin Y105.

In vitro evaluation of the antimicrobial effect of a raw bacteriocin extract in combination with chemical preservatives employed in meat industry

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Luis A. Aguado Bautista

2010-12-01

Full Text Available Biopreservation can be defined as the foods shelf life extension employing antibacterial products like bacteriocins. The objective of this work was to determinate the efficacy of E. faecium MXVK29 bacteriocin in combination with chemical preservatives against spoilage and pathogens microorganisms. Bacteriocin raw extrac antimicrobial activity was 46.34 UA/g of protein. Growth of Pseudomonas putida was not affected by the preservatives employed at the conditions employed. Antimicrobial response was different for other microorganisms since a synergetic effect of the preservatives combination inhibited Brochothrix thermosphacta and Escherichia coli growth. Sodium lactate had additive effect only against Listeria innocua.

Coordinated Bacteriocin Expression and Competence in Streptococcus pneumoniae Contributes to Genetic Adaptation through Neighbor Predation.

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Wei-Yun Wholey

2016-02-01

Full Text Available Streptococcus pneumoniae (pneumococcus has remained a persistent cause of invasive and mucosal disease in humans despite the widespread use of antibiotics and vaccines. The resilience of this organism is due to its capacity for adaptation through the uptake and incorporation of new genetic material from the surrounding microbial community. DNA uptake and recombination is controlled by a tightly regulated quorum sensing system that is triggered by the extracellular accumulation of competence stimulating peptide (CSP. In this study, we demonstrate that CSP can stimulate the production of a diverse array of blp bacteriocins. This cross stimulation occurs through increased production and secretion of the bacteriocin pheromone, BlpC, and requires a functional competence regulatory system. We show that a highly conserved motif in the promoter of the operon encoding BlpC and its transporter mediates the upregulation by CSP. The accumulation of BlpC following CSP stimulation results in augmented activation of the entire blp locus. Using biofilm-grown organisms as a model for competition and genetic exchange on the mucosal surface, we demonstrate that DNA exchange is enhanced by bacteriocin secretion suggesting that co-stimulation of bacteriocins with competence provides an adaptive advantage. The blp and com regulatory pathways are believed to have diverged and specialized in a remote ancestor of pneumococcus. Despite this, the two systems have maintained a regulatory connection that promotes competition and adaptation by targeting for lysis a wide array of potential competitors while simultaneously providing the means for incorporation of their DNA.

Cysteine S-glycosylation, a new post-translational modification found in glycopeptide bacteriocins

Czech Academy of Sciences Publication Activity Database

Stepper, J.; Shastri, S.; Loo, T. S.; Preston, J. C.; Novák, Petr; Man, Petr; Moore, Ch. H.; Havlíček, Vladimír; Patchett, M. L.; Norris, G. E.

2011-01-01

Roč. 585, č. 4 (2011), s. 645-650 ISSN 0014-5793 Institutional research plan: CEZ:AV0Z50200510 Keywords : Post-translational modification * Glycosylation * Bacteriocin Subject RIV: CE - Biochemistry Impact factor: 3.538, year: 2011

Exploration and conservation of bacterial genetic resources as bacteriocin producing inhibitory microorganisms to pathogen bacteria in livestock

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Chotiah S

2013-06-01

Full Text Available Exploration and conservation of microorganisms producing bacteriocin was done as the primary study towards the collection of potential bacteria and its application in improving livestock health condition and inhibit food borne pathogens. Diferent kinds of samples such as beef cattle rectal swab, rumen fluids, cow’s milk, chicken gut content, goat’s milk were collected at Bogor cattle slaughter houses, poultry slaughter houses, dairy cattle and goat farms. A total of 452 bacterial isolates consisted of 73 Gram negative bacteria and 379 Gram positive bacteria were isolated from samples collected and screened for bacteriocin activity. Determination of bacteriocin activity with bioassay using agar spot tests were carried out on liquid and semisolid medium assessing 8 kins of indicators of pathogenic bacteria and food borne pathogens. A total of 51 bacteriocin producing strains were collected and some of the strains had high inhibitory zone such as Lactobacillus casei SS14C (26 mm, Enterobacter cloacae SRUT (24mm, Enterococcus faecalis SK39 (21mm and Bifidobacterium dentium SS14T (20mm respectively, to Salmonella typhimurium BCC B0046/ATCC 13311, E. coli O157 hemolytic BCC B2717, Listeria monocytogenes BCC B2767/ATCC 7764 and Escherichia coli VTEC O157 BCC B2687. Evaluation after conservation ex situ to all bacterocin producing strain at 5oC for 1 year in freeze drying ampoules in vacuum and dry condition revealed the decreasing viability starting from log 0.8 CFU/ml for Lactococcus and Leuconostoc to log 2.2. CFU/ml for Streptococcus. Result of the study showed that the bacteriocin producing strains obtained were offered a potential resource for preventing disease of livestock and food borne diseases.

Bacteriocins with a broader antimicrobial spectrum prevail in enterococcal symbionts isolated from the hoopoe's uropygial gland.

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Ruiz-Rodríguez, Magdalena; Martínez-Bueno, Manuel; Martín-Vivaldi, Manuel; Valdivia, Eva; Soler, Juan J

2013-09-01

The use of compounds produced by symbiotic bacteria against pathogens in animals is one of the most exciting discoveries in ecological immunology. The study of those antibiotic metabolites will enable an understanding of the defensive strategies against pathogenic infections. Here, we explore the role of bacteriocins explaining the antimicrobial properties of symbiotic bacteria isolated from the uropygial gland of the hoopoe (Upupa epops). The antagonistic activity of 187 strains was assayed against eight indicator bacteria, and the presence of six bacteriocin genes was detected in the genomic DNA. The presence of bacteriocin genes correlated with the antimicrobial activity of isolates. The most frequently detected bacteriocin genes were those encoding for the MR10 and AS-48 enterocins, which confer the highest inhibition capacity. All the isolates belonged to the genus Enterococcus, with E. faecalis as the most abundant species, with the broadest antimicrobial spectrum and the highest antagonistic activity. The vast majority of E. faecalis strains carried the genes of MR10 and AS-48 in their genome. Therefore, we suggest that fitness-related benefits for hoopoes associated with harbouring the most bactericidal symbionts cause the highest frequency of strains carrying MR10 and AS-48 genes. The study of mechanisms associated with the acquisition and selection of bacterial symbionts by hoopoes is necessary, however, to reach further conclusions. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Factors affecting production of an antilisterial bacteriocin by Carnobacterium piscicola strain A9b in laboratory media and model fish systems

DEFF Research Database (Denmark)

Himelbloom, B.; Nilsson, Lilian; Gram, Lone

2001-01-01

in APT broth when a low inoculum level (0.001%) was used. In contrast, inoculum level did not influence bacteriocin production in BHI and MRS7 without glucose. Bacteriocin production in APT was induced by the presence of an extracellular compound present in the sterile, filtered, cell- free supernatant...

Characterization of Bacteriocin like inhibitory substance produced by a new Strain Brevibacillus borstelensis AG1 Isolated from ‘Marcha’

Science.gov (United States)

Sharma, Nivedita; Gupta, Anupama; Gautam, Neha

2014-01-01

In the present study, a bacterium isolated from Marcha- a herbal cake used as traditional starter culture to ferment local wine in North East India, was evaluated for bacteriocin like inhibitory substance production and was tested against six food borne/spoilage causing pathogens viz. Listeria monocytogenes MTCC 839, Bacillus subtilis MTCC 121, Clostridium perfringens MTCC 450, Staphylococcus aureus, Lactobacillus plantarum and Leuconostoc mesenteroides MTCC 107 by using bit/disc method followed by well diffusion method. The bacterial isolate was identified as Brevibacillus borstelensis on the basis of phenotypic, biochemical and molecular characteristics using 16Sr RNA gene technique. Bacteriocin like inhibitory substance produced by Brevibacillus borstelensis AG1 was purified by gel exclusion chromatography. The molecular mass of the Brevibacillus borstelensis AG1 was found to be 12 kDa. Purified bacteriocin like inhibitory substance of Brevibacillus borstelensis was further characterized by studying the effect of temperature, pH, proteolytic enzyme and stability. Bacteriocin like inhibitory substance was found to be thermostable upto 100 °C, active at neutral pH, sensitive to trypsin, and partially stable till third week of storage thus showing a bright prospective to be used as a potential food biopreservative. PMID:25477937

Multi-digit maximum voluntary torque production on a circular object

Science.gov (United States)

SHIM, JAE KUN; HUANG, JUNFENG; HOOKE, ALEXANDER W.; LATSH, MARK L.; ZATSIORSKY, VLADIMIR M.

2010-01-01

Individual digit-tip forces and moments during torque production on a mechanically fixed circular object were studied. During the experiments, subjects positioned each digit on a 6-dimensional force/moment sensor attached to a circular handle and produced a maximum voluntary torque on the handle. The torque direction and the orientation of the torque axis were varied. From this study, it is concluded that: (1) the maximum torque in the closing (clockwise) direction was larger than in the opening (counter clockwise) direction; (2) the thumb and little finger had the largest and the smallest share of both total normal force and total moment, respectively; (3) the sharing of total moment between individual digits was not affected by the orientation of the torque axis or by the torque direction, while the sharing of total normal force between the individual digit varied with torque direction; (4) the normal force safety margins were largest and smallest in the thumb and little finger, respectively. PMID:17454086

Antagonistic Activity of Lactobacillus plantarum C11: Two New Two-Peptide Bacteriocins, Plantaricins EF and JK, and the Induction Factor Plantaricin A

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Anderssen, Erlend L.; Diep, Dzung Bao; Nes, Ingolf F.; Eijsink, Vincent G. H.; Nissen-Meyer, Jon

1998-01-01

Six bacteriocinlike peptides (plantaricin A [PlnA], PlnE, PlnF, PlnJ, PlnK, and PlnN) produced by Lactobacillus plantarum C11 were detected by amino acid sequencing and mass spectrometry. Since purification to homogeneity was problematic, all six peptides were obtained by solid-phase peptide synthesis and were tested for bacteriocin activity. It was found that L. plantarum C11 produces two two-peptide bacteriocins (PlnEF and PlnJK); a strain-specific antagonistic activity was detected at nanomolar concentrations when PlnE and PlnF were combined and when PlnJ and PlnK were combined. Complementary peptides were at least 103 times more active when they were combined than when they were present individually, and optimal activity was obtained when the complementary peptides were present in approximately equal amounts. The interaction between complementary peptides was specific, since neither PlnE nor PlnF could complement PlnJ or PlnK, and none of these peptides could complement the peptides constituting the two-peptide bacteriocin lactococcin G. Interestingly, PlnA, which acts as an extracellular signal (pheromone) that triggers bacteriocin production, also possessed a strain-specific antagonistic activity. No bacteriocin activity could be detected for PlnN. PMID:9603847

Leuconostoc carnosum 4010 has the potential for use as a protective culture for vacuum-packed meats: culture isolation, bacteriocin identification, and meat application experiments

DEFF Research Database (Denmark)

Budde, B.B.; Hornbæk, T.; Jacobsen, T.

2003-01-01

A new culture, Leuconostoc carnosum 4010, for biopreservation of vacuum-packed meats is described. The culture originated from bacteriocin-producing lactic acid bacteria (LAB) naturally present in vacuum-packed meat products. Approximately, 72,000 colonies were isolated from 48 different vacuum......-packed meat products and examined for antibacterial activity. Bacteriocin-producing colonies were isolated from 46% of the packages examined. Leuc. carnosum was the predominant bacteriocin-producing strain and Leuc. carnosum 4010 was selected for further experiments because it showed strong antilisterial...... activity corresponding to molecular sizes of 4.6 and 5.3 kDa. N-terminal amino acid sequencing showed that Leuc. carnosum 4010 produced two bacteriocins highly similar or identical to leucocin A and leucocin C. Application experiments showed that the addition of 10(7) cfu/g Leuc. carnosum 4010 to a vacuum...

Salivaricin P, One of a Family of Two-Component Antilisterial Bacteriocins Produced by Intestinal Isolates of Lactobacillus salivarius▿

Science.gov (United States)

Barrett, Eoin; Hayes, Maria; O'Connor, Paula; Gardiner, Gillian; Fitzgerald, Gerald F.; Stanton, Catherine; Ross, R. Paul; Hill, Colin

2007-01-01

Lactobacillus salivarius DPC6005, a porcine intestinal isolate, produces a two-component bacteriocin, salivaricin P, with homology to ABP-118 produced by a human probiotic L. salivarius strain. Indeed, molecular characterization revealed that while the peptides Sln1 and ABP-118α are identical, their companion peptides (Sln2 and ABP-118β, respectively) differ by two amino acids. This observation suggests that two-component bacteriocins may be a common feature of intestinal L. salivarius strains. PMID:17416691

Administrative Circulars

CERN Document Server

Département des Ressources humaines

2004-01-01

Administrative Circular N° 2 (Rev. 2) - May 2004 Guidelines and procedures concerning recruitment and probation period of staff members This circular has been revised. It cancels and replaces Administrative Circular N° 2 (Rev. 1) - March 2000. Administrative Circular N° 9 (Rev. 3) - May 2004 Staff members contracts This circular has been revised. It cancels and replaces Administrative Circular N° 9 (Rev. 2) - March 2000. Administrative Circular N° 26 (Rev. 4) - May 2004 Procedure governing the career evolution of staff members This circular has also been revised. It Administrative Circulars Administrative Circular N° 26 (Rev. 3) - December 2001 and brings up to date the French version (Rev. 4) published on the HR Department Web site in January 2004. Operational Circular N° 7 - May 2004 Work from home This circular has been drawn up. Operational Circular N° 8 - May 2004 Dealing with alcohol-related problems...

The Curing Agent Sodium Nitrite, Used in the Production of Fermented Sausages, Is Less Inhibiting to the Bacteriocin-Producing Meat Starter Culture Lactobacillus curvatus LTH 1174 under Anaerobic Conditions

Science.gov (United States)

Verluyten, Jurgen; Messens, Winy; De Vuyst, Luc

2003-01-01

Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage. The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was investigated in vitro by laboratory fermentations with modified MRS broth. The strain was highly sensitive to nitrite; even a concentration of 10 ppm of curing agent inhibited its growth and both volumetric and specific bacteriocin production. A meat simulation medium containing 5 ppm of sodium nitrite was tested to investigate the influence of the gas phase on the growth and bacteriocin production of L. curvatus LTH 1174. Aerating the culture during growth had no effect on biomass formation, but the oxidative stress caused a higher level of specific bacteriocin production and led to a metabolic shift toward acetic acid production. Anaerobic conditions, on the other hand, led to an increased biomass concentration and less growth inhibition. Also, higher maximum volumetric bacteriocin activities and a higher level of specific bacteriocin production were obtained in the presence of sodium nitrite than in fermentations under aerobic conditions or standard conditions of air supply. These results indicate that the inhibitory effect of the curing agent is at least partially masked under anaerobic conditions. PMID:12839751

The curing agent sodium nitrite, used in the production of fermented sausages, is less inhibiting to the bacteriocin-producing meat starter culture Lactobacillus curvatus LTH 1174 under anaerobic conditions.

Science.gov (United States)

Verluyten, Jurgen; Messens, Winy; De Vuyst, Luc

2003-07-01

Curvacin A is a listericidal bacteriocin produced by Lactobacillus curvatus LTH 1174, a strain isolated from fermented sausage. The response of this strain to an added curing agent (sodium nitrite) in terms of cell growth and bacteriocin production was investigated in vitro by laboratory fermentations with modified MRS broth. The strain was highly sensitive to nitrite; even a concentration of 10 ppm of curing agent inhibited its growth and both volumetric and specific bacteriocin production. A meat simulation medium containing 5 ppm of sodium nitrite was tested to investigate the influence of the gas phase on the growth and bacteriocin production of L. curvatus LTH 1174. Aerating the culture during growth had no effect on biomass formation, but the oxidative stress caused a higher level of specific bacteriocin production and led to a metabolic shift toward acetic acid production. Anaerobic conditions, on the other hand, led to an increased biomass concentration and less growth inhibition. Also, higher maximum volumetric bacteriocin activities and a higher level of specific bacteriocin production were obtained in the presence of sodium nitrite than in fermentations under aerobic conditions or standard conditions of air supply. These results indicate that the inhibitory effect of the curing agent is at least partially masked under anaerobic conditions.

Anti-bacterial Efficacy of Bacteriocin Produced by Marine Bacillus subtilis Against Clinically Important Extended Spectrum Beta-Lactamase Strains and Methicillin-Resistant Staphylococcus aureus

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Suresh Mickymaray

2018-02-01

Full Text Available Objective: To investigate the anti-bacterial efficacy of bacteriocin produced by Bacillus subtilis SM01 (GenBank accession no: KY612347, a Gram-positive marine bacterium, against Extended Spectrum Beta-Lactamase (ESBL producing Gram-negative pathogens Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli, and Gram-positive pathogen Methicillin-Resistant Staphylococcus aureus (MRSA. Methods: A marine bacterium was isolated from mangrove sediment from the Red Sea coast of Jeddah, Kingdom of Saudi Arabia, and identified based on its morphological, biochemical, and molecular characteristics. The bacteriocin production using this isolate was carried out in brain heart infusion broth (BHIB medium. The Anti-bacterial activity of bacteriocin was evaluated against selected ESBL strains and MRSA by the well agar method. The effects of incubation time, pH, and temperature on the Anti-bacterial activity were studied. Results: The bacteriocin Bac-SM01 produced by B. subtilis SM01 demonstrated broad-spectrum Anti-bacterial activity against both Gram-negative and -positive bacteria. The present study is the first report that the bacteriocin Bac-SM01 inhibits the growth of ESBL producing Gram-negative strains A. baumannii, P. aeruginosa, and E. coli, and a Gram-positive MRSA strain. The optimum incubation time, pH, and temperature for the Anti-bacterial activity of Bac-SM01 was 24 h, 7, and 37°C respectively. Conclusion: The overall investigation can conclude that the bacteriocin Bac-SM01 from the marine isolate Bacillus subtilis SM01 could be used as an alternative Anti-bacterial agent in pharmaceutical products.

An application in cheddar cheese manufacture for a strain of Lactococcus lactis producing a novel broad-spectrum bacteriocin, lacticin 3147.

Science.gov (United States)

Ryan, M P; Rea, M C; Hill, C; Ross, R P

1996-01-01

Lactococcus lactis DPC3147, a strain isolated from an Irish kefir grain, produces a bacteriocin with a broad spectrum of inhibition. The bacteriocin produced is heat stable, particularly at a low pH, and inhibits nisin-producing (Nip+) lactococci. On the basis of the observation that the nisin structural gene (nisA) does not hybridize to DPC3147 genomic DNA, the bacteriocin produced was considered novel and designated lacticin 3147. The genetic determinants which encode lacticin 3147 are contained on a 63-kb plasmid, which was conjugally mobilized to a commercial cheese starter, L. lactis subsp. cremoris DPC4268. The resultant transconjugant, DPC4275, both produces and is immune to lacticin 3147. The ability of lacticin 3147-producing lactococci to perform as cheddar cheese starters was subsequently investigated in cheesemaking trials. Bacteriocin-producing starters (which included the transconjugant strain DPC4275) produced acid at rates similar to those of commercial strains. The level of lacticin 3147 produced in cheese remained constant over 6 months of ripening and correlated with a significant reduction in the levels of nonstarter lactic acid bacteria. Such results suggest that these starters provide a means of controlling developing microflora in ripened fermented products. PMID:8593062

Purification and Partial Characterization of a Novel Bacteriocin Synthesized by Lactobacillus paracasei HD1-7 Isolated from Chinese Sauerkraut Juice.

Science.gov (United States)

Ge, Jingping; Sun, Yanyang; Xin, Xing; Wang, Ying; Ping, Wenxiang

2016-01-14

Bacteriocins have antimicrobial activities against food-spoiling bacteria and food-borne pathogens. Paracin 1.7, a bacteriocin synthesized by Lactobacillus paracasei HD1-7 isolated from Chinese sauerkraut juice, was studied. Following partial purification with ammonium sulfate precipitation, CM Sepharose Fast Flow, and Sephadex G-10 chromatography, the molecular weight of Paracin 1.7 was about 10 kDa based on Tricine-SDS-PAGE results. A 2.87 fold purified bacteriocin was produced, reaching a final yield of 39.93% and the specific activity of 1.56 × 10(3) AU/mg. The N-terminal amino acid sequence of Paracin 1.7 was VSNTFFA, and the LC/LTQ results revealed that the N-terminal amino acid sequence was similar to that of ABC-type oligopeptide transport system protein and N-acetylmuramoyl-L-alanine amidase. Paracin 1.7 was sensitive to protease K, had antimicrobial activities at a broad pH range (3.0-8.0), and was heat resistant (121 °C for 20 min). Paracin 1.7 from Lactobacillus paracasei HD1-7 is a novel bacteriocin that has potential applications in food preservation.

Purification and Genetic Characterization of Enterocin I from Enterococcus faecium 6T1a, a Novel Antilisterial Plasmid-Encoded Bacteriocin Which Does Not Belong to the Pediocin Family of Bacteriocins

Science.gov (United States)

Floriano, Belén; Ruiz-Barba, José L.; Jiménez-Díaz, Rufino

1998-01-01

Enterocin I (ENTI) is a novel bacteriocin produced by Enterococcus faecium 6T1a, a strain originally isolated from a Spanish-style green olive fermentation. The bacteriocin is active against many olive spoilage and food-borne gram-positive pathogenic bacteria, including clostridia, propionibacteria, and Listeria monocytogenes. ENTI was purified to homogeneity by ammonium sulfate precipitation, binding to an SP-Sepharose fast-flow column, and phenyl-Sepharose CL-4B and C2/C18 reverse-phase chromatography. The purification procedure resulted in a final yield of 954% and a 170,000-fold increase in specific activity. The primary structure of ENTI was determined by amino acid and nucleotide sequencing. ENTI consists of 44 amino acids and does not show significant sequence similarity with any other previously described bacteriocin. Sequencing of the entI structural gene, which is located on the 23-kb plasmid pEF1 of E. faecium 6T1a, revealed the absence of a leader peptide at the N-terminal region of the gene product. A second open reading frame, ORF2, located downstream of entI, encodes a putative protein that is 72.7% identical to ENTI. entI and ORF2 appear to be cotranscribed, yielding an mRNA of ca. 0.35 kb. A gene encoding immunity to ENTI was not identified. However, curing experiments demonstrated that both enterocin production and immunity are conferred by pEF1. PMID:9835578

Evaluation of Potential Probiotic Properties of Enterococcus mundtii, Its Survival in Boza and in situ Bacteriocin Production

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Svetoslav D. Todorov

2009-01-01

Full Text Available Boza is a low-pH and low-alcohol cereal-based beverage produced in the Balkan Peninsula. Barley was cooked and prepared according to a traditional recipe and inoculated with Enterococcus mundtii ST4V (a potential probiotic and bacteriocin-producing strain, commercially produced boza, Saccharomyces cerevisiae, and a combination of strain E. mundtii ST4V and Saccharomyces cerevisiae. Fermentation was carried out at 37 °C for 3 h. The organoleptic properties of fermented products were evaluated by a qualified taste panel. No significant differences in rheological properties were observed, suggesting that E. mundtii ST4V had no effect on the quality of the final product. Microbial cell numbers remained relatively unchanged during one week of storage. The preservative properties of bacteriocin ST4V were evaluated by contaminating boza with Lactobacillus sakei DSM 20017. Changes in microbial populations were monitored by using classical microbiological methods, PCR with species-specific primers and denaturing gradient gel electrophoresis (DGGE. Adsorption of bacteriocin ST4V to target cells is pH-dependent, with the highest adsorption (88 % recorded at pH=8.0 and pH=10.0. Maximum adsorption of bacteriocin ST4V (75 % to Enterococcus faecalis and Listeria innocua was recorded at 25 to 37 °C. Growth of E. mundtii ST4V was inhibited only by a few antibiotics and anti-inflammatory medicaments, suggesting that the strain may be used as a probiotic by individuals receiving medical treatment.

Antibacterial activity of bacteriocin-like substance P34 on Listeria monocytogenes in chicken sausage

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Voltaire Sant'Anna

2013-12-01

Full Text Available The antimicrobial activity of the bacteriocin-like substance (BLS P34 against Listeria monocytogenes was investigated in chicken sausage. The BLS was applied to chicken sausages (256 AU g-1 previously inoculated with a suspension of 10² cfu g-1 of L. monocytogenes. BLS P34 inhibited the indicator microorganism in situ in all incubation times for up to 10 days at 5 °C. The effectiveness of BLS P34 was increased when it was added in combination with nisin. The bacteriocin was also tested in natural eatable natural bovine wrapping (salty semi-dried tripe against the same indicator microorganism, also showing inhibitory capability in vitro. BLS P34 showed potential to control L. monocytogenes in refrigerated meat products.

Partial Characterisation of Bacteriocins Produced by Bacillus cereus Isolates from Milk and Milk Products

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Bojana Bogović Matijašić

2003-01-01

Full Text Available Thirty one (19.2 % out of 161 Bacillus cereus isolates from raw milk and milk products were found to produce proteinaceous substances which inhibit the growth of other B. cereus isolates. The detection of antibacterial activity depended on medium and method used. Bactericidal activity was detected in 23 (14 % or 19 (12 % of the tested strains on the triptic soya agar and brain-heart infusion with glucose, respectively, while 11 (7 % of the strains produced bactericidal substances on both media. Nineteen percent of isolates from raw milk and 20 % of isolates from milk products were found to produce bacteriocins. Four B. cereus isolates inhibited the growth of individual test strains belonging to B. licheniformis, B. subtilis, Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, Lactobacillus helveticus and L. casei species. The bacteriocins of four B. cereus isolates were studied in more detail. The production and activity of these substances were detected in stationary- phase of bacterial culture. Two of them were stable after heating at 60 °C, while only one was stable after heating at 75 °C for 15 minutes. All of them were active over a range of pH=3–10. The apparent molecular weights of four bacteriocins detected by SDS-PAGE electrophoresis were in the range of 1 to 8 kDa.

Identification of the propionicin F bacteriocin immunity gene (pcfI) and development of a food-grade cloning system for Propionibacterium freudenreichii.

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Brede, Dag Anders; Lothe, Sheba; Salehian, Zhian; Faye, Therese; Nes, Ingolf F

2007-12-01

This report describes the first functional analysis of a bacteriocin immunity gene from Propionibacterium freudenreichii and its use as a selection marker for food-grade cloning. Cloning of the pcfI gene (previously orf5 [located as part of the pcfABC propionicin F operon]) rendered the sensitive host 1,000-fold more tolerant to the propionicin F bacteriocin. The physiochemical properties of the 127-residue large PcfI protein resemble those of membrane-bound immunity proteins from bacteriocin systems found in lactic acid bacteria. The high level of immunity conferred by pcfI allowed its use as a selection marker for plasmid transformation in P. freudenreichii. Electroporation of P. freudenreichii IFO12426 by use of the pcfI expression plasmid pSL102 and propionicin F selection (200 bacteriocin units/ml) yielded 10(7) transformants/microg DNA. The 2.7-kb P. freudenreichii food-grade cloning vector pSL104 consists of the pLME108 replicon, a multiple cloning site, and pcfI expressed from the constitutive P(pampS) promoter for selection. The pSL104 vector efficiently facilitated cloning of the propionicin T1 bacteriocin in P. freudenreichii. High-level propionicin T1 production (640 BU/ml) was obtained with the IFO12426 strain, and the food-grade propionicin T1 expression plasmid pSL106 was maintained by approximately 91% of the cells over 25 generations in the absence of selection. To the best of our knowledge this is the first report of an efficient cloning system that facilitates the generation of food-grade recombinant P. freudenreichii strains.

Purification, Characterization, and Optimum Conditions of Fermencin SD11, a Bacteriocin Produced by Human Orally Lactobacillus fermentum SD11.

Science.gov (United States)

Wannun, Phirawat; Piwat, Supatcharin; Teanpaisan, Rawee

2016-06-01

Fermencin SD11, a bacteriocin produced by human orally Lactobacillus fermentum SD11, was purified, characterized, and optimized in conditions for bacterial growth and bacteriocin production. Fermencin SD11 was purified using three steps of ammonium sulfate precipitation, gel filtration chromatography, and reverse-phase high-performance liquid chromatography. The molecular weight was found to be 33,000 Da using SDS-PAGE and confirmed as 33,593.4 Da by liquid chromatography-mass spectrometry. Fermencin SD11 exhibited activity against a wide range of oral pathogens including cariogenic and periodontogenic pathogens and Candida. The active activity was stable between 60 - 80 °C in a pH range of 3.0 to 7.0. It was sensitive to proteolytic enzymes (proteinase K and trypsin), but it was not affected by α-amylase, catalase, lysozyme, and saliva. The optimum conditions for growth and bacteriocin production of L. fermentum SD11 were cultured at acidic with pH of 5.0-6.0 at 37 or 40 °C under aerobic or anaerobic conditions for 12 h. It is promising that L. fermentum SD11 and its bacteriocin may be an alternative approach for promoting oral health or prevention of oral diseases, e.g., dental caries and periodontitis, which would require further clinical trials.

Topology of a type I secretion system for bacteriocins of Lactococcus lactis

NARCIS (Netherlands)

Franke, Christian Marc

1998-01-01

This thesis describes the analysis of a number of aspects of the secretion and muturation machinery of the bacteriocin lactococcin A (LcnA) from Lactococcus lactis, whick is initially synthesized as a precursor protein (preLcnA), containing an N-terminal extension of 20 amino acids (the leader)....

Bacteriocin formation by dominant aerobic sporeformers isolated from traditional maari

DEFF Research Database (Denmark)

Kaboré, Donatien; Thorsen, Line; Nielsen, Dennis Sandris

2012-01-01

that the antimicrobial substances produced were heat stable, in-sensitive to catalase, sensitive to protease and trypsin but resistant to the proteolytic action of papain and proteinase K and equally active at pH values ranging from 3 to 11. Bacteriocin secretion started in late exponential growth phase and maximum...

Time-dependent fermentation control strategies for enhancing synthesis of marine bacteriocin 1701 using artificial neural network and genetic algorithm.

Science.gov (United States)

Peng, Jiansheng; Meng, Fanmei; Ai, Yuncan

2013-06-01

The artificial neural network (ANN) and genetic algorithm (GA) were combined to optimize the fermentation process for enhancing production of marine bacteriocin 1701 in a 5-L-stirred-tank. Fermentation time, pH value, dissolved oxygen level, temperature and turbidity were used to construct a "5-10-1" ANN topology to identify the nonlinear relationship between fermentation parameters and the antibiotic effects (shown as in inhibition diameters) of bacteriocin 1701. The predicted values by the trained ANN model were coincided with the observed ones (the coefficient of R(2) was greater than 0.95). As the fermentation time was brought in as one of the ANN input nodes, fermentation parameters could be optimized by stages through GA, and an optimal fermentation process control trajectory was created. The production of marine bacteriocin 1701 was significantly improved by 26% under the guidance of fermentation control trajectory that was optimized by using of combined ANN-GA method. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cloning strategies for heterologous expression of the bacteriocin enterocin A by Lactobacillus sakei Lb790, Lb. plantarum NC8 and Lb. casei CECT475.

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Jiménez, Juan J; Diep, Dzung B; Borrero, Juan; Gútiez, Loreto; Arbulu, Sara; Nes, Ingolf F; Herranz, Carmen; Cintas, Luis M; Hernández, Pablo E

2015-10-15

Bacteriocins produced by lactic acid bacteria (LAB) attract considerable interest as natural and nontoxic food preservatives and as therapeutics whereas the bacteriocin-producing LAB are considered potential probiotics for food, human and veterinary applications, and in the animal production field. Within LAB the lactobacilli are increasingly used as starter cultures for food preservation and as probiotics. The lactobacilli are also natural inhabitants of the gastrointestinal (GI) tract and attractive vectors for delivery of therapeutic peptides and proteins, and for production of bioactive peptides. Research efforts for production of bacteriocins in heterologous hosts should be performed if the use of bacteriocins and the LAB bacteriocin-producers is ever to meet the high expectations deposited in these antimicrobial peptides. The recombinant production and functional expression of bacteriocins by lactobacilli would have an additive effect on their probiotic functionality. The heterologous production of the bacteriocin enterocin A (EntA) was evaluated in different Lactobacillus spp. after fusion of the versatile Sec-dependent signal peptide (SP usp45 ) to mature EntA plus the EntA immunity gene (entA + entiA) (fragment UAI), and their cloning into plasmid vectors that permitted their inducible (pSIP409 and pSIP411) or constitutive (pMG36c) production. The amount, antimicrobial activity (AA) and specific antimicrobial activity (SAA) of the EntA produced by Lactobacillus sakei Lb790, Lb. plantarum NC8 and Lb. casei CECT475 transformed with the recombinant plasmids pSIP409UAI, pSIP411UAI and pMGUAI varied depending of the expression vector and the host strain. The Lb. casei CECT475 recombinant strains produced the largest amounts of EntA, with the highest AA and SAA. Supernatants from Lb. casei CECT (pSIP411UAI) showed a 4.9-fold higher production of EntA with a 22.8-fold higher AA and 4.7-fold higher SAA than those from Enterococcus faecium T136, the natural

Antibacterial activity and optimisation of bacteriocin producing lactic acid bacteria isolated from beef (red meat) samples

International Nuclear Information System (INIS)

Ali, N.M.; Mazhar, B.; Khadija, I.; Kalim, B.

2016-01-01

Bacteriocin producing bacteria are commonly found in meat products to enhance their shelf-life. In the present study, bacterial species were isolated from meat samples (beef) from different localities of Lahore, Pakistan. MRS agar medium was used to isolate lactic acid bacteria (LAB) through spread and streak methods (incubated for 72 h at 37 degree C). Identification of bacteriocinogenic LAB strains was done by using staining techniques, morphology based characteristics and biochemical tests. These strains were BSH 1b, BSH 3a, BIP 4a, BIP 3a, BIP 1b and BRR 3a. Antibacterial activity of LAB was performed against food borne pathogens viz., Escherichia coli and Staphylococcus aureus through paper disc diffusion method. Three bacterial strains showed maximum inhibition and characterised by ribotyping viz., BIP 4a was identified as Lactobacillus curvatures, BIP 3a was Staphylococcus warneri and BIP 1b was Lactobacillus graminis . Optimum pH 5-6.5 and 30-37 degree C temperature for isolated bacterial strains was recorded. Protein concentration measured was 0.07 mg/mL for BSH 1b, 0.065 mg/mL for BSH 3a, 0.057 mg/mL for BIP 4a, 0.062 mg/mL for BIP 1b, 0.065 mg/mL for BIP 3a and for BRR 3a 0.078 mg/mL, respectively. Bacteriocin of all isolates except BIP 3a was found to be sensitive towards pepsin and resistant towards Rnase. Bacteriocin production was stable at between pH 5.0 and 6.0 and resistant temperature was 40 degree C. It was concluded that lactic acid bacteria (LAB) from meat can be helpful as antibacterial agents against food-borne bacterial pathogens because of thermostable producing bacteriocin. (author)

The Leaderless Bacteriocin Enterocin K1 Is Highly Potent against Enterococcus faecium: A Study on Structure, Target Spectrum and Receptor.

Science.gov (United States)

Ovchinnikov, Kirill V; Kristiansen, Per Eugen; Straume, Daniel; Jensen, Marianne S; Aleksandrzak-Piekarczyk, Tamara; Nes, Ingolf F; Diep, Dzung B

2017-01-01

Enterocin K1 (EntK1), enterocin EJ97 (EntEJ97), and LsbB are three sequence related leaderless bacteriocins. Yet LsbB kills only lactococci while EntK1 and EntEJ97 target wider spectra with EntK1 being particularly active against Enterococcus faecium , including nosocomial multidrug resistant isolates. NMR study of EntK1 showed that it had a structure very similar to LsbB - both having an amphiphilic N-terminal α-helix and an unstructured C-terminus. The α-helix in EntK1 is, however, about 3-4 residues longer than that of LsbB. Enterococcal mutants highly resistant to EntEJ97 and EntK1 were found to have mutations within rseP , a gene encoding a stress response membrane-bound Zn-dependent protease. Heterologous expression of the enterococcal rseP rendered resistant cells of Streptococcus pneumoniae sensitive to EntK1 and EntEJ97, suggesting that RseP likely serves as the receptor for EntK1 and EntEJ97. It was also shown that the conserved proteolytic active site in E. faecalis RseP is partly required for EntK1 and EntEJ97 activity, since alanine substitutions of its conserved residues (HExxH) reduced the sensitivity of the clones to the bacteriocins. RseP is known to be involved in bacterial stress response. As expected, the growth of resistant mutants with mutations within rseP was severely affected when they were exposed to higher (stressing) growth temperatures, e.g., at 45°C, at which wild type cells still grew well. These findings allow us to design a hurdle strategy with a combination of the bacteriocin(s) and higher temperature that effectively kills bacteriocin sensitive bacteria and prevents the development of resistant cells.

The Leaderless Bacteriocin Enterocin K1 Is Highly Potent against Enterococcus faecium: A Study on Structure, Target Spectrum and Receptor

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Kirill V. Ovchinnikov

2017-05-01

Full Text Available Enterocin K1 (EntK1, enterocin EJ97 (EntEJ97, and LsbB are three sequence related leaderless bacteriocins. Yet LsbB kills only lactococci while EntK1 and EntEJ97 target wider spectra with EntK1 being particularly active against Enterococcus faecium, including nosocomial multidrug resistant isolates. NMR study of EntK1 showed that it had a structure very similar to LsbB – both having an amphiphilic N-terminal α-helix and an unstructured C-terminus. The α-helix in EntK1 is, however, about 3–4 residues longer than that of LsbB. Enterococcal mutants highly resistant to EntEJ97 and EntK1 were found to have mutations within rseP, a gene encoding a stress response membrane-bound Zn-dependent protease. Heterologous expression of the enterococcal rseP rendered resistant cells of Streptococcus pneumoniae sensitive to EntK1 and EntEJ97, suggesting that RseP likely serves as the receptor for EntK1 and EntEJ97. It was also shown that the conserved proteolytic active site in E. faecalis RseP is partly required for EntK1 and EntEJ97 activity, since alanine substitutions of its conserved residues (HExxH reduced the sensitivity of the clones to the bacteriocins. RseP is known to be involved in bacterial stress response. As expected, the growth of resistant mutants with mutations within rseP was severely affected when they were exposed to higher (stressing growth temperatures, e.g., at 45°C, at which wild type cells still grew well. These findings allow us to design a hurdle strategy with a combination of the bacteriocin(s and higher temperature that effectively kills bacteriocin sensitive bacteria and prevents the development of resistant cells.

Application of anti-listerial bacteriocins: monitoring enterocin expression by multiplex relative reverse transcription-PCR.

Science.gov (United States)

Williams, D Ross; Chanos, Panagiotis

2012-12-01

Listeriosis is a deadly food-borne disease, and its incidence may be limited through the biotechnological exploitation of a number of anti-listerial biocontrol agents. The most widely used of these agents are bacteriocins and the Class II enterocins are characterized by their activity against Listeria. Enterocins are primarily produced by enterococci, particularly Enterococcus faecium and many strains have been described, often encoding multiple bacteriocins. The use of these strains in food will require that they are free of virulence functions and that they exhibit a high level expression of anti-listerial enterocins in fermentation conditions. Multiplex relative RT (reverse transcription)-PCR is a technique that is useful in the discovery of advantageous expression characteristics among enterocin-producing strains. It allows the levels of individual enterocin gene expression to be monitored and determination of how expression is altered under different growth conditions.

Assessment of hemolytic activity, enzyme production and bacteriocin characterization of Bacillus subtilis LR1 isolated from the gastrointestinal tract of fish.

Science.gov (United States)

Banerjee, Goutam; Nandi, Ankita; Ray, Arun Kumar

2017-01-01

In the present investigation, probiotic potential (antagonistic activity, enzyme production, hemolytic activity, biosafety, antibiotic sensitivity and bile tolerance level) of Bacillus subtilis LR1 was evaluated. Bacteriocin produced by the bacterial strain B. subtilis LR1 isolated from the gastrointestinal tract of Labeo rohita was purified and characterized. The molecular weight of the purified bacteriocin was ~50 kDa in 12 % Native PAGE and showed inhibitory activity against four fish pathogens such as Bacillus mycoides, Aeromonas salmonicida, Pseudomonas fluorescens and Aeromonas hydrophila. The purified bacteriocin was maximally active at temperature 40 °C and pH 7.0, while none of the tested surfactants affect the bacteriocin activity. Extracellular enzyme activity of the selected bacterial strain was also evaluated. Amylase activity was estimated to be highest (38.23 ± 1.15 µg of maltose liberated mg -1  protein ml -1 of culture filtrate) followed by cellulase and protease activity. The selected bacterium was sensitive to most of the antibiotics used in this experiment, can tolerate 0.25 % bile salt and non-hemolytic in nature. Finally, the efficiency of the proposed probiotic candidate was evaluated in in vivo condition. It was detected that the bacterial strain can effectively reduce bacterial pathogenicity in Indian major carps.

Monitoring of multiple bacteriocins through a developed dual extraction protocol and comparison of HPLC-DAD with turbidometry as their quantification system.

Science.gov (United States)

Katharopoulos, Efstathios; Touloupi, Katerina; Touraki, Maria

2016-08-01

The present study describes the development of a simple and efficient screening system that allows identification and quantification of nine bacteriocins produced by Lactococcus lactis. Cell-free L. lactis extracts presented a broad spectrum of antibacterial activity, including Gram-negative bacteria, Gram-positive bacteria, and fungi. The characterization of their sensitivity to pH, and heat, showed that the extracts retained their antibacterial activity at extreme pH values and in a wide temperature range. The loss of antibacterial activity following treatment of the extracts with lipase or protease suggests a lipoproteinaceous nature of the produced antimicrobials. The extracts were subjected to a purification protocol that employs a two phase extraction using ammonium sulfate precipitation and organic solvent precipitation, followed by ion exchange chromatography, solid phase extraction and HPLC. In the nine fractions that presented antimicrobial activity, bacteriocins were quantified by the turbidometric method using a standard curve of nisin and by the HPLC method with nisin as the external standard, with both methods producing comparable results. Turbidometry appears to be unique in the qualitative determination of bacteriocins but the only method suitable to both separate and quantify the bacteriocins providing increased sensitivity, accuracy, and precision is HPLC. Copyright © 2016 Elsevier B.V. All rights reserved.

Purification and characterization of Plantaricin ZJ5, a new bacteriocin produced by Lactobacillus plantarum ZJ5.

Science.gov (United States)

Song, Da-Feng; Zhu, Mu-Yuan; Gu, Qing

2014-01-01

The aim of this study is to investigate the antimicrobial potential of Lactobacillus plantarum ZJ5, a strain isolated from fermented mustard with a broad range of inhibitory activity against both Gram-positive and Gram-negative bacteria. Here we present the peptide plantaricin ZJ5 (PZJ5), which is an extreme pH and heat-stable. However, it can be digested by pepsin and proteinase K. This peptide has strong activity against Staphylococcus aureus. PZJ5 has been purified using a multi-step process, including ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic interactions and reverse-phase chromatography. The molecular mass of the peptide was found to be 2572.9 Da using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The primary structure of this peptide was determined using amino acid sequencing and DNA sequencing, and these analyses revealed that the DNA sequence translated as a 44-residue precursor containing a 22-amino-acid N-terminal extension that was of the double-glycine type. The bacteriocin sequence exhibited no homology with known bacteriocins when compared with those available in the database, indicating that it was a new class IId bacteriocin. PZJ5 from a food-borne strain may be useful as a promising probiotic candidate.

Purification and characterization of Plantaricin ZJ5, a new bacteriocin produced by Lactobacillus plantarum ZJ5.

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Da-Feng Song

Full Text Available The aim of this study is to investigate the antimicrobial potential of Lactobacillus plantarum ZJ5, a strain isolated from fermented mustard with a broad range of inhibitory activity against both Gram-positive and Gram-negative bacteria. Here we present the peptide plantaricin ZJ5 (PZJ5, which is an extreme pH and heat-stable. However, it can be digested by pepsin and proteinase K. This peptide has strong activity against Staphylococcus aureus. PZJ5 has been purified using a multi-step process, including ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic interactions and reverse-phase chromatography. The molecular mass of the peptide was found to be 2572.9 Da using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS. The primary structure of this peptide was determined using amino acid sequencing and DNA sequencing, and these analyses revealed that the DNA sequence translated as a 44-residue precursor containing a 22-amino-acid N-terminal extension that was of the double-glycine type. The bacteriocin sequence exhibited no homology with known bacteriocins when compared with those available in the database, indicating that it was a new class IId bacteriocin. PZJ5 from a food-borne strain may be useful as a promising probiotic candidate.

In vitro evaluation of bacteriocin-like inhibitory substances produced by lactic acid bacteria isolated during traditional Sicilian cheese making

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Giusi Macaluso

2016-02-01

Full Text Available Bacteriocins are antimicrobial proteins produced by bacteria that inhibit the growth of other bacteria with a bactericidal or bacteriostatic mode of action. Many lactic acid bacteria (LAB produce a high diversity of different bacteriocins. Bacteriocinogenic LAB are generally recognised as safe (GRAS and useful to control the frequent development of pathogens and spoilage microorganisms. For this reason they are commonly used as starter cultures in food fermentations. In this study, the authors describe the results of a screening on 699 LAB isolated from wooden vat surfaces, raw milk and traditional Sicilian cheeses, for the production of bacteriocin-like inhibitory substances, by comparing two alternative methods. The antagonistic activity of LAB and its proteinaceous nature were evaluated using the spot-on-the-lawn and the well-diffusion assay (WDA and the sensitivity to proteolytic (proteinase K, protease B and trypsin, amylolytic (α-amylase and lipolytic (lipase enzymes. The indicator strains used were: Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Salmonella enteritidis. A total of 223 strains (belonging to the species Enterococcus spp., Lactobacillus spp., Pediococcus spp., Streptococcus spp., Leuconostoc spp. and Lactococcus lactis were found to inhibit the growth of Listeria monocytogenes by using the spot-on-the-lawn method; only 37 of these were confirmed by using the WDA. The direct addition of bacteriocin-producing cultures into dairy products can be a more practical and economic option for the improvement of the safety and quality of the final product.

Bacteriocin-like inhibitory activities of seven Lactobacillus delbrueckii subsp. bulgaricus strains against antibiotic susceptible and resistant Helicobacter pylori strains.

Science.gov (United States)

Boyanova, L; Gergova, G; Markovska, R; Yordanov, D; Mitov, I

2017-12-01

The aim of the study was to detect anti-Helicobacter pylori activity of seven Lactobacillus delbrueckii subsp. bulgaricus (GLB) strains by four cell-free supernatant (CFS) types. Activity of non-neutralized and non-heat-treated (CFSs1), non-neutralized and heat-treated (CFSs2), pH neutralized, catalase-treated and non-heat-treated (CFSs3), or neutralized, catalase- and heat-treated (CFSs4) CFSs against 18 H. pylori strains (11 of which with antibiotic resistance) was evaluated. All GLB strains produced bacteriocin-like inhibitory substances (BLISs), the neutralized CFSs of two GLB strains inhibited >81% of test strains and those of four GLB strains were active against >71% of antibiotic resistant strains. Two H. pylori strains were BLIS resistant. The heating did not reduce the CFS activity. Briefly, all GLB strains evaluated produced heat-stable BLISs, although GLB and H. pylori strain susceptibility patterns exhibited differences. Bacteriocin-like inhibitory substance activity can be an advantage for the probiotic choice for H. pylori infection control. In this study, anti-Helicobacter pylori activity of seven Lactobacillus delbrueckii subsp. bulgaricus (GLB) strains was evaluated by four cell-free supernatant (CFS) types. The GLB strains produced heat-stable bacteriocin-like inhibitory substances (BLISs) with a strong anti-H. pylori activity and some neutralized, catalase- and heat-treated CFSs inhibited >83% of the test strains. Bacteriocin-like inhibitory substance production of GLB strains can render them valuable probiotics in the control of H. pylori infection. © 2017 The Society for Applied Microbiology.

Release of Bacteriocins from Nanofibers Prepared with Combinations of Poly(D,L-lactide (PDLLA and Poly(Ethylene Oxide (PEO

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Leon Dicks

2011-03-01

Full Text Available Plantaricin 423, produced by Lactobacillus plantarum, and bacteriocin ST4SA produced by Enterococcus mundtii, were electrospun into nanofibers prepared from different combinations of poly(D,L-lactide (PDLLA and poly(ethylene oxide (PEO dissolved in N,N-dimethylformamide (DMF. Both peptides were released from the nanofibers with a high initial burst and retained 88% of their original antimicrobial activity at 37 °C. Nanofibers have the potential to serve as carrier matrix for bacteriocins and open a new field in developing controlled antimicrobial delivery systems for various applications.

Bacteriocins - exploring alternatives to antibiotics in mastitis treatment.

Science.gov (United States)

Pieterse, Reneé; Todorov, Svetoslav D

2010-07-01

Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. In this review we have focus on the pathogenesis of the mastitis in dairy cows, existing antibiotic treatments and possible alternative for application of bacteriocins from lactic acid bacteria in the treatment and prevention of this disease.

PRESERVATIVE POTENTIAL OF PURIFIED BACTERIOCIN PRODUCED FROM BREVIBACILLUS BORSTELENSIS AG1 ISOLATED FROM MARCHA – A TRADITIONAL WINE STARTER CULTURE CAKE IN TOMATO PASTE

Directory of Open Access Journals (Sweden)

Anupama Gupta

2015-04-01

Full Text Available Purified bacteriocin produced from Brevibacillus borstelensis AG1 isolated from Marcha a local wine starter herbal cake, was used to enhance the shelf life of tomato paste. Preservative effect of purified bacteriocin was studied for nine days in tomato paste inoculated with food borne pathogens and was compared to commercial biopreservative – nisin and chemical preservative – sodium benzoate. The indicator strains i.e. Listeria monocytogenes MTCC839, Bacillus subtilis CRI and Clostridium perfringens MTCC1739 were used at the amount 8.16, 8.13 and 8.18 log CFU/ml. Viable cells were counted periodically and a consistent reduction in number of viable cells of each tested pathogen was observed. It was found antagonistic against L. monocytogenes MTCC839, B. subtilis CRI and C. perfringes MTCC1739 which are the most challengeable and food borne pathogens found in processed vegetables products. Purified bacteriocin was found active over a wide pH range i.e. 3.0 to 11.0 and was able to withstand temperature up to 100oC. It showed a better preservative potential by reducing pathogenic load of the tested strains (by 2.02, 2.05 and 2.02 log cycles (CFU/ml of L. monocytogenes MTCC839, B. subtilis CRI and C. perfringes MTCC1739, respectively in tomato paste as compared to control (without bacteriocin. This proves efficiency of bacteriocin produced by B. borstelensis AG1 as biopreservative to enhance the safety and shelf life of acidic foods.

Identification of the Propionicin F Bacteriocin Immunity Gene (pcfI) and Development of a Food-Grade Cloning System for Propionibacterium freudenreichii▿ †

Science.gov (United States)

Brede, Dag Anders; Lothe, Sheba; Salehian, Zhian; Faye, Therese; Nes, Ingolf F.

2007-01-01

This report describes the first functional analysis of a bacteriocin immunity gene from Propionibacterium freudenreichii and its use as a selection marker for food-grade cloning. Cloning of the pcfI gene (previously orf5 [located as part of the pcfABC propionicin F operon]) rendered the sensitive host 1,000-fold more tolerant to the propionicin F bacteriocin. The physiochemical properties of the 127-residue large PcfI protein resemble those of membrane-bound immunity proteins from bacteriocin systems found in lactic acid bacteria. The high level of immunity conferred by pcfI allowed its use as a selection marker for plasmid transformation in P. freudenreichii. Electroporation of P. freudenreichii IFO12426 by use of the pcfI expression plasmid pSL102 and propionicin F selection (200 bacteriocin units/ml) yielded 107 transformants/μg DNA. The 2.7-kb P. freudenreichii food-grade cloning vector pSL104 consists of the pLME108 replicon, a multiple cloning site, and pcfI expressed from the constitutive PpampS promoter for selection. The pSL104 vector efficiently facilitated cloning of the propionicin T1 bacteriocin in P. freudenreichii. High-level propionicin T1 production (640 BU/ml) was obtained with the IFO12426 strain, and the food-grade propionicin T1 expression plasmid pSL106 was maintained by ∼91% of the cells over 25 generations in the absence of selection. To the best of our knowledge this is the first report of an efficient cloning system that facilitates the generation of food-grade recombinant P. freudenreichii strains. PMID:17933941

Mechanism of protection of transepithelial barrier function by Lactobacillus salivarius: strain dependence and attenuation by bacteriocin production.

Science.gov (United States)

Miyauchi, Eiji; O'Callaghan, John; Buttó, Ludovica F; Hurley, Gráinne; Melgar, Silvia; Tanabe, Soichi; Shanahan, Fergus; Nally, Kenneth; O'Toole, Paul W

2012-11-01

Enhanced barrier function is one mechanism whereby commensals and probiotic bacteria limit translocation of foreign antigens or pathogens in the gut. However, barrier protection is not exhibited by all probiotic or commensals and the strain-specific molecules involved remain to be clarified. We evaluated the effects of 33 individual Lactobacillus salivarius strains on the hydrogen peroxide (H(2)O(2))-induced barrier impairment in human epithelial Caco-2 cells. These strains showed markedly different effects on H(2)O(2)-induced reduction in transepithelial resistance (TER). The effective strains such as UCC118 and CCUG38008 attenuated H(2)O(2)-induced disassembly and relocalization of tight junction proteins, but the ineffective strain AH43324 did not. Strains UCC118 and CCUG38008 induced phosphorylation of extracellular signal-regulated kinase (ERK) in Caco-2 cells, and the ERK inhibitor U0126 attenuated the barrier-protecting effect of these strains. In contrast, the AH43324 strain induced phosphorylation of Akt and p38, which was associated with an absence of a protective effect. Global transcriptome analysis of UCC118 and AH43324 revealed that some genes in a bacteriocin gene cluster were upregulated in AH43324 under TER assay conditions. A bacteriocin-negative UCC118 mutant displayed significantly greater suppressive effect on H(2)O(2)-induced reduction in TER compared with wild-type UCC118. The wild-type strain augmented H(2)O(2)-induced phosphorylation of Akt and p38, whereas a bacteriocin-negative UCC118 mutant did not. These observations indicate that L. salivarius strains are widely divergent in their capacity for barrier protection, and this is underpinned by differences in the activation of intracellular signaling pathways. Furthermore, bacteriocin production appears to have an attenuating influence on lactobacillus-mediated barrier protection.

Toxicity of bovicin HC5 against mammalian cell lines and the role of cholesterol in bacteriocin activity.

Science.gov (United States)

Paiva, Aline Dias; de Oliveira, Michelle Dias; de Paula, Sérgio Oliveira; Baracat-Pereira, Maria Cristina; Breukink, Eefjan; Mantovani, Hilário Cuquetto

2012-11-01

Bacteriocins are ribosomally synthesized antimicrobial peptides produced by Bacteria and some Archaea. The assessment of the toxic potential of antimicrobial peptides is important in order to apply these peptides on an industrial scale. The aim of the present study was to investigate the in vitro cytotoxic and haemolytic potential of bovicin HC5, as well as to determine whether cholesterol influences bacteriocin activity on model membranes. Nisin, for which the mechanism of action is well described, was used as a reference peptide in our assays. The viability of three distinct eukaryotic cell lines treated with bovicin HC5 or nisin was analysed by using the MTT assay and cellular morphological changes were determined by light microscopy. The haemolytic potential was evaluated by using the haemoglobin liberation assay and the role of cholesterol on bacteriocin activity was examined by using model membranes composed of DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) and DPoPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine). The IC(50) of bovicin HC5 and nisin against Vero cells was 65.42 and 13.48 µM, respectively. When the MTT assay was performed with MCF-7 and HepG2 cells, the IC(50) obtained for bovicin HC5 was 279.39 and 289.30 µM, respectively, while for nisin these values were 105.46 and 112.25 µM. The haemolytic activity of bovicin HC5 against eukaryotic cells was always lower than that determined for nisin. The presence of cholesterol did not influence the activity of either bacteriocin on DOPC model membranes, but nisin showed reduced carboxyfluorescein leakage in DPoPC membranes containing cholesterol. In conclusion, bovicin HC5 only exerted cytotoxic effects at concentrations that were greater than the concentration needed for its biological activity, and the presence of cholesterol did not affect its interaction with model membranes.

Circular Coinduction

Science.gov (United States)

Rosu, Grigore; Goguen, Joseph; Norvig, Peter (Technical Monitor)

2001-01-01

Circular coinduction is a technique for behavioral reasoning that extends cobasis coinduction to specifications with circularities. Because behavioral satisfaction is not recursively enumerable, no algorithm can work for every behavioral statement. However. algorithms using circular coinduction can prove every practical behavioral result that we know. This paper proves the correctness of circular coinduction and some consequences.

Potential of bacteriocin-producing lactic acid bacteria for safety improvements of traditional Thai fermented meat and human health.

Science.gov (United States)

Swetwiwathana, Adisorn; Visessanguan, Wonnop

2015-11-01

Lactic acid bacteria (LAB) are very important in converting of agricultural products into safe, delicious and shelf stable foods for human consumption. The preservative activity of LAB in foods is mainly attributed to the production of anti-microbial metabolites such as organic acids and bacteriocins which enables them to grow and control the growth of pathogens and spoilage microorganisms. Besides ensuring safety, bacteriocin-producing LAB with their probiotic potentials could also be emerging as a means to develop functional meat products with desirable health benefits. Nevertheless, to be qualified as a candidate probiotic culture, other prerequisite probiotic properties of bacteriocin-producing LAB have to be assessed according to regulatory guidelines for probiotics. Nham is an indigenous fermented sausage of Thailand that has gained popularity and acceptance among Thais. Since Nham is made from raw meat and is usually consumed without cooking, risks due to undesirable microorganisms such as Salmonella spp., Staphylococcus aureus, and Listeria monocytogenes, are frequently observed. With an ultimate goal to produce safer and healthier product, our research attempts on the development of a variety of new Nham products are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of a noncytotoxic bacteriocin from probiotic Lactobacillus plantarum DM5 with potential as a food preservative.

Science.gov (United States)

Das, Deeplina; Goyal, Arun

2014-10-01

The aim of this work was to purify and characterize the bacteriocin produced by probiotic Lactobacillus plantarum DM5 in order to evaluate its potential as nutraceuticals. Lb. plantarum DM5 exhibited in vitro probiotic properties such as high resistance to gastric juice and bile salt, adherence to human adenocarcinoma (HT-29) cells, bile salt hydrolase and cholesterol assimilation activity. Moreover, Lb. plantarum DM5 showed bacteriocin activity against several major food borne pathogens. Zymogram analysis of purified bacteriocin (plantaricin DM5) showed a molecular size of ∼15.2 kDa. Plantaricin DM5 was sensitive to proteolytic enzymes but stable in the pH range of 2.0-10.0, and it was heat resistant (121 °C for 15 min) and remained active upon treatment with surfactants and detergents. Cytotoxicity analysis of plantaricin DM5 on human embryonic kidney 293 (HEK 293) and human cervical cancer (HeLa) cell lines revealed its nontoxic and biocompatible nature. To the best of our knowledge, this is the first study on the isolated strain expressing probiotic properties and broad antimicrobial activity without any cytotoxic effect on mammalian cells from indigenous fermented beverage Marcha from India, and thus contributes to the food industry as a novel bio-preservant.

Bacteriocins from lactic acid bacteria: purification, properties and use as biopreservatives

OpenAIRE

Parada,José Luis; Caron,Carolina Ricoy; Medeiros,Adriane Bianchi P.; Soccol,Carlos Ricardo

2007-01-01

Biopreservation systems in foods are of increasing interest for industry and consumers. Bacteriocinogenic lactic acid bacteria and/or their isolated bacteriocins are considered safe additives (GRAS), useful to control the frequent development of pathogens and spoiling microorganisms in foods and feed. The spreading of bacterial antibiotic resistance and the demand for products with fewer chemicals create the necessity of exploring new alternatives, in order to reduce the abusive use of therap...

Complete genome sequence of Lactobacillus plantarum LZ95, a potential probiotic strain producing bacteriocins and B-group vitamin riboflavin.

Science.gov (United States)

Li, Ping; Gu, Qing

2016-07-10

Lactobacillus plantarum LZ95 is a potential probiotic isolated from newborn infant fecal and it is identified to produce riboflavin with great antimicrobial activity. The complete genome sequence of this strain was reported in the present study. The genome contains a 3,261,418-bp chromosome and two plasmids. Genes, related to the biosynthesis of bacteriocins and riboflavin, were identified. This work will facilitate to reveal the biosynthetic mechanism of bacteriocins and B-group vitamins in lactic acid bacteria and provide evidence for its potential application in food industry. Copyright © 2016 Elsevier B.V. All rights reserved.

From Ownership to Access: How the Sharing Economy is Changing the Consumer Behavior

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Cătălin Mihail Barbu

2018-05-01

Full Text Available Promoting the principles of circular economy and the new business models advocated by the circular economy can represent a solution for a more prosperous society, less dependent on primary and energy resources and more environmentally friendly. The sharing economy, which primarily involves the transformation of traditional market behaviors into collaborative consumption models, that ensure a more efficient and sustainable use of resources, is part of the circular economy and has generated business models that are compatible with it. This article discusses the possibility for the sharing economy to bring about profound changes in consumer behavior towards products and services and to highlight the factors that drive consumers’ shift towards the sharing economy. For this purpose we developed and tested a model in which the change in consumer mindset has as the main direct determinants the satisfaction with the services of the sharing economy and the intention to access such products and services. The study uses data collected through a questionnaire, applied to a sample of 320 customers of Uber – a symbol of the sharing economy, and processed using structural equation modelling. Research results show that there are premises for switching to an access-based consumption model

Bacteriocins: exploring alternatives to antibiotics in mastitis treatment

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Reneé Pieterse

2010-10-01

Full Text Available Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. In this review we have focus on the pathogenesis of the mastitis in dairy cows, existing antibiotic treatments and possible alternative for application of bacteriocins from lactic acid bacteria in the treatment and prevention of this disease.

Injection and extraction techniques in circular accelerators

International Nuclear Information System (INIS)

Tang Jingyu

2008-01-01

Injection and extraction are usually the key systems in circular accelerators. They play important roles in transferring the beam from one stage acceleration to the other or to experimental stations. It is also in the injection and extraction regions where beam losses happen mostly. Due to the tight space and to reduce the perturbation to the circulating orbit, the devices are usually designed to meet special requirements such as compactness, small stray field, fast rise time or fall time, etc. Usual injection and extraction devices include septum magnets, kicker magnets, electrostatic deflectors, slow bump magnets and strippers. In spite of different accelerators and specification for the injection and extraction devices, many techniques are shared in the design and manufacturing. This paper gives a general review on the techniques employed in the major circular accelerators in China. (authors)

Expression of Genes Involved in Bacteriocin Production and Self-Resistance in Lactobacillus brevis 174A Is Mediated by Two Regulatory Proteins.

Science.gov (United States)

Noda, Masafumi; Miyauchi, Rumi; Danshiitsoodol, Narandalai; Matoba, Yasuyuki; Kumagai, Takanori; Sugiyama, Masanori

2018-04-01

We have previously shown that the lactic acid bacterium Lactobacillus brevis 174A, isolated from Citrus iyo fruit, produces a bacteriocin designated brevicin 174A, which is comprised of two antibacterial polypeptides (designated brevicins 174A-β and 174A-γ). We have also found a gene cluster, composed of eight open reading frames (ORFs), that contains genes for the biosynthesis of brevicin 174A, self-resistance to its own bacteriocin, and two transcriptional regulatory proteins. Some lactic acid bacterial strains have a system to start the production of bacteriocin at an adequate stage of growth. Generally, the system consists of a membrane-bound histidine protein kinase (HPK) that senses a specific environmental stimulus and a corresponding response regulator (RR) that mediates the cellular response. We have previously shown that although the HPK- and RR-encoding genes are not found on the brevicin 174A biosynthetic gene cluster in the 174A strain, two putative regulatory genes, designated breD and breG , are in the gene cluster. In the present study, we demonstrate that the expression of brevicin 174A production and self-resistance is positively controlled by two transcriptional regulatory proteins, designated BreD and BreG. BreD is expressed together with BreE as the self-resistance determinant of L. brevis 174A. DNase I footprinting analysis and a promoter assay demonstrated that BreD binds to the breED promoter as a positive autoregulator. The present study also demonstrates that BreG, carrying a transmembrane domain, binds to the common promoter of breB and breC , encoding brevicins 174A-β and 174A-γ, respectively, for positive regulation. IMPORTANCE The problem of the appearance of bacteria that are resistant to practical antibiotics and the increasing demand for safe foods have increased interest in replacing conventional antibiotics with bacteriocin produced by the lactic acid bacteria. This antibacterial substance can inhibit the growth of pathogenic

In silico Prediction, in vitro Antibacterial Spectrum, and Physicochemical Properties of a Putative Bacteriocin Produced by Lactobacillus rhamnosus Strain L156.4

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Letícia de C. Oliveira

2017-05-01

Full Text Available A bacteriocinogenic Lactobacillus rhamnosus L156.4 strain isolated from the feces of NIH mice was identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. The entire genome was sequenced using Illumina, annotated in the PGAAP, and RAST servers, and deposited. Conserved genes associated with bacteriocin synthesis were predicted using BAGEL3, leading to the identification of an open reading frame (ORF that shows homology with the L. rhamnosus GG (ATCC 53103 prebacteriocin gene. The encoded protein contains a conserved protein motif associated a structural gene of the Enterocin A superfamily. We found ORFs related to the prebacteriocin, immunity protein, ABC transporter proteins, and regulatory genes with 100% identity to those of L. rhamnosus HN001. In this study, we provide evidence of a putative bacteriocin produced by L. rhamnosus L156.4 that was further confirmed by in vitro assays. The antibacterial activity of the substances produced by this strain was evaluated using the deferred agar-spot and spot-on-the lawn assays, and a wide antimicrobial activity spectrum against human and foodborne pathogens was observed. The physicochemical characterization of the putative bacteriocin indicated that it was sensitive to proteolytic enzymes, heat stable and maintained its antibacterial activity in a pH ranging from 3 to 9. The activity against Lactobacillus fermentum, which was used as an indicator strain, was detected during bacterial logarithmic growth phase, and a positive correlation was confirmed between bacterial growth and production of the putative bacteriocin. After a partial purification from cell-free supernatant by salt precipitation, the putative bacteriocin migrated as a diffuse band of approximately 1.0–3.0 kDa by SDS-PAGE. Additional studies are being conducted to explore its use in the food industry for controlling bacterial growth and for probiotic applications.

In silico Prediction, in vitro Antibacterial Spectrum, and Physicochemical Properties of a Putative Bacteriocin Produced by Lactobacillus rhamnosus Strain L156.4

Science.gov (United States)

Oliveira, Letícia de C.; Silveira, Aline M. M.; Monteiro, Andréa de S.; dos Santos, Vera L.; Nicoli, Jacques R.; Azevedo, Vasco A. de C.; Soares, Siomar de C.; Dias-Souza, Marcus V.; Nardi, Regina M. D.

2017-01-01

A bacteriocinogenic Lactobacillus rhamnosus L156.4 strain isolated from the feces of NIH mice was identified by 16S rRNA gene sequencing and MALDI-TOF mass spectrometry. The entire genome was sequenced using Illumina, annotated in the PGAAP, and RAST servers, and deposited. Conserved genes associated with bacteriocin synthesis were predicted using BAGEL3, leading to the identification of an open reading frame (ORF) that shows homology with the L. rhamnosus GG (ATCC 53103) prebacteriocin gene. The encoded protein contains a conserved protein motif associated a structural gene of the Enterocin A superfamily. We found ORFs related to the prebacteriocin, immunity protein, ABC transporter proteins, and regulatory genes with 100% identity to those of L. rhamnosus HN001. In this study, we provide evidence of a putative bacteriocin produced by L. rhamnosus L156.4 that was further confirmed by in vitro assays. The antibacterial activity of the substances produced by this strain was evaluated using the deferred agar-spot and spot-on-the lawn assays, and a wide antimicrobial activity spectrum against human and foodborne pathogens was observed. The physicochemical characterization of the putative bacteriocin indicated that it was sensitive to proteolytic enzymes, heat stable and maintained its antibacterial activity in a pH ranging from 3 to 9. The activity against Lactobacillus fermentum, which was used as an indicator strain, was detected during bacterial logarithmic growth phase, and a positive correlation was confirmed between bacterial growth and production of the putative bacteriocin. After a partial purification from cell-free supernatant by salt precipitation, the putative bacteriocin migrated as a diffuse band of approximately 1.0–3.0 kDa by SDS-PAGE. Additional studies are being conducted to explore its use in the food industry for controlling bacterial growth and for probiotic applications. PMID:28579977

Circular Solutions

NARCIS (Netherlands)

Annevelink, E.; Bos, H.L.; Meesters, K.P.H.; Oever, van den M.J.A.; Haas, de W.; Kuikman, P.J.; Rietra, R.P.J.J.; Sikirica, N.

2016-01-01

The fifth part of this report on Circular Solutions is about the circular principle From Waste to Resource. The purpose of this study is to select promising options for the implementation of this circular principle and to elaborate these options further.

Effects of curing sodium nitrite additive and natural meat fat on growth control of Listeria monocytogenes by the bacteriocin-producing Lactobacillus curvatus strain CWBI-B28.

Science.gov (United States)

Kouakou, P; Ghalfi, H; Destain, J; Dubois-Dauphin, R; Evrard, P; Thonart, P

2009-09-01

In realistic model meat systems, the separate and combined effects of fat content and sodium nitrite on the antilisterial activity of the bacteriocin of Lactobacillus curvatus CWBI-B28 were studied. In laboratory fermentations where Listeria monocytogenes was co-cultured at 4 degrees C with bacteriocin-producing CWBI-B28 in lean pork meat (fat content: 13%) without added nitrite, a strong antilisterial effect was observed after one week. The effect was maintained for an additional week, after which a slight and very gradual rebound was observed. Both added nitrite (20 ppm) and a high-fat content (43%) were found to antagonise this antilisterial effect, the Listeria cfu count reached after six weeks being 200 times as high in high-fat meat with added nitrite than in lean meat without nitrite. This antagonism could not be attributed to slower growth of the bacteriocin-producing strain, since CWBI-B28 grew optimally in fat-rich meat with 20 ppm sodium nitrite. Bacteriocin activity was also measured in the samples. The observed activity levels are discussed in relation to the degree of antilisterial protection conferred.

Sonorensin: an antimicrobial peptide, belonging to the heterocycloanthracin subfamily of bacteriocins, from a new marine isolate, Bacillus sonorensis MT93.

Science.gov (United States)

Chopra, Lipsy; Singh, Gurdeep; Choudhary, Vikas; Sahoo, Debendra K

2014-05-01

Marine environments are the greatest fronts of biodiversity, representing a resource of unexploited or unknown microorganisms and new substances having potential applications. Among microbial products, antimicrobial peptides (AMPs) have received great attention recently due to their applications as food preservatives and therapeutic agents. A new marine soil isolate producing an AMP was identified as Bacillus sonorensis based on 16S rRNA gene sequence analysis. It produced an AMP that showed a broad spectrum of activity against both Gram-positive and Gram-negative bacteria. The peptide, named sonorensin, was purified to homogeneity using a combination of chromatographic techniques. The intact molecular mass of the purified peptide, 6,274 Da, as revealed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), was in agreement with Tricine-SDS-PAGE analysis. A PCR array of primers was used to identify AMP structural genes, which allowed the successful amplification of the related genes from strain MT93. The putative open reading frame of sonorensin was amplified, cloned into the pET-32a(+) vector, expressed as a thioredoxin (Trx) fusion protein in Escherichia coli, and then purified. Sequence alignment analysis revealed that the bacteriocin being reported could belong to new subfamily of bacteriocins, heterocycloanthracin. The peptide indicated its potential as a biocontrol agent or food antimicrobial agent, due to its antimicrobial activity against bacteria such as Listeria monocytogenes and Staphylococcus aureus. This is the first report of the production, purification, and characterization of wild-type and recombinant bacteriocin by B. sonorensis and the first bacteriocin of the heterocycloanthracin subfamily to be characterized.

Enterocin F4-9, a Novel O-Linked Glycosylated Bacteriocin

OpenAIRE

Maky, Mohamed Abdelfattah; Ishibashi, Naoki; Zendo, Takeshi; Perez, Rodney Honrada; Doud, Jehan Ragab; Karmi, Mohamed; Sonomoto, Kenji

2015-01-01

Enterococcus faecalis F4-9 isolated from Egyptian salted-fermented fish produces a novel bacteriocin, termed enterocin F4-9. Enterocin F4-9 was purified from the culture supernatant by three steps, and its molecular mass was determined to be 5,516.6 Da by mass spectrometry. Amino acid and DNA sequencing showed that the propeptide consists of 67 amino acid residues, with a leader peptide containing a double glycine cleavage site to produce a 47-amino-acid mature peptide. Enterocin F4-9 is modi...

Inhibition of Listeria monocytogenes on Ready-to-Eat Meats Using Bacteriocin Mixtures Based on Mode-of-Action

Directory of Open Access Journals (Sweden)

Paul Priyesh Vijayakumar

2017-03-01

Full Text Available Bacteriocin-producing (Bac+ lactic acid bacteria (LAB comprising selected strains of Lactobacillus curvatus, Lactococcus lactis, Pediococcus acidilactici, and Enterococcus faecium and thailandicus were examined for inhibition of Listeria monocytogenes during hotdog challenge studies. The Bac+ strains, or their cell-free supernatants (CFS, were grouped according to mode-of-action (MOA as determined from prior studies. Making a mixture of as many MOAs as possible is a practical way to obtain a potent natural antimicrobial mixture to address L. monocytogenes contamination of RTE meat products (i.e., hotdogs. The heat resistance of the bacteriocins allowed the use of pasteurization to eliminate residual producer cells for use as post-process surface application or their inclusion into hotdog meat emulsion during cooking. The use of Bac+ LAB comprising 3× MOAs directly as co-inoculants on hotdogs was not effective at inhibiting L. monocytogenes. However, the use of multiple MOA Bac+ CFS mixtures in a variety of trials demonstrated the effectiveness of this approach by showing a >2-log decrease of L. monocytogenes in treatment samples and 6–7 log difference vs. controls. These data suggest that surface application of multiple mode-of-action bacteriocin mixtures can provide for an Alternative 2, and possibly Alternative 1, process category as specified by USDA-FSIS for control of L. monocytogenes on RTE meat products.

Operational circular No. 1 (Rev. 1) – Operational circulars

CERN Multimedia

HR Department

2011-01-01

Operational Circular No. 1 (Rev. 1) is applicable to members of the personnel and other persons concerned. Operational Circular No. 1 (Rev. 1) entitled "Operational circulars", approved following discussion at the Standing Concertation Committee meeting on 4 May 2011, is available on the intranet site of the Human Resources Department: https://hr-docs.web.cern.ch/hr-docs/opcirc/opcirc.asp It cancels and replaces Operational Circular No. 1 entitled "Operational Circulars” of December 1996. This new version clarifies, in particular, that operational circulars do not necessarily arise from the Staff Rules and Regulations, and the functional titles have been updated to bring them into line with the current CERN organigram. Department Head Office  

Enterocin X, a novel two-peptide bacteriocin from Enterococcus faecium KU-B5, has an antibacterial spectrum entirely different from those of its component peptides.

Science.gov (United States)

Hu, Chih-Bo; Malaphan, Wanna; Zendo, Takeshi; Nakayama, Jiro; Sonomoto, Kenji

2010-07-01

Enterocin X, composed of two antibacterial peptides (Xalpha and Xbeta), is a novel class IIb bacteriocin from Enterococcus faecium KU-B5. When combined, Xalpha and Xbeta display variably enhanced or reduced antibacterial activity toward a panel of indicators compared to each peptide individually. In E. faecium strains that produce enterocins A and B, such as KU-B5, only one additional bacteriocin had previously been known.

Purification and characterization of enterocin 62-6, a two-peptide bacteriocin produced by a vaginal strain of Enterococcus faecium: Potential significance in bacterial vaginosis

Science.gov (United States)

Dezwaan, Diane C.; Mequio, Michael J.; Littell, Julia S.; Allen, Jonathan P.; Rossbach, Silvia; Pybus, Vivien

2009-01-01

A bacteriocin produced by a vaginal isolate of Enterococcus faecium strain 62-6, designated enterocin 62-6, was characterized following purification and DNA sequence analysis and compared to previously described bacteriocins. Enterocin 62-6 was isolated from brain heart infusion (BHI) culture supernatants using ammonium sulfate precipitation followed by elution from a Sepharose cation exchange column using a continuous salt gradient (0.1–0.7 M NaCl). SDS-PAGE of an active column fraction resulted in an electrophoretically pure protein, which corresponded to the growth inhibition of the sensitive Lactobacillus indicator strain in the gel overlay assay. Purified enterocin 62-6 was shown to be heat- and pH-stable, and sensitive to the proteolytic enzymes α-chymotrypsin and pepsin. Results from mass spectrometry suggested that it comprised two peptides of 5206 and 5219±1 Da, which was confirmed by DNA sequence analysis. The characteristics of enterocin 62-6 as a small, heat- and pH-stable, cationic, hydrophobic, two-peptide, plasmid-borne bacteriocin, with an inhibitory spectrum against a broad range of Gram-positive but not Gram-negative bacteria, were consistent with its classification as a class IIc bacteriocin. Furthermore, its wide spectrum of growth inhibitory activity against Gram-positive bacteria of vaginal origin including lactobacilli, and stability under the acidic conditions of the vagina, are consistent with our hypothesis that it could have potential significance in disrupting the ecology of the vaginal tract and pave the way for the establishment of the abnormal microbiota associated with the vaginal syndrome bacterial vaginosis. This is the first class IIc bacteriocin produced by a strain of E. faecium of vaginal origin to be characterized. PMID:19578555

Expression of Streptococcus pneumoniae Bacteriocins Is Induced by Antibiotics via Regulatory Interplay with the Competence System

NARCIS (Netherlands)

Kjos, Morten; Miller, Eric; Slager, Jelle; Lake, Frank B; Gericke, Oliver; Roberts, Ian S; Rozen, Daniel E; Veening, Jan-Willem

2016-01-01

Pneumococcal bacteriocins (pneumocins) are antibacterial toxins that mediate intra-species competition within the human host. However, the triggers of pneumocin expression are poorly understood. Using RNA-sequencing, we mapped the regulon of the pneumocin cluster (blp) of Streptococcus pneumoniae

PRESERVATIVE POTENTIAL OF PURIFIED BACTERIOCIN PRODUCED FROM BREVIBACILLUS BORSTELENSIS AG1 ISOLATED FROM MARCHA – A TRADITIONAL WINE STARTER CULTURE CAKE IN TOMATO PASTE

OpenAIRE

Anupama Gupta; Nivedita Sharma; Neha Gautam

2015-01-01

Purified bacteriocin produced from Brevibacillus borstelensis AG1 isolated from Marcha a local wine starter herbal cake, was used to enhance the shelf life of tomato paste. Preservative effect of purified bacteriocin was studied for nine days in tomato paste inoculated with food borne pathogens and was compared to commercial biopreservative – nisin and chemical preservative – sodium benzoate. The indicator strains i.e. Listeria monocytogenes MTCC839, Bacillus subtilis CRI and Clostridium perf...

Analysis of Lactobacillus Products for Phages and Bacteriocins That Inhibit Vaginal Lactobacilli

Directory of Open Access Journals (Sweden)

Lin Tao

1997-01-01

Full Text Available Objective: Bacterial vaginosis is associated with an unexplained loss of vaginal lactobacilli. Previously, we have identified certain vaginal lactobacilli-released phages that can inhibit in vitro other vaginal lactobacilli. However, there is no apparent route for phages to be transmitted among women. The purpose of this study was to identify whether certain Lactobacillus products commonly used by women release phages or bacteriocins that can inhibit vaginal lactobacilli.

Enterocin X, a Novel Two-Peptide Bacteriocin from Enterococcus faecium KU-B5, Has an Antibacterial Spectrum Entirely Different from Those of Its Component Peptides▿

Science.gov (United States)

Hu, Chih-Bo; Malaphan, Wanna; Zendo, Takeshi; Nakayama, Jiro; Sonomoto, Kenji

2010-01-01

Enterocin X, composed of two antibacterial peptides (Xα and Xβ), is a novel class IIb bacteriocin from Enterococcus faecium KU-B5. When combined, Xα and Xβ display variably enhanced or reduced antibacterial activity toward a panel of indicators compared to each peptide individually. In E. faecium strains that produce enterocins A and B, such as KU-B5, only one additional bacteriocin had previously been known. PMID:20418437

Administrative circular

CERN Multimedia

2003-01-01

• N° 21 - August 2003 Special leave This circular has been amended. Copies of this circular are available in the Divisional Secretariats. In addition, administrative and operational circulars, as well as the lists of those in force, are available for consultation on the Web at: http://cern.ch/hr-div/internal/admin_services/admincirc/listadmincirc.asp Human Resources Division Tel. 74128

Circular dichroism spectral data and metadata in the Protein Circular Dichroism Data Bank (PCDDB): a tutorial guide to accession and deposition.

Science.gov (United States)

Janes, Robert W; Miles, A J; Woollett, B; Whitmore, L; Klose, D; Wallace, B A

2012-09-01

The Protein Circular Dichroism Data Bank (PCDDB) is a web-based resource containing circular dichroism (CD) and synchrotron radiation circular dichroism spectral and associated metadata located at http://pcddb.cryst.bbk.ac.uk. This resource provides a freely available, user-friendly means of accessing validated CD spectra and their associated experimental details and metadata, thereby enabling broad usage of this material and new developments across the structural biology, chemistry, and bioinformatics communities. The resource also enables researchers utilizing CD as an experimental technique to have a means of storing their data at a secure site from which it is easily retrievable, thereby making their results publicly accessible, a current requirement of many grant-funding agencies world-wide, as well as meeting the data-sharing requirements for journal publications. This tutorial provides extensive information on searching, accessing, and downloading procedures for those who wish to utilize the data available in the data bank, and detailed information on deposition procedures for creating and validating entries, including comprehensive explanations of their contents and formats, for those who wish to include their data in the data bank. Copyright © 2012 Wiley Periodicals, Inc.

Administrative Circulars Rev.

CERN Multimedia

2003-01-01

Administrative Circular N° 19 (Rev. 3) - April 2003 Subsistence indemnity - Other expenses necessarily incurred in the course of duty travelAdministrative Circular N° 25 (Rev. 2) - April 2003 Shift work - Special provisions for the Fire and Rescue Service - These circulars have been revised. Human Resources Division Tel. 74128Copies of these circulars are available in the Divisional Secretariats. In addition, administrative and operational circulars, as well as the lists of those in force, are available for consultation on the Web at: http://humanresources.web.cern.ch/humanresources/internal/admin_services/admincirc/listadmincirc.asp

THE IMPORTANCE OF BACTERIOCINS IN MEAT AND MEAT PRODUCTS

Directory of Open Access Journals (Sweden)

Meltem SERDAROĞLU

2000-03-01

Full Text Available There is an increasing consumer demand for food products which are free of chemical additives, reduced in salt and processed as little as possible. These minimally processed foods require special application to assure their microbiological safety. The use of microorganisms and enzymes for food preservatives is called biopreservation. The most important group of microorganisms with antimicrobial effect used in the production of foods is the lactic acid bacteria. In meats although lactic acid bacteria constitue apart of the initial microflora, they become dominant during the processing of meats. In this research bacteriocins of lactic acid bacteria and their usage in meat and meat products for biopreservation are discussed.

Bacteriocins – Exploring Alternatives to Antibiotics in Mastitis Treatment

Science.gov (United States)

Pieterse, Reneé; Todorov, Svetoslav D.

2010-01-01

Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. In this review we have focus on the pathogenesis of the mastitis in dairy cows, existing antibiotic treatments and possible alternative for application of bacteriocins from lactic acid bacteria in the treatment and prevention of this disease. PMID:24031528

Isolation and characterization of large spectrum and multiple bacteriocin-producing Enterococcus faecium strain from raw bovine milk.

Science.gov (United States)

Gaaloul, N; ben Braiek, O; Hani, K; Volski, A; Chikindas, M L; Ghrairi, T

2015-02-01

To assess the antimicrobial properties of lactic acid bacteria from Tunisian raw bovine milk. A bacteriocin-producing Enterococcus faecium strain was isolated from raw cow milk with activity against Gram-positive and Gram-negative bacteria. Antimicrobial substances produced by this strain were sensitive to proteolytic enzymes and were thermostable and resistant to a broad range of pH (2-10). Mode of action of antimicrobial substances was determined as bactericidal. Maximum activity was reached at the end of the exponential growth phase when checked against Listeria ivanovii BUG 496 (2366.62 AU ml(-1)). However, maximum antimicrobial activity against Pseudomonas aeruginosa 28753 was recorded at the beginning of the exponential growth phase. Enterococcus faecium GGN7 was characterized as free from virulence factors and was susceptible to tested antibiotics. PCR analysis of the micro-organism's genome revealed the presence of genes coding for enterocins A and B. Mass spectrometry analysis of RP-HPLC active fractions showed molecular masses corresponding to enterocins A (4835.77 Da) and B (5471.56 Da), and a peptide with a molecular mass of 3215.5 Da active only against Gram-negative indicator strains. The latter was unique in the databases. Enterococcus faecium GGN7 produces three bacteriocins with different inhibitory spectra. Based on its antimicrobial properties and safety, Ent. faecium GGN7 is potentially useful for food biopreservation. The results suggest the bacteriocins from GGN7 strain could be useful for food biopreservation. © 2014 The Society for Applied Microbiology.

Bacteriocins: molecules of fundamental impact on the microbial ecology and potential food biopreservatives

Directory of Open Access Journals (Sweden)

Evandro Leite de Souza

2005-07-01

Full Text Available Bacteriocins are proteic molecules synthesized for various lineages of Gram-positive and Gram-negative bacteria when exposed to stressful conditions. Bacteriocins have been characterized as molecules of high antimicrobial property even at low concentrations, provoking the microbial survival inhibition by antibiosis. These substances have their synthesis mediated for genetic mechanisms and develop their lethal action on the microbial cell by multiples mechanisms that can act of isolated or concomitant way culminating with microbial cell killing. This molecules class presents characteristic of stability to heat, low pH, refrigeration and freezing, and resistance to weak organics solvents, salts and enzymes. On the other hand, they are very sensitive to proteolytic enzymes action. Bacteriocins could appear as potential agents to be applied in food conservation systems in order to provide microbiologically stable foods.Bacteriocinas são moléculas protéicas sintetizadas por várias linhagens de bactérias Gram-positivas e Gram-negativas quando submetidas a condições de stress. São ainda caracterizadas como moléculas de alto poder antimicrobiano mesmo em baixas concentrações, provocando a inibição da sobrevivência microbiana através de uma ação de antibiose. As bacteriocinas têm seu processo de síntese mediado por mecanismos genéticos, e desenvolvem sua ação letal sobre a célula microbiana por intermédio de múltiplos mecanismos que podem agir de forma isolada ou concomitante culminando com a morte da célula microbiana. Estas moléculas apresentam características de estabilidade ao calor, baixo pH, refrigeração, congelamento, resistência a ácidos orgânicos fracos, sais e enzimas, porém são muito sensíveis à enzimas proteolíticas. Assim, as bacteriocinas podem aparecer como potenciais agentes para serem aplicados em sistemas de conservação de alimentos com objetivo de prover alimentos microbiologicamente estáveis.

Bacteriocin AS-48 binding to model membranes and pore formation as revealed by coarse-grained simulations

NARCIS (Netherlands)

Cruz, Victor L.; Ramos, Javier; Martinez-Salazar, Javier; Melo, Manuel N.

Bacteriocin AS-48 is a membrane-interacting peptide that acts as a broad-spectrum antimicrobial against Gram-positive and Gram-negative bacteria. Prior Nuclear Magnetic Resonance experiments and the high resolution crystal structure of AS-48 have suggested a mechanism for the molecular activity of

Operational Circulars

CERN Multimedia

2003-01-01

Operational Circular N° 4 - April 2003 Conditions for use by members of the CERN personnel of vehicles belonging to or rented by CERN - This circular has been drawn up. Operational Circular N° 5 - October 2000 Use of CERN computing facilities - Further details on the personal use of CERN computing facilities Operational Circular N° 5 and its Subsidiary Rules http://cern.ch/ComputingRules defines the rules for the use of CERN computing facilities. One of the basic principles governing such use is that it must come within the professional duties of the user concerned, as defined by the user's divisional hierarchy. However, personal use of the computing facilities is tolerated or allowed provided : a) It is in compliance with Operational Circular N° 5 and not detrimental to official duties, including those of other users; b) the frequency and duration is limited and there is a negligible use of CERN resources; c) it does not constitute a political, commercial and/or profit-making activity; d) it is not...

Information Circulars

International Nuclear Information System (INIS)

1969-01-01

Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars which were of current interest on 15 January 1969 is given below, followed by an index to their subject matter. Other circulars can be traced by reference to earlier issues of the present document.

Information Circulars

Energy Technology Data Exchange (ETDEWEB)

NONE

1969-01-24

Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars which were of current interest on 15 January 1969 is given below, followed by an index to their subject matter. Other circulars can be traced by reference to earlier issues of the present document.

Purification and Characterization of Plantaricin JLA-9: A Novel Bacteriocin against Bacillus spp. Produced by Lactobacillus plantarum JLA-9 from Suan-Tsai, a Traditional Chinese Fermented Cabbage.

Science.gov (United States)

Zhao, Shengming; Han, Jinzhi; Bie, Xiaomei; Lu, Zhaoxin; Zhang, Chong; Lv, Fengxia

2016-04-06

Bacteriocins are ribosomally synthesized peptides with antimicrobial activity produced by numerous bacteria. A novel bacteriocin-producing strain, Lactobacillus plantarum JLA-9, isolated from Suan-Tsai, a traditional Chinese fermented cabbage, was screened and identified by its physiobiochemical characteristics and 16S rDNA sequence analysis. A new bacteriocin, designated plantaricin JLA-9, was purified using butanol extraction, gel filtration, and reverse-phase high-performance liquid chromatography. The molecular mass of plantaricin JLA-9 was shown to be 1044 Da by MALDI-TOF-MS analyses. The amino acid sequence of plantaricin JLA-9 was predicted to be FWQKMSFA by MALDI-TOF-MS/MS, which was confirmed by Edman degradation. This bacteriocin exhibited broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, especially Bacillus spp., high thermal stability (20 min, 121 °C), and narrow pH stability (pH 2.0-7.0). It was sensitive to α-chymotrypsin, pepsin, alkaline protease, and papain. The mode of action of this bacteriocin responsible for outgrowth inhibition of Bacillus cereus spores was studied. Plantaricin JLA-9 had no detectable effects on germination initiation over 1 h on monitoring the hydration, heat resistance, and 2,6-pyridinedicarboxylic acid (DPA) release of spores. Rather, germination initiation is a prerequisite for the action of plantaricin JLA-9. Plantaricin JLA-9 inhibited growth by preventing the establishment of oxidative metabolism and disrupting membrane integrity in germinating spores within 2 h. The results suggest that plantaricin JLA-9 has potential applications in the control of Bacillus spp. in the food industry.

Production of a bacteriocin-like inhibitory substance by Leuconostoc mesenteroides subsp. dextranicum 213M0 isolated from Mongolian fermented mare milk, airag.

Science.gov (United States)

Arakawa, Kensuke; Yoshida, Saki; Aikawa, Hiroki; Hano, Chihiro; Bolormaa, Tsognemekh; Burenjargal, Sedkhuu; Miyamoto, Taku

2016-03-01

Strain 213M0 was selected with productivity of a bacteriocin-like inhibitory substance (BLIS) among 235 strains of lactic acid bacteria (LAB) isolated from Mongolian fermented milk 'airag'. Strain 213M0 was species-identified as Leuconostoc mesenteroides subsp. dextranicum by morphological observation, carbohydrate fermentation profiling and sequencing the 16S rRNA gene. Incubation temperature proper to produce the BLIS was 25°C rather than 30 and 37°C, and the production actively proceeded during the exponential growth phase of the producer cells. Antibacterial effect of BLIS 213M0 was limited to all nine strains of Listeria sp. bacteria and seven strains of LAB cocci among 53 tested strains, which corresponds to a typical feature of the class IIa pediocin-like bacteriocins. BLIS 213M0 was not inactivated in every broad pH range solution (pH 2.0-11.0), and was stable against storage at 25°C for 1 week and heating at 121°C for 15 min under pH 4.5. Peptide frame of BLIS 213M0 was confirmed by inactivation with some peptidases, and then its molecular weight was estimated to be 2.6-3.0 kDa using an in situ activity assay following sodium dodecyl sulfate polyacrylamide gel electrophoresis. The estimated size was different from the other Leuconostoc bacteriocins already reported. These results suggest that BLIS 213M0 would be a novel listericidal bacteriocin. © 2015 Japanese Society of Animal Science.

Characterization of the genetic locus responsible for the production of ABP-118, a novel bacteriocin produced by the probiotic bacterium Lactobacillus salivarius subsp. salivarius UCC118.

Science.gov (United States)

Flynn, Sarah; van Sinderen, Douwe; Thornton, Gerardine M; Holo, Helge; Nes, Ingolf F; Collins, J Kevin

2002-04-01

ABP-118, a small heat-stable bacteriocin produced by Lactobacillus salivarius subsp. salivarius UCC118, a strain isolated from the ileal-caecal region of the human gastrointestinal tract, was purified to homogeneity. Using reverse genetics, a DNA fragment specifying part of ABP-118 was identified on a 10769 bp chromosomal region. Analysis of this region revealed that ABP-118 was a Class IIb two-peptide bacteriocin composed of Abp118alpha, which exhibited the antimicrobial activity, and Abp118beta, which enhanced the antimicrobial activity. The gene conferring strain UCC118 immunity to the action of ABP-118, abpIM, was identified downstream of the abp118beta gene. Located further downstream of abp118beta, several ORFs were identified whose deduced proteins resembled those of proteins involved in bacteriocin regulation and secretion. Heterologous expression of ABP-118 was achieved in Lactobacillus plantarum, Lactococcus lactis and Bacillus cereus. In addition, the abp118 locus encoded an inducing peptide, AbpIP, which was shown to play a role in the regulation of ABP-118 production. This novel bacteriocin is, to the authors' knowledge, the first to be isolated from a known human probiotic bacterium and to be characterized at the genetic level.

Characterization and Application of Enterocin RM6, a Bacteriocin from Enterococcus faecalis

OpenAIRE

Huang, En; Zhang, Liwen; Chung, Yoon-Kyung; Zheng, Zuoxing; Yousef, Ahmed E.

2013-01-01

Use of bacteriocins in food preservation has received great attention in recent years. The goal of this study is to characterize enterocin RM6 from Enterococcus faecalis OSY-RM6 and investigate its efficacy against Listeria monocytogenes in cottage cheese. Enterocin RM6 was purified from E. faecalis culture supernatant using ion exchange column, multiple C18-silica cartridges, followed by reverse-phase high-performance liquid chromatography. The molecular weight of enterocin RM6 is 7145.0823 ...

Design for Circular Behaviour: Considering Users in a Circular Economy

Directory of Open Access Journals (Sweden)

Thomas Wastling

2018-05-01

Full Text Available In a linear economy, a product is manufactured and sold to a customer. Then, little concern is given to what the user actually does with it when they have it. However, in a circular economy where the aim is to circulate products at their highest level of value, the customer’s behaviour can become an important part of the system. Circular design strategies have tended to focus on the physical aspects of a product (e.g., disassembly, material selection, but the design of products and services can also have an influence on user behaviour and, to date, this aspect of circular design has not been fully explored. This project aims to define what key user behaviours are required for circular business models to work and to outline how design can enable these ‘circular behaviours’. This research project consists of a literature review, case study analysis and expert interviews with practitioners. A theoretical framework for designing products and services to encourage circular behaviour is developed. This work provides an initial step towards a better understanding of the user’s role in the transition to a circular economy as well as a preliminary model for how design for behaviour change strategies could be implemented in this context.

A food-grade process for isolation and partial purification of bacteriocins of lactic acid bacteria that uses diatomite calcium silicate.

Science.gov (United States)

Coventry, M J; Gordon, J B; Alexander, M; Hickey, M W; Wan, J

1996-01-01

Bacteriocins, including nisin, pediocin PO2, brevicin 286, and piscicolin 126, were extracted from fermentation media by adsorption onto Micro-Cel (a food-grade diatomite calcium silicate anticaking agent) and subsequent desorption. The optimal conditions for desorption of piscicolin 126 were determined and applied to other bacteriocins, and the relative purities of the desorbed preparations were compared. Piscicolin was not successfully desorbed from Micro-Cel at pH 1.0 to 12.0, with organic solvents, or by increase of ionic strength up to 1 M NaCl. However, 25 and 75% of the bacteriocin activity was desorbed by using 1% sodium deoxycholate and 1% sodium dodecyl sulfate (SDS), respectively. Higher levels (up to 100%) of desorption were achieved by repeated elution or by an increase in surfactant concentration. Desorption of piscicolin with 1/10 volume of SDS solution resulted in a preparation with 10 times concentration in activity, equivalent to that of ammonium sulfate preparations (409,600 to 819,200 activity units/ml). Determination of organic nitrogen (N) content revealed that the desorbed piscicolin preparations were substantially free of proteinaceous substances (approximately 92 to 99%) compared with original culture supernatants and ammonium sulfate preparations. Nisin, pediocin, and brevicin were also desorbed with 1% SDS with a similar level of purification. PMID:8633875

Potential Applications of the Cyclic Peptide Enterocin AS-48 in the Preservation of Vegetable Foods and Beverages.

Science.gov (United States)

Abriouel, Hikmate; Lucas, Rosario; Omar, Nabil Ben; Valdivia, Eva; Gálvez, Antonio

2010-06-01

Bacteriocins are antimicrobial peptides produced by bacteria. Among them, the enterococcal bacteriocin (enterocin) AS-48 stands for its peculiar characteristics and broad-spectrum antimicrobial activity. AS-48 belongs to the class of circular bacteriocins and has been studied in depth in several aspects: peptide structure, genetic determinants, and mode of action. Recently, a wealth of knowledge has accumulated on the antibacterial activity of this bacteriocin against foodborne pathogenic and spoilage bacteria in food systems, especially in vegetable foods and drinks. This work provides a general overview on the results from tests carried out with AS-48 in different vegetable food categories (such as fruit juices, ciders, sport and energy drinks, fresh fruits and vegetables, pre-cooked ready to eat foods, canned vegetables, and bakery products). Depending on the food substrate, the bacteriocin has been tested alone or as part of hurdle technology, in combination with physico-chemical treatments (such as mild heat treatments or high-intensity pulsed electric fields) and other antimicrobial substances (such as essential oils, phenolic compounds, and chemical preservatives). Since the work carried out on bacteriocins in preservation of vegetable foods and drinks is much more limited compared to meat and dairy products, the results reported for AS-48 may open new possibilities in the field of bacteriocin applications.

Circular defects detection in welded joints using circular hough transform

International Nuclear Information System (INIS)

Hafizal Yazid; Mohd Harun; Shukri Mohd; Abdul Aziz Mohamed; Shaharudin Sayuti; Muhamad Daud

2007-01-01

Conventional radiography is one of the common non-destructive testing which employs manual image interpretation. The interpretation is very subjective and depends much on the inspector experience and working conditions. It is therefore useful to have pattern recognition system in order to assist human interpreter in evaluating the quality of the radiograph sample, especially radiographic image of welded joint. This paper describes a system to detect circular discontinuities that is present in the joints. The system utilizes together 2 different algorithms, which is separability filter to identify the best object candidate and Circular Hough Transform to detect the present of circular shape. The result of the experiment shows a promising output in recognition of circular discontinuities in a radiographic image. This is based on 81.82-100% of radiography film with successful circular detection by using template movement of 10 pixels. (author)

Rapid and efficient purification method for small, hydrophobic, cationic bacteriocins : Purification of lactococcin B and pediocin PA-1

NARCIS (Netherlands)

Venema, Koen; Chikindas, Michael L.; Seegers, Jos F.M.L.; Haandrikman, Alfred J.; Leenhouts, Kees J.; Venema, Gerard; Kok, Jan

The bacteriocins lactococcin B and pediocin PA 1 were purified by ethanol precipitation, preparative isoelectric focusing, and ultrafiltration. The procedure reproducibly leads to high final yields in comparison to the generally low yields obtained by column chromatography. Specifically, during

Purification and characterization of enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4.

Science.gov (United States)

Joosten, H M; Nunez, M; Devreese, B; Van Beeumen, J; Marugg, J D

1996-01-01

A simple two-step procedure was developed to obtain pure enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4. Chemical and genetic characterization revealed that the primary structure of enterocin 4 is identical to that of peptide antibiotic AS-48 from Enterococcus faecalis S-48. In contrast to the reported inhibitory spectrum of AS-48, enterocin 4 displayed no activity against gram-negative bacteria. PMID:8900014

Purification and characterization of enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4.

OpenAIRE

Joosten, H M; Nunez, M; Devreese, B; Van Beeumen, J; Marugg, J D

1996-01-01

A simple two-step procedure was developed to obtain pure enterocin 4, a bacteriocin produced by Enterococcus faecalis INIA 4. Chemical and genetic characterization revealed that the primary structure of enterocin 4 is identical to that of peptide antibiotic AS-48 from Enterococcus faecalis S-48. In contrast to the reported inhibitory spectrum of AS-48, enterocin 4 displayed no activity against gram-negative bacteria.

Optimization of growth and bacteriocin activity of the food bioprotective Carnobacterium divergens V41 in an animal origin protein free medium

Directory of Open Access Journals (Sweden)

Anne BRILLET-VIEL

2016-08-01

Full Text Available Optimization of Carnobacterium divergens V41 growth and bacteriocin activity in a culture medium deprived of animal protein, needs for food bioprotection, was performed by using a statistical approach. In a screening experiment, twelve factors (pH, temperature, carbohydrates, NaCl, yeast extract, soy peptone, sodium acetate, ammonium citrate, magnesium sulphate, manganese sulphate, ascorbic acid and thiamine were tested for their influence on the maximal growth and bacteriocin activity using a two-level incomplete factorial design with 192 experiments performed in microtiter plate wells. Based on results, a basic medium was developed and three variables (pH, temperature and carbohydrates concentration were selected for a scale-up study in bioreactor. A 23 complete factorial design was performed, allowing the estimation of linear effects of factors and all the first order interactions. The best conditions for the cell production were obtained with a temperature of 15°C and a carbohydrates concentration of 20 g/l whatever the pH (in the range 6.5-8, and the best conditions for bacteriocin activity were obtained at 15°C and pH 6.5 whatever the carbohydrates concentration (in the range 2-20 g/l. The predicted final count of C. divergens V41 and the bacteriocin activity under the optimized conditions (15°C, pH 6.5, 20 g/l carbohydrates were 2.4 x 1010 CFU/ml and 819200 AU/ml respectively. C. divergens V41 cells cultivated in the optimized conditions were able to grow in cold-smoked salmon and totally inhibited the growth of Listeria monocytogenes (< 50 CFU g-1 during five weeks of vacuum storage at 4° and 8°C.

Characterization of a Bacteriocin-Like Substance Produced by a Vaginal Lactobacillus salivarius Strain

Science.gov (United States)

Ocaña, Virginia S.; Pesce de Ruiz Holgado, Aída A.; Nader-Macías, María Elena

1999-01-01

A novel bacteriocin-like substance produced by vaginal Lactobacillus salivarius subsp. salivarius CRL 1328 with activity against Enterococcus faecalis, Enterococcus faecium, and Neisseria gonorrhoeae was characterized. The highest level of production of this heat-resistant peptide or protein occurred during the late exponential phase. Its mode of action was shown to be bactericidal. L. salivarius subsp. salivarius CRL 1328 could be used for the design of a probiotic to prevent urogenital infections. PMID:10584033

Purification, Characterization, and Mode of Action of Pentocin JL-1, a Novel Bacteriocin Isolated from Lactobacillus pentosus, against Drug-Resistant Staphylococcus aureus

Directory of Open Access Journals (Sweden)

Han Jiang

2017-01-01

Full Text Available Staphylococcus aureus and its drug-resistant strains, which threaten public health and food safety, are in need of effective control by biopreservatives. A novel bacteriocin, pentocin JL-1, produced by Lactobacillus pentosus that was isolated from the intestinal tract of Chiloscyllium punctatum, was purified by a four-step chromatographic process. Mass spectrometry based on MALDI-TOF indicated that pentocin JL-1 has a molecular mass of 2987.23 Da. Only six of the twenty-five amino acids could be identified by Edman degradation. This bacteriocin is thermostable and tolerates a pH range of 5–7. Also, it is sensitive to proteinase K, trypsin, pepsin, and alkaline protease. This bacteriocin has a broad inhibitory spectrum against both Gram-positive and Gram-negative strains and in particular is effective against multidrug-resistant S. aureus. Additionally, we showed that the cell membrane is the target of pentocin JL-1 against methicillin-resistant S. aureus (MRSA, causing a loss of proton motive force. Furthermore, pentocin JL-1 has a drastic impact on the structure and integrity of MRSA cells. These results suggest that pentocin JL-1 has potential as a biopreservative in the food industry.

Characterization and purification of a bacteriocin from Lactobacillus paracasei subsp. paracasei BMK2005, an intestinal isolate active against multidrug-resistant pathogens.

Science.gov (United States)

Bendjeddou, Kamel; Fons, Michel; Strocker, Pierre; Sadoun, Djamila

2012-04-01

A strain of Lactobacillus paracasei subsp. paracasei BMK2005 isolated from healthy infant faeces has shown a remarkable antibacterial activity against 32 bacterial pathogenic strains of human clinical isolates. Among them, 13 strains belonging to species of Escherichia coli, Citrobacter freundii, Citrobacter diversus, Klebsiella oxytoca, Enterobacter cloacae and Pseudomonas aeruginosa were resistant to Cefotaxime (CTX) and Ceftazidime (CAZ), and 4 strains of Staphylococcus aureus were resistant to Methicillin (MRSA). This antibacterial activity was attributed to a bacteriocin designated as Paracaseicin A. It was heat-stable up to 120°C for 5 min and active within the pH range of 2-5. Its activity was lost when treated with proteases, which reveals its proteinaceous nature. This bacteriocin was successfully purified only by two steps of reversed phase chromatography. Its molecular mass, determined by mass spectrometry analysis, was 2,462.5 Da. To our knowledge, the present study is the first report on characterization and purification of a bacteriocin, produced by a L. paracasei subsp. paracasei strain exhibiting an antibacterial activity against various multidrug-resistant species of Gram-positive and Gram-negative bacteria, which reveals its potential for use in prevention or treatment of infections caused by multidrug-resistant species especially in cases of antibiotics-associated diarrhea (AAD).

Bacteriocin production by Lactobacillus pentosus ST712BZ isolated from boza Bacteriocina produzida por Lactobacillus pentosus ST712BZ isolad de boza

Directory of Open Access Journals (Sweden)

Svetoslav D. Todorov

2007-03-01

Full Text Available Bacteriocin ST712BZ (14.0kDa in size inhibits the growth of Lactobacillus casei,Escherichia coli, Pseudomonas aeruginosa,Enterococcus faecalis, Klebsiella pneumoniae and Lactobacillus curvatus. Growth of strain ST712BZ in BHI, M17, soy milk and molasses was similar to growth in MRS, with optimal bacteriocin production (12800AU/mL recorded in MRS after 24h. The same level of bacteriocin production (12800AU/mL was recorded in MRS broth with an initial pH of 6.5, 6.0 and 5.5. However, MRS broth (pH 6.5 supplemented with 1mM EDTA, yielded only 6400AU/mL. Low levels of bacteriocin activity were recorded in MRS broth with an initial pH of 5.0 and 4.5. Of all media compositions tested, MRS supplemented with tryptone (20.0g/L, glucose (20.0 to 40.0g/L, mannose (20.0g/L, vitamin B12, or vitamin C yielded 12800AU/mL. Glycerol concentrations of 1.0g/L and higher repressed bacteriocin production. Maximal bacteriocin activity (25600AU/mL was recorded in MRS supplemented with Vit. B1 or DL-6,8-thioctic acid.A bacteriocina ST712BZ produzida par Lactobacillus pentosus (peso molecular de 14,0kDa inibe o crescimento de Lactobacillus casei,Escherichia coli, Pseudomonas aeruginosa,Enterococcus faecalis, Klebsiella pneumoniae e Lactobacillus curvatus. O crescimento de L. pentosus ST712BZ em BHI, M17, leite de soja e melaços foi semelhante ao observado em MRS, registando-se a produção máxima de bacteriocina (12800UA/mL em MRS após 24 h. Observou-se o mesmo nível de produção de bacteriocina (12800UA/mL em caldo MRS com pH inicial de 6,5, 6,0 e 5,5. No entanto, em caldo MRS (pH 6,5 suplementado com 1 mM de EDTA a produção apenas atingiu 6400UA/mL. Os níveis de atividade bacteriocinogênica detectados em caldo MRS com um pH inicial de 5,0 e 4,5 foram baixos. De todas as fórmulas de meios de cultura testadas a que apresentou a atividade máxima 12800UA/mL foi MRS suplemento de triptona (20,0g/L, glicose (20,0 e 40,0 g/L, manose (20.0 g/L, vitamina B12 e

A New Kind of Shift Operators for Infinite Circular and Spherical Wells

Directory of Open Access Journals (Sweden)

Guo-Hua Sun

2014-01-01

Full Text Available A new kind of shift operators for infinite circular and spherical wells is identified. These shift operators depend on all spatial variables of quantum systems and connect some eigenstates of confined systems of different radii R sharing energy levels with a common eigenvalue. In circular well, the momentum operators P±=Px±iPy play the role of shift operators. The Px and Py operators, the third projection of the orbital angular momentum operator Lz, and the Hamiltonian H form a complete set of commuting operators with the SO(2 symmetry. In spherical well, the shift operators establish a novel relation between ψlm(r and ψ(l ± 1(m±1(r.

Isolation and characterization of a new bacteriocin, termed enterocin M, produced by environmental isolate Enterococcus faecium AL41.

Science.gov (United States)

Mareková, Mária; Lauková, Andrea; Skaugen, Morten; Nes, Ingolf

2007-08-01

The new bacteriocin, termed enterocin M, produced by Enterococcus faecium AL 41 showed a wide spectrum of inhibitory activity against the indicator organisms from different sources. It was purified by (NH4)2SO4 precipitation, cation-exchange chromatography and reverse phase chromatography (FPLC). The purified peptide was sequenced by N-terminal amino acid Edman degradation and a mass spectrometry analysis was performed. By combining the data obtained from amino acid sequence (39 N-terminal amino acid residues was determined) and the molecular weight (determined to be 4628 Da) it was concluded that the purified enterocin M is a new bacteriocin, which is very similar to enterocin P. However, its molecular weight is different from enterocin P (4701.25). Of the first 39 N-terminal residues of enterocin M, valine was found in position 20 and a lysine in position 35, while enterocin P has tryptophane residues in these positions.

Information Circulars

Energy Technology Data Exchange (ETDEWEB)

NONE

1973-09-10

Information circulars are published from time to time under the symbol INFCIRC/.. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A subject index to the circulars is presented overleaf. It covers all those published in the last five years (that is, since the beginning of 1968 and ending with INFCIRC/192), as well as others which, for one reason or another, are still considered to be of current rather than merely historical interest. Such circulars can be traced by reference to the indexes that were included in earlier revisions of the present document.

Information Circulars

International Nuclear Information System (INIS)

1973-01-01

Information circulars are published from time to time under the symbol INFCIRC/.. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A subject index to the circulars is presented overleaf. It covers all those published in the last five years (that is, since the beginning of 1968 and ending with INFCIRC/192), as well as others which, for one reason or another, are still considered to be of current rather than merely historical interest. Such circulars can be traced by reference to the indexes that were included in earlier revisions of the present document.

Purification and biochemical characterization of a highly thermostable bacteriocin isolated from Brevibacillus brevis strain GM100.

Science.gov (United States)

Ghadbane, Mouloud; Harzallah, Daoud; Laribi, Atef Ibn; Jaouadi, Bassem; Belhadj, Hani

2013-01-01

A bacteriocin-producing (11,000 AU mL(-1)) strain was isolated from the rhizosphere of healthy Algerian plants Ononis angustissima Lam., and identified as Brevibacillus brevis strain GM100. The bacteriocin, called Bac-GM100, was purified to homogeneity from the culture supernatant, and, based on MALDI-TOF/MS analysis, was a monomer protein with a molecular mass of 4375.66 Da. The 21 N-terminal residues of Bac-GM100 displayed 65% homology with thurincin H from Bacillus thuringiensis. Bac-GM100 was extremely heat-stable (20 min at 120 °C), and was stable within a pH range of 3-10. It proved sensitive to various proteases, which demonstrated its protein nature. It was also found to display a bactericidal mode of action against gram-negative (Salmonella enteric ATCC 43972, Pseudomonas aeruginosa ATCC 49189, and Agrobacterium tumefaciens C58) and gram-positive (Enterococcus faecalis ENSAIA 631 and Staphylococcus aureus ATCC 6538) bacteria, and a fungistatic mode of action against the pathogenic fungus Candida tropicalis R2 CIP 203.

Pentocin MQ1: A Novel, Broad-Spectrum, Pore-Forming Bacteriocin From Lactobacillus pentosus CS2 With Quorum Sensing Regulatory Mechanism and Biopreservative Potential

Directory of Open Access Journals (Sweden)

Samson B. Wayah

2018-03-01

Full Text Available Micrococcus luteus, Listeria monocytogenes, and Bacillus cereus are major food-borne pathogenic and spoilage bacteria. Emergence of antibiotic resistance and consumer demand for foods containing less of chemical preservatives led to a search for natural antimicrobials. A study aimed at characterizing, investigating the mechanism of action and regulation of biosynthesis and evaluating the biopreservative potential of pentocin from Lactobacillus pentosus CS2 was conducted. Pentocin MQ1 is a novel bacteriocin isolated from L. pentosus CS2 of coconut shake origin. The purification strategy involved adsorption-desorption of bacteriocin followed by RP-HPLC. It has a molecular weight of 2110.672 Da as determined by MALDI-TOF mass spectrometry and a molar extinction value of 298.82 M−1 cm−1. Pentocin MQ1 is not plasmid-borne and its biosynthesis is regulated by a quorum sensing mechanism. It has a broad spectrum of antibacterial activity, exhibited high chemical, thermal and pH stability but proved sensitive to proteolytic enzymes. It is potent against M. luteus, B. cereus, and L. monocytogenes at micromolar concentrations. It is quick-acting and exhibited a bactericidal mode of action against its targets. Target killing was mediated by pore formation. We report for the first time membrane permeabilization as a mechanism of action of the pentocin from the study against Gram-positive bacteria. Pentocin MQ1 is a cell wall-associated bacteriocin. Application of pentocin MQ1 improved the microbiological quality and extended the shelf life of fresh banana. This is the first report on the biopreservation of banana using bacteriocin. These findings place pentocin MQ1 as a potential biopreservative for further evaluation in food and medical applications.

Purification and characterization of the bacteriocin Thuricin Bn1 produced by Bacillus thuringiensis subsp. kurstaki Bn1 isolated from a hazelnut pest.

Science.gov (United States)

Ugras, Serpil; Sezen, Kazim; Kati, Hatice; Demirbag, Zihni

2013-02-01

A novel bioactive molecule produced by Bacillus thuringiensis subsp. kurstaki Bn1 (Bt-Bn1), isolated from a common pest of hazelnut, Balaninus nucum L. (Coleoptera: Curculionidae), was determined, purified, and characterized in this study. The Bt-Bn1 strain was investigated for antibacterial activity with an agar spot assay and well diffusion assay against B. cereus, B. weinhenstephenensis, L. monocytogenes, P. savastanoi, P. syringae, P. lemoignei, and many other B. thuringiensis strains. The production of bioactive molecule was determined at the early logarithmic phase in the growth cycle of strain Bt-Bn1 and its production continued until the beginning of the stationary phase. The mode of action of this molecule displayed bacteriocidal or bacteriolytic effect depending on the concentration. The bioactive molecule was purified 78-fold from the bacteria supernatant with ammonium sulfate precipitation, dialysis, ultrafiltration, gel filtration chromatography, and HPLC, respectively. The molecular mass of this molecule was estimated via SDS-PAGE and confirmed by the ESI-TOFMS as 3,139 Da. The bioactive molecule was also determined to be a heat-stable, pH-stable (range 6-8), and proteinase K sensitive antibacterial peptide, similar to bacteriocins. Based on all characteristics determined in this study, the purified bacteriocin was named as thuricin Bn1 because of the similarities to the previously identified thuricin-like bacteriocin produced by the various B. thuringiensis strains. Plasmid elution studies showed that gene responsible for the production of thuricin Bn1 is located on the chromosome of Bt-Bn1. Therefore, it is a novel bacteriocin and the first recorded one produced by an insect originated bacterium. It has potential usage for the control of many different pathogenic and spoilage bacteria in the food industry, agriculture, and various other areas.

Information Circulars

International Nuclear Information System (INIS)

1965-01-01

Information circulars are published from time to time under the symbol INFCIRC/. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current on 31 December 1964 is given, followed by an index to their subject matter.

Information circulars

International Nuclear Information System (INIS)

1992-08-01

The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. This revision contains INFCIRCs published up to mid-August 1992. A complete numerical lift of Information Circulars with their titles is reproduced in an Annex

Information Circulars

Energy Technology Data Exchange (ETDEWEB)

NONE

1965-01-18

Information circulars are published from time to time under the symbol INFCIRC/. for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current on 31 December 1964 is given, followed by an index to their subject matter.

Description of two Enterococcus strains isolated from traditional Peruvian artisanal-produced cheeses with a bacteriocin-like inhibitory activity

Directory of Open Access Journals (Sweden)

Aguilar Galvez A.

2009-01-01

Full Text Available The aim of this work was to isolate and to characterize strains of lactic acid bacteria (LAB with bacteriocin-like inhibitory activity from 27 traditional cheeses artisanal-produced obtained from different Peruvian regions. Twenty Gram+ and catalasenegative strains among 2,277 isolates exhibited bacteriocin-like inhibitory activity against Listeria monocytogenes CWBIB2232 as target strain. No change in inhibitory activity was observed after organic acid neutralization and treatment with catalase of the cell-free supernatant (CFS. The proteinic nature of the antimicrobial activity was confirmed for the twenty LAB strains by proteolytic digestion of the CFS. Two strains, CWBI-B1431 and CWBI-B1430, with the best antimicrobial activity were selected for further researches. These strains were taxonomically identified by phenotypic and genotypic analyses as Enterococcus mundtii (CWBI-B1431 and Enterococcus faecium (CWBI-B1430. The two strains were sensitive to vancomycin (MIC 2 μg.ml-1 and showed absence of haemolysis.

Lacticin LC14, a new bacteriocin produced by Lactococcus lactis BMG6.14: isolation, purification and partial characterization.

Science.gov (United States)

Lasta, Samar; Ouzari, Hadda; Andreotti, Nicolas; Fajloun, Ziad; Mansuelle, Pascal; Boudabous, Abdellatif; Sampieri, Francois; Sabatier, Jean Marc

2012-08-01

A new bacteriocin, lacticin LC14, produced by Lactococcus lactis BMG6.14, was isolated and characterized. It was purified to homogeneity from overnight broth culture by ammonium sulfate precipitation, Sep-Pak chromatography, and two steps of reversed-phase HPLC. Lacticin LC14 showed bactericidal-type antimicrobial activity against several lactic acid bacteria and pathogenic strains including Listeria monocytogenes. It was inactivated by proteinase K and pronase E, but was resistant to papain, lysozyme, lipase and catalase. Lacticin LC14 was heat resistant, stable over a wide range of pH (2-10) and after treatment by solvents and detergents. Its N-terminal end was found unreactive towards Edman sequencing. Based on MALDI-TOF mass spectrometry, its molecular mass was 3333.7 Da. LC14 amino acid composition revealed a high proportion of hydrophobic residues, but no modified ones. LC14 may be able to challenge other well known other bacteriocins in probiotic and therapeutic applications.

Information circulars

International Nuclear Information System (INIS)

1997-02-01

The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to February 1997, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex

Information circulars

International Nuclear Information System (INIS)

1994-08-01

Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to mid-August 1994. A complete numerical list of information circulars is reproduced with their titles in the Annex

Information circulars

International Nuclear Information System (INIS)

2002-05-01

Information circulars are published from time to time under the symbol INFCIRC/... for the purpose of bringing matters of general interest to the attention of all Members of the Agency. The present revision contains INFCIRCs published up to the end of April 2002. A complete numerical list of information circulars is reproduced with their titles in the Annex

Information circulars

International Nuclear Information System (INIS)

1999-06-01

The document summarizes the Information Circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Member States. This revision contains INFCIRCs published up to the end of May 1999, grouped by field of activity. A complete list of information circulars in numerical order is given in an annex

Information Circulars

International Nuclear Information System (INIS)

1966-01-01

Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current or on the press on 15 May 1966 is given, followed by an index to their subject matter.

Information Circulars

Energy Technology Data Exchange (ETDEWEB)

NONE

1966-06-10

Information circulars are published from time to time under the symbol INFCIRC/. . . . for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A list of the circulars that were current or on the press on 15 May 1966 is given, followed by an index to their subject matter.

Transposable elements and circular DNAs

KAUST Repository

Mourier, Tobias

2016-09-26

Circular DNAs are extra-chromosomal fragments that become circularized by genomic recombination events. We have recently shown that yeast LTR elements generate circular DNAs through recombination events between their flanking long terminal repeats (LTRs). Similarly, circular DNAs can be generated by recombination between LTRs residing at different genomic loci, in which case the circular DNA will contain the intervening sequence. In yeast, this can result in gene copy number variations when circles contain genes and origins of replication. Here, I speculate on the potential and implications of circular DNAs generated through recombination between human transposable elements.

Transposable elements and circular DNAs

KAUST Repository

Mourier, Tobias

2016-01-01

Circular DNAs are extra-chromosomal fragments that become circularized by genomic recombination events. We have recently shown that yeast LTR elements generate circular DNAs through recombination events between their flanking long terminal repeats (LTRs). Similarly, circular DNAs can be generated by recombination between LTRs residing at different genomic loci, in which case the circular DNA will contain the intervening sequence. In yeast, this can result in gene copy number variations when circles contain genes and origins of replication. Here, I speculate on the potential and implications of circular DNAs generated through recombination between human transposable elements.

Application of the broad-spectrum bacteriocin enterocin AS-48 to inhibit Bacillus coagulans in canned fruit and vegetable foods.

Science.gov (United States)

Lucas, R; Grande, M A J; Abriouel, H; Maqueda, M; Ben Omar, N; Valdivia, E; Martínez-Cañamero, M; Gálvez, A

2006-10-01

The enterococcal bacteriocin (enterocin) AS-48 is a broad-spectrum cyclic peptide. Enterocin AS-48 was tested against Bacillus coagulans in three vegetable canned foods: tomato paste (pH 4.64), syrup from canned peaches (pH 3.97), and juice from canned pineapple (pH 3.65). When vegetative cells of B. coagulans CECT (Spanish Type Culture Collection) 12 were inoculated in tomato paste supplemented with 6 microg/ml AS-48 and stored at different temperatures, viable cell counts were reduced by approximately 2.37 (4 degrees C), 4.3 (22 degrees C) and 3.0 (37 degrees C) log units within 24 h storage. After 15-days storage, no viable cells were detected in any sample. Strain B. coagulans CECT 561 showed a poor survival in tomato paste, but surviving cells were also killed by AS-48. The bacteriocin was also very active against B. coagulans CECT 12 vegetative cells in juice from canned pineapple stored at 22 degrees C, and slightly less active in syrup from canned peaches. In food samples supplemented with 1.5% lactic acid, enterocin AS-48 (6 microg/ml) rapidly reduced viable counts of vegetative cells below detection limits within 24 h storage. Addition of glucose and sucrose (10% and 20%) significantly increased bacteriocin activity against vegetative cells of B. coagulans CECT 12. Enterocin AS-48 had no significant effect on B. coagulans CECT 12 spores. However, the combined application of AS-48 and heat (80-95 degrees C for 5 min) significantly increased the effect of thermal treatments on spores.

The effect of the rotational orientation of circular photomultipliers in a PET camera block detector design

International Nuclear Information System (INIS)

Uribe, J.; Wong, Wai-Hoi; Hu, Guoju

1996-01-01

This is a study of the effects of geometric asymmetries in circular photomultipliers (PMT) on the design of PET position-sensitive block detectors. The dynodes of linear-focus circular PMT's are asymmetric relative to the axis of the photocathode, despite the rotational symmetry of the photocathode. Hence, there are regional photocathode differences in the anode signal, which affect the decoding characteristics of position sensitive block detectors. This orientation effect, as well as the effect of introducing light diffusers, are studied in a block detector design (BGO) using the PMT-quadrant-sharing configuration. The PMT studied is the Philips XP-1911 (19mm diameter). Seven symmetrical and representative orientations of the four decoding PMT were investigated, as well as one asymmetric orientation. The measurements performed include block-composite pulse-height spectra and crystal decoding maps. Two orientation effects were observed: (A) distortion variation in decoding maps, and (B) decoding resolution variation. The introduction of circular plastic pieces, used as light diffusers, prove to be useful by improving the decoding of crystals on the periphery of the detector block and minimizing distortion in the decoding map. These measurements have shown optimal PMT orientations for the PMT-quadrant-sharing design, as well as for conventional block designs

Iconography in Bradshaw rock art: breaking the circularity.

Science.gov (United States)

Pettigrew, Jack

2011-09-01

Interpreting the symbols found in the rock art of an extinct culture is hampered by the fact that such symbols are culturally determined. How does one break the circularity inherent in the fact that the knowledge of both the symbols and the culture comes from the same source? In this study, the circularity is broken for the Bradshaw rock art of the Kimberley by seeking anchors from outside the culture. Bradshaw rock art in the Kimberley region of Australia and Sandawe rock art in the Kolo region of Eastern Tanzania were surveyed in six visits on foot, by vehicle, by helicopter and from published or shared images, as well as from the published and online images of Khoisan rock art. Uniquely shared images between Bradshaw and Sandawe art, such as the 'mushroom head' symbol of psilocybin use, link the two cultures and indicate that they were shamanistic. Therefore, many mysterious features in the art can be understood in terms of trance visualisations. A number of other features uniquely link Bradshaw and Sandawe cultures, such as a special affinity for small mammals. There are also many references to baobabs in early Bradshaw art but not later. This can be explained in the context of the Toba super-volcano, the likely human transport of baobabs to the Kimberley and the extraordinary utility of the baobab. Many more mysterious symbols in Bradshaw rock art might await interpretation using the approaches adopted here. © 2011 The Author. Clinical and Experimental Optometry © 2011 Optometrists Association Australia.

Detection of Bacteriocins by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

OpenAIRE

Rose, Natisha L.; Sporns, Peter; McMullen, Lynn M.

1999-01-01

The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the detection of bacteriocins was investigated. A 30-s water wash of the sample on the MALDI-TOF MS probe was effective in removing contaminants of the analyte. This method was used for rapid detection of nisin, pediocin, brochocin A and B, and enterocin A and B from culture supernatants and for detection of enterocin B throughout its purification.

A peptide factor secreted by Staphylococcus pseudintermedius exhibits properties of both bacteriocins and virulence factors.

Science.gov (United States)

Wladyka, Benedykt; Piejko, Marcin; Bzowska, Monika; Pieta, Piotr; Krzysik, Monika; Mazurek, Łukasz; Guevara-Lora, Ibeth; Bukowski, Michał; Sabat, Artur J; Friedrich, Alexander W; Bonar, Emilia; Międzobrodzki, Jacek; Dubin, Adam; Mak, Paweł

2015-09-28

Staphylococcus pseudintermedius is a common commensal bacterium colonizing the skin and mucosal surfaces of household animals. However, it has recently emerged as a dangerous opportunistic pathogen, comparable to S. aureus for humans. The epidemiological situation is further complicated by the increasing number of methicillin-resistant S. pseudintermedius infections and evidence of gene transmission driving antibiotic resistance between staphylococci colonizing human and zoonotic hosts. In the present study, we describe a unique peptide, BacSp222, that possesses features characteristic of both bacteriocins and virulence factors. BacSp222 is secreted in high quantities by S. pseudintermedius strain 222 isolated from dog skin lesions. This linear, fifty-amino-acid highly cationic peptide is plasmid-encoded and does not exhibit significant sequence similarities to any other known peptides or proteins. BacSp222 kills gram-positive bacteria (at doses ranging from 0.1 to several micromol/l) but also demonstrates significant cytotoxic activities towards eukaryotic cells at slightly higher concentrations. Moreover, at nanomolar concentrations, the peptide also possesses modulatory properties, efficiently enhancing interferon gamma-induced nitric oxide release in murine macrophage-like cell lines. BacSp222 appears to be one of the first examples of multifunctional peptides that breaks the convention of splitting bacteriocins and virulence factors into two unrelated groups.

Genotypic and Phylogenic Analysis of Lactobacilli Producing Bacteriocin Isolated from Traditional Dairy Products and Food

Directory of Open Access Journals (Sweden)

Frazaneh Tafvizi

2012-09-01

Full Text Available Background & Objective: Lactic acid bacteria (LAB are a group of Gram-positive, non-spore forming, cocci or rod shaped, catalase negative organisms, considered as Generally Recognized as Safe (GRAS organisms. These bacteria are used for thousands of years for production of fermented foods because of their ability to produce desirable changes in taste, flavor and texture. Different antimicrobial molecules such as bacteriocins produced by these bacteria that can inhibit food pathogens, so enhancing the shelf life and improving the safety of food products. Because of important role of LAB to improving the human health, molecular identification and phylogenic analysis of these bacteria based on 16S rRNA sequencing play the critical role in investigation of local sources of LAB in Iran. Materials & Methods: 5 isolates were selected from 20 isolates for molecular identification. These strains produced the high level of bacteriocin. Total genomic DNA was extracted by lysosyme extraction protocol. PCR-mediated amplification was carried out by degenerate primers. Sequencing was performed after purification of PCR product. Results: Isolates were deposited as novel strains of Lactobacillus casei and Entrococcus facium in GenBank. Conclusion: Because of high potential of local probiotic bacteria in Iran, these strains may be useful and could be used in the food industry.

Information circulars

International Nuclear Information System (INIS)

1987-06-01

The document summarizes the information circulars published by the IAEA for the purpose of bringing matters of general interest to the attention of all Members of the Agency. In the main body of the document only those documents which are regarded as likely to be of current interest are listed. A complete numerical list of information circulars with their titles is reproduced in the Annex

Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

Science.gov (United States)

Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

2015-11-17

We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

Bacteriocins from Lactobacillus plantarum production, genetic organization and mode of action: produção, organização genética e modo de ação Bacteriocinas de Lactobacillus plantarum

Directory of Open Access Journals (Sweden)

Svetoslav D. Todorov

2009-06-01

Full Text Available Bacteriocins are biologically active proteins or protein complexes that display a bactericidal mode of action towards usually closely related species. Numerous strains of bacteriocin producing Lactobacillus plantarum have been isolated in the last two decades from different ecological niches including meat, fish, fruits, vegetables, and milk and cereal products. Several of these plantaricins have been characterized and the aminoacid sequence determined. Different aspects of the mode of action, fermentation optimization and genetic organization of the bacteriocin operon have been studied. However, numerous of bacteriocins produced by different Lactobacillus plantarum strains have not been fully characterized. In this article, a brief overview of the classification, genetics, characterization, including mode of action and production optimization for bacteriocins from Lactic Acid Bacteria in general, and where appropriate, with focus on bacteriocins produced by Lactobacillus plantarum, is presented.Bacteriocinas são proteínas ou complexos protéicos biologicamente ativos que apresentam atividade bactericida contra espécies relacionadas. Nas ultimas duas décadas, várias cepas de Lactobacillus plantarum produtoras de bacteriocinas foram isoladas de diferentes nichos ecológicos como carnes, peixes, frutas, vegetais e produtos lácteos e de cereais. Várias plantaricinas foram caracterizadas e suas seqüências de aminoácidos determinadas. Diferentes aspectos do modo de ação, otimização da fermentação e organização genética já foram estudados. Entretanto, muitas bacteriocinas produzidas por diferentes cepas de Lactobacillus plantarum ainda não foram completamente caracterizadas.Nesse artigo, apresenta-se uma breve revisão sobre a classificação, genética, caracterização, modo de ação, e otimização da produção de bacteriocinas de bactérias láticas em geral, e, quando apropriado, de bacteriocinas de Lactobacillus plantarum.

Large-Scale Purification, Characterization, and Spore Outgrowth Inhibitory Effect of Thurincin H, a Bacteriocin Produced by Bacillus thuringiensis SF361.

Science.gov (United States)

Wang, Gaoyan; Manns, David C; Guron, Giselle K; Churey, John J; Worobo, Randy W

2014-06-01

Large-scale purification of the highly hydrophobic bacteriocin thurincin H was accomplished via a novel and simple two-step method: ammonia sulfate precipitation and C18 solid-phase extraction. The inhibition spectrum and stability of thurincin H as well as its antagonistic activity against Bacillus cereus F4552 spores were further characterized. In the purification method, secreted proteins contained in the supernatant of a 40 h incubated culture of B. thuringiensis SF361 were precipitated by 68 % ammonia sulfate and purified by reverse-phase chromatography, with a yield of 18.53 mg/l of pure thurincin H. Silver-stained SDS-PAGE, high-performance liquid chromatography, and liquid chromatography-mass spectrometry confirmed the high purity of the prepared sample. Thurincin H exhibited a broad antimicrobial activity against 22 tested bacterial strains among six different genera including Bacillus, Carnobacterium, Geobacillus, Enterococcus, Listeria, and Staphylococcus. There was no detectable activity against any of the selected yeast or fungi. The bacteriocin activity was stable for 30 min at 50 °C and decreased to undetectable levels within 10 min at temperatures above 80 °C. Thurincin H is also stable from pH 2-7 for at least 24 h at room temperature. Thurincin H is germicidal against B. cereus spores in brain heart infusion broth, but not in Tris-NaCl buffer. The efficient purification method enables the large-scale production of pure thurincin H. The broad inhibitory spectrum of this bacteriocin may be of interest as a potential natural biopreservative in the food industry, particularly in post-processed and ready-to-eat food.

Heterologous expression and purification of plantaricin NC8, a two-peptide bacteriocin against Salmonella spp. from Lactobacillus plantarum ZJ316.

Science.gov (United States)

Jiang, Han; Li, Ping; Gu, Qing

2016-11-01

Bacteriocin, which is produced by lactic acid bacteria (LAB), has the potential to act as natural preservatives in the food industry. To develop strategies to overproduce such peptides, plantaricin NC8, a class IIb LAB bacteriocin that consists of two peptides, PLNC8α and PLNC8β, was successfully heterologously expressed in Escherichia coli BL21 (DE3). PLNC8α and PLNC8β peptides were expressed as His6-tag fusion proteins and were separated by Ni(2+) chelating affinity chromatography. To get the PLNC8α and PLNC8β peptides without extra amino acids in the N-terminus, the fusion proteins were cleaved by enterokinase and further purified using the Ni-NTA Sefinose™ Resin Kit. The molecular masses of peptides were checked using Tricine-SDS-PAGE and MALDI-TOF-MS. The yield of purified PLNC8α was around 2-2.5 mg/L, and the yield of PLNC8β was around 1.5-2 mg/L. The antimicrobial spectrum of cleaved peptides was detected and the synergistic action of PLNC8α and PLNC8β was preliminarily confirmed. It was found that E. coli was a suitable host for heterologous expression of plantaricin NC8 with a significant yield. Importantly, the bacteriocin appeared to be very active for controlling and inhibiting the food-borne pathogenic Gram-negative bacteria Salmonella spp., and might be useful as a natural preservative candidate. Copyright © 2016 Elsevier Inc. All rights reserved.

Publication of administrative circular

CERN Multimedia

HR Department

2009-01-01

ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee on 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in Departmental Secretariats. Human Resources Department Tel. 78003

PUBLICATION OF ADMINISTRATIVE CIRCULAR

CERN Multimedia

HR Department

2008-01-01

ADMINISTRATIVE CIRCULAR NO. 23 (REV. 2) – SPECIAL WORKING HOURS Administrative Circular No. 23 (Rev. 2) entitled "Special working hours", approved following discussion in the Standing Concertation Committee meeting of 9 December 2008, will be available on the intranet site of the Human Resources Department as from 19 December 2008: http://cern.ch/hr-docs/admincirc/admincirc.asp It cancels and replaces Administrative Circular No. 23 (Rev. 1) entitled "Stand-by duty" of April 1988. A "Frequently Asked Questions" information document on special working hours will also be available on this site. Paper copies of this circular will shortly be available in departmental secretariats. Human Resources Department Tel. 78003

Licheniocin 50.2 and Bacteriocins from Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 Inhibit Biofilms of Coagulase Negative Staphylococci and Listeria monocytogenes Clinical Isolates.

Science.gov (United States)

Cirkovic, Ivana; Bozic, Dragana D; Draganic, Veselin; Lozo, Jelena; Beric, Tanja; Kojic, Milan; Arsic, Biljana; Garalejic, Eliana; Djukic, Slobodanka; Stankovic, Slavisa

2016-01-01

Coagulase negative staphylococci (CoNS) and Listeria monocytogenes have important roles in pathogenesis of various genital tract infections and fatal foetomaternal infections, respectively. The aim of our study was to investigate the inhibitory effects of two novel bacteriocins on biofilms of CoNS and L. monocytogenes genital isolates. The effects of licheniocin 50.2 from Bacillus licheniformis VPS50.2 and crude extract of bacteriocins produced by Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 (BGBU1-4 crude extract) were evaluated on biofilm formation and formed biofilms of eight CoNS (four S. epidermidis, two S. hominis, one S. lugdunensis and one S. haemolyticus) and 12 L. monocytogenes genital isolates. Licheniocin 50.2 and BGBU1-4 crude extract inhibited the growth of both CoNS and L. monocytogenes isolates, with MIC values in the range between 200-400 AU/ml for licheniocin 50.2 and 400-3200 AU/ml for BGBU1-4 crude extract. Subinhibitory concentrations (1/2 × and 1/4 × MIC) of licheniocin 50.2 inhibited biofilm formation by all CoNS isolates (p < 0.05, respectively), while BGBU1-4 crude extract inhibited biofilm formation by all L. monocytogenes isolates (p < 0.01 and p < 0.05, respectively). Both bacteriocins in concentrations of 100 AU/mL and 200 AU/mL reduced the amount of 24 h old CoNS and L. monocytogenes biofilms (p < 0.05, p < 0.01, p < 0.001). This study suggests that novel bacteriocins have potential to be used for genital application, to prevent biofilm formation and/or to eradicate formed biofilms, and consequently reduce genital and neonatal infections by CoNS and L. monocytogenes.

Antibacterial and Synergistic Activity Against β-Lactamase-Producing Nosocomial Bacteria by Bacteriocin of LAB Isolated From Lesser Known Traditionally Fermented Products of India

Directory of Open Access Journals (Sweden)

Koel Biswas

2017-04-01

Full Text Available There is an ever-growing need to control antibiotic-resistance owing to alarming resistance to commonly available antimicrobial agents for which contemporary and alternative approaches are being explored. The present study assessed the antibacterial activity of bacteriocins from lactic acid bacteria (LAB from lesser known traditionally fermented products of India for their synergistic potential with common antibiotics against clinical β-lactamases producing pathogens. A total of 84 isolates of LAB were screened for their antibacterial efficacy against Streptococcus pyogenes, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Bacillus cereus as well as against clinical pathogens harbouring β-lactamase genes such as blaCTX-M, blaVIM, blaIMP, blaSHV and blaNDM. Synergistic activity of bacteriocins were determined in combination with antibiotics namely, cefotaxime, polymyxin B, imipenem and tigecycline. Purified bacteriocins from Lactobacillus, Pediococcus and Enterococcus inhibited the growth of β-lactamase harbouring clinical pathogens which significantly higher inhibitions when compared with antibiotics alone. Minimum inhibitory concentration of the extracts ranged from 6.66 to 26.66 mg/ml and 10 to 33.33 mg/ml for Pediococcus pentosaceus LU11 and Lactobacillus plantarum LS6. The bacteriocinogenic activity of LAB opens scope for bioprospection of antibacterial components in the current struggle against increasing pandrug resistance and slowing down the expansion of multi-drug resistance.

A Sequential Statistical Approach towards an Optimized Production of a Broad Spectrum Bacteriocin Substance from a Soil Bacterium Bacillus sp. YAS 1 Strain

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Amira M. Embaby

2014-01-01

Full Text Available Bacteriocins, ribosomally synthesized antimicrobial peptides, display potential applications in agriculture, medicine, and industry. The present study highlights integral statistical optimization and partial characterization of a bacteriocin substance from a soil bacterium taxonomically affiliated as Bacillus sp. YAS 1 after biochemical and molecular identifications. A sequential statistical approach (Plackett-Burman and Box-Behnken was employed to optimize bacteriocin (BAC YAS 1 production. Using optimal levels of three key determinants (yeast extract (0.48% (w/v, incubation time (62 hrs, and agitation speed (207 rpm in peptone yeast beef based production medium resulted in 1.6-fold enhancement in BAC YAS 1 level (470 AU/mL arbitrary units against Erwinia amylovora. BAC YAS 1 showed activity over a wide range of pH (1–13 and temperature (45–80°C. A wide spectrum antimicrobial activity of BAC YAS 1 against the human pathogens (Clostridium perfringens, Staphylococcus epidermidis, Campylobacter jejuni, Enterobacter aerogenes, Enterococcus sp., Proteus sp., Klebsiella sp., and Salmonella typhimurium, the plant pathogen (E. amylovora, and the food spoiler (Listeria innocua was demonstrated. On top and above, BAC YAS 1 showed no antimicrobial activity towards lactic acid bacteria (Lactobacillus bulgaricus, L. casei, L. lactis, and L. reuteri. Promising characteristics of BAC YAS 1 prompt its commercialization for efficient utilization in several industries.

Structure and properties of the metastable bacteriocin Lcn972 from Lactococcus lactis

Science.gov (United States)

Turner, David L.; Lamosa, Pedro; Rodríguez, Ana; Martínez, Beatriz

2013-01-01

Lactococcus lactis subsp. lactis IPLA 972 produces a polypeptide bacteriocin of 7.5 kDa which has a bactericidal effect on sensitive lactococci, inhibiting septum formation in dividing cells. The active form is a monomer that is metastable under normal conditions but is stabilised by glycerol. The NMR structure of Lcn972 shows a β-sandwich comprising two three-stranded antiparallel β-sheets. Detaching the final strand could allow the sandwich to open, and the irreversible unfolding leads to a loss of antibacterial activity. Covalent linkage of the final strand should increase the stability of Lcn972 and facilitate the study of its interaction with lipid II.

Effect of bacteriocin and exopolysaccharides isolated from probiotic on P. aeruginosa PAO1 biofilm.

Science.gov (United States)

Sharma, Vivek; Harjai, Kusum; Shukla, Geeta

2018-03-01

Microorganisms develop biofilms on indwelling medical devices and are associated with biofilm-related infections, resulting in substantial morbidity and mortality. Therefore, to prevent and control biofilm-associated infections, the present study was designed to assess the anti-biofilm potential of postbiotics derived from probiotic organisms against most prevalent biofilm-forming Pseudomonas aeruginosa PAO1. Eighty lactic acid bacteria isolated from eight neonatal fecal samples possessed antibacterial activity against P. aeruginosa PAO1. Among these, only four lactic acid bacteria produced both bacteriocin and exopolysaccharides but only one isolate was found to maximally attenuate the P. aeruginosa PAO1 biofilm. More specifically, the phenotypic and probiotic characterization showed that the isolated lactic acid bacteria were gram positive, non-motile, and catalase and oxidase negative; tolerated acidic and alkaline pH; has bile salt concentration; showed 53% hydrophobicity; and was found to be non-hemolytic. Phylogenetically, the organism was found to be probiotic Lactobacillus fermentum with accession no. KT998657. Interestingly, pre-coating of a microtiter plate either with bacteriocin or with exopolysaccharides as well as their combination significantly (p < 0.05) reduced the number of viable cells forming biofilms to 41.7% compared with simultaneous coating of postbiotics that had 72.4% biofilm-forming viable cells as observed by flow cytometry and confocal laser scanning microscopy. Therefore, it can be anticipated that postbiotics as the natural biointerventions can be employed as the prophylactic agents for medical devices used to treat gastrointestinal and urinary tract infections.

Political economies and environmental futures for the sharing economy

Science.gov (United States)

Frenken, Koen

2017-05-01

The sudden rise of the sharing economy has sparked an intense public debate about its definition, its effects and its future regulation. Here, I attempt to provide analytical guidance by defining the sharing economy as the practice that consumers grant each other temporary access to their under-utilized physical assets. Using this definition, the rise of the sharing economy can be understood as occurring at the intersection of three salient economic trends: peer-to-peer exchange, access over ownership and circular business models. I shortly discuss some of the environmental impacts of online sharing platforms and then articulate three possible futures of the sharing economy: a capitalist future cumulating in monopolistic super-platforms allowing for seamless services, a state-led future that shifts taxation from labour to capital and redistributes the gains of sharing from winners to losers, and a citizen-led future based on cooperatively owned platforms under democratic control. The nature and size of the social and environmental impacts are expected to differ greatly in each of the three scenarios. This article is part of the themed issue 'Material demand reduction'.

Effects of the presence of the curing agent sodium nitrite, used in the production of fermented sausages, on bacteriocin production by Weissella paramesenteroides DX grown in meat simulation medium.

Science.gov (United States)

Papagianni, M; Sergelidis, D

2013-06-10

Weissellin A is a listericidal bacteriocin produced by the sausage-isolated strain of Weissella paramesenteroides DX. The response of the strain to various concentrations of the added curing agent NaNO2 (0.0025, 0.005 and 0.01g/L) was evaluated in bioreactor fermentations using a meat simulation medium. The presence of nitrite suppressed bacteriocin production - the effect being more pronounced with increasing concentrations. Weissellin A was produced as a growth-associated metabolite in the absence of nitrite or its presence in the low concentration of 0.005g/L under aerobic conditions. The suppressive effect of nitrite was apparent under conditions supporting increased specific production rates, e.g. 50% and 100% dissolved oxygen tension, but no effect was observed under anaerobic conditions. As the latter prevail in the microenvironment of fermented meat products, the absence of any influence of nitrite on bacteriocin production is an important finding that enlightens the role of this species of lactic acid bacteria in its common substrates. Copyright © 2013 Elsevier Inc. All rights reserved.

Kinetic studies of the action of Lactacin F, a bacteriocin produced by Lactobacillus johnsonii that forms poration complexes in the cytoplasmic membrane.

NARCIS (Netherlands)

Abee, T.; Klaenhammer, T.R.; Letellier, L.

1994-01-01

The bacteriocin lactacin F is bactericidal against Lactobacillus delbrueckii, Lactobacillus helveticus, and Enterococcus faecalis. Activity against L. delbrueckii was recently shown to be dependent on two peptides, LafA and LafX, which are encoded within the lactacin F operon (T. R. Klaenhammer,

Bacteriocin- producing strain of Enterococcus faecium EK 13 with probiotic character and its application in the digestive tract of rabbits

Czech Academy of Sciences Publication Activity Database

Lauková, A.; Strompfová, V.; Skřivanová, V.; Volek, Z.; Jindřichová, E.; Marounek, Milan

2006-01-01

Roč. 61, č. 6 (2006), s. 779-782 ISSN 0006-3088. [ Probiotic Conference /2./. Košice, 15.09.2006-19.09.2006] Grant - others:VEGA 2/5139/25 Institutional research plan: CEZ:AV0Z50450515 Keywords : probiotic * bacteriocin * enterocin Subject RIV: GH - Livestock Nutrition Impact factor: 0.213, year: 2006

Circular states of atomic hydrogen

International Nuclear Information System (INIS)

Lutwak, R.; Holley, J.; Chang, P.P.; Paine, S.; Kleppner, D.; Ducas, T.

1997-01-01

We describe the creation of circular states of hydrogen by adiabatic transfer of a Rydberg state in crossed electric and magnetic fields, and also by adiabatic passage in a rotating microwave field. The latter method permits rapid switching between the two circular states of a given n manifold. The two methods are demonstrated experimentally, and results are presented of an analysis of the field ionization properties of the circular states. An application for the circular states is illustrated by millimeter-wave resonance in hydrogen of the n=29→n=30 transition. copyright 1997 The American Physical Society

ABC transporter content diversity in Streptococcus pneumoniae impacts competence regulation and bacteriocin production.

Science.gov (United States)

Wang, Charles Y; Patel, Nisha; Wholey, Wei-Yun; Dawid, Suzanne

2018-06-19

The opportunistic pathogen Streptococcus pneumoniae (pneumococcus) uses natural genetic competence to increase its adaptability through horizontal gene transfer. One method of acquiring DNA is through predation of neighboring strains with antimicrobial peptides called "bacteriocins." Competence and production of the major family of pneumococcal bacteriocins, pneumocins, are regulated by the quorum-sensing systems com and blp , respectively. In the classical paradigm, the ABC transporters ComAB and BlpAB each secretes its own system's signaling pheromone and in the case of BlpAB also secretes the pneumocins. While ComAB is found in all pneumococci, only 25% of strains encode an intact version of BlpAB [BlpAB(+)] while the rest do not [BlpAB(-)]. Contrary to the classical paradigm, it was previously shown that BlpAB(-) strains can activate blp through ComAB-mediated secretion of the blp pheromone during brief periods of competence. To better understand the full extent of com - blp crosstalk, we examined the contribution of each transporter to competence development and pneumocin secretion. We found that BlpAB(+) strains have a greater capacity for competence activation through BlpAB-mediated secretion of the com pheromone. Similarly, we show that ComAB and BlpAB are promiscuous and both can secrete pneumocins. Consequently, differences in pneumocin secretion between BlpAB(+) and BlpAB(-) strains derive from the regulation and kinetics of transporter expression rather than substrate specificity. We speculate that BlpAB(-) strains (opportunists) use pneumocins mainly in a narrowly tailored role for DNA acquisition and defense during competence while BlpAB(+) strains (aggressors) expand their use for the general inhibition of rival strains. Copyright © 2018 the Author(s). Published by PNAS.

The Cyclic Antibacterial Peptide Enterocin AS-48: Isolation, Mode of Action, and Possible Food Applications

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María José Grande Burgos

2014-12-01

Full Text Available Enterocin AS-48 is a circular bacteriocin produced by Enterococcus. It contains a 70 amino acid-residue chain circularized by a head-to-tail peptide bond. The conformation of enterocin AS-48 is arranged into five alpha-helices with a compact globular structure. Enterocin AS-48 has a wide inhibitory spectrum on Gram-positive bacteria. Sensitivity of Gram-negative bacteria increases in combination with outer-membrane permeabilizing treatments. Eukaryotic cells are bacteriocin-resistant. This cationic peptide inserts into bacterial membranes and causes membrane permeabilization, leading ultimately to cell death. Microarray analysis revealed sets of up-regulated and down-regulated genes in Bacillus cereus cells treated with sublethal bacteriocin concentration. Enterocin AS-48 can be purified in two steps or prepared as lyophilized powder from cultures in whey-based substrates. The potential applications of enterocin AS-48 as a food biopreservative have been corroborated against foodborne pathogens and/or toxigenic bacteria (Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella enterica and spoilage bacteria (Alicyclobacillus acidoterrestris, Bacillus spp., Paenibacillus spp., Geobacillus stearothermophilus, Brochothrix thermosphacta, Staphylococcus carnosus, Lactobacillus sakei and other spoilage lactic acid bacteria. The efficacy of enterocin AS-48 in food systems increases greatly in combination with chemical preservatives, essential oils, phenolic compounds, and physico-chemical treatments such as sublethal heat, high-intensity pulsed-electric fields or high hydrostatic pressure.

The Cyclic Antibacterial Peptide Enterocin AS-48: Isolation, Mode of Action, and Possible Food Applications.

Science.gov (United States)

Grande Burgos, María José; Pulido, Rubén Pérez; Del Carmen López Aguayo, María; Gálvez, Antonio; Lucas, Rosario

2014-12-08

Enterocin AS-48 is a circular bacteriocin produced by Enterococcus. It contains a 70 amino acid-residue chain circularized by a head-to-tail peptide bond. The conformation of enterocin AS-48 is arranged into five alpha-helices with a compact globular structure. Enterocin AS-48 has a wide inhibitory spectrum on Gram-positive bacteria. Sensitivity of Gram-negative bacteria increases in combination with outer-membrane permeabilizing treatments. Eukaryotic cells are bacteriocin-resistant. This cationic peptide inserts into bacterial membranes and causes membrane permeabilization, leading ultimately to cell death. Microarray analysis revealed sets of up-regulated and down-regulated genes in Bacillus cereus cells treated with sublethal bacteriocin concentration. Enterocin AS-48 can be purified in two steps or prepared as lyophilized powder from cultures in whey-based substrates. The potential applications of enterocin AS-48 as a food biopreservative have been corroborated against foodborne pathogens and/or toxigenic bacteria (Listeria monocytogenes, Bacillus cereus, Staphylococcus aureus, Escherichia coli, Salmonella enterica) and spoilage bacteria (Alicyclobacillus acidoterrestris, Bacillus spp., Paenibacillus spp., Geobacillus stearothermophilus, Brochothrix thermosphacta, Staphylococcus carnosus, Lactobacillus sakei and other spoilage lactic acid bacteria). The efficacy of enterocin AS-48 in food systems increases greatly in combination with chemical preservatives, essential oils, phenolic compounds, and physico-chemical treatments such as sublethal heat, high-intensity pulsed-electric fields or high hydrostatic pressure.

Political economies and environmental futures for the sharing economy.

Science.gov (United States)

Frenken, Koen

2017-06-13

The sudden rise of the sharing economy has sparked an intense public debate about its definition, its effects and its future regulation. Here, I attempt to provide analytical guidance by defining the sharing economy as the practice that consumers grant each other temporary access to their under-utilized physical assets. Using this definition, the rise of the sharing economy can be understood as occurring at the intersection of three salient economic trends: peer-to-peer exchange, access over ownership and circular business models. I shortly discuss some of the environmental impacts of online sharing platforms and then articulate three possible futures of the sharing economy: a capitalist future cumulating in monopolistic super-platforms allowing for seamless services, a state-led future that shifts taxation from labour to capital and redistributes the gains of sharing from winners to losers, and a citizen-led future based on cooperatively owned platforms under democratic control. The nature and size of the social and environmental impacts are expected to differ greatly in each of the three scenarios.This article is part of the themed issue 'Material demand reduction'. © 2017 The Authors.

Political economies and environmental futures for the sharing economy

Science.gov (United States)

2017-01-01

The sudden rise of the sharing economy has sparked an intense public debate about its definition, its effects and its future regulation. Here, I attempt to provide analytical guidance by defining the sharing economy as the practice that consumers grant each other temporary access to their under-utilized physical assets. Using this definition, the rise of the sharing economy can be understood as occurring at the intersection of three salient economic trends: peer-to-peer exchange, access over ownership and circular business models. I shortly discuss some of the environmental impacts of online sharing platforms and then articulate three possible futures of the sharing economy: a capitalist future cumulating in monopolistic super-platforms allowing for seamless services, a state-led future that shifts taxation from labour to capital and redistributes the gains of sharing from winners to losers, and a citizen-led future based on cooperatively owned platforms under democratic control. The nature and size of the social and environmental impacts are expected to differ greatly in each of the three scenarios. This article is part of the themed issue ‘Material demand reduction’. PMID:28461431

Solid Angle Computations for a Circular Radiator and a Circular Detector

Energy Technology Data Exchange (ETDEWEB)

Konijn, J; Tollander, B

1963-02-15

The problem of particle detection, when using an isotropic neutron point source at different distances from a circular target or a radioactive source as seen by a circular detector, e. g. a solid state counter, is dealt with. Tables are given for different distances of the source when the reaction at the target has an isotropic or a cosine angular distribution in the laboratory system.

Antennas on circular cylinders

DEFF Research Database (Denmark)

Knudsen, H. L.

1959-01-01

On the basis of the results obtained by Silver and Saunders [4] for the field radiated from an arbitrary slot in a perfectly conducting circular cylinder, expressions have been derived for the field radiated by a narrow helical slot, with an arbitrary aperture field distribution, in a circular...... antenna in a circular cylinder. By a procedure similar to the one used by Silver and Saunders, expressions have been derived for the field radiated from an arbitrary surface current distribution on a cylinder surface coaxial with a perfectly conducting cylinder. The cases where the space between the two...

Towards Circular Business Models

DEFF Research Database (Denmark)

Guldmann, Eva; Remmen, Arne

The present report concerns the practical process of developing initiatives based on the circular economy in eight Danish companies. The report outlines how the process of integrating the circular economy was approached in each of the participating companies during 2014 and 2015 and what came out...

Circularity and Lambda Abstraction

DEFF Research Database (Denmark)

Danvy, Olivier; Thiemann, Peter; Zerny, Ian

2013-01-01

unknowns from what is done to them, which we lambda-abstract with functions. The circular unknowns then become dead variables, which we eliminate. The result is a strict circu- lar program a la Pettorossi. This transformation is reversible: given a strict circular program a la Pettorossi, we introduce...

Medical and Personal Care Applications of Bacteriocins Produced by Lactic Acid Bacteria

Science.gov (United States)

Dicks, L. M. T.; Heunis, T. D. J.; van Staden, D. A.; Brand, A.; Noll, K. Sutyak; Chikindas, M. L.

The frequent use of antibiotics has led to a crisis in the antibiotic ­resistance of pathogens associated with humans and animals. Antibiotic resistance and the emergence of multiresistant bacterial pathogens have led to the investigation of alternative antimicrobial agents to treat and prevent infections in both humans and animals. Research on antimicrobial peptides, with a special interest on bacteriocins of lactic acid bacteria, is entering a new era with novel applications other than food preservation. Many scientists are now focusing on the application of these peptides in medicinal and personal care products. However, it is difficult to assess the success of such ventures due to the dearth of information that has been published and the lack of clinical trials.

The generalized circular model

NARCIS (Netherlands)

Webers, H.M.

1995-01-01

In this paper we present a generalization of the circular model. In this model there are two concentric circular markets, which enables us to study two types of markets simultaneously. There are switching costs involved for moving from one circle to the other circle, which can also be thought of as

Best Practice Examples of Circular Business Models

DEFF Research Database (Denmark)

Guldmann, Eva

Best practice examples of circular business models are presented in this report. The purpose is to inform and inspire interested readers, in particular companies that aspire to examine the potentials of the circular economy. Circular business models in two different sectors are examined, namely...... the textile and clothing sector as well as the durable goods sector. In order to appreciate the notion of circular business models, the basics of the circular economy are outlined along with three frameworks for categorizing the various types of circular business models. The frameworks take point of departure...... in resource loops, value bases and business model archetypes respectively, and they are applied for analysing and organizing the business models that are presented throughout the report. The investigations in the report show that circular business models are relevant to businesses because they hold...

Garvicin A, a Novel Class IId Bacteriocin from Lactococcus garvieae That Inhibits Septum Formation in L. garvieae Strains

Science.gov (United States)

Cárdenas, Nivia; Martínez, Beatriz; Ruiz-Barba, José Luis; Fernández-Garayzábal, José F.; Rodríguez, Juan M.; Gibello, Alicia

2013-01-01

Lactococcus garvieae 21881, isolated in a human clinical case, produces a novel class IId bacteriocin, garvicin A (GarA), which is specifically active against other L. garvieae strains, including fish- and bovine-pathogenic isolates. Purification from active supernatants, sequence analyses, and plasmid-curing experiments identified pGL5, one of the five plasmids found in L. garvieae [M. Aguado-Urda et al., PLoS One 7(6):e40119, 2012], as the coding plasmid for the structural gene of GarA (lgnA), its putative immunity protein (lgnI), and the ABC transporter and its accessory protein (lgnC and lgnD). Interestingly, pGL5-cured strains were still resistant to GarA. Other putative bacteriocins encoded by the remaining plasmids were not detected during purification, pointing to GarA as the main inhibitor secreted by L. garvieae 21881. Mode-of-action studies revealed a potent bactericidal activity of GarA. Moreover, transmission microscopy showed that GarA seems to act by inhibiting septum formation in L. garvieae cells. This potent and species-specific inhibition by GarA holds promise for applications in the prevention or treatment of infections caused by pathogenic strains of L. garvieae in both veterinary and clinical settings. PMID:23666326

Effect of supplementation of yeast with bacteriocin and culture on growth performance, cecal fermentation, microbiota composition, and blood characteristics in broiler chickens

Directory of Open Access Journals (Sweden)

C. Y. Chen

2017-02-01

Full Text Available Objective The aim of the present study was to investigate the effect of yeast with bacteriocin and Lactobacillus cultures (mixture of Lactobacillus agilis BCRC 10436 and Lactobacillus reuteri BCRC 17476 supplements, alone or in combination, on broiler chicken performance. Methods A total of 300, 1-d-old healthy broiler chickens were randomly divided into five treatment groups: i basal diet (control, ii basal diet+0.25% yeast (Saccharomyces cerevisiae (YC, iii basal diet+0.25% yeast with bacteriocin (BA, iv basal diet+Lactobacillus cultures (LAB, and v basal diet +0.25% yeast with bacteriocin+Lactobacillus cultures (BA+LAB. Growth performance, cecal microbiota, cecal fermentation products, and blood biochemistry parameters were determined when chickens were 21 and 35 d old. Results The supplementation of YC, BA, and BA+LAB resulted in a significantly better feed conversion rate (FCR than that of the control group during 1 to 21 d (p<0.05. The LAB supplementation had a significant effect on the presence of Lactobacillus in the ceca at 35 d. None of the supplements had an effect on relative numbers of L. agilis and L. reuter at 21 d, but the BA supplementation resulted in the decrease of both Lactobacillus strains at 35 d. The BA+LAB supplementation resulted in higher short chain fatty acid (SCFA in the ceca, but LAB supplementation significantly decreased the SCFA at 35 d (p<0.05. All treatments tended to decrease ammonia concentration in the ceca at 21 d, especially in the LAB treatment group. The BA supplementation alone decreased the triacylglycerol (TG concentration significantly at 21 d (p<0.05, but the synergistic effect of BA and LAB supplementation was required to reduce the TG concentration at 35 d. The YC supplementation tended to increase the plasma cholesterol at 21 d and 35 d. However, the BA supplementation significantly decreased the cholesterol and low density lipoprotein cholesterol level at 35 d. In conclusion, the BA

Bacteriocin-like substances of Lactobacillus curvatus P99: characterization and application in biodegradable films for control of Listeria monocytogenes in cheese.

Science.gov (United States)

Marques, Juliana de Lima; Funck, Graciele Daiana; Dannenberg, Guilherme da Silva; Cruxen, Claudio Eduardo Dos Santos; Halal, Shanise Lisie Mello El; Dias, Alvaro Renato Guerra; Fiorentini, Ângela Maria; Silva, Wladimir Padilha da

2017-05-01

The aim of this study was to evaluate the effectiveness of a biodegradable film, with antimicrobial metabolites produced by Lactobacillus curvatus P99 incorporated, targeting the control of Listeria monocytogenes in sliced "Prato" cheese. Tests were performed to evaluate the spectrum of action of cell-free supernatant (CFS) of P99 against different microorganisms, as well as to detect the minimum inhibitory (MIC) and bactericidal (MBC) concentrations against L. monocytogenes Scott A. The detection of genes that encode for the production of bacteriocins and evaluation of their expression were performed. Antimicrobial films were prepared, followed by in vitro and in situ analysis. The MIC and MBC of CFS against L. monocytogenes Scott A was 15.6 μL/mL and 62.5 μL/mL, respectively. Lactobacillus curvatus P99 presented two genes coding for the bacteriocins, which were expressed. Films with added MBC showed activity against different indicator microorganisms and were able to control L. monocytogenes Scott A when used in sliced "Prato" cheese. Copyright © 2016 Elsevier Ltd. All rights reserved.

Detection and characterization of bacteriocin-producing Lactococcus lactis strains Detecção e caracterização de Lactococcus lactis produtores de bacteriocinas

Directory of Open Access Journals (Sweden)

Izildinha Moreno

1999-04-01

Full Text Available One hundred sixty seven strains of Lactococcus lactis were screened for bacteriocin production by well diffusion assay of GM17 agar. Fourteen (8.4% produced antimicrobial activity other than organic acids, bacteriophages or hydrogen peroxide. The frequency of bacteriocin production ranged from 2% in L. lactis subsp. cremoris up to 12% in L. lactis subsp. lactis. Antimicrobial activities were not observed in any strain of L. lactis subsp. lactis var. diacetylactis. Among thirteen bacteriocin-producing strains and two nisin-producing strains (L. lactis subsp. lactis ATCC 11454 and L. lactis subsp. lactis CNRZ 150, eight (53% were characterized as lactose-positive (Lac+ and proteinase-negative (Prt-. The bacteriocin-producing cultures were also characterized on the basis of plasmid content. All strains had 2 to 7 plasmids with molecular weights varying from 0.5 to 28.1 Mdal. Four strains (ITAL 435, ITAL 436, ITAL 437 and ITAL 438 showed identical profiles and the other were quite distinct.Um total de 167 linhagens de L. lactis foi selecionado para os testes de produção de bacteriocinas pelo método de difusão em poços em agar GM17. Desse total, 14 (8.4% produziram substâncias inibidoras que não foram associadas com ácidos orgânicos, peróxido de hidrogênio e bacteriófagos. A frequência de produção de bacteriocinas variou de 2% em L. lactis subsp. cremoris a 12% em L. lactis subsp. lactis. Nenhuma das linhagens de L. lactis subsp. lactis var. diacetylactis produziu substâncias inibidoras. De 13 linhagens produtoras de bacteriocinas e duas de nisina (L. lactis subsp. lactis ATCC 11454 e L. lactis subsp. lactis CNRZ 150, 8 (53% foram caracterizadas como lactose-positivas (Lac+ e proteinase-negativas (Prt-. As linhagens produtoras de bacteriocinas também foram caracterizadas no seu conteúdo de plasmídios. Elas apresentaram de 2 a 7 plasmídios, com pesos moleculares aproximados de 0.5 a 28.1 Mdal. Quatro linhagens (ITAL 435, ITAL 436

Characterization of a bacteriocin-like substance produced from a novel isolated strain of Bacillus subtilis SLYY-3

Science.gov (United States)

Li, Junfeng; Li, Hongfang; Zhang, Yuanyuan; Duan, Xiaohui; Liu, Jie

2014-12-01

In the present research, the strain SLYY-3 was isolated from sediments of Jiaozhou Bay, Qingdao, China. The strain SLYY-3, which produced a bacteriocin-like substance (BLS), was characterized to be a strain of Bacillus subtillis by biochemical profiling and 16S rDNA sequence analysis. It is the first time to report that Bacillus subtilis from Jiaozhou Bay sediments could produce a BLS. The BLS of B. subtillis SLYY-3 exhibited strong inhibitory activity against gram-positive bacteria (including Staphylococcus aureus and B. subtillis) and some fungi (including Penicillium glaucum, Aspergillus niger and Aspergillus flavus). The antimicrobial activity was detected from culture in the exponential growth phase and reached its maximum when culture entered into stationary growth phase. It was thermo-tolerant even when being kept at 100°C for 60 min without losing any activity and stable over a wide pH range from 1.0 to 12.0 while being inactivated by proteolytic enzyme and trypsin, indicating the proteinaceous nature of the BLS. The BLS was purified by precipitation with hydrochloric acid (HCl) and gel filteration (Sephadex G-100). SDS-PAGE analysis of the extracellular peptides of SLYY-3 revealed a bacteriocin-like protein with a molecular mass of 66 kDa. Altogether, these characteristics indicate the potential of the BLS for food industry as a protection against pathogenic and spoilage microorganisms.

Bacteriocin-Producing Enterococcus faecium LCW 44: A High Potential Probiotic Candidate from Raw Camel Milk.

Science.gov (United States)

Vimont, Allison; Fernandez, Benoît; Hammami, Riadh; Ababsa, Ahlem; Daba, Hocine; Fliss, Ismaïl

2017-01-01

Bacterial isolates from raw camel milk were screened for antibacterial activity using the agar diffusion assay. Ten isolates selected for their inhibition of Gram-positive bacteria were identified by 16S sequencing as Enterococcus faecium or durans . An isolate named E. faecium LCW 44 exhibited the broadest antibacterial spectrum with an inhibitory activity against several Gram-positive strains belonging to the genera Clostridium , Listeria , Staphylococcus , and Lactobacillus. E. faecium LCW 44 was shown to produce N-formylated enterocins L50A and L50B, as revealed by mass spectrometry and PCR analyses. This isolate did not harbor any of the virulence factors tested and was shown to be sensitive to all tested antibiotics. It showed high resistance to gastric and intestinal conditions (78 ± 4% survival). Its adhesion index was evaluated at 176 ± 86 and 24 ± 86 on Caco-2 cells and HT-29 cells, respectively, and it significantly reduced adhesion of Listeria monocytogenes by 65 and 49%, respectively. In Macfarlane broth (simulating the nutrient content of the colon), counts of L. monocytogenes were reduced by 2 log 10 cycles after 24 h in co-culture with E. faecium LCW 44, compared to the increase of 4 log 10 cycles when cultured alone. Comparison with a bacteriocin-non-producing mutant of E. faecium LCW 44 strongly suggests that inhibition of L. monocytogenes was due to bacteriocin production. Altogether, E. faecium LCW 44 thus has potential for use as a probiotic for humans and veterinary medicine.

Bacteriocin-Producing Enterococcus faecium LCW 44: A High Potential Probiotic Candidate from Raw Camel Milk

Directory of Open Access Journals (Sweden)

Allison Vimont

2017-05-01

Full Text Available Bacterial isolates from raw camel milk were screened for antibacterial activity using the agar diffusion assay. Ten isolates selected for their inhibition of Gram-positive bacteria were identified by 16S sequencing as Enterococcus faecium or durans. An isolate named E. faecium LCW 44 exhibited the broadest antibacterial spectrum with an inhibitory activity against several Gram-positive strains belonging to the genera Clostridium, Listeria, Staphylococcus, and Lactobacillus. E. faecium LCW 44 was shown to produce N-formylated enterocins L50A and L50B, as revealed by mass spectrometry and PCR analyses. This isolate did not harbor any of the virulence factors tested and was shown to be sensitive to all tested antibiotics. It showed high resistance to gastric and intestinal conditions (78 ± 4% survival. Its adhesion index was evaluated at 176 ± 86 and 24 ± 86 on Caco-2 cells and HT-29 cells, respectively, and it significantly reduced adhesion of Listeria monocytogenes by 65 and 49%, respectively. In Macfarlane broth (simulating the nutrient content of the colon, counts of L. monocytogenes were reduced by 2 log10 cycles after 24 h in co-culture with E. faecium LCW 44, compared to the increase of 4 log10 cycles when cultured alone. Comparison with a bacteriocin-non-producing mutant of E. faecium LCW 44 strongly suggests that inhibition of L. monocytogenes was due to bacteriocin production. Altogether, E. faecium LCW 44 thus has potential for use as a probiotic for humans and veterinary medicine.

Different bacteriocin activities of Streptococcus mutans reflect distinct phylogenetic lineages

DEFF Research Database (Denmark)

Balakrishnan, M; Simmonds, RS; Kilian, Mogens

2002-01-01

Bacteriocins produced by mutans streptococci are known as mutacins. In this study 16 broadly active mutacin-producing Streptococcus mutans strains from New Zealand, North America and Europe were classified into four groups (A-D) on the basis of differences in their activity in deferred antagonism...... described by Caufield and co-workers. One of the New Zealand isolates of group A (S. mutans strain N) appeared to produce inhibitory activity similar to that of the group I prototype strain UA140. Four other New Zealand isolates of group B (S. mutans strains M19, M34, B34 and D14) had mutacin II......-like activity. The group B mutacin producers differed from the group A mutacin producers in their additional activity against Staph. aureus 46. Seven S. mutans strains (M46, B46, B57, M12, M28, B28 and 13M) were distinguished from the group A and group B mutacin producers in that they inhibited E. faecium TE1...

Circular arc structures

KAUST Repository

Bo, Pengbo

2011-07-01

The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.

A Conceptual Framework for Circular Design

Directory of Open Access Journals (Sweden)

Mariale Moreno

2016-09-01

Full Text Available Design has been recognised in the literature as a catalyst to move away from the traditional model of take-make-dispose to achieve a more restorative, regenerative and circular economy. As such, for a circular economy to thrive, products need to be designed for closed loops, as well as be adapted to generate revenues. This should not only be at the point of purchase, but also during use, and be supported by low-cost return chains and reprocessing structures, as well as effective policy and regulation. To date, most academic and grey literature on the circular economy has focused primarily on the development of new business models, with some of the latter studies addressing design strategies for a circular economy, specifically in the area of resource cycles and design for product life extension. However, these studies primarily consider a limited spectrum of the technical and biological cycles where materials are recovered and restored and nutrients (e.g., materials, energy, water are regenerated. This provides little guidance or clarity for designers wishing to design for new circular business models in practice. As such, this paper aims to address this gap by systematically analysing previous literature on Design for Sustainability (DfX (e.g., design for resource conservation, design for slowing resource loops and whole systems design and links these approaches to the current literature on circular business models. A conceptual framework is developed for circular economy design strategies. From this conceptual framework, recommendations are made to enable designers to fully consider the holistic implications for design within a circular economy.

Asymptotic theory of circular polarization memory.

Science.gov (United States)

Dark, Julia P; Kim, Arnold D

2017-09-01

We establish a quantitative theory of circular polarization memory, which is the unexpected persistence of the incident circular polarization state in a strongly scattering medium. Using an asymptotic analysis of the three-dimensional vector radiative transfer equation (VRTE) in the limit of strong scattering, we find that circular polarization memory must occur in a boundary layer near the portion of the boundary on which polarized light is incident. The boundary layer solution satisfies a one-dimensional conservative scattering VRTE. Through a spectral analysis of this boundary layer problem, we introduce the dominant mode, which is the slowest-decaying mode in the boundary layer. To observe circular polarization memory for a particular set of optical parameters, we find that this dominant mode must pass three tests: (1) this dominant mode is given by the largest, discrete eigenvalue of a reduced problem that corresponds to Fourier mode k=0 in the azimuthal angle, and depends only on Stokes parameters U and V; (2) the polarization state of this dominant mode is largely circular polarized so that |V|≫|U|; and (3) the circular polarization of this dominant mode is maintained for all directions so that V is sign-definite. By applying these three tests to numerical calculations for monodisperse distributions of Mie scatterers, we determine the values of the size and relative refractive index when circular polarization memory occurs. In addition, we identify a reduced, scalar-like problem that provides an accurate approximation for the dominant mode when circular polarization memory occurs.

How to Assess Product Performance in the Circular Economy? Proposed Requirements for the Design of a Circularity Measurement Framework

OpenAIRE

Saidani , Michael; YANNOU , Bernard; Leroy , Yann; Cluzel , François

2017-01-01

International audience; Assessing product circularity performance is not straightforward. Meanwhile, it gains increasingly importance for businesses and industrial practitioners who are willing to effectively take benefits from circular economy promises. Thus, providing methods and tools to evaluate then enhance product performance—in the light of circular economy—becomes a significant but still barely addressed topic. Following a joint agreement on the need to measure product circularity per...

Computational simulations of hydrogen circular migration in protonated acetylene induced by circularly polarized light

Energy Technology Data Exchange (ETDEWEB)

Shi, Xuetao; Li, Wen; Schlegel, H. Bernhard, E-mail: hbs@chem.wayne.edu [Department of Chemistry, Wayne State University, Detroit, Michigan 48202 (United States)

2016-08-28

The hydrogens in protonated acetylene are very mobile and can easily migrate around the C{sub 2} core by moving between classical and non-classical structures of the cation. The lowest energy structure is the T-shaped, non-classical cation with a hydrogen bridging the two carbons. Conversion to the classical H{sub 2}CCH{sup +} ion requires only 4 kcal/mol. The effect of circularly polarized light on the migration of hydrogens in oriented C{sub 2}H{sub 3}{sup +} has been simulated by Born-Oppenheimer molecular dynamics. Classical trajectory calculations were carried out with the M062X/6-311+G(3df,2pd) level of theory using linearly and circularly polarized 32 cycle 7 μm cosine squared pulses with peak intensity of 5.6 × 10{sup 13} W/cm{sup 2} and 3.15 × 10{sup 13} W/cm{sup 2}, respectively. These linearly and circularly polarized pulses transfer similar amounts of energy and total angular momentum to C{sub 2}H{sub 3}{sup +}. The average angular momentum vectors of the three hydrogens show opposite directions of rotation for right and left circularly polarized light, but no directional preference for linearly polarized light. This difference results in an appreciable amount of angular displacement of the three hydrogens relative to the C{sub 2} core for circularly polarized light, but only an insignificant amount for linearly polarized light. Over the course of the simulation with circularly polarized light, this corresponds to a propeller-like motion of the three hydrogens around the C{sub 2} core of protonated acetylene.

Circular Updates

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Circular Updates are periodic sequentially numbered instructions to debriefing staff and observers informing them of changes or additions to scientific and specimen...

Circular RNAs as Promising Biomarkers: A mini-review

Directory of Open Access Journals (Sweden)

Nadiah Abu

2016-08-01

Full Text Available The interest in circular RNAs has resurfaced in the past few years. What was considered as junk for nearly two decades is now one of the most interesting molecules. Circular RNAs are non-coding RNAs that are formed by back-splicing events and have covalently closed loops with no poly-adenylated tails. The regulation of circular RNAs is distinctive and they are selectively abundant in different types of tissues. Based on the current knowledge of circular RNAs, these molecules have the potential to be the next big thing especially as biomarkers for different diseases. This mini-review attempts to concisely look at the biology of circular RNAs, the putative functional activities, the prevalence of circular RNAs, and the possible role of circular RNA as biomarkers for diagnosis or measuring drug response.

Enterocin C, a class IIb bacteriocin produced by E. faecalis C901, a strain isolated from human colostrum.

Science.gov (United States)

Maldonado-Barragán, Antonio; Caballero-Guerrero, Belén; Jiménez, Esther; Jiménez-Díaz, Rufino; Ruiz-Barba, José L; Rodríguez, Juan M

2009-07-31

Enterocin C (EntC), a class IIb bacteriocin was purified from culture supernatants of Enterococcus faecalis C901, a strain isolated from human colostrum. Enterocin C consists of two distinct peptides, named EntC1 and EntC2, whose complementary action is required for full antimicrobial activity. The structural genes entC1 and entC2 encoding enterocins EntC1 and EntC2, respectively, and that encoding the putative immunity protein (EntCI) are located in the 9-kb plasmid pEntC, harboured by E. faecalis C901. The N-terminal sequence of both antimicrobial peptides revealed that EntC1 (4284 Da) is identical to Ent1071A, one of the two peptides that form enterocin 1071 (Ent1071), a bacteriocin produced by E. faecalis BFE 1071. In contrast, EntC2 (3867 Da) presents the non-polar alanine residue at position 17 (Ala(17)) instead of the polar threonine residue (Thr(17)) in Ent1071B, the second peptide constituting Ent1071. In spite of peptide similarities, EntC differs from Ent1071 in major aspects, including the complementary activity among its constitutive peptides and its wider inhibitory spectrum of activity. Different amphiphilic alpha-helical conformations between EntC2 and Ent1071B could explain both, acquired complementary activity and increased antimicrobial spectrum.

An isolate of Haemophilus haemolyticus produces a bacteriocin-like substance that inhibits the growth of nontypeable Haemophilus influenzae.

Science.gov (United States)

Latham, Roger D; Gell, David A; Fairbairn, Rory L; Lyons, A Bruce; Shukla, Shakti D; Cho, Kum Yin; Jones, David A; Harkness, Nick M; Tristram, Stephen G

2017-04-01

Nontypeable Haemophilus influenzae (NTHi) frequently colonises the upper respiratory tract and is an important cause of respiratory infections. Resistance to antibiotics is an emerging trend in NTHi and alternative prevention or treatment strategies are required. Haemophilus haemolyticus is a common commensal occupying the same niche as NTHi and, if able to produce substances that inhibit NTHi growth, may have a role as a probiotic. In this study, ammonium sulphate extracts from broth culture of 100 H. haemolyticus isolates were tested for the presence of substances inhibitory to NTHi using a well diffusion assay. One isolate produced a substance that consistently inhibited the growth of NTHi. The substance was inactivated by protease enzymes and had a molecular size of ca. 30 kDa as determined by size exclusion chromatography. When the substance was tested against bacteria from eight Gram-negative and three Gram-positive genera, only Haemophilus spp. were inhibited. Quantitative PCR testing showed the substance to be different to 'haemocin', the previously described bacteriocin of H. influenzae type b. These molecular characteristics, together with narrow-spectrum activity, suggest the substance may be a novel bacteriocin, and there is potential for this H. haemolyticus isolate to function as a probiotic for reduction of colonisation and subsequent infection with NTHi. Copyright © 2017 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.

Broadband Circularly Polarized Slot Antenna Loaded by a Multiple-Circular-Sector Patch.

Science.gov (United States)

Trinh-Van, Son; Yang, Youngoo; Lee, Kang-Yoon; Hwang, Keum Cheol

2018-05-15

In this paper, a microstrip-fed broadband circularly polarized (CP) slot antenna is presented. CP operation can be attained simply by embedding an S-shaped strip. By loading with a multiple-circular-sector patch, which consists of 12 circular-sector patches with identical central angles of 30° and different radii, the 3 dB axial ratio (AR) bandwidth is significantly broadened. To validate the performance of the proposed antenna, an antenna prototype is fabricated and tested. The fabricated antenna is 54 mm × 54 mm × 0.8 mm in size. The measured -10 dB reflection and 3 dB AR bandwidths are 81.06% (1.68⁻3.97 GHz) and 70.55% (1.89⁻3.95 GHz), respectively. Within the 3 dB AR bandwidth, the measured peak gain is 3.81 dBic. Reasonable agreement is also obtained between the measured and simulated results.

Circular Business: Collaborate and Circulate : a bookreview

NARCIS (Netherlands)

Timmermans, Ratna W.; Witjes, S.|info:eu-repo/dai/nl/381088200

2016-01-01

With their book, “Circular Business: Collaborate and Circulate”, Circular Collaboration, Amersfoort, ISBN: 978-90-824902-0-6, €35, Kraaijenhagen et al. (2016) give companies practical guidance on their contribution to the development of a more circular economy by presenting a practical 10-step

Purification of a Novel Bacteriocin-Like Inhibitory Substance Produced by Enterococcus faecium ICIS 8 and Characterization of Its Mode of Action.

Science.gov (United States)

Vasilchenko, Alexey S; Rogozhin, Eugene A; Valyshev, Alexander V

2017-06-01

The aim of this work was to purify and characterize a bacteriocin-like antimicrobial substance produced by an antagonistic active strain of Enterococcus faecium. A novel bacteriocin-like inhibitory substance (BLIS) produced by the E. faecium ICIS 8 strain was purified and characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and N-terminal amino acid sequencing revealed the following partial sequence: NH 2 -APKEKCFPKYCV. The proteinaceous nature of purified BLIS was assessed by treatment with proteolytic enzyme. Studies of the action of BLIS using bacteriological and bioluminescence assays revealed a dose-dependent inhibition of Listeria monocytogenes 88BK and Escherichia coli K12 TG1 lac::lux viability. The interaction of the BLIS with the bacterial surface led to the compensation of a negative charge value, as shown by zeta-potential measurements. Assessments of membrane integrity using fluorescent probes and atomic force microscopy revealed the permeabilization of the cellular barrier structures in both L. monocytogenes and E. coli. The novel BLIS from E. faecium ICIS 8 was characterized by a unique primary peptide sequence and exerted bactericidal activity against L. monocytogenes and E. coli by disrupting membrane integrity.

Symplectic methods in circular accelerators

International Nuclear Information System (INIS)

Forest, E.

1994-01-01

By now symplectic integration has been applied to many problems in classical mechanics. It is my conviction that the field of particle simulation in circular rings is ideally suited for the application of symplectic integration. In this paper, I present a short description symplectic tools in circular storage rings

76 FR 60593 - Title VI; Proposed Circular

Science.gov (United States)

2011-09-29

..., several of them related to ambiguous language in the existing Circular. The proposed Circular reorganizes... regional entity, and inclusive of public and private entities. This term is used exclusively in Chapter IV... revisions to the Title VI Circular. The section that addresses the existing requirement for a Language...

Cygnus X-1: Discovery of variable circular polarization

International Nuclear Information System (INIS)

Michalsky, J.J.; Swedlund, J.B.; Stokes, R.A.

1975-01-01

HDE 226868, the optical counterpart of Cyg X-1, has been observed for circular polarization during 1974. Observations in five colors suggest that circular polarization results from an interstellar effect. Measurements of the blue polarization reveal circular polarization variations synchronous with the 5)./sub /6 orbital period. The circular polarization variation appears to be similar to the blue intensity variation

Development pattern of circular economy in Jiangsu coastland

OpenAIRE

Wang, Liang

2009-01-01

Circular economy is an effective development pattern to balance economic growth, social development and environmental protection. Based on apprehending the connotation of circular economy, this paper fully considers and studies on the future trends in this area according to the theory of circular economy and the empirical circumstances of Jiangsu Coastland. This paper also discusses the circular economy development pattern adopted by Jiangsu coastland during economic and social development fr...

Total and Differential Efficiencies for a Circular Detector Viewing a Circular Radiator of Finite Thickness

Energy Technology Data Exchange (ETDEWEB)

Lauber, A; Tollander, B

1967-08-15

Total and differential detection efficiencies have been computed for a circular detector viewing a circular radiator of finite thickness. Isotropic, cosines and n-p scattering angular emission distributions of the radiated particles are considered. Tables are given for the total efficiencies as well as for the differential efficiencies in the n-p scattering case.

Circular codes revisited: a statistical approach.

Science.gov (United States)

Gonzalez, D L; Giannerini, S; Rosa, R

2011-04-21

In 1996 Arquès and Michel [1996. A complementary circular code in the protein coding genes. J. Theor. Biol. 182, 45-58] discovered the existence of a common circular code in eukaryote and prokaryote genomes. Since then, circular code theory has provoked great interest and underwent a rapid development. In this paper we discuss some theoretical issues related to the synchronization properties of coding sequences and circular codes with particular emphasis on the problem of retrieval and maintenance of the reading frame. Motivated by the theoretical discussion, we adopt a rigorous statistical approach in order to try to answer different questions. First, we investigate the covering capability of the whole class of 216 self-complementary, C(3) maximal codes with respect to a large set of coding sequences. The results indicate that, on average, the code proposed by Arquès and Michel has the best covering capability but, still, there exists a great variability among sequences. Second, we focus on such code and explore the role played by the proportion of the bases by means of a hierarchy of permutation tests. The results show the existence of a sort of optimization mechanism such that coding sequences are tailored as to maximize or minimize the coverage of circular codes on specific reading frames. Such optimization clearly relates the function of circular codes with reading frame synchronization. Copyright © 2011 Elsevier Ltd. All rights reserved.

Building a Circular Future

DEFF Research Database (Denmark)

Merrild, Heidi

2016-01-01

Natural resources are scarce and construction accounts for 40 percent of the material and energy consumption in Europe. This means that a switch to a circular future is necessary. ’Building a Circular Future’ maps out where we are, where we are going, and what is needed for this conversion to take...... on the project’s strategies. The financial result is a profit of DKK 35 million on the structure alone in the demolition of a building built for the cost of DKK 860 million. The total potential for the whole building, calculated in projected material prices, is estimated to be up to 16% of the total construction...... of the circular strategies is not only in the future. Increased flexibility, optimized operation and maintenance, as well as a healthier building, is low-hanging fruit that can be harvested today. The project’s principles can be implemented in industrialized construction in a large scale today. That is proven...

ADMINISTRATIVE CIRCULARS

CERN Multimedia

Division des ressources humaines

2000-01-01

N° 2 (Rev. 1) - March 2000Guidelines and procedures concerning recruitment and probation period of staff membersN° 9 (Rev. 2) - March 2000Staff members contractsN° 16 (Rev. 2) - January 2000TrainingN° 30 (Rev. 1) - January 2000Indemnities and reimbursements upon taking up appointment and termination of contractN° 32 - February 2000Principles and procedures governing complaints of harassmentThese circular have been amended (No 2, N° 9, N° 16 and N° 30) or drawn up (N° 32).Copies are available in the Divisional Secretariats.Note:\tAdministrative and operational circulars, as well as the lists of those in force, are available for consultation in the server SRV4_Home in the Appletalk zone NOVELL (as GUEST or using your Novell username and password), volume PE Division Data Disk.The Word files are available in the folder COM, folder Public, folder ADM.CIRC.docHuman Resources DivisionTel. 74128

Update on the development of a novel dry cow therapy using a bismuth-based intramammary teat seal in combination with the bacteriocin lacticin 3147

Directory of Open Access Journals (Sweden)

Crispie Fiona

2004-11-01

Full Text Available Public concerns over the widespread prophylactic use of antibiotics have led to a search for alternatives to dry cow therapy for the prevention of intramammary infections. A popular alternative is to infuse a teat seal at drying-off. The teat seal is a viscous non-antibiotic formulation and when it is infused into the teat canal and the teat sinus it forms an internal seal that provides a physical barrier to invasion by mastitis-causing pathogens. Enhancement of teat seal formulations may be achieved using non-antibiotic additives such as bacteriocins, potent proteins produced by some bacteria that have the ability to kill other microorganisms. This paper traces the history of investigations at Moorepark Research Centre into the efficacy of teat seal plus lacticin 3147, a bacteriocin produced by Lactococcus lactis DPC3147, in the prevention of intramammary infections in dry cows. Indications from on-going investigations are that a dry cow formulation combining the two products has considerable potential as a non-antibiotic prophylactic product.

Perceptions of Circular Business Models in SMEs

Directory of Open Access Journals (Sweden)

Sebastian-Ion Ceptureanu

2018-05-01

Full Text Available Testing circular economy business models is crucial in understanding Circular Economy features across various industries. This paper analyses Circular Economy perceptions in Romanian SMEs by investigating entrepreneurs from PVC joinery industry. Using a multidimensional framework, ReSOLVE, as a conceptual model, and Lewandowski systematization, we measured 6 business actions and their relations with Value creation. The results of our survey can be described as mixed. Of the 6 business actions of ReSOLVE framework, for half of them (Regenerate, Optimize and Exchange we can definitely conclude that these are correlated with Circular Economy in terms of Value Creation, while for a fourth there are variables significantly correlated without being able to conclude its overall contribution in terms of Value creation. Our empirical investigation contributes to literature development on Circular Economy research in SMEs and a step forward to shape future research initiatives.

Localization of CO2 Leakage from a Circular Hole on a Flat-Surface Structure Using a Circular Acoustic Emission Sensor Array

Directory of Open Access Journals (Sweden)

Xiwang Cui

2016-11-01

Full Text Available Leak localization is essential for the safety and maintenance of storage vessels. This study proposes a novel circular acoustic emission sensor array to realize the continuous CO2 leak localization from a circular hole on the surface of a large storage vessel in a carbon capture and storage system. Advantages of the proposed array are analyzed and compared with the common sparse arrays. Experiments were carried out on a laboratory-scale stainless steel plate and leak signals were obtained from a circular hole in the center of this flat-surface structure. In order to reduce the influence of the ambient noise and dispersion of the acoustic wave on the localization accuracy, ensemble empirical mode decomposition is deployed to extract the useful leak signal. The time differences between the signals from the adjacent sensors in the array are calculated through correlation signal processing before estimating the corresponding distance differences between the sensors. A hyperbolic positioning algorithm is used to identify the location of the circular leak hole. Results show that the circular sensor array has very good directivity toward the circular leak hole. Furthermore, an optimized method is proposed by changing the position of the circular sensor array on the flat-surface structure or adding another circular sensor array to identify the direction of the circular leak hole. Experiential results obtained on a 100 cm × 100 cm stainless steel plate demonstrate that the full-scale error in the leak localization is within 0.6%.

Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

DEFF Research Database (Denmark)

Nikolova, L.; Todorov, T.; Ivanov, M.

1997-01-01

We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

DEFF Research Database (Denmark)

Kaminski, Maciej; Cukras, Janusz; Pecul, Magdalena

2015-01-01

We present a computational methodology to calculate the intensity of circular dichroism (CD) in spinforbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet–singlet transitions in chiral compounds. The protocol is based...

Self-complementary circular codes in coding theory.

Science.gov (United States)

Fimmel, Elena; Michel, Christian J; Starman, Martin; Strüngmann, Lutz

2018-04-01

Self-complementary circular codes are involved in pairing genetic processes. A maximal [Formula: see text] self-complementary circular code X of trinucleotides was identified in genes of bacteria, archaea, eukaryotes, plasmids and viruses (Michel in Life 7(20):1-16 2017, J Theor Biol 380:156-177, 2015; Arquès and Michel in J Theor Biol 182:45-58 1996). In this paper, self-complementary circular codes are investigated using the graph theory approach recently formulated in Fimmel et al. (Philos Trans R Soc A 374:20150058, 2016). A directed graph [Formula: see text] associated with any code X mirrors the properties of the code. In the present paper, we demonstrate a necessary condition for the self-complementarity of an arbitrary code X in terms of the graph theory. The same condition has been proven to be sufficient for codes which are circular and of large size [Formula: see text] trinucleotides, in particular for maximal circular codes ([Formula: see text] trinucleotides). For codes of small-size [Formula: see text] trinucleotides, some very rare counterexamples have been constructed. Furthermore, the length and the structure of the longest paths in the graphs associated with the self-complementary circular codes are investigated. It has been proven that the longest paths in such graphs determine the reading frame for the self-complementary circular codes. By applying this result, the reading frame in any arbitrary sequence of trinucleotides is retrieved after at most 15 nucleotides, i.e., 5 consecutive trinucleotides, from the circular code X identified in genes. Thus, an X motif of a length of at least 15 nucleotides in an arbitrary sequence of trinucleotides (not necessarily all of them belonging to X) uniquely defines the reading (correct) frame, an important criterion for analyzing the X motifs in genes in the future.

A product design framework for a circular economy

NARCIS (Netherlands)

Van den Berg, M.R.; Bakker, C.A.

2015-01-01

The paper provides a circular economy framework from a product design perspective with tools to aid product designers in applying circular product design in practice. Design research for circular economy has so far mainly been limited to referring to existing fields of research such as design for

Zernike vs. Bessel circular functions in visual optics.

Science.gov (United States)

Trevino, Juan P; Gómez-Correa, Jesus E; Iskander, D Robert; Chávez-Cerda, Sabino

2013-07-01

We propose the Bessel Circular Functions as alternatives of the Zernike Circle Polynomials to represent relevant circular ophthalmic surfaces. We assess the fitting capabilities of the orthogonal Bessel Circular Functions by comparing them to Zernike Circle Polynomials for approximating a variety of computationally generated surfaces which can represent ophthalmic surfaces. The Bessel Circular Functions showed better modelling capabilities for surfaces with abrupt variations such as the anterior eye surface at the limbus region, and influence functions. From our studies we find that the Bessel Circular Functions can be more suitable for studying particular features of post surgical corneal surfaces. We show that given their boundary conditions and free oscillating properties, the Bessel Circular Functions are an alternative for representing specific wavefronts and can be better than the Zernike Circle Polynomials for some important cases of corneal surfaces, influence functions and the complete anterior corneal surface. © 2013 The Authors Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Information circulars

International Nuclear Information System (INIS)

1989-04-01

The document summarizes the Information Circulars published by the IAEA under the symbol INFCIRC/ for the purpose of bringing matters of general interest to the attention of all Members of the Agency. A complete list of INFCIRCs in numerical order with their titles is given in the Annex

Photoexcitation circular dichroism in chiral molecules

Science.gov (United States)

Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

2018-05-01

Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

Enterocin F4-9, a Novel O-Linked Glycosylated Bacteriocin.

Science.gov (United States)

Maky, Mohamed Abdelfattah; Ishibashi, Naoki; Zendo, Takeshi; Perez, Rodney Honrada; Doud, Jehan Ragab; Karmi, Mohamed; Sonomoto, Kenji

2015-07-01

Enterococcus faecalis F4-9 isolated from Egyptian salted-fermented fish produces a novel bacteriocin, termed enterocin F4-9. Enterocin F4-9 was purified from the culture supernatant by three steps, and its molecular mass was determined to be 5,516.6 Da by mass spectrometry. Amino acid and DNA sequencing showed that the propeptide consists of 67 amino acid residues, with a leader peptide containing a double glycine cleavage site to produce a 47-amino-acid mature peptide. Enterocin F4-9 is modified by two molecules of N-acetylglucosamine β-O-linked to Ser37 and Thr46. The O-linked N-acetylglucosamine moieties are essential for the antimicrobial activity of enterocin F4-9. Further analysis of the enterocin F4-9 gene cluster identified enfC, which has high sequence similarity to a glycosyltransferase. The antimicrobial activity of enterocin F4-9 covered a limited range of bacteria, including, interestingly, a Gram-negative strain, Escherichia coli JM109. Enterocin F4-9 is sensitive to protease, active at a wide pH range, and moderately resistant to heat. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Breaking the fault tree circular logic

International Nuclear Information System (INIS)

Lankin, M.

2000-01-01

Event tree - fault tree approach to model failures of nuclear plants as well as of other complex facilities is noticeably dominant now. This approach implies modeling an object in form of unidirectional logical graph - tree, i.e. graph without circular logic. However, genuine nuclear plants intrinsically demonstrate quite a few logical loops (circular logic), especially where electrical systems are involved. This paper shows the incorrectness of existing practice of circular logic breaking by elimination of part of logical dependencies and puts forward a formal algorithm, which enables the analyst to correctly model the failure of complex object, which involves logical dependencies between system and components, in form of fault tree. (author)

Influence of adhesion and bacteriocin production by Lactobacillus salivarius on the intestinal epithelial cell transcriptional response.

Science.gov (United States)

O'Callaghan, John; Buttó, Ludovica F; MacSharry, John; Nally, Kenneth; O'Toole, Paul W

2012-08-01

Lactobacillus salivarius strain UCC118 is a human intestinal isolate that has been extensively studied for its potential probiotic effects in human and animal models. The objective of this study was to determine the effect of L. salivarius UCC118 on gene expression responses in the Caco-2 cell line to improve understanding of how the strain might modulate intestinal epithelial cell phenotypes. Exposure of Caco-2 cells to UCC118 led to the induction of several human genes (TNFAIP3, NFKBIA, and BIRC3) that are negative regulators of inflammatory signaling pathways. Induction of chemokines (CCL20, CXCL-1, and CXCL-2) with antimicrobial functions was also observed. Disruption of the UCC118 sortase gene srtA causes reduced bacterial adhesion to epithelial cells. Transcription of three mucin genes was reduced significantly when Caco-2 cells were stimulated with the ΔsrtA derivative of UCC118 compared to cells stimulated with the wild type, but there was no significant change in the transcription levels of the anti-inflammatory genes. UCC118 genes that were significantly upregulated upon exposure to Caco-2 cells were identified by bacterial genome microarray and consisted primarily of two groups of genes connected with purine metabolism and the operon for synthesis of the Abp118 bacteriocin. Following incubation with Caco-2 cells, the bacteriocin synthesis genes were transcribed at higher levels in the wild type than in the ΔsrtA derivative. These data indicate that L. salivarius UCC118 influences epithelial cells both through modulation of the inflammatory response and by modulation of intestinal cell mucin production. Sortase-anchored cell surface proteins of L. salivarius UCC118 have a central role in promoting the interaction between the bacterium and epithelial cells.

NUMERICAL MODELING OF STRESSES NEAR THE SURFACE IN THE INGOT OF CIRCULAR SECTION, CRYSTALLIZABLE AT CIRCULAR TORCH SECONDARY COOLING

Directory of Open Access Journals (Sweden)

A. N. Chichko

2004-01-01

Full Text Available The results of computer calculations of the stresses, generated in outside layer of ingot of steel 20 of circular section with diameter 300 mm, in application to one of the industrial technological schemas of RUP “BMZ”, are presented. The segments of compressive and tensile stresses formation along the length of ingot are determined and the principal possibility of production of continuously cast slug of circular section at circular-torch spray cooling is shown.

Co-Producing a Vision and Approach for the Transition towards a Circular Economy: Perspectives from Government Partners

Directory of Open Access Journals (Sweden)

Anne P. M. Velenturf

2018-05-01

Full Text Available The United Kingdom’s (UK economy is overly reliant on unsustainable production and consumption practices that deplete finite resources at rates that will increase production costs, business risk, and economic instability; it also produces emissions and waste that cause climate change and environmental degradation, impacting on well-being in the UK and beyond. The Resource Recovery from Waste programme (RRfW promotes a transition towards waste and resource management in a circular economy that restores the environment, creates societal benefits, and promotes clean growth by engaging relevant actors in academia, government, and industry to co-produce a shared vision and approach that will realise such a transition. Sharing the RRfW’s government engagement results, this article presents a positive outlook for changing the UK economy and society through waste and resource management practices that maximise the values of materials by circulating them in the economy for as long as possible. Key themes, regulatory instruments, a stable policy framework, and an approach for effective academic–government collaboration are proposed. Comparing the results to government plans in four UK nations shows great differences in progress towards realising a circular economy. The article concludes with recommendations to capitalise on opportunities for growth, innovation, and resilient infrastructure whilst contributing to quality jobs and welfare throughout the UK.

The Baltics on Their Way towards a Circular Economy

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Grigoryan A. A.

2017-10-01

Full Text Available Circular economy has been studied extensively both in Europe and worldwide. It is largely viewed as a potential strategy for societal development, aimed to increase prosperity while reducing dependence on raw materials and energy. Many businesses regard circular economy as a way to enhance economic growth and increase profits. Governments across the world actively engage in the discussion about the benefits of a transition to a circular economy and about its impact on employment, economic growth, and the environment. This paper aims to study the major issues of circular economy, to identify its advantages, and to offer an insight into the transition stage the Baltic States are undergoing today on their way to circular economy. It is stressed that the Baltic countries are not fully using the opportunities offered by a circular economy. For example, Latvia’s, Lithuania’s, and Estonia’s recycling rates are significantly below those of other European countries. The Baltics depend heavily on EU financial support. An increase in funding will contribute to the implementation of circular economy technologies.

University Students Alternative Conceptions On Circular Motion

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Ian Phil Canlas

2015-08-01

Full Text Available This study attempted to find out university students alternative conceptions on circular motion. An 18-item researcher-compiled and content-validated questionnaire was administered to twenty-six 26 students taking up a program in Bachelor in Secondary Education-Physical Science in their second year enrolled in a course on mechanics. Results revealed that majority of the students possess alternative conceptions on circular motion specifically along velocity acceleration and force. Moreover results showed the inconsistencies in the students understanding of circular motion concepts.

Architectural Surfaces and Structures from Circular Arcs

KAUST Repository

Shi, Ling

2013-01-01

the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how

Molecular Detection and Sensitivity to Antibiotics and Bacteriocins of Pathogens Isolated from Bovine Mastitis in Family Dairy Herds of Central Mexico

Directory of Open Access Journals (Sweden)

Ma. Fabiola León-Galván

2015-01-01

Full Text Available Thirty-two farms (n=535 cows located in the state of Guanajuato, Mexico, were sampled. Pathogens from bovine subclinical mastitis (SCM and clinical mastitis (CLM were identified by 16S rDNA and the sensitivity to both antibiotics and bacteriocins of Bacillus thuringiensis was tested. Forty-six milk samples were selected for their positive California Mastitis Test (CMT (≥3 and any abnormality in the udder or milk. The frequency of SCM and CLM was 39.1% and 9.3%, respectively. Averages for test day milk yield (MY, lactation number (LN, herd size (HS, and number of days in milk (DM were 20.6 kg, 2.8 lactations, 16.7 animals, and 164.1 days, respectively. MY was dependent on dairy herd (DH, LN, HS, and DM P<0.01, and correlations between udder quarters from the CMT were around 0.49 P<0.01. Coagulase-negative staphylococci were mainly identified, as well as Staphylococcus aureus, Streptococcus uberis, Brevibacterium stationis, B. conglomeratum, and Staphylococcus agnetis. Bacterial isolates were resistant to penicillin, clindamycin, ampicillin, and cefotaxime. Bacteriocins synthesized by Bacillus thuringiensis inhibited the growth of multiantibiotic resistance bacteria such as S. agnetis, S. equorum, Streptococcus uberis, Brevibacterium stationis, and Brachybacterium conglomeratum, but they were not active against S. sciuri, a microorganism that showed an 84% resistance to antibiotics tested in this study.

Environmental issues elimination through circular economy

Energy Technology Data Exchange (ETDEWEB)

Špirková, M., E-mail: marta.spirkova@stuba.sk; Pokorná, E.; Šujanová, J.; Samáková, J. [Paulínska 16, 917 24 Trnava, Slovakia, Slovak University of Technology in Bratislava, Faculty of Materials Science and Technology in Trnava (Slovakia)

2016-04-21

Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

Environmental issues elimination through circular economy

International Nuclear Information System (INIS)

Špirková, M.; Pokorná, E.; Šujanová, J.; Samáková, J.

2016-01-01

Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

Environmental issues elimination through circular economy

Science.gov (United States)

Špirková, M.; Pokorná, E.; Šujanová, J.; Samáková, J.

2016-04-01

Environmental efforts of European Union are currently going towards circular economy. Tools like Extended Producer Responsibility and Eco-design were established. The circular economy deals with resources availability issue on one hand and waste management on the other hand. There are few pioneering companies all over the world with some kind of circular economy practice. Generally the concept is not very wide-spread. The paper aims to evaluate possibility of transition towards circular economy in Slovak industrial companies. They need to have an active approach to material treatment of their products after usage stage. Innovation is another important pre-condition for the transition. Main problem of current cradle to grave system is landfilling of valuable materials after one cycle of usage. Their potential value for next manufacturing cycles is lost. Companies may do not see connection between waste management and material resource prices and volatility of supplies. Municipalities are responsible for municipal waste collection and treatment in Slovakia. The circular economy operates by cradle to cradle principle. Company manages material flow until the material comes back to the beginning of manufacturing process by itself or by another partners. Stable material supplies with quite low costs are provided this way. It is necessary to deal with environmental problems in phase of product design. Questionnaire survey results show on one hand low involvement of industrial companies in waste management area, however on the other hand they are open to environmental innovations in future.

The Circular Economy between Desiderates and Realities.

Directory of Open Access Journals (Sweden)

Tăchiciu Laurentiu

2018-05-01

Full Text Available The present issue of Amfiteatru Economic Journal addresses the subject of the circular economy, bringing together research contributions to a better understanding of the current state and perspectives of the adoption of economic and business models conceived to give resources’ highest utility and value in every stage by reducing waste, reusing and recycling. Contributors are approaching the circular economy from different perspectives. Some are concerned with the macroeconomic and social conditions accompanying a higher circularity in the economy, while others focus on businesses’ and individuals’ behaviours.

The Circular Economy: In Practice-focused Undergraduate Engineering Education

DEFF Research Database (Denmark)

Knudby, Torben; Larsen, Samuel

2017-01-01

The growth of the planet’s population makes the traditional industrial model of “take, make and waste” unsustainable. The circular economy, in which resources are continuously reused, offers a solution. For manufacturers of durable goods the circular economy requires a well-functioning circular...

Flow-induced vibration of circular cylindrical structures

International Nuclear Information System (INIS)

Chen, S.S.

1985-06-01

This report summarizes the flow-induced vibration of circular cylinders in quiescent fluid, axial flow, and crossflow, and applications of the analytical methods and experimental data in design evaluation of various system components consisting of circular cylinders. 219 figs., 30 tabs

Optics modules for circular accelerator design

International Nuclear Information System (INIS)

Brown, K.L.; Servranckx, R.V.

1986-05-01

The first-order differential equations of motion for a single particle in a closed circular machine are solved, introducing the concepts of phase shift, beta functions, and the Courant-Snyder invariant. The transfer matrix between two points in the machine is derived as a function of the phase shift and the parameters contained in the Courant-Snyder invariant. Typical optical modules used in circular machine designs are introduced and related to their characteristic transfer matrix elements, the phase shift through them, and the Courant-Snyder-Twiss parameters. The systematics of some elementary phase ellipse matching problems between optical modules are discussed. Second-order optical modules are discussed, including how they are used to provide the momentum bandwidth needed for the design of a typical circular machine

Equatorial circular motion in Kerr spacetime

International Nuclear Information System (INIS)

Pugliese, Daniela; Quevedo, Hernando; Ruffini, Remo

2011-01-01

We analyze the properties of circular orbits of test particles on the equatorial plane of a rotating central mass whose gravitational field is described by the Kerr spacetime. For rotating black holes and naked singularities we explore all the spatial regions where circular orbits can exist and analyze the behavior of the energy and the angular momentum of the corresponding test particles. In particular, we find all the radii at which a test particle can have zero angular momentum due to the repulsive gravity effects generated by naked singularities. We classify all the stability zones of circular orbits. It is shown that the geometric structure of the stability zones of black holes is completely different from that of naked singularities.

Characteristics of a Circular Logic and Its Treatment

International Nuclear Information System (INIS)

Lim, Ho-Gon; Han, Sang-Hoon; Yang, Joon Eon

2007-01-01

A circular logic or a logical loop is defined as the infinite circulation of supporting relations due to their mutual dependencies among the systems in the Fault Tree Analysis (FTA). While many methods to break the circular logic have been developed and used in the fault tree quantification codes, the general solution for a circular logic and its breaking methods are not generally known as yet. This paper presents an analytic solution for circular logics in which the systems are linearly interrelated with each other. Then, a general treatment of circular logics is discussed. To formulate the analytic solution, the relations among systems in the fault tree structure are described by the Boolean equations. The solution is, then, obtained from the successive substitutions of the Boolean equations, which is equivalent to the attaching processes of interrelated system's fault tree to a given fault tree. The solution for three interrelated systems and their independent fault tree structures are given as an example

Circular arc structures

KAUST Repository

Bo, Pengbo; Pottmann, Helmut; Kilian, Martin; Wang, Wen Ping; Wallner, Johannes

2011-01-01

and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where

Production of bioactive substances by intestinal bacteria as a basis for explaining probiotic mechanisms: bacteriocins and conjugated linoleic acid.

Science.gov (United States)

O'Shea, Eileen F; Cotter, Paul D; Stanton, Catherine; Ross, R Paul; Hill, Colin

2012-01-16

The mechanisms by which intestinal bacteria achieve their associated health benefits can be complex and multifaceted. In this respect, the diverse microbial composition of the human gastrointestinal tract (GIT) provides an almost unlimited potential source of bioactive substances (pharmabiotics) which can directly or indirectly affect human health. Bacteriocins and fatty acids are just two examples of pharmabiotic substances which may contribute to probiotic functionality within the mammalian GIT. Bacteriocin production is believed to confer producing strains with a competitive advantage within complex microbial environments as a consequence of their associated antimicrobial activity. This has the potential to enable the establishment and prevalence of producing strains as well as directly inhibiting pathogens within the GIT. Consequently, these antimicrobial peptides and the associated intestinal producing strains may be exploited to beneficially influence microbial populations. Intestinal bacteria are also known to produce a diverse array of health-promoting fatty acids. Indeed, certain strains of intestinal bifidobacteria have been shown to produce conjugated linoleic acid (CLA), a fatty acid which has been associated with a variety of systemic health-promoting effects. Recently, the ability to modulate the fatty acid composition of the liver and adipose tissue of the host upon oral administration of CLA-producing bifidobacteria and lactobacilli was demonstrated in a murine model. Importantly, this implies a potential therapeutic role for probiotics in the treatment of certain metabolic and immunoinflammatory disorders. Such examples serve to highlight the potential contribution of pharmabiotic production to probiotic functionality in relation to human health maintenance. Copyright © 2011 Elsevier B.V. All rights reserved.

Purification and characterization of bacteriocin like substance produced from bacillus lentus with perspective of a new biopreservative for food preservation

International Nuclear Information System (INIS)

Sharma, N.; Gautam, N.

2009-01-01

Molecular weight of bacteriocin like substance (BLIS) of a new strain of Bacillus lentus 121 was found to be approximately 11 kDa. Purification of BLIS was attained by single step gel exclusion chromatography. BLIS was characterized by studying the inhibitory spectrum. It was active at broad pH range, high temperature and high NaCl concentration and showed sensitivity to proteolytic enzymes like trypsin, alpha-chymotrypsin and papain, the characters desirable for food preservation. BLIS extended the shelf stability of milk upto 21 days as a biopreservative. (author)

The circular economy applied to local communities

NARCIS (Netherlands)

van der Blonk, Heico; van Spijk, Alex; van der Schoor, Tineke

2015-01-01

Based on a theoretical discussion the main difference between models of lineair economy and circular economy are elaborated; (1) Elimination of waste is essential the circulation of circular flows and reclamation of (raw) materials; this requires mechanisms for the return of obsolete materials. (2)

Radical Circular Economy

NARCIS (Netherlands)

Prins, M.; Mohammadi, S.; Slob, N.

2015-01-01

Recently the Circular Economy (CE) concept has gained momentum in the Netherlands, propounding that environmental impact reduction can provide a significant positive economical impulse. The government, larger parts of the industry as a whole, as well as the construction industry, has warmly received

METHOD OF CONJUGATED CIRCULAR ARCS TRACING

Directory of Open Access Journals (Sweden)

N. Ageyev Vladimir

2017-01-01

Full Text Available The geometric properties of conjugated circular arcs connecting two points on the plane with set directions of tan- gent vectors are studied in the work. It is shown that pairs of conjugated circular arcs with the same conditions in frontier points create one-parameter set of smooth curves tightly filling all the plane. One of the basic properties of this set is the fact that all coupling points of circular arcs are on the circular curve going through the initially given points. The circle radius depends on the direction of tangent vectors. Any point of the circle curve, named auxiliary in this work, determines a pair of conjugated arcs with given boundary conditions. One more condition of the auxiliary circle curve is that it divides the plane into two parts. The arcs going from the initial point are out of the circle limited by this circle curve and the arcs coming to the final point are inside it. These properties are the basis for the method of conjugated circular arcs tracing pro- posed in this article. The algorithm is rather simple and allows to fulfill all the needed plottings using only the divider and ruler. Two concrete examples are considered. The first one is related to the problem of tracing of a pair of conjugated arcs with the minimal curve jump when going through the coupling point. The second one demonstrates the possibility of trac- ing of the smooth curve going through any three points on the plane under condition that in the initial and final points the directions of tangent vectors are given. The proposed methods of conjugated circular arcs tracing can be applied in solving of a wide variety of problems connected with the tracing of cam contours, for example pattern curves in textile industry or in computer-aided-design systems when programming of looms with numeric control.

Lactococcin G is a potassium ion-conducting, two-component bacteriocin.

Science.gov (United States)

Moll, G; Ubbink-Kok, T; Hildeng-Hauge, H; Nissen-Meyer, J; Nes, I F; Konings, W N; Driessen, A J

1996-02-01

Lactococcin G is a novel lactococcal bacteriocin whose activity depends on the complementary action of two peptides, termed alpha and beta. Peptide synthesis of the alpha and beta peptides yielded biologically active lactococcin G, which was used in mode-of-action studies on sensitive cells of Lactococcus lactis. Approximately equivalent amounts of both peptides were required for optimal bactericidal effect. No effect was observed with either the alpha or beta peptide in the absence of the complementary peptide. The combination of alpha and beta peptides (lactococcin G) dissipates the membrane potential (delta omega), and as a consequence cells release alpha-aminoisobutyrate, a non-metabolizable alanine analog that is accumulated through a proton motive-force dependent mechanism. In addition, the cellular ATP level is dramatically reduced, which results in a drastic decrease of the ATP-driven glutamate uptake. Lactococcin G does not form a proton-conducting pore, as it has no effect on the transmembrane pH gradient. Dissipation of the membrane potential by uncouplers causes a slow release of potassium (rubidium) ions. However, rapid release of potassium was observed in the presence of lactococcin G. These data suggest that the bactericidal effect of lactococcin G is due to the formation of potassium-selective channels by the alpha and beta peptides in the target bacterial membrane.

Culture as a Caveat Towards Circular Economy

DEFF Research Database (Denmark)

Guerrieri, Valeria

2015-01-01

Circular economy represents an economic and political challenge, as well as a cultural one, requiring a massive transformation on all levels of society. But why is cultural change so important to understanding today’s economy and how can the circular model be considered a truly cross-cultural...

Primal-dual path-following algorithms for circular programming

Directory of Open Access Journals (Sweden)

Baha Alzalg

2017-06-01

Full Text Available Circular programming problems are a new class of convex optimization problems that include second-order cone programming problems as a special case‎. ‎Alizadeh and Goldfarb [Math‎. ‎Program‎. ‎Ser‎. ‎A 95 (2003 3--51] introduced primal-dual path-following algorithms for solving second-order cone programming problems‎. ‎In this paper‎, ‎we generalize their work by using the machinery of Euclidean Jordan algebras associated with the circular cones to derive primal-dual path-following interior point algorithms for circular programming problems‎. ‎We prove polynomial convergence of the proposed algorithms by showing that the circular logarithmic barrier is a strongly self-concordant barrier‎. ‎The numerical examples show the path-following algorithms are simple and efficient‎.

Engineered strains of Streptococcus macedonicus towards an osmotic stress resistant phenotype retain their ability to produce the bacteriocin macedocin under hyperosmotic conditions.

Science.gov (United States)

Anastasiou, Rania; Driessche, Gonzalez Van; Boutou, Effrossyni; Kazou, Maria; Alexandraki, Voula; Vorgias, Constantinos E; Devreese, Bart; Tsakalidou, Effie; Papadimitriou, Konstantinos

2015-10-20

Streptococcus macedonicus ACA-DC 198 produces the bacteriocin macedocin in milk only under low NaCl concentrations (<1.0%w/v). The thermosensitive plasmid pGh9:ISS1 was employed to generate osmotic stress resistant (osmr) mutants of S. macedonicus. Three osmr mutants showing integration of the vector in unique chromosomal sites were identified and the disrupted loci were characterized. Interestingly, the mutants were able to grow and to produce macedocin at considerably higher concentrations of NaCl compared to the wild-type (up to 4.0%w/v). The production of macedocin under hyperosmotic conditions solely by the osmr mutants was validated by the well diffusion assay and by mass spectrometry analysis. RT-PCR experiments demonstrated that the macedocin biosynthetic regulon was transcribed at high salt concentrations only in the mutants. Mutant osmr3, the most robust mutant, was converted in its markerless derivative (osmr3f). Co-culture of S. macedonicus with spores of Clostridium tyrobutyricum in milk demonstrated that only the osmr3f mutant and not the wild-type inhibited the growth of the spores under hyperosmotic conditions (i.e., 2.5%w/v NaCl) due to the production of macedocin. Our study shows how genetic manipulation of a strain towards a stress resistant phenotype could improve bacteriocin production under conditions of the same stress. Copyright © 2015 Elsevier B.V. All rights reserved.

Biochemical and Genetic Characterization of Coagulin, a New Antilisterial Bacteriocin in the Pediocin Family of Bacteriocins, Produced by Bacillus coagulans I4

Science.gov (United States)

Le Marrec, Claire; Hyronimus, Bertrand; Bressollier, Philippe; Verneuil, Bernard; Urdaci, Maria C.

2000-01-01

A plasmid-linked antimicrobial peptide, named coagulin, produced by Bacillus coagulans I4 has recently been reported (B. Hyronimus, C. Le Marrec and M. C. Urdaci, J. Appl. Microbiol. 85:42–50, 1998). In the present study, the complete, unambiguous primary amino acid sequence of the peptide was obtained by a combination of both N-terminal sequencing of purified peptide and the complete sequence deduced from the structural gene harbored by plasmid I4. Data revealed that this peptide of 44 residues has an amino acid sequence similar to that described for pediocins AcH and PA-1, produced by different Pediococcus acidilactici strains and 100% identical. Coagulin and pediocin differed only by a single amino acid at their C terminus. Analysis of the genetic determinants revealed the presence, on the pI4 DNA, of the entire 3.5-kb operon of four genes described for pediocin AcH and PA-1 production. No extended homology was observed between pSMB74 from P. acidilactici and pI4 when analyzing the regions upstream and downstream of the operon. An oppositely oriented gene immediately dowstream of the bacteriocin operon specifies a 474-amino-acid protein which shows homology to Mob-Pre (plasmid recombination enzyme) proteins encoded by several small plasmids extracted from gram-positive bacteria. This is the first report of a pediocin-like peptide appearing naturally in a non-lactic acid bacterium genus. PMID:11097892

How do children learn to follow gaze, share joint attention, imitate their teachers, and use tools during social interactions?

Science.gov (United States)

Grossberg, Stephen; Vladusich, Tony

2010-01-01

How does an infant learn through visual experience to imitate actions of adult teachers, despite the fact that the infant and adult view one another and the world from different perspectives? To accomplish this, an infant needs to learn how to share joint attention with adult teachers and to follow their gaze towards valued goal objects. The infant also needs to be capable of view-invariant object learning and recognition whereby it can carry out goal-directed behaviors, such as the use of tools, using different object views than the ones that its teachers use. Such capabilities are often attributed to "mirror neurons". This attribution does not, however, explain the brain processes whereby these competences arise. This article describes the CRIB (Circular Reactions for Imitative Behavior) neural model of how the brain achieves these goals through inter-personal circular reactions. Inter-personal circular reactions generalize the intra-personal circular reactions of Piaget, which clarify how infants learn from their own babbled arm movements and reactive eye movements how to carry out volitional reaches, with or without tools, towards valued goal objects. The article proposes how intra-personal circular reactions create a foundation for inter-personal circular reactions when infants and other learners interact with external teachers in space. Both types of circular reactions involve learned coordinate transformations between body-centered arm movement commands and retinotopic visual feedback, and coordination of processes within and between the What and Where cortical processing streams. Specific breakdowns of model processes generate formal symptoms similar to clinical symptoms of autism. Copyright © 2010 Elsevier Ltd. All rights reserved.

Research on the development and countermeasures for circular economy

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

Ecological economics and sustainable development economics are the basic theories to research on circular economy. Through the systemically research on the relationship of the three above, this paper thinks that the reuse and recycle of circular economy ts a way that the stall is mended after a sheep is lost. Although the reduction technically controls the production process, it cannot solve the waste caused by blind production and excess competition. We have experienced variety obstacles when implementing the circular economy, whose main reason ts the conflict between the individual ration and the social ration. Therefore, only when the individual ration and social ration incline to conformity,the cooperating Nash equilibrium will be appeared. In order to realize the harmony of ecology, economy and society, we have to explore effective evaluation theory. This paper cites the "five flows of wealth operation theory"from professor Ma Chuandong to search operation mechanism of circular economy, makes clear the developing thoughts of circular economy based on the realities, and brings forward some countermeasures to develop circular economy based on the above theoretical analysis.

Circular Bioassay Platforms for Applications in Microwave-Accelerated Techniques.

Science.gov (United States)

Mohammed, Muzaffer; Clement, Travis C; Aslan, Kadir

2014-12-02

In this paper, we present the design of four different circular bioassay platforms, which are suitable for homogeneous microwave heating, using theoretical calculations (i.e., COMSOL™ multiphysics software). Circular bioassay platforms are constructed from poly(methyl methacrylate) (PMMA) for optical transparency between 400-800 nm, has multiple sample capacity (12, 16, 19 and 21 wells) and modified with silver nanoparticle films (SNFs) to be used in microwave-accelerated bioassays (MABs). In addition, a small monomode microwave cavity, which can be operated with an external microwave generator (100 W), for use with the bioassay platforms in MABs is also developed. Our design parameters for the circular bioassay platforms and monomode microwave cavity during microwave heating were: (i) temperature profiles, (ii) electric field distributions, (iii) location of the circular bioassay platforms inside the microwave cavity, and (iv) design and number of wells on the circular bioassay platforms. We have also carried out additional simulations to assess the use of circular bioassay platforms in a conventional kitchen microwave oven (e.g., 900 W). Our results show that the location of the circular bioassay platforms in the microwave cavity was predicted to have a significant effect on the homogeneous heating of these platforms. The 21-well circular bioassay platform design in our monomode microwave cavity was predicted to offer a homogeneous heating pattern, where inter-well temperature was observed to be in between 23.72-24.13°C and intra-well temperature difference was less than 0.21°C for 60 seconds of microwave heating, which was also verified experimentally.

Purification of the bacteriocin bavaricin MN and characterization of its mode of action against Listeria monocytogenes Scott A cells and lipid vesicles.

OpenAIRE

Kaiser, A L; Montville, T J

1996-01-01

Bavaricin MN was purified from Lactobacillus sake culture supernatant 135-fold with a final yield of 11%. Sequence analysis revealed bavaricin MN to be a 42-amino-acid peptide having a molecular weight of 4,769 and a calculated pI of 10.0. Computer analysis indicated that the C-terminal region may form an alpha-helical structure with an amphipathic nature deemed important in the interaction of bacteriocins with biological membranes. Bavaricin MN rapidly depleted the membrane potential (delta ...

Designing the Business Models for Circular Economy—Towards the Conceptual Framework

Directory of Open Access Journals (Sweden)

Mateusz Lewandowski

2016-01-01

Full Text Available Switching from the current linear model of economy to a circular one has recently attracted increased attention from major global companies e.g., Google, Unilever, Renault, and policymakers attending the World Economic Forum. The reasons for this are the huge financial, social and environmental benefits. However, the global shift from one model of economy to another also concerns smaller companies on a micro-level. Thus, comprehensive knowledge on designing circular business models is needed to stimulate and foster implementation of the circular economy. Existing business models for the circular economy have limited transferability and there is no comprehensive framework supporting every kind of company in designing a circular business model. This study employs a literature review to identify and classify the circular economy characteristics according to a business model structure. The investigation in the eight sub-domains of research on circular business models was used to redefine the components of the business model canvas in the context of the circular economy. Two new components—the take-back system and adoption factors—have been identified, thereby leading to the conceptualization of an extended framework for the circular business model canvas. Additionally, the triple fit challenge has been recognized as an enabler of the transition towards a circular business model. Some directions for further research have been outlined, as well.

Heterologous Coproduction of Enterocin A and Pediocin PA-1 by Lactococcus lactis: Detection by Specific Peptide-Directed Antibodies

Science.gov (United States)

Martínez, José M.; Kok, Jan; Sanders, Jan W.; Hernández, Pablo E.

2000-01-01

Antibodies against enterocin A were obtained by immunization of rabbits with synthetic peptides PH4 and PH5 designed, respectively, on the N- and C-terminal amino acid sequences of enterocin A and conjugated to the carrier protein KLH. Anti-PH4-KLH antibodies not only recognized enterocin A but also pediocin PA-1, enterocin P, and sakacin A, three bacteriocins which share the N-terminal class IIa consensus motif (YGNGVXC) that is contained in the sequence of the peptide PH4. In contrast, anti-PH5-KLH antibodies only reacted with enterocin A because the amino acid sequences of the C-terminal parts of class IIa bacteriocins are highly variable. Enterocin A and/or pediocin PA-1 structural and immunity genes were introduced in Lactococcus lactis IL1403 to achieve (co)production of the bacteriocins. The level of production of the two bacteriocins was significantly lower than that obtained by the wild-type producers, a fact that suggests a low efficiency of transport and/or maturation of these bacteriocins by the chromosomally encoded bacteriocin translocation machinery of IL1403. Despite the low production levels, both bacteriocins could be specifically detected and quantified with the anti-PH5-KLH (anti-enterocin A) antibodies isolated in this study and the anti-PH2-KLH (anti-pediocin PA-1) antibodies previously generated (J. M. Martínez, M. I. Martínez, A. M. Suárez, C. Herranz, P. Casaus, L. M. Cintas, J. M. Rodríguez, and P. E. Hernández, Appl. Environ. Microbiol. 64:4536–4545, 1998). In this work, the availability of antibodies for the specific detection and quantification of enterocin A and pediocin PA-1 was crucial to demonstrate coproduction of both bacteriocins by L. lactis IL1403(pJM04), because indicator strains that are selectively inhibited by each bacteriocin are not available. PMID:10919819

The protein circular dichroism data bank, a Web-based site for access to circular dichroism spectroscopic data.

Science.gov (United States)

Whitmore, Lee; Woollett, Benjamin; Miles, Andrew J; Janes, Robert W; Wallace, B A

2010-10-13

The Protein Circular Dichroism Data Bank (PCDDB) is a newly released resource for structural biology. It is a web-accessible (http://pcddb.cryst.bbk.ac.uk) data bank for circular dichroism (CD) and synchrotron radiation circular dichroism (SRCD) spectra and their associated experimental and secondary metadata, with links to protein sequence and structure data banks. It is designed to provide a public repository for CD spectroscopic data on macromolecules, to parallel the Protein Data Bank (PDB) for crystallographic, electron microscopic, and nuclear magnetic resonance spectroscopic data. Similarly to the PDB, it includes validation checking procedures to ensure good practice and the integrity of the deposited data. This paper reports on the first public release of the PCDDB, which provides access to spectral data that comprise standard reference datasets. Copyright © 2010 Elsevier Ltd. All rights reserved.

Codon Distribution in Error-Detecting Circular Codes

Directory of Open Access Journals (Sweden)

Elena Fimmel

2016-03-01

Full Text Available In 1957, Francis Crick et al. suggested an ingenious explanation for the process of frame maintenance. The idea was based on the notion of comma-free codes. Although Crick’s hypothesis proved to be wrong, in 1996, Arquès and Michel discovered the existence of a weaker version of such codes in eukaryote and prokaryote genomes, namely the so-called circular codes. Since then, circular code theory has invariably evoked great interest and made significant progress. In this article, the codon distributions in maximal comma-free, maximal self-complementary C3 and maximal self-complementary circular codes are discussed, i.e., we investigate in how many of such codes a given codon participates. As the main (and surprising result, it is shown that the codons can be separated into very few classes (three, or five, or six with respect to their frequency. Moreover, the distribution classes can be hierarchically ordered as refinements from maximal comma-free codes via maximal self-complementary C3 codes to maximal self-complementary circular codes.

Codon Distribution in Error-Detecting Circular Codes.

Science.gov (United States)

Fimmel, Elena; Strüngmann, Lutz

2016-03-15

In 1957, Francis Crick et al. suggested an ingenious explanation for the process of frame maintenance. The idea was based on the notion of comma-free codes. Although Crick's hypothesis proved to be wrong, in 1996, Arquès and Michel discovered the existence of a weaker version of such codes in eukaryote and prokaryote genomes, namely the so-called circular codes. Since then, circular code theory has invariably evoked great interest and made significant progress. In this article, the codon distributions in maximal comma-free, maximal self-complementary C³ and maximal self-complementary circular codes are discussed, i.e., we investigate in how many of such codes a given codon participates. As the main (and surprising) result, it is shown that the codons can be separated into very few classes (three, or five, or six) with respect to their frequency. Moreover, the distribution classes can be hierarchically ordered as refinements from maximal comma-free codes via maximal self-complementary C(3) codes to maximal self-complementary circular codes.

A novel x-ray circularly polarized ranging method

International Nuclear Information System (INIS)

Song Shi-Bin; Xu Lu-Ping; Zhang Hua; Shen Yang-He; Gao Na

2015-01-01

Range measurement has found multiple applications in deep space missions. With more and further deep space exploration activities happening now and in the future, the requirement for range measurement has risen. In view of the future ranging requirement, a novel x-ray polarized ranging method based on the circular polarization modulation is proposed, termed as x-ray circularly polarized ranging (XCPolR). XCPolR utilizes the circular polarization modulation to process x-ray signals and the ranging information is conveyed by the circular polarization states. As the circular polarization states present good stability in space propagation and x-ray detectors have light weight and low power consumption, XCPolR shows great potential in the long-distance range measurement and provides an option for future deep space ranging. In this paper, we present a detailed illustration of XCPolR. Firstly, the structure of the polarized ranging system is described and the signal models in the ranging process are established mathematically. Then, the main factors that affect the ranging accuracy, including the Doppler effect, the differential demodulation, and the correlation error, are analyzed theoretically. Finally, numerical simulation is carried out to evaluate the performance of XCPolR. (paper)

Circular relativistic motion of two identical bodies

International Nuclear Information System (INIS)

Shavokhina, N.S.

1983-01-01

Circular relativistic motion of two bodies as a solution of the earlier obtained equations with a deflecting argument where the self-deflection of the argument is an unknown function of time is considered. In case of circular motion the argument deflection is independent from time and it is the root of the transcendental equation obtained in the paper

Single particle dynamics in circular accelerators

International Nuclear Information System (INIS)

Ruth, R.D.

1986-10-01

The purpose of this paper is to introduce the reader to the theory associated with the transverse dynamics of single particle, in circular accelerators. The discussion begins with a review of Hamiltonian dynamics and canonical transformations. The case of a single particle in a circular accelerator is considered with a discussion of non-linear terms and chromaticity. The canonical perturbation theory is presented and nonlinear resonances are considered. Finally, the concept of renormalization and residue criterion are examined. (FI)

Purification and characterization of a new bacteriocin active against Campylobacter produced by Lactobacillus salivarius SMXD51.

Science.gov (United States)

Messaoudi, Soumaya; Kergourlay, Gilles; Dalgalarrondo, Michèle; Choiset, Yvan; Ferchichi, Mounir; Prévost, Hervé; Pilet, Marie-France; Chobert, Jean-Marc; Manai, Mohamed; Dousset, Xavier

2012-10-01

Strain SMXD51, isolated from chicken ceca and identified as Lactobacillus salivarius, produced a component that inhibits the growth of Gram-positive and Gram-negative bacteria and especially Campylobacter jejuni. The active peptide from the cell-free supernatant of Lb. salivarius SMXD51 was purified in three steps: (i) precipitation with 80% saturated ammonium sulfate, (ii) elution on a reversed phase SPE UPTI-CLEAN cartridge using different concentrations of acetonitrile, (iii) final purification by reversed phase HPLC on a C(18) column. The mode of action of this peptide of 5383.2 Da was identified as bactericidal, and its amino acid composition was established. This new bacteriocin SMXD51 appears potentially very useful to reduce Campylobacter in poultry prior to processing. Copyright © 2012 Elsevier Ltd. All rights reserved.

Nearest Neighbor Estimates of Entropy for Multivariate Circular Distributions

Directory of Open Access Journals (Sweden)

Neeraj Misra

2010-05-01

Full Text Available In molecular sciences, the estimation of entropies of molecules is important for the understanding of many chemical and biological processes. Motivated by these applications, we consider the problem of estimating the entropies of circular random vectors and introduce non-parametric estimators based on circular distances between n sample points and their k th nearest neighbors (NN, where k (≤ n – 1 is a fixed positive integer. The proposed NN estimators are based on two different circular distances, and are proven to be asymptotically unbiased and consistent. The performance of one of the circular-distance estimators is investigated and compared with that of the already established Euclidean-distance NN estimator using Monte Carlo samples from an analytic distribution of six circular variables of an exactly known entropy and a large sample of seven internal-rotation angles in the molecule of tartaric acid, obtained by a realistic molecular-dynamics simulation.

Administrative Circular No. 26 (Rev.10) - Recognition of merit

CERN Multimedia

2014-01-01

Administrative Circular No. 26 (Rev. 10) entitled “Recognition of Merit”, approved by the Director-General following discussion at the Standing Concertation Committee meeting of 5 December 2013 and entering into force on 1 January 2014, is available on the intranet site of the Human Resources Department (see here).   This circular is applicable to staff members. It cancels and replaces Administrative Circular No. 26 (Rev. 9) entitled “Recognition of Merit” of December 2011. The circular was revised in order to take into account the work performed in the framework of an elective mandate during the exercise of merit recognition of staff members. In addition, the circular was revised to provide that, in the case of staff members on special leave for professional reasons for a period equal to or longer than half a year, it will no longer be possible to grant an exceptional advancement. Department Head Office HR Department

Propagation and radiation characteristics of the circular electric, circular magnetic and hybrid waveguide modes

International Nuclear Information System (INIS)

Crenn, J.P.

1996-06-01

The field distributions and propagation constants of the circular electric, circular magnetic and hybrid modes of oversized waveguides are expressed, taking the effects of walls into account. The near and far field patterns are derived in the case of real wall functions. It is shown that, for very oversized waveguides, the terms containing wall functions can be ignored in the calculations, and it results that the expressions of fields and propagation constants become independent of the types of waveguides. An application to corrugated waveguides for Electron Cyclotron Resonance Heating experiments shows the variations of the radiation characteristics versus geometric parameters of the corrugations and determines the ranges of interest for these parameters. (author)

Administrative Circular No. 23 (Rev. 4) - Special working hours

CERN Document Server

Department Head Office - HR Department

2016-01-01

Administrative Circular No. 23 (Rev. 4) entitled "Special working hours", approved by the Director-General following discussion in the Standing Concertation Committee meeting on 22 March 2016, will be available on 1st September 2016 via the following link: https://cds.cern.ch/record/2208539.   This revised circular cancels and replaces Administrative Circular No. 23 (Rev. 3) also entitled "Special working hours" of January 2013. This document contains modifications to reflect the new career structure and ensuring the provision consistent with practice that compensation or remuneration of special working hours performed remotely is possible only in case of emergency.   This circular will enter into force on 1st September 2016.

Shear strength of reinforced concrete circular cross-section beams

Directory of Open Access Journals (Sweden)

P. W. G. N. Teixeira

Full Text Available A proposed adequation of NBR 6118, Item 7.4, related to shear strength of reinforced concrete beams is presented with aims to application on circular cross-section. The actual expressions are most suitable to rectangular cross-section and some misleading occurs when applied to circular sections at determination of VRd2, Vc and Vsw, as consequence of bw (beam width and d (effective depth definitions as well as the real effectiveness of circular stirrups. The proposed adequation is based on extensive bibliographic review and practical experience with a great number of infrastructure elements, such as anchored retaining pile walls, where the use of circular reinforced concrete members is frequent.

Modeling of circular-grating surface-emitting lasers

Science.gov (United States)

Shams-Zadeh-Amiri, Ali M.

Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

Molecular photoelectron holography with circularly polarized laser pulses.

Science.gov (United States)

Yang, Weifeng; Sheng, Zhihao; Feng, Xingpan; Wu, Miaoli; Chen, Zhangjin; Song, Xiaohong

2014-02-10

We investigate the photoelectron momentum distribution of molecular-ion H2+driven by ultrashort intense circularly polarized laser pulses. Both numerical solutions of the time-dependent Schrödinger equation (TDSE) and a quasiclassical model indicate that the photoelectron holography (PH) with circularly polarized pulses can occur in molecule. It is demonstrated that the interference between the direct electron wave and rescattered electron wave from one core to its neighboring core induces the PH. Moreover, the results of the TDSE predict that there is a tilt angle between the interference pattern of the PH and the direction perpendicular to the molecular axis. Furthermore, the tilt angle is sensitively dependent on the wavelength of the driven circularly polarized pulse, which is confirmed by the quasiclassical calculations. The PH induced by circularly polarized laser pulses provides a tool to resolve the electron dynamics and explore the spatial information of molecular structures.

[Mode of action of plantaricin L-1, an antilisteria bacteriocin produced by Lactobacillus plantarum].

Science.gov (United States)

Zhou, Wei; Liu, Guo-rong; Li, Ping-lan; Dai, Yun-qing; Zhou, Kang

2007-04-01

Plantaricin L-1, an anti-Listeria bacteriocin, was produced by Lactobacillus plantarum and successfully purified by SP-Sepharose FF cation exchange chromatography. The mechanism on energized cells of Listeria monocytogenes was studied with purified plantaricin L-1. After adding plantaricin L-1 to Listeria monocytogenes at 64 AU/mL, leakage of intercellular K+ ions, inorganic phosphate, lactic dehydrogenase, UV-absorbing materials and the intracellular ATP was observed, and the action resulted in the dissipation of the membrane potential (delta psi) and pH gradient (delta psi), two components of the proton motive force (PMF). All the data suggested that the primary site of action of plantaricin L-1 was the cytoplasmic membrane of sensitive cells. By forming the nonselective pores which leak ions and small organic compounds plantaricin L-1 induced the cells death, this action was similar to membrane corruption caused by peptide effect. Penetrability increased due to the enlarged pore and dysfuction of membrane transporters, which ensured efficient killing of target bacteria.

Low-Cost and High-Gain SIW Circularly Polarized Circular-Horn-Loaded Antenna for Broadband Millimeter-Wave Applications

Directory of Open Access Journals (Sweden)

Ming Du

2017-09-01

Full Text Available A wideband, low-cost and high-gain circularly polarized (CP circular-horn-loaded antenna based on substrate integrated waveguide (SIW technology operating at Ka band is presented. The proposed antenna, which is built on a single-layer substrate, consists of five parts: a short-ended SIW, a centro-symmetric wide slot, an L-shaped probe, a circular horn and a transition from SIW to air-filled rectangular waveguide for measurement. The slot is etched on the upper ground of the SIW, while the L-shaped probe for generating CP wave is printed inside the slot and connected to the SIW. A circular horn is also loaded on the surface of the SIW slot for high gain. Then, the proposed antenna with a dimension of 45×45×24.16 mm3 was fabricated and measured. The measured results show that the antenna has a wide impedance matching bandwidth of 28.6% from 30 to 40 GHz for |S11| ≤10 dB and a wide axial ratio (AR bandwidth of 22.8% from 31.5 to 39.6 GHz for AR ≤ 3 dB. The measured maximum gain is 15.6 dBi at 36 GHz with slight fluctuations over the 30–40-GHz frequency range. This kind of antenna merits low cost and easy integration with common differential circuits at the same time.

On the optimum joint decoding capacity of wyner circular GCMAC by exploiting hadamard inequality

KAUST Repository

Shakir, Muhammad

2010-09-01

This paper presents an original expression of the theoretical upper bound for the optimum joint decoding capacity of Wyner Circular Gaussian Cellular Multiple Access Channel (C-GCMAC). This upper bound is a novel application of the Hadamard inequality established by exploiting the Hadamard operation between the channel fading (G) and channel slow gain (Ω) matrices. This paper demonstrates that the theoretical upper bound converges to the actual capacity for negligible channel slow gain among the mobile terminals and the base stations for the entire range of Signal to Noise Ratios (SNRs). The behaviour of the theoretical bound is critically observed when the intercell and the intra-cell time sharing schemes are employed. © 2010 IEEE.

System for circular and complex tomography

International Nuclear Information System (INIS)

Hellstrom, M.J.

1979-01-01

This invention discloses a system for conducting circular as well as complex tomographic procedures utilizing apparatus which has no mechanical linkage between the X-ray source and the X-ray receptor. The path of travel of the X-ray source both circularly and linearly is sensed by electromagnetic radiation and more particularly by light radiation which is generated by a laser. The linear travel is sensed by means of reflected laser radiation directed to the X-ray source and fed to an interferometer. The circular travel, on the other hand, is sensed by means of a laser gyroscope also receiving light radiation from a laser. Optical energy sensing means is thus used to generate command signals which are coupled to respective drive motors which act to rotate and when desirable, translate the X-ray receptor so that its motion follows the motion, both orbital and linear, of the X-ray source for performing any desired type of tomographic procedure

Circular economy and waste to energy

Science.gov (United States)

Rada, E. C.; Ragazzi, M.; Torretta, V.; Castagna, G.; Adami, L.; Cioca, L. I.

2018-05-01

Waste management in European Union has long being regulated by the 4Rs principle, i.e. reduction, reuse, recycling, recovery, with landfill disposal as the last option. This vision recently led the European Union (especially since 2015) to the introduction of virtuous goals based on the rejection of linear economy in favour of circular economy strongly founded on materials recovery. In this scenario, landfill disposal option will disappear, while energy recovery may appear controversial when not applied to biogas production from anaerobic digestion. The present work aims to analyse the effects that circular economy principles introduced in the European Union context will have on the thermochemical waste treatment plants design. Results demonstrate that indirect combustion (gasification + combustion) along with integrated vitrification of the non-combustible fraction of treated waste will have a more relevant role in the field of waste treatment than in the past, thanks to the compliance of this option with the principles of circular economy.

Advisory Circular checklist and status of other FAA publications

Science.gov (United States)

1997-08-15

This 1997 circular transmits the revised checklist of the Federal Aviation : Administration's (FAA) Advisory Circulars (AC's). It also lists certain other : FAA publications sold by the Superintendent of Documents.

Circular RNAs

DEFF Research Database (Denmark)

Han, Yi-Neng; Xia, Shengqiang; Zhang, Yuan-Yuan

2017-01-01

Circular RNAs (circRNAs) are a novel type of universal and diverse endogenous noncoding RNAs (ncRNAs) and they form a covalently closed continuous loop without 5' or 3' tails unlike linear RNAs. Most circRNAs are presented with characteristics of abundance, stability, conservatism, and often exhi...... and expression regulators, RBP sponges in cancer as well as current research methods of circRNAs, providing evidence for the significance of circRNAs in cancer diagnosis and clinical treatment....

Circular fringe projection profilometry.

Science.gov (United States)

Zhao, Hong; Zhang, Chunwei; Zhou, Changquan; Jiang, Kejian; Fang, Meiqi

2016-11-01

In this Letter, a novel three-dimensional (3D) measurement method, called the circular fringe projection profilometry (CFPP), is proposed. Similar to the conventional fringe projection profilometry, CFPP also requires fringe pattern projection and capture, phase demodulation, and phase unwrapping. However, it works with a totally different mechanism. CFPP recovers the height of a point by calculating its distance to the optical center of a projector along the optical axis. This distance is calculated with the aid of the divergence angle of a projected light ray and the distance between the measured point and the optical axis. The distance between the measured point and the optical axis is detected by a camera with telecentric lenses, while the divergence angle can be calculated from the phase of a captured circular fringe pattern. The validity of CFPP is confirmed by a set of experiments.

Experimental investigation of complex circular Airy beam characteristics

Science.gov (United States)

Porfirev, A. P.; Fomchenkov, S. A.; Khonina, S. N.

2018-04-01

We demonstrate a new type of circular Airy beams, the so-called azimuthally modulated circular Airy beams, generated by utilizing a diffraction element, whose transmission function is the sum of the transmission function of the element generating a "petal" pattern and the transmission function of the element generating a circular Airy beam. We experimentally investigate the propagation dynamics of such beams and demonstrate that their autofocusing and selfhealing properties are strongly dependent on the number of generated petals. These beams are a combination of a conventional circular Airy beam and vortex laser beams (or their superpositions). Using a spatial light modulator, we demonstrate that these beams have unique properties such as autofocusing, "nondiffractive" propagation and self-healing after passing through an obstacle. The experimental results are in good agreement with the simulation. We believe that these results can be very useful for lensless laser fabrication and laser manipulation techniques, as well as for development of new filament plasma multi-channel formation methods.

12 CFR 563g.8 - Use of the offering circular.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Use of the offering circular. 563g.8 Section 563g.8 Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY SECURITIES OFFERINGS § 563g.8 Use of the offering circular. (a) An offering circular or amendment declared effective by the...

Isolation of Lactococcus lactis Mutants Simultaneously Resistant to the Cell Wall-Active Bacteriocin Lcn972, Lysozyme, Nisin, and Bacteriophage c2

Science.gov (United States)

Roces, Clara; Courtin, Pascal; Kulakauskas, Saulius; Rodríguez, Ana; Chapot-Chartier, Marie-Pierre

2012-01-01

Lactococcin 972 (Lcn972) is a nonlantibiotic bacteriocin that inhibits cell wall biosynthesis by binding to lipid II. In this work, two mutants resistant to Lcn972, Lactococcus lactis D1 and D1-20, with high (>320 arbitrary units [AU]/ml) and low (80 AU/ml) susceptibilities, respectively, have been isolated. Resistance to Lcn972 did not impose a burden to growth under laboratory conditions, nor did it substantially alter the physicochemical properties of the cell surface. However, the peptidoglycan of the mutants featured a higher content of muropeptides with tripeptide side chains than the wild-type strain, linking for the first time peptidoglycan remodelling to bacteriocin resistance. Moreover, L. lactis lacking a functional d,d-carboxypeptidase DacA (i.e., with a high content of pentapeptide side chain muropeptides) was shown to be more susceptible to Lcn972. Cross-resistance to lysozyme and nisin and enhanced susceptibility to penicillin G and bacitracin was also observed. Intriguingly, the Lcn972-resistant mutants were not infected by the lytic phage c2 and less efficiently infected by phage sk1. Lack of c2 infectivity was linked to a 22.6-kbp chromosomal deletion encompassing the phage receptor protein gene pip. The deletion also included maltose metabolic genes and the two-component system (TCS) F. However, a clear correlation between these genes and resistance to Lcn972 could not be clearly established, pointing to the presence of as-yet-unidentified mutations that account for Lcn972 resistance. PMID:22504807

Characterization and application of enterocin RM6, a bacteriocin from Enterococcus faecalis.

Science.gov (United States)

Huang, En; Zhang, Liwen; Chung, Yoon-Kyung; Zheng, Zuoxing; Yousef, Ahmed E

2013-01-01

Use of bacteriocins in food preservation has received great attention in recent years. The goal of this study is to characterize enterocin RM6 from Enterococcus faecalis OSY-RM6 and investigate its efficacy against Listeria monocytogenes in cottage cheese. Enterocin RM6 was purified from E. faecalis culture supernatant using ion exchange column, multiple C18-silica cartridges, followed by reverse-phase high-performance liquid chromatography. The molecular weight of enterocin RM6 is 7145.0823 as determined by mass spectrometry (MS). Tandem mass spectrometry (MS/MS) analysis revealed that enterocin RM6 is a 70-residue cyclic peptide with a head-to-tail linkage between methionine and tryptophan residues. The peptide sequence of enterocin RM6 was further confirmed by sequencing the structural gene of the peptide. Enterocin RM6 is active against Gram-positive bacteria, including L. monocytogenes, Bacillus cereus, and methicillin-resistant Staphylococcus aureus (MRSA). Enterocin RM6 (final concentration in cottage cheese, 80 AU/mL) caused a 4-log reduction in population of L. monocytogenes inoculated in cottage cheese within 30 min of treatment. Therefore, enterocin RM6 has potential applications as a potent antimicrobial peptide against foodborne pathogens in food.

Swarm Robotics with Circular Formation Motion Including Obstacles Avoidance

Directory of Open Access Journals (Sweden)

Nabil M. Hewahi

2017-07-01

Full Text Available The robots science has been developed over the past few years, where robots have become used to accomplish difficult, repetitive or accurate tasks, which are very hard for humans to carry out. In this paper, we propose an algorithm to control the motion of a swarm of robots and make them able to avoid obstacles. The proposed solution is based on forming the robots in circular fashion. A group set of robots consists of multiple groups of robots, each group of robots consists of robots forming a circular shape and each group set is a circular form of robots. The proposed algorithm is concerned with first locating the randomly generated robots in groups and secondly with the swarm robot motion and finally with the swarm obstacle avoidance and swarm reorganization after crossing the obstacle. The proposed algorithm has been simulated with five different obstacles with various numbers of randomly generated robots. The results show that the swarm in the circular form can deal with the obstacles very effectively by passing the obstacles smoothly. The proposed algorithm has been compared with flocking algorithm and it is shown that the circular formation algorithm does not need extensive computation after obstacle avoidance whereas the flocking algorithm needs extensive computation. In addition, the circular formation algorithm maintains every robot in its group after avoiding the obstacles whereas with flocking algorithm does not.

FUCHS—towards full circular RNA characterization using RNAseq

Directory of Open Access Journals (Sweden)

Franziska Metge

2017-02-01

Full Text Available Circular RNAs (circRNAs belong to a recently re-discovered species of RNA that emerge during RNA maturation through a process called back-splicing. A downstream 5′ splice site is linked to an upstream 3′ splice site to form a circular transcript instead of a canonical linear transcript. Recent advances in next-generation sequencing (NGS have brought circRNAs back into the focus of many scientists. Since then, several studies reported that circRNAs are differentially expressed across tissue types and developmental stages, implying that they are actively regulated and not merely a by-product of splicing. Though functional studies have shown that some circRNAs could act as miRNA-sponges, the function of most circRNAs remains unknown. To expand our understanding of possible roles of circular RNAs, we propose a new pipeline that could fully characterizes candidate circRNA structure from RNAseq data—FUCHS: FUll CHaracterization of circular RNA using RNA-Sequencing. Currently, most computational prediction pipelines use back-spliced reads to identify circular RNAs. FUCHS extends this concept by considering all RNA-seq information from long reads (typically >150 bp to learn more about the exon coverage, the number of double break point fragments, the different circular isoforms arising from one host-gene, and the alternatively spliced exons within the same circRNA boundaries. This new knowledge will enable the user to carry out differential motif enrichment and miRNA seed analysis to determine potential regulators during circRNA biogenesis. FUCHS is an easy-to-use Python based pipeline that contributes a new aspect to the circRNA research.

Functional analysis of circular and linear bacteriocins of Gram-positive bacteria

NARCIS (Netherlands)

Kemperman, Robèr Antoine

2005-01-01

SUMMARY & GENERAL DISCUSSION Preservation methods such as drying and fermenting to store food products for longer periods of time have been used for centuries. Nowadays, people desire fresh and minimally processed food, to be prepared with minimal cooking. This sets new targets for the food

On the Recognition of Fuzzy Circular Interval Graphs

OpenAIRE

Oriolo, Gianpaolo; Pietropaoli, Ugo; Stauffer, Gautier

2011-01-01

Fuzzy circular interval graphs are a generalization of proper circular arc graphs and have been recently introduced by Chudnovsky and Seymour as a fundamental subclass of claw-free graphs. In this paper, we provide a polynomial-time algorithm for recognizing such graphs, and more importantly for building a suitable representation.

5 CFR 1310.5 - List of current circulars.

Science.gov (United States)

2010-01-01

... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false List of current circulars. 1310.5 Section 1310.5 Administrative Personnel OFFICE OF MANAGEMENT AND BUDGET OMB DIRECTIVES OMB CIRCULARS § 1310.5... and Use of Voluntary Consensus Standards and in Conformity Assessment Activities” A-122—“Cost...

An analysis of near-circular lunar mapping orbits

Indian Academy of Sciences (India)

Numerical investigations have been carried out to analyse the evolution of lunar circular orbits and the influence of the higher order harmonics of the lunar gravity field. The aim is to select the appropriate near-circular orbit characteristics, which extend orbit life through passive orbit maintenance. The spherical harmonic ...

University Students Alternative Conceptions On Circular Motion

OpenAIRE

Ian Phil Canlas

2015-01-01

This study attempted to find out university students alternative conceptions on circular motion. An 18-item researcher-compiled and content-validated questionnaire was administered to twenty-six 26 students taking up a program in Bachelor in Secondary Education-Physical Science in their second year enrolled in a course on mechanics. Results revealed that majority of the students possess alternative conceptions on circular motion specifically along velocity acceleration and force. Moreover res...

The study of evaluation index system on construction enterprise’s circular economy

Science.gov (United States)

Yi, Lu; Liu, Zhigang

2017-06-01

The development of circular economy is an important way to judge quality of enterprise development and to realize the sustainable development of enterprises. This paper will combine the characteristics of the development of circular economy in construction enterprise to construct circular economy evaluation index system. Then it uses fuzzy mathematics theory and hierarchical analysis evaluation method for comprehensive evaluation of circular economy development level. Through the empirical analysis, the paper provides the reference basis for construction enterprises to further improve the level of circular economy.

A study of an arbiter function in the structures of a shared bus

Science.gov (United States)

Seck, J.-P.

The results of a comparative study of synchronous and asynchronous arbiters for managing user access to a shared bus is presented. The best available method is determined to be modular arbiter structures attached only to the decision module. Linear and circular arbitration strategies are examined for suitability for automatic decision-making. A multiple strategies arbiter scheme is devised, involving the superposition of various strategies of one sequential machine into another. It is then possible to modify the strategy on-line if the current strategy is ineffective. The utilization of a multiple structure of cascading arbiter devices is noted to be effective if response time is not a critical matter. Finally, attention is given to automatic circuit testing and fault detection. An example is furnished in terms of a management system for a shared memory in a multimicroprocessor structure.

Fabrication of circular microfluidic network in enzymatically-crosslinked gelatin hydrogel

Energy Technology Data Exchange (ETDEWEB)

He, Jiankang, E-mail: jiankanghe@mail.xjtu.edu.cn; Chen, Ruomeng; Lu, Yongjie; Zhan, Li; Liu, Yaxiong; Li, Dichen; Jin, Zhongmin

2016-02-01

It is a huge challenge to engineer vascular networks in vital organ tissue engineering. Although the incorporation of artificial microfluidic network into thick tissue-engineered constructs has shown great promise, most of the existing microfluidic strategies are limited to generate rectangle cross-sectional channels rather than circular vessels in soft hydrogels. Here we present a facile approach to fabricate branched microfluidic network with circular cross-sections in gelatin hydrogels by combining micromolding and enzymatically-crosslinking mechanism. Partially crosslinked hydrogel slides with predefined semi-circular channels were molded, assembled and in situ fully crosslinked to form a seamless and circular microfluidic network. The bonding strength of the resultant gelatin hydrogels was investigated. The morphology and the dimension of the resultant circular channels were characterized using scanning electron microscopy (SEM) and micro-computerized tomography (μCT). Computational fluid dynamic simulation shows that the fabrication error had little effect on the distribution of flow field but affected the maximum velocity in comparison with designed models. The microfluidic gelatin hydrogel facilitates the attachment and spreading of human umbilical endothelial cells (HUVECs) to form a uniform endothelialized layer around the circular channel surface, which successfully exhibited barrier functions. The presented method might provide a simple way to fabricate circular microfluidic networks in biologically-relevant hydrogels to advance various applications of in vitro tissue models, organ-on-a-chip systems and tissue engineering. - Highlights: • A facile method was proposed to build a circular fluidic network in gelatin hydrogel. • The fluidic network is mechanically robust and supports physiological flow. • HUVECs formed endothelialized layer around the channel to express barrier function.

Circular Business Models: Defining a Concept and Framing an Emerging Research Field

Directory of Open Access Journals (Sweden)

Julia L. K. Nußholz

2017-10-01

Full Text Available To aid companies in transitioning towards a circular economy and adopting strategies such as reuse, repair, and remanufacturing, the concept of circular business models has been developed. Although the concept draws on contributions from various academic disciplines, and despite its increasingly frequent use, few scholars clearly define what a circular business model is. Understanding about what makes a business model circular is diverse, hampering the theoretical development and practical application of circular business models. This study aims to help frame the field of circular business model research, by clarifying the fundamentals of the concept from the perspectives of resource efficiency and business model innovation. Expanding on these findings, a review of how the concept is used in recent academic literature is provided. It shows that a coherent view is lacking on which resource efficiency strategies classify a business model as circular. This study clarifies which resource efficiency strategies can be deemed as relevant key strategies for circular business models, and suggests a new definition of the concept. With the definition grounded in analysis of the fundamentals in terms of resource efficiency and business models, the study contributes to theoretical advancement and effective implementation of circular business models.

Complete genome sequence of Lactobacillus paracasei CAUH35, a new strain isolated from traditional fermented dairy product koumiss in China.

Science.gov (United States)

Wang, Guohong; Xiong, Yao; Xu, Qi; Yin, Jia; Hao, Yanling

2015-11-20

Lactobacillus paracasei CAUH35 was isolated from homemade koumiss, a traditional fermented dairy product with beneficial effects on human health. The genome consists of a circular 2,770,411 bp chromosome and four plasmids. Genome analysis revealed the presence of gene clusters involved in the production of exopolysaccharides and bacteriocin. The complete genome sequence of L. paracasei CAUH35 will provide genetic basis for further comparative and functional genomic analyses. Copyright © 2015. Published by Elsevier B.V.

12 CFR 563g.2 - Offering circular requirement.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Offering circular requirement. 563g.2 Section 563g.2 Banks and Banking OFFICE OF THRIFT SUPERVISION, DEPARTMENT OF THE TREASURY SECURITIES OFFERINGS § 563g.2 Offering circular requirement. (a) General. No savings association shall offer or sell, directly...

Band vs. Circular Sawmills: Relative Labor & Maintenance Costs

Science.gov (United States)

Philip H. Steele; Philip A. Araman

1997-01-01

Substantial sawmill lumber yield increases from kerf and sawing variation reductions can be realized by employing band rather than circular headrigs. Softwood sawmills rapidly adopted bandsaw headrig technology to the extent that it is currently unusual to find circular saw headrigs in a softwood sawmill. Hardwood sawmills, faced with a different economic situation,...

How can design science contribute to a circular economy?

DEFF Research Database (Denmark)

Pigosso, Daniela Cristina Antelmi; McAloone, Tim C.

2017-01-01

Circular Economy is increasingly seen as a key approach to operationalising goals and supporting the transition to a sustainable society by enhancing competitiveness and economic growth. Creating a Circular Economy requires fundamental changes throughout the value chain, from innovation, product...... design and production processes all the way to end of life, new business models and consumption patterns. This paper explores how design science can support the transition from the traditional linear 'take-make-consume-dispose' approach, to a Circular Economy. By means of a systematic literature review...

Calibration of circular aperture area using vision probe at inmetro

Directory of Open Access Journals (Sweden)

Costa Pedro Bastos

2016-01-01

Full Text Available Circular aperture areas are standards of high importance for the realization of photometric and radiometric measurements, where the accuracy of these measures is related to the accuracy of the circular aperture area calibrations. In order to attend the requirement for traceability was developed in Brazilian metrology institute, a methodology for circular aperture area measurement as requirements from the radiometric and photometric measurements. In the developed methodology apertures are measured by non-contact measurement through images of the aperture edges captured by a camera. These images are processed using computer vision techniques and then the values of the circular aperture area are determined.

¿Son diferentes los migrantes circulares? La integración, el bienestar y la intención de quedarse de los que migran por primera vez y de los migrantes circulares (Are circular migrants different? Integration, wellbeing, and intention to stay of first-time and circular migrants

Directory of Open Access Journals (Sweden)

Michael Braun

2010-12-01

Full Text Available ResumenCon datos tomados del proyecto PIONEUR sobre la migración interna en la Unión Europea, definiremos (una forma débil de migrantes circulares como el colectivo de aquellos migrantes que ya habían experimentado una estancia prolongada en el país de residencia (en lo sucesivo abreviado a PDR antes de su traslado definitivo. A continuación, se ofrecerá una descripción de este colectivo junto con sus características sociodemográficas y se emplearán análisis de regresión (multinivel para determinar si la migración circular explica las diferencias en algunas variables dependientes (como el dominio del idioma, el apego al PDR que arrojan esos migrantes teniendo en cuenta las características sociodemográficas. De este modo, la migración circular estaría relacionada con un mayor contacto con la cultura del PDR y con una decisión consciente de regresar al país.AbstractUsing data from the PIONEUR project on intra-European migration, (a weak form of circular migrants will be defined by the group of migrants who experienced a prolonged sojourn in the country of residence (in the following abbreviated as CoR already before the final move. Then this group will be described along socio-demographic characteristics and (multilevel regression analysis will be used to determine whether circular migration explains differences in some outcome variables (such as language proficiency, attachment to the CoR, net of the socio-demographic characteristics these migrants have. Circular migration would then be related to additional exposure to the culture of the CoR and a conscious decision to re-enter the country.

Effect of Temperature on Topological States of Circular DNA

Science.gov (United States)

Fan, Yang-Tao; Li, Xiu-Yan; Liu, Yan-Hui; Chen, Hu

2017-07-01

The different topological states of circular double-stranded DNA can be defined by their linking number. The equilibrium distribution of linking number can be obtained by circularizing a linear DNA into a circle by ligase. Based on the recent experimental results that the DNA bending rigidity and twist rigidity strongly depend on temperature, the reduced bending rigidity can be approximated by g=(3.19× {10}-19-T\\cdot 4.14× {10}-22) {erg}\\cdot {cm} over the temperature interval (5 ∼ 53) °C, and the temperature dependence of twist rigidity can be fitted by C(T)=(4588.89{exp} (-T/117.04)-251.33) nm. The temperature dependence of the linking number distribution of circular DNAs can be predicted by using Monte Carlo simulation. The variance of linking number distribution on temperature is in accordance with the previous experimental results. Compared with the temperature dependence of bending rigidity, the temperature dependence of twist rigidity causes a noticeable fluctuation in linking number distribution and mainly contribute towards the variance change of linking number distribution of circular DNA. The variance of the writhe number and twist number in the equation = + depends on the length of circular DNA. When the length of circular DNA is less than 230 nm, the variance of twist number is dominant over the variance of writhe number ( ), whereas for the condition that the length of the circular DNA is larger than 370 nm. Supported by the National Natural Science Foundation of China under Grant Nos. 11047022, 11204045, and 11464004, Guizhou Provincial Tracking Key Program of Social Development (SY20123089, SZ20113069), the General Financial Grant from the China Postdoctoral Science Foundation (2014M562341), the Research Foundation for Young University Teachers from Guizhou University (201311), and College Innovation Talent Team of Guizhou Province (2014)32

Breaking the Barriers to the Circular Economy

OpenAIRE

Kirchherr, J.W.; Hekkert, M.P.; Bour, Ruben; Huijbrechtse-Truijens, Anne; Kostense-Smit, Erica; Muller, Jennifer

2017-01-01

The Copernicus Institute of Sustainable Development, Utrecht University, the Netherlands and Deloitte have jointly carried out research on barriers to the Circular Economy (CE) in the European Union. For this research, a survey with 153 businesses, 55 government officials and expert interviews with forty-seven thought leaders on the circular economy from businesses, governments, academia and NGOs have been carried out. Two types of barriers emerged as main barriers Firstly, there are the cult...

Performance limits of ion extraction systems with non-circular apertures

Energy Technology Data Exchange (ETDEWEB)

Shagayda, A., E-mail: shagayda@gmail.com; Madeev, S. [Keldysh Research Centre, Onezhskaya, 8, 125438 Moscow (Russian Federation)

2016-04-15

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

Performance limits of ion extraction systems with non-circular apertures.

Science.gov (United States)

Shagayda, A; Madeev, S

2016-04-01

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

Performance limits of ion extraction systems with non-circular apertures

Science.gov (United States)

Shagayda, A.; Madeev, S.

2016-04-01

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

Performance limits of ion extraction systems with non-circular apertures

International Nuclear Information System (INIS)

Shagayda, A.; Madeev, S.

2016-01-01

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.

Circular polarimetry of the magnetic compact binary AM Herculis

Energy Technology Data Exchange (ETDEWEB)

Piirola, V; Vilhu, O; Tuominen, I

1982-01-01

Circular polarimetry in the red and simultaneous photometric observations in the UBVRI bands during the period June 1 to 3, 1981, of AM Herculis are discussed. Peak value of negative circular polarization (- 15 %) is stronger than observed in 1976 to 1979. Variations in the shape of the polarization and light curves occur from night to night. Positive crossover and reversal of the sign of the circular polarization are only marginal. Long term changes in polarization may be partly due to precession of the axis of rotation of the white dwarf about the binary axis. However, the duration of the phase interval where circular polarization remains close to zero changes on a time scale of days, casting doubt on precession models. The changing shape and position of the accretion columns with respect to the magnetic axis could explain short term variations. (ESA)

Soil and land management in a circular economy.

Science.gov (United States)

Breure, A M; Lijzen, J P A; Maring, L

2018-05-15

This article elaborates the role of soil and land management in a circular economy. The circular economy is highly dependent on the functioning of soils and land for the production of food and other biomass; the storage, filtration and transformation of many substances including water, carbon, and nitrogen; the provision of fresh mineral resources and fossil fuels; and the use of their functions as the platform for nature and human activities. Resource demand is increasing as a result of the growing human population. In addition to the shrinking availability of resources resulting from their unsustainable use in the past, our planet's diminishing potential for resource production, due to a range of reasons, is leading to resource scarcity, especially in the case of depletable resources. As an economic system that focuses on maximizing the reuse of resources and products and minimizing their depreciation, the circular economy greatly influences, and depends on, soil and land management. The concise management of the resources, land and soil is thus necessary, to make a circular economy successful. Copyright © 2017 Elsevier B.V. All rights reserved.

Second-harmonic generation circular dichroism spectroscopy from tripod-like chiral molecular films

International Nuclear Information System (INIS)

Wang Xiao-Ou; Chen Li-An; Chen Li-Xue; Sun Xiu-Dong; Li Jun-Qing; Li Chun-Fei

2010-01-01

The second-harmonic generation (SHG) circular dichroism in the light of reflection from chiral films of tripod-like chiral molecules is investigated. The expressions of the second-harmonic generation circular dichroism are derived from our presented three-coupled-oscillator model for the tripod-like chiral molecules. Spectral dependence of the circular dichroism of SHG from film surface composed of tripod-like chiral molecules is simulated numerically and analysed. Influence of chiral parameters on the second-harmonic generation circular dichroism spectrum in chiral films is studied. The result shows that the second-harmonic generation circular dichroism is a sensitive method of detecting chirality compared with the ordinary circular dichroism in linear optics. All of our work indicates that the classical molecular models are very effective to explain the second-harmonic generation circular dichroism of chiral molecular system. The classical molecular model theory can give us a clear physical picture and brings us very instructive information about the link between the molecular configuration and the nonlinear processes

Inkjet printed circularly polarized antennas for GPS applications

KAUST Repository

Farooqui, Muhammad Fahad

2014-07-01

Two novel, inkjet printed circularly polarized antenna designs are presented for GPS applications. First antenna design comprises a planar monopole which has been made circularly polarized by the introduction of an L-shaped slit. The antenna shows a gain of 0.2 dBi at 1.575 GHz with 3-dB axial ratio bandwidth of 3.8%. The second antenna design comprises a modified monopole in the form of an inverted L and has been termed as circularly polarized inverted L antenna (CILA). The antenna shows a gain of -2 dBi at 1.575 GHz with 3-dB axial ratio bandwidth of 4.1%. Both the antenna designs are attractive for mobile applications.

Administrative Circular No. 26 (Rev. 7) – May 2007

CERN Multimedia

HR Department

2007-01-01

Recognition of Merit of Staff Members Administrative Circular No. 26 (Rev. 7) is now available on the intranet site of the Human Resources Department. This circular cancels and replaces Administrative Circular No. 26 (Rev. 6) - Procedures governing the career development of staff members. Copies will shortly be available in Departmental secretariats. If you require any additional information on the new staff-member merit assessment and recognition system, you may consult the FAQ, which has been available on the Human Resources Department intranet site since February 2007. Human Resources Department Tel. 78003

Quantitative analysis of the flexibility effect of cisplatin on circular DNA

Science.gov (United States)

Ji, Chao; Zhang, Lingyun; Wang, Peng-Ye

2013-10-01

We study the effects of cisplatin on the circular configuration of DNA using atomic force microscopy (AFM) and observe that the DNA gradually transforms to a complex configuration with an intersection and interwound structures from a circlelike structure. An algorithm is developed to extract the configuration profiles of circular DNA from AFM images and the radius of gyration is used to describe the flexibility of circular DNA. The quantitative analysis of the circular DNA demonstrates that the radius of gyration gradually decreases and two processes on the change of flexibility of circular DNA are found as the cisplatin concentration increases. Furthermore, a model is proposed and discussed to explain the mechanism for understanding the complicated interaction between DNA and cisplatin.

Circularly polarized luminescence of syndiotactic polystyrene

Science.gov (United States)

Rizzo, Paola; Abbate, Sergio; Longhi, Giovanna; Guerra, Gaetano

2017-11-01

Syndiotactic polystyrene (s-PS) films, when crystallized from the amorphous state by temporary sorption of non-racemic guest molecules (like carvone) not only exhibit unusually high optical activity, both in the UV-Visible and Infrared ranges, but also present circularly polarized luminescence (CPL) with high dissymmetry ratios (g = ΔI/I values in the range 0.02-0.03). Experimental evidences provide support, rather than to the usual molecular circular dichroism, to a supramolecular chiral optical response being extrinsic to the site of photon absorption and emission, possibly associated with a helical morphology of s-PS crystallites.

Magnetic field generation by circularly polarized laser light and inertial plasma confinement in a miniature 'Magnetic Bottle' induced by circularly polarized laser light

International Nuclear Information System (INIS)

Kolka, E.

1993-07-01

A new concept of hot plasma confinement in a miniature magnetic bottle induced by circularly polarized laser light is suggested in this work. Magnetic fields generated by circularly polarized laser light may be of the order of megagauss. In this configuration the circularly polarized laser light is used to get confinement of a plasma contained in a good conductor vessel. The poloidal magnetic field induced by the circularly polarized laser and the efficiency of laser absorption by the plasma are calculated in this work. The confinement in this scheme is supported by the magnetic forces and the Lawson criterion for a DT plasma might be achieved for number density n=5*10 21 cm -3 and confinement time τ= 20 nsec. The laser and the plasma parameters required to get an energetic gain are calculated. (authors)

Modified circular velocity law

Science.gov (United States)

Djeghloul, Nazim

2018-05-01

A modified circular velocity law is presented for a test body orbiting around a spherically symmetric mass. This law exhibits a distance scale parameter and allows to recover both usual Newtonian behaviour for lower distances and a constant velocity limit at large scale. Application to the Galaxy predicts the known behaviour and also leads to a galactic mass in accordance with the measured visible stellar mass so that additional dark matter inside the Galaxy can be avoided. It is also shown that this circular velocity law can be embedded in a geometrical description of spacetime within the standard general relativity framework upon relaxing the usual asymptotic flatness condition. This formulation allows to redefine the introduced Newtonian scale limit in term of the central mass exclusively. Moreover, a satisfactory answer to the galactic escape speed problem can be provided indicating the possibility that one can also get rid of dark matter halo outside the Galaxy.

Diverse circular replication-associated protein encoding viruses circulating in invertebrates within a lake ecosystem.

Science.gov (United States)

Dayaram, Anisha; Galatowitsch, Mark L; Argüello-Astorga, Gerardo R; van Bysterveldt, Katherine; Kraberger, Simona; Stainton, Daisy; Harding, Jon S; Roumagnac, Philippe; Martin, Darren P; Lefeuvre, Pierre; Varsani, Arvind

2016-04-01

Over the last five years next-generation sequencing has become a cost effective and efficient method for identifying known and unknown microorganisms. Access to this technique has dramatically changed the field of virology, enabling a wide range of environmental viral metagenome studies to be undertaken of organisms and environmental samples from polar to tropical regions. These studies have led to the discovery of hundreds of highly divergent single stranded DNA (ssDNA) virus-like sequences encoding replication-associated proteins. Yet, few studies have explored how viruses might be shared in an ecosystem through feeding relationships. Here we identify 169 circular molecules (160 CRESS DNA molecules, nine circular molecules) recovered from a New Zealand freshwater lake, that we have tentatively classified into 51 putatively novel species and five previously described species (DflaCV-3, -5, -6, -8, -10). The CRESS DNA viruses identified in this study were recovered from molluscs (Echyridella menzeisii, Musculium novaezelandiae, Potamopyrgus antipodarum and Physella acuta) and insect larvae (Procordulia grayi, Xanthocnemis zealandica, and Chironomus zealandicus) collected from Lake Sarah, as well as from the lake water and benthic sediments. Extensive diversity was observed across most CRESS DNA molecules recovered. The putative capsid protein of one viral species was found to be most similar to those of members of the Tombusviridae family, thus expanding the number of known RNA-DNA hybrid viruses in nature. We noted a strong association between the CRESS DNA viruses and circular molecules identified in the water and browser organisms (C. zealandicus, P. antipodarum and P. acuta), and between water sediments and undefended prey species (C. zealandicus). However, we were unable to find any significant correlation of viral assemblages to the potential feeding relationships of the host aquatic invertebrates. Copyright © 2016 Elsevier B.V. All rights reserved.

Circular blurred shape model for multiclass symbol recognition.

Science.gov (United States)

Escalera, Sergio; Fornés, Alicia; Pujol, Oriol; Lladós, Josep; Radeva, Petia

2011-04-01

In this paper, we propose a circular blurred shape model descriptor to deal with the problem of symbol detection and classification as a particular case of object recognition. The feature extraction is performed by capturing the spatial arrangement of significant object characteristics in a correlogram structure. The shape information from objects is shared among correlogram regions, where a prior blurring degree defines the level of distortion allowed in the symbol, making the descriptor tolerant to irregular deformations. Moreover, the descriptor is rotation invariant by definition. We validate the effectiveness of the proposed descriptor in both the multiclass symbol recognition and symbol detection domains. In order to perform the symbol detection, the descriptors are learned using a cascade of classifiers. In the case of multiclass categorization, the new feature space is learned using a set of binary classifiers which are embedded in an error-correcting output code design. The results over four symbol data sets show the significant improvements of the proposed descriptor compared to the state-of-the-art descriptors. In particular, the results are even more significant in those cases where the symbols suffer from elastic deformations.

Lung Cancer-Specific Circular RNAs as Biomarkers

Science.gov (United States)

2017-08-01

determine whether differential expression of circular RNAs can also be detected in cell culture models. Third, we will determine whether circular RNAs can...four of them as representative differentially expressed circRNAs in Table 1. For example , hsa_circRNA_400633 and hsa_circRNA_101100 were upregulated...sequence for hsa_circRNA_400633 and hsa_circRNA_101100, as shown in Figs. 1 and 2 as an example . The top part is the actual sequence and the

Unleashing the Power of the Circular Economy

Energy Technology Data Exchange (ETDEWEB)

Kok, L.; Wurpel, G.; Ten Wolde, A. [IMSA Amsterdam, Amsterdam (Netherlands)

2013-04-15

The concept of circular economy is an economic and industrial system that focuses on the reusability of products and raw materials, reduces value destruction in the overall system and aims at value creation within each tier of the system. This report for Circle Economy (CE) outlines the general direction and concrete steps that must be taken to accomplish a breakthrough to a circular economy. It also provides a knowledge base behind the concept, connecting it to sustainability.

Molecular electron recollision dynamics in intense circularly polarized laser pulses

Science.gov (United States)

Bandrauk, André D.; Yuan, Kai-Jun

2018-04-01

Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

Circular polarization observed in bioluminescence

NARCIS (Netherlands)

Wynberg, H.; Meijer, E.W.; Hummelen, J.C.; Dekkers, H.P.J.M.; Schippers, P.H.; Carlson, A.D.

1980-01-01

The left and right lanterns of live larvae of the fireflies Photuris lucicrescens and P. versicolor emitted circularly polarized light of opposite sense. A possible mechanism is discussed. [on SciFinder (R)

The potential of a circular economy in the Netherlands: summary report

NARCIS (Netherlands)

Bastein, T.; Roelofs, E.; Rietveld, E.; Hoogendoorn, A.

2013-01-01

For the Dutch Parliament, TNO has assessed the opportunities for a circular economy in The Netherlands. TNO estimates the value of a circular economy to be about 7.3 billion euro. The results and conclusions of the TNO-rapport ‘The potential of a circular economy in the Netherlands’ are sent to the

Circular braiding take-up speed generation using inverse kinematics

NARCIS (Netherlands)

van Ravenhorst, J.H.; Akkerman, Remko

2014-01-01

Circular overbraiding of composite preforms on complex mandrels currently lacks automatic generation of machine control data. To solve this limitation, an inverse kinematics-based procedure was designed and implemented for circular braiding machines with optional guide rings, resulting in a take-up

Generation of circular polarization of the cosmic microwave background

International Nuclear Information System (INIS)

Alexander, Stephon; Ochoa, Joseph; Kosowsky, Arthur

2009-01-01

The standard cosmological model, which includes only Compton scattering photon interactions at energy scales near recombination, results in zero primordial circular polarization of the cosmic microwave background. In this paper we consider a particular renormalizable and gauge-invariant standard model extension coupling photons to an external vector field via a Chern-Simons term, which arises as a radiative correction if gravitational torsion couples to fermions. We compute the transport equations for polarized photons from a Boltzmann-like equation, showing that such a coupling will source circular polarization of the microwave background. For the particular coupling considered here, the circular polarization effect is always negligible compared to the rotation of the linear polarization orientation, also derived using the same formalism. We note the possibility that limits on microwave background circular polarization may probe other photon interactions and related fundamental effects such as violations of Lorentz invariance.

A systematic review on drivers, barriers, and practices towards circular economy

DEFF Research Database (Denmark)

Govindan, Kannan; Hasanagic, Mia

2018-01-01

identified that emerge from the application of a circular economy, no concrete studies exist that investigate current state-of-the-art drivers, barriers and practices in this relevant field. An in-depth exploration of current practices would enhance the circular economy’s significance and would help...... understand its present level of implementation. With this concern, this study provides an analysis of the drivers, barriers and practices that influence the implementation of the circular economy in the context of supply chains through a systematic review. In order to analyse the circular economy’s level...... of implementation, we correlate stakeholders’ perspectives with drivers, barriers, and practices; thus, a multi-perspective framework is proposed. From the results, it is evident that among various stakeholders, the governmental perspective has the maximum positive impact on the implementation of the circular...