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Antimicrobial Compounds (antimicrobial + compound)
Selected AbstractsEffectiveness of Some Natural Antimicrobial Compounds in Controlling Pathogen or Spoilage Bacteria in Lightly Fermented Chinese CabbageJOURNAL OF FOOD SCIENCE, Issue 9 2005Yasuhiro Inatsu ABSTRACT: This study was designed to evaluate the bactericidal or bacteriostatic effect of chitosan, an allyl isothiocyanate (AIT) product, and nisin for the artificially inoculated pathogenic bacteria (Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes) or natural microflora of fermented Chinese cabbage. Addition of 0.1% chitosan decreased the population of pathogens from 0.7 to 1.7 log colony-forming units (CFU)/g after 4 d of storage at 10 °C. The bactericidal activity of chitosan was found to be stronger than that of nisin (0.05 mg/g). Addition of 0.2% of the AIT product (containing AIT and hop extract) exhibited a bacteriostatic effect. However, a combination of AIT product and chitosan enhanced bactericidal efficacy against L. monocytogenes. The addition of chitosan or AIT product was observed to suppress the populations of mesophilic and coliform bacteria during storage at 10 °C for 4 d. Moreover, the use of chitosan or the AIT product did not change the sensory quality of the lightly fermented vegetable. Therefore, these results suggest that chitosan or the AIT product could be useful to improve the microbial safety and quality of lightly fermented vegetable. [source] Conformational Study of Short Peptoid Models for Future Applications as Potent Antimicrobial CompoundsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 3 2007Fateh Singh Nandel Abstract Development of peptides as clinically useful drugs is limited by their poor metabolic stability and low bioavailability. Recent progresses in chemical synthesis and design have led to several strategies for producing potent mimetics. This study aims to analyze sequence/structure requirements and composition for antimicrobial peptoid designs, as use of peptoids is one of the most representative approaches to meet the goal of biomimicry. Analysis of the designs showed that for maximum activity and minimum hemolysis, the plane of the aromatic residues should be at an angle between 0 and 90,° with respect to membranes, cationic residues need not be at the terminal position, and central positions should be uniform in NIle, NLys, and NPhe residues. [source] Clean and Efficient Microwave Solvent-Free Synthesis of Some Antimicrobial Compounds from 2-Aminothiadiazine.CHEMINFORM, Issue 5 2006V. M. Patel Abstract For Abstract see ChemInform Abstract in Full Text. [source] Study of the anti-lactic acid bacteria compounds in table olivesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2009Eduardo Medina Summary The analysis and formation of anti-lactic acid bacteria compounds in olive brines was performed for the main worldwide olive varieties intended for table olives. The results demonstrated that the growth of lactic acid bacteria in the brines of olives non-treated with NaOH is, in some way, variety dependant. Likewise, the most active antimicrobial compound, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol, was not detected in fresh fruits but it was formed during brining from the hydrolysis of oleuropein and this reaction was enzymatically catalysed. Thus, the inactivation of the enzyme by heating the olives produced (i) an accumulation of oleuropein in olives and brines, (ii) the inhibition of the formation of antimicrobials and (iii) the growth of Lactobacillus pentosus in olive brines. These results provide tools for a full understanding of the growth or inhibition of lactic acid bacteria during fermentation of table olives. [source] Active Packaging of Fresh Chicken Breast, with Allyl Isothiocyanate (AITC) in Combination with Modified Atmosphere Packaging (MAP) to Control the Growth of PathogensJOURNAL OF FOOD SCIENCE, Issue 2 2010Joongmin Shin ABSTRACT:,Listeria monocytogenes,and,Salmonella typhimurium,are major bacterial pathogens associated with poultry products. Ally isothiocyanate (AITC), a natural antimicrobial compound, is reportedly effective against these pathogenic organisms. A device was designed for the controlled release of AITC with modified atmosphere packaging (MAP), and then evaluated for its ability to control the growth of,L. monocytogenes,and,S. typhimurium,on raw chicken breast during refrigerated storage. In order to obtain controlled release during the test period, a glass vial was filled with AITC and triglyceride. It was then sealed using high-density polyethylene film. The release of AITC was controlled by the concentration (mole fraction) of AITC in the triglyceride and by the AITC vapor permeability through the film. The fresh chicken samples were inoculated with one or the other of the pathogens at 104 CFU/g, and the packages (with and without AITC-controlled release device) were flushed with ambient air or 30% CO2/70% N2 before sealing, and then stored at 4 °C for up to 21 d. The maximum reduction in MAP plus AITC (compared to MAP alone) was 0.77 log CFU/g for,L.,monocytogenes,and 1.3 log CFU/g for,S.,typhimurium. The color of the chicken breast meat was affected by the concentration of AITC. Overall, a release rate of 0.6 ,g/h of AITC was found to not affect the color, whereas at 1.2 ,g/h of AITC the surface of the chicken was discolored. [source] Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beefLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009M. Turgis Abstract Aims:, In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces. Methods and Results:, Ground beef samples inoculated with Salmonella Typhi (106 CFU g,1) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a 60Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D10 value in the absence/presence of antimicrobial compound. Conclusions:, Depending on the compound tested, the addition of antimicrobial compound decreased the D10 value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef. Significance and Impact of the Study:, These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi. [source] Isolation of an antimicrobial compound from Impatiens balsamina L. using bioassay-guided fractionationPHYTOTHERAPY RESEARCH, Issue 8 2001Xiaolong Yang Abstract By using brine shrimp (Artemia salina) lethality test-guided fractionation, a single bioactive compound (LC50=26,ppm) was isolated from the 95% ethanol extract of the dried aerial parts of Impatiens balsamina L. and subsequently identified as 2-methoxy-1,4-naphthoquinone (MNQ). The structure of MNQ was confirmed by UV, FT-IR, MS, and 1-and 2-D NMR spectroscopy. The antimicrobial activity of MNQ was evaluated using 12 bacterial and eight fungal strains. Five gram-positive and two gram-negative bacteria as well as all eight fungi (including multi-drug resistant strains) tested were highly sensitive to MNQ. A tea prepared according to traditional methods was found to contain sufficient MNQ to account for its antimicrobial properties. Copyright © 2001 John Wiley & Sons, Ltd. [source] RESIN COLLECTION AND SOCIAL IMMUNITY IN HONEY BEESEVOLUTION, Issue 11 2009Michael Simone Diverse animals have evolved an ability to collect antimicrobial compounds from the environment as a means of reducing infection risk. Honey bees battle an extensive assemblage of pathogens with both individual and "social" defenses. We determined if the collection of resins, complex plant secretions with diverse antimicrobial properties, acts as a colony-level immune defense by honey bees. Exposure to extracts from two sources of honey bee propolis (a mixture of resins and wax) led to a significantly lowered expression of two honey bee immune-related genes (hymenoptaecin and AmEater in Brazilian and Minnesota propolis, respectively) and to lowered bacterial loads in the Minnesota (MN) propolis treated colonies. Differences in immune expression were also found across age groups (third-instar larvae, 1-day-old and 7-day-old adults) irrespective of resin treatment. The finding that resins within the nest decrease investment in immune function of 7-day-old bees may have implications for colony health and productivity. This is the first direct evidence that the honey bee nest environment affects immune-gene expression. [source] Multifunctional host defense peptides: antiparasitic activitiesFEBS JOURNAL, Issue 22 2009Amram Mor Whereas significant knowledge is accumulating on the antibacterial and antifungal properties of host defense peptides (HDPs) and their synthetic mimics, much less is known of their activities against parasites. A variety of in vitro and in vivo antiparasitic assays suggest that these notorious antimicrobial compounds could represent a powerful tool for the development of novel drugs to fight parasites in the vertebrate host or to complement current therapeutic strategies, albeit the fact that HDPs essentially act by nonspecific mechanisms casts serious doubt on their ability to exert sufficient selectivity to be considered ideal candidates for drug development. This minireview summarizes recent efforts to assess the antiparasitic properties of HDPs and their synthetic derivatives, focusing on two of the most used models ,Plasmodium and Leishmania species , for antiparasitic assays against the different development stages. [source] Effects of inoculation with plant growth-promoting rhizobacteria on resident rhizosphere microorganismsFEMS MICROBIOLOGY LETTERS, Issue 1 2007Susana Castro-Sowinski Abstract Plant growth-promoting rhizobacteria (PGPR) are exogenous bacteria introduced into agricultural ecosystems that act positively upon plant development. However, amendment reproducibility as well as the potential effects of inoculation upon plant root-associated microbial communities can be sources of concern. To address these questions, an understanding of mutual interactions between inoculants and resident rhizosphere microorganisms is required. Mechanisms used by PGPR can be direct or indirect; the former entails the secretion of growth regulators and the latter occurs through the production of antimicrobial compounds that reduce the deleterious effects of phytopathogens. The different modes of action may lead to different relationships between an inoculant and root microbial communities. Rhizobacterial communities are also affected by the plant, engineered genes, environmental stresses and agricultural practices. These factors appear to determine community structure more than an exogenous, active PGPR introduced at high levels. [source] The Helicobacter hepaticus hefA Gene is Involved in Resistance to AmoxicillinHELICOBACTER, Issue 1 2009Clara Belzer Abstract Background:, Gastrointestinal infections with pathogenic Helicobacter species are commonly treated with combination therapies, which often include amoxicillin. Although this treatment is effective for eradication of Helicobacter pylori, the few existing reports are less clear about antibiotic susceptibility of other Helicobacter species. In this study we have determined the susceptibility of gastric and enterohepatic Helicobacter species to amoxicillin, and have investigated the mechanism of amoxicillin resistance in Helicobacter hepaticus. Materials and methods:, The minimal inhibitory concentration (MIC) of antimicrobial compounds was determined by E -test and agar/broth dilution assays. The hefA gene of H. hepaticus was inactivated by insertion of a chloramphenicol resistance gene. Transcription was measured by quantitative real-time polymerase chain reaction. Results:, Three gastric Helicobacter species (H. pylori, H. mustelae, and H. acinonychis) were susceptible to amoxicillin (MIC < 0.25 mg/L). In contrast, three enterohepatic Helicobacter species (H. rappini, H. bilis, and H. hepaticus) were resistant to amoxicillin (MIC of 8, 16, and 6,64 mg/L, respectively). There was no detectable ,-lactamase activity in H. hepaticus, and inhibition of ,-lactamases did not change the MIC of amoxicillin of H. hepaticus. A H. hepaticus hefA (hh0224) mutant, encoding a TolC-component of a putative efflux system, resulted in loss of amoxicillin resistance (MIC 0.25 mg/L), and also resulted in increased sensitivity to bile acids. Finally, transcription of the hefA gene was not responsive to amoxicillin, but induced by bile acids. Conclusions:, Rodents are frequently colonized by a variety of enterohepatic Helicobacter species, and this may affect their global health status and intestinal inflammatory responses. Animal facilities should have treatment strategies for Helicobacter infections, and hence resistance of enterohepatic Helicobacter species to amoxicillin should be considered when designing eradication programs. [source] Probiotics and their fermented food products are beneficial for healthJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2006S. Parvez Abstract Probiotics are usually defined as microbial food supplements with beneficial effects on the consumers. Most probiotics fall into the group of organisms' known as lactic acid-producing bacteria and are normally consumed in the form of yogurt, fermented milks or other fermented foods. Some of the beneficial effect of lactic acid bacteria consumption include: (i) improving intestinal tract health; (ii) enhancing the immune system, synthesizing and enhancing the bioavailability of nutrients; (iii) reducing symptoms of lactose intolerance, decreasing the prevalence of allergy in susceptible individuals; and (iv) reducing risk of certain cancers. The mechanisms by which probiotics exert their effects are largely unknown, but may involve modifying gut pH, antagonizing pathogens through production of antimicrobial compounds, competing for pathogen binding and receptor sites as well as for available nutrients and growth factors, stimulating immunomodulatory cells, and producing lactase. Selection criteria, efficacy, food and supplement sources and safety issues around probiotics are reviewed. Recent scientific investigation has supported the important role of probiotics as a part of a healthy diet for human as well as for animals and may be an avenue to provide a safe, cost effective, and ,natural' approach that adds a barrier against microbial infection. This paper presents a review of probiotics in health maintenance and disease prevention. [source] Antilisterial activity of lactic acid bacteria isolated from rigouta, a traditional Tunisian cheeseJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2004T. Ghrairi Abstract Aims:, Screening for lactic acid bacteria (LAB) producing bacteriocins and other antimicrobial compounds is of a great significance for the dairy industry to improve food safety. Methods and Results:, Six-hundred strains of LAB isolated from ,rigouta', a Tunisian fermented cheese, were tested for antilisterial activity. Eight bacteriocinogenic strains were selected and analysed. Seven of these strains were identified as Lactococcus lactis and produced nisin Z as demonstrated by mass spectrometry analysis of the purified antibacterial compound. Polymerase chain reaction experiments using nisin gene-specific primers confirmed the presence of nisin operon. Plasmid profiles analysis suggests the presence of, at least, three different strains in this group. MMT05, the eighth strain of this antilisterial collection was identified, at molecular level, as Enterococcus faecalis. The purified bacteriocin produced by this strain showed a molecular mass of 10 201·33 ± 0·85 Da. This new member of class III bacteriocins was termed enterocin MMT05. Conclusions:, Seven lactococcal strains producing nisin Z were selected and could be useful as bio-preservative starter cultures. Additional experiments are needed to evaluate the promising strain MMT05 as bio-preservative as Enterococci could exert detrimental or beneficial role in foods. Significance and Impact of the Study:, Only a few antibacterial strains isolated from traditional African dairy products were described. The new eight strains described herein contribute to the knowledge of this poorly studied environment and constitute promising strains for fermented food safety. [source] Determining the spatial distribution of viable and nonviable bacteria in hydrated microcosm dental plaques by viability profilingJOURNAL OF APPLIED MICROBIOLOGY, Issue 3 2002C.K. Hope Aims: The aim of this study was to use confocal laser scanning microscopy (CLSM) to examine the spatial distribution of both viable and nonviable bacteria within microcosm dental plaques grown in vitro. Previous in vivo studies have reported upon the distribution of viable bacteria only. Methods and Results: Oral biofilms were grown on hydroxyapatite (HA) discs in a constant-depth film fermenter (CDFF) from a saliva inoculum. The biofilms were stained with the BacLightTM LIVE/DEAD system and examined by CLSM. Fluorescence intensity profiles through the depth of the biofilm showed an offset between the maximum viable intensity and the maximum nonviable intensity. Topographical differences between the surface properties of the viable and nonviable biofilm virtual surfaces were also measured. Conclusions: The profile of fluorescence intensity from viable and nonviable staining suggested that the upper layers of the biofilm contain proportionally more viable bacteria than the lower regions of the biofilm. Significance and Impact of Study: Viability profiling records the transition from predominantly viable to nonviable bacteria through biofilms suggesting that this technique may be of use for quantifying the effects of antimicrobial compounds upon biofilms. The distribution of viable bacteria was similar to that found in dental plaque in vivo suggesting that the CDFF produces in vitro biofilms which are comparable to their in vivo counterparts in terms of the spatial distribution of viable bacteria. [source] BEHAVIOR OF AVIRULENT YERSINIA PESTIS IN LIQUID WHOLE EGG AS AFFECTED BY STORAGE TEMPERATURE, ANTIMICROBIALS AND THERMAL PASTEURIZATIONJOURNAL OF FOOD SAFETY, Issue 3 2010JOSHUA B. GURTLER ABSTRACT Yersinia spp. are psychrotrophic bacteria capable of growth at temperatures as low as ,2C, known to contaminate shell eggs and liquid eggs in the U.S.A. and South America. A study was performed to determine the thermal sensitivity of avirulent Yersinia pestis in liquid whole egg (LWE), evaluate the growth pattern of the bacterium in LWE at temperatures of 4,22C and assess the ability of 10 antimicrobial compounds to inhibit the growth of attenuated Y. pestis in LWE. The estimated decimal reduction values of avirulent Y. pestis in LWE at 54C (D54) were 1.39,1.58 min, and D60 values were 13.8 and 11.4 s by the addition of 0 and 965 IU of nisin (MP Biomedicals, LLC, Solon, OH), respectively. Low molecular weight chitosan (0.5%) and an activated lactoperoxidase system (2.18 U/mL) were ineffective at inhibiting growth of Y. pestis, while 500 IU/mL of nisin inhibited populations by up to 1 log cfu/mL at 4, 10 and 15C when compared with the control. Allyl isothiocyanate, diacetyl, diethyl dicarbonate, ethylenediaminetetraacetic acid, methylparaben, monolaurin and benzoyl peroxide inhibited the growth of attenuated Y. pestis when added at high levels. PRACTICAL APPLICATIONS The genus Yersinia does not currently pose a problem in pasteurized liquid egg products, although it has been isolated from eggs in the U.S.A. and Argentina. Yersiniae, which are psychrotrophic bacteria, can grow at temperatures as low as ,2C; therefore, incidental or intentional contamination of liquid whole egg (LWE) with Yersinia spp. could result in multiplication to high populations, even when stored under refrigeration (ca. 4C). We have shown that avirulent Yersinia pestis is able to multiply to populations of >2, 5 and 8 log cfu/mL in LWE at 4C within 6, 14 and 26 days, respectively. This study provides information that will be helpful in determining thermal and nonthermal means of controlling yersiniae in LWE products. [source] LISTERIA MONOCYTOGENES AND ESCHERICHIA COLI O157:H7 INHIBITION IN VITRO BY LIPOSOME-ENCAPSULATED NISIN AND ETHYLENE DIAMINETETRAACETIC ACIDJOURNAL OF FOOD SAFETY, Issue 2 2008T. MATTHEW TAYLOR ABSTRACT Encapsulation technologies that effectively reduce antimicrobial interaction with food components or protect antimicrobial compounds from food processing measures have the potential to improve the microbiological safety of ready-to-eat foods. Recent application of liposomes for the preservation of cheese has spurred research into their utility in other food matrices. To ascertain the feasibility of encapsulated antimicrobial for the control of Listeria monocytogenes and Escherichia coli O157:H7 growth in a model system, nisin (5.0 and 10.0 µg/mL) and the chelator ethylene diaminetetraacetic acid were entrapped in phospholipid liposomes. While phosphatidylcholine (PC) liposomes did not produce significant inhibition of target pathogens, PC/phosphatidylglycerol 8/2 and 6/4 (mol%) produced significant inhibition of pathogens. Near-complete inhibition of E. coli O157:H7 with liposomal antimicrobials at concentrations below those reported necessary for unencapsulated antimicrobial and chelator suggests that liposomes may represent a powerful technology for the encapsulation of antimicrobials and the control of foodborne pathogens. PRACTICAL APPLICATIONS The activity of many antimicrobials is abolished in many food products for a variety of reasons. Interference and cross-reactions of the antimicrobial and various food constituents, such as protein and fat, are difficult to overcome and often require large amounts of antimicrobial in order to gain significant reductions in the pathogen load in a product. Loss of solubility of some antimicrobials based on pH or ionic strength will negatively affect the antimicrobial potential of a compound like nisin. Liposome encapsulation technologies, such as that reported here, may allow for the maintenance of antimicrobial activity by protecting the antimicrobial against cross-reactions with food components. Additionally, the liposome core represents a microenvironment which can be manipulated by the manufacturer in order to preserve optimal antimicrobial solubility and stability conditions until the time of release. [source] High Relative Humidity In-Package of Fresh-Cut Fruits and Vegetables: Advantage or Disadvantage Considering Microbiological Problems and Antimicrobial Delivering Systems?JOURNAL OF FOOD SCIENCE, Issue 4 2008J.F. Ayala-Zavala ABSTRACT:, This hypothesis article states that the high relative humidity (RH) of packaged fresh-cut fruits or vegetables that is associated with spoilage can be used as an advantageous way to deliver antimicrobial compounds using cyclodextrins (CDs) as carriers. CDs can function as antimicrobial delivery systems as they can release antioxidant and antimicrobial compounds (guest molecules) as the humidity levels increase in the headspace. Hydrophobic antimicrobial guests can be complexed with CDs due to the amphiphatic nature of the host. Then, at high RH values, due to the water,CDs interaction, host,guest interactions are weakened; consequently, the antimicrobial molecule is released and should protect the product against the microbial growth. Potential antimicrobial compounds capable of forming complexes with CDs are discussed, as well as possible applications to preserve fresh-cut produce and future research in this area. [source] Pyridazine and phthalazine derivatives with potential antimicrobial activityJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2007Roxana M. Butnariu Fifteen new pyridazine and phthalazine derivatives were prepared (in good to excellent yields) and tested in vitro as antimicrobial compounds. All the compounds have proved to have a remarkable activity against Gram positive germs, the results on Sarciria Luteea being spectacular. Correlation structure - biological activity have been done. Stereo- and region- chemistry involved in these reactions are discussed. [source] Chewing sticks: timeless natural toothbrushes for oral cleansingJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2001C. D. Wu It is generally accepted that oral hygiene maintenance through regular removal of dental plaque and food deposits is an essential factor in the prevention of dental caries and periodontal disease. Methods for oral hygiene vary from country to country and from culture to culture. Despite the widespread use of toothbrushes and toothpastes, natural methods of tooth cleaning using chewing sticks selected and prepared from the twigs, stems or roots from a variety of plant species have been practised for thousands of years in Asia, Africa, the Middle East and the Americas. Selected clinical studies have shown that chewing sticks, when properly used, can be as efficient as toothbrushes in removing dental plaque due to the combined effect of mechanical cleaning and enhanced salivation. It has also been suggested that antimicrobial substances that naturally protect plants against various invading microorganisms or other parasites may leach out into the oral cavity, and that these compounds may benefit the users by protection against cariogenic and periodontopathic bacteria. Some clinical epidemiological studies are in support of this, and many laboratory investigations have suggested the presence of heterogeneous antimicrobial components extractable using different chemical procedures. A few recent studies have identified some of the active antimicrobial compounds. Today, chewing sticks are still used in many developing countries because of religion and/or tradition, and because of their availability, low cost and simplicity. The World Health Organization also encourages their use. The Year 2000 Consensus Report on Oral Hygiene states that chewing sticks may have a role to play in the promotion of oral hygiene, and that evaluation of their effectiveness warrants further research. [source] Competitive exclusion as a mode of action of a novel Bacillus cereus aquaculture biological agentLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2010R. Lalloo Abstract Aims:, To determine the contribution of potential modes of action of a Bacillus cereus aquaculture biological control agent in inhibition of the fish pathogen, Aeromonas hydrophila. Methods and Results:, When B. cereus was tested in plate well inhibition studies, no production of antimicrobial compounds was detected. Bacillus cereus had a high growth rate (0·96 h,1), whereas Aer. hydrophila concentration decreased by c. 70% in co-culture experiments. In nutrient limitation studies, B. cereus had a significantly higher growth rate when cultured under glucose (P < 0·05) and iron (P < 0·01) limitation in comparison with Aer. hydrophila. Bacillus cereus glucose (0·30 g l,1 h,1) and iron (0·60 mg l,1 h,1) uptake rates were also significantly higher (P < 0·01) than the Aer. hydrophila glucose (0·14 g l,1 h,1) and iron (0·43 mg l,1 h,1) uptake rates. Iron uptake was facilitated by siderophore production shown in time profile studies where relative siderophore production was c. 60% through the late exponential and sporulation phases. Conclusions:, Competitive exclusion by higher growth rate, competition for organic carbon and iron, facilitated by siderophore production, could be identified as mechanisms of pathogen growth inhibition by B. cereus. Significance and Impact of the Study:, This study is the first elucidation of the mechanism of action of our novel B. cereus biological agent in growth attenuation of pathogenic Aer. hydrophila. This study enhances the application knowledge and attractiveness for adoption of B. cereus NRRL 100132 for exploitation in aquaculture. [source] Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beefLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009M. Turgis Abstract Aims:, In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces. Methods and Results:, Ground beef samples inoculated with Salmonella Typhi (106 CFU g,1) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a 60Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D10 value in the absence/presence of antimicrobial compound. Conclusions:, Depending on the compound tested, the addition of antimicrobial compound decreased the D10 value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef. Significance and Impact of the Study:, These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi. [source] Tolerance to the antimicrobial peptide colistin in Pseudomonas aeruginosa biofilms is linked to metabolically active cells, and depends on the pmr and mexAB-oprM genesMOLECULAR MICROBIOLOGY, Issue 1 2008Sünje Johanna Pamp Summary Bacteria living as biofilm are frequently reported to exhibit inherent tolerance to antimicrobial compounds, and might therefore contribute to the persistence of infections. Antimicrobial peptides are attracting increasing interest as new potential antimicrobial therapeutics; however, little is known about potential mechanisms, which might contribute to resistance or tolerance development towards these compounds in biofilms. Here we provide evidence that a spatially distinct subpopulation of metabolically active cells in Pseudomonas aeruginosa biofilms is able to develop tolerance to the antimicrobial peptide colistin. On the contrary, biofilm cells exhibiting low metabolic activity were killed by colistin. We demonstrate that the subpopulation of metabolically active cells is able to adapt to colistin by inducing a specific adaptation mechanism mediated by the pmr operon, as well as an unspecific adaptation mechanism mediated by the mexAB-oprM genes. Mutants defective in either pmr -mediated lipopolysaccharide modification or in mexAB-oprM -mediated antimicrobial efflux were not able to develop a tolerant subpopulation in biofilms. In contrast to the observed pattern of colistin-mediated killing in biofilms, conventional antimicrobial compounds such as ciprofloxacin and tetracycline were found to specifically kill the subpopulation of metabolically active biofilm cells, whereas the subpopulation exhibiting low metabolic activity survived the treatment. Consequently, targeting the two physiologically distinct subpopulations by combined antimicrobial treatment with either ciprofloxacin and colistin or tetracycline and colistin almost completely eradicated all biofilm cells. [source] cDNA-AFLP reveals genes differentially expressed during the hypersensitive response of cassavaMOLECULAR PLANT PATHOLOGY, Issue 2 2005BENJAMIN P. KEMP SUMMARY The tropical staple cassava is subject to several major diseases, such as cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis. Disease-resistant genotypes afford the only practical solution, yet despite the global importance of this crop, little is known about its defence mechanisms. cDNA-AFLP was used to isolate cassava genes differentially expressed during the hypersensitive reaction (HR) of leaves in response to an incompatible Pseudomonas syringae pathovar. Seventy-eight transcript-derived fragments (TDFs) showing differential expression (c. 75% up-regulated, 25% down-regulated) were identified. Many encoded putative homologues of known defence-related genes involved in signalling (e.g. calcium transport and binding, ACC oxidases and a WRKY transcription factor), cell wall strengthening (e.g. cinnamoyl coenzyme A reductase and peroxidase), programmed cell death (e.g. proteases, 26S proteosome), antimicrobial activity (e.g. proteases and ,-1,3-glucanases) and the production of antimicrobial compounds (e.g. DAHP synthase and cytochrome P450s). Full-length cDNAs including a probable matrix metalloprotease and a WRKY transcription factor were isolated from six TDFs. RT-PCR or Northern blot analysis showed HR-induced TDFs were maximally expressed at 24 h, although some were produced by 6 h; some were induced, albeit more slowly, in response to wounding. This work begins to reveal potential defence-related genes of this understudied, major crop. [source] The role of lipopolysaccharides in induction of plant defence responsesMOLECULAR PLANT PATHOLOGY, Issue 5 2003Gitte Erbs SUMMARY Lipopolysaccharides (LPS) are ubiquitous, indispensable components of the cell surface of Gram-negative bacteria that apparently have diverse roles in bacterial pathogenesis of plants. As an outer membrane component, LPS may contribute to the exclusion of plant-derived antimicrobial compounds promoting the ability of a bacterial plant pathogen to infect plants. In contrast, LPS can be recognized by plants to directly trigger some plant defence-related responses. LPS also sensitize plant tissue to respond more rapidly or to a greater extent to subsequently inoculated phytopathogenic bacteria. Sensitization is manifested by an accelerated synthesis of antimicrobial hydroxycinnamoyl-tyramine conjugates, in the expression patterns of genes coding for some pathogenesis-related (PR) proteins, and prevention of the hypersensitive reaction caused by avirulent bacteria. The description at the molecular level of the various effects of LPS on plants is a necessary step towards an understanding of the signal transduction mechanisms through which LPS triggers these responses. A definition of these signal transduction pathways should allow an assessment of the contribution that LPS signalling makes to plant disease resistance in both natural infections and biocontrol. [source] Crystallization and preliminary X-ray analysis of glutathione transferases from cyanobacteriaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2009Susanne C. Feil Glutathione S -transferases (GSTs) are a group of multifunctional enzymes that are found in animals, plants and microorganisms. Their primary function is to remove toxins derived from exogenous sources or the products of metabolism from the cell. Mammalian GSTs have been extensively studied, in contrast to bacterial GSTs which have received relatively scant attention. A new class of GSTs called Chi has recently been identified in cyanobacteria. Chi GSTs exhibit a high glutathionylation activity towards isothiocyanates, compounds that are normally found in plants. Here, the crystallization of two GSTs are presented: TeGST produced by Thermosynechococcus elongates BP-1 and SeGST from Synechococcus elongates PCC 6301. Both enzymes formed crystals that diffracted to high resolution and appeared to be suitable for further X-ray diffraction studies. The structures of these GSTs may shed further light on the evolution of GST catalytic activity and in particular why these enzymes possess catalytic activity towards plant antimicrobial compounds. [source] Investigation of the Substrate Specificity of Lacticin 481 Synthetase by Using Nonproteinogenic Amino AcidsCHEMBIOCHEM, Issue 5 2009Matthew R. Levengood Abstract One enzyme, many substrates. The substrate specificity of a lantibiotic biosynthetic enzyme, lacticin 481 synthetase, was probed by using synthetic prepeptides containing a variety of nonproteinogenic amino acids, including unnatural ,-amino acids, ,-amino acids, D -amino acids, and peptoids. Lantibiotics are peptide antimicrobial compounds that are characterized by the thioether-bridged amino acids lanthionine and methyllanthionine. For lacticin 481, these structures are installed in a two-step post-translational modification process by a bifunctional enzyme, lacticin 481 synthetase (LctM). LctM catalyzes the dehydration of Ser and Thr residues to generate dehydroalanine or dehydrobutyrine, respectively, and the subsequent intramolecular regio- and stereospecific Michael-type addition of cysteines onto the dehydroamino acids. In this study, semisynthetic substrates containing nonproteinogenic amino acids were prepared by expressed protein ligation and [3+2]-cycloaddition of azide and alkyne-functionalized peptides. LctM demonstrated broad substrate specificity toward substrates containing ,-amino acids, D -amino acids, and N -alkyl amino acids (peptoids) in certain regions of its peptide substrate. These findings showcase its promise for use in lantibiotic and peptide-engineering applications, whereby nonproteinogenic amino acids might impart improved stability or modulated biological activities. Furthermore, LctM permitted the incorporation of an alkyne-containing amino acid that can be utilized for the site-selective modification of mature lantibiotics and used in target identification. [source] | ||||||||||||||||