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1.
Sami Hraiech Julien Hiblot John Lafleur Hubert Lepidi Laurent Papazian Jean-Marc Rolain Didier Raoult Mikael Elias Mark W. Silby Janek Bzdrenga Fabienne Bregeon Eric Chabriere 《PloS one》2014,9(10)
Rationale
The effectiveness of antibiotic molecules in treating Pseudomonas aeruginosa pneumonia is reduced as a result of the dissemination of bacterial resistance. The existence of bacterial communication systems, such as quorum sensing, has provided new opportunities of treatment. Lactonases efficiently quench acyl-homoserine lactone-based bacterial quorum sensing, implicating these enzymes as potential new anti-Pseudomonas drugs that might be evaluated in pneumonia.Objectives
The aim of the present study was to evaluate the ability of a lactonase called SsoPox-I to reduce the mortality of a rat P. aeruginosa pneumonia.Methods
To assess SsoPox-I-mediated quorum quenching, we first measured the activity of the virulence gene lasB, the synthesis of pyocianin, the proteolytic activity of a bacterial suspension and the formation of biofilm of a PAO1 strain grown in the presence of lactonase. In an acute lethal model of P. aeruginosa pneumonia in rats, we evaluated the effects of an early or deferred intra-tracheal treatment with SsoPox-I on the mortality, lung bacterial count and lung damage.Measurements and Primary Results
SsoPox-I decreased PAO1 lasB virulence gene activity, pyocianin synthesis, proteolytic activity and biofilm formation. The early use of SsoPox-I reduced the mortality of rats with acute pneumonia from 75% to 20%. Histological lung damage was significantly reduced but the lung bacterial count was not modified by the treatment. A delayed treatment was associated with a non-significant reduction of mortality.Conclusion
These results demonstrate the protective effects of lactonase SsoPox-I in P. aeruginosa pneumonia and open the way for a future therapeutic use. 相似文献2.
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Elias M Dupuy J Merone L Mandrich L Porzio E Moniot S Rochu D Lecomte C Rossi M Masson P Manco G Chabriere E 《Journal of molecular biology》2008,379(5):1017-1028
Organophosphates are the largest class of known insecticides, several of which are potent nerve agents. Consequently, organophosphate-degrading enzymes are of great scientific interest as bioscavengers and biodecontaminants. Recently, a hyperthermophilic phosphotriesterase (known as SsoPox), from the Archaeon Sulfolobus solfataricus, has been isolated and found to possess a very high lactonase activity. Here, we report the three-dimensional structures of SsoPox in the apo form (2.6 Å resolution) and in complex with a quorum-sensing lactone mimic at 2.0 Å resolution. The structure also reveals an unexpected active site topology, and a unique hydrophobic channel that perfectly accommodates the lactone substrate. Structural and mutagenesis evidence allows us to propose a mechanism for lactone hydrolysis and to refine the catalytic mechanism established for phosphotriesterases. In addition, SsoPox structures permit the correlation of experimental lactonase and phosphotriesterase activities and this strongly suggests lactonase activity as the cognate function of SsoPox. This example demonstrates that promiscuous activities probably constitute a large and efficient reservoir for the creation of novel catalytic activities. 相似文献
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Wen-Zhao Wang Tomohiro Morohoshi Masashi Ikenoya Nobutaka Someya Tsukasa Ikeda 《Applied and environmental microbiology》2010,76(8):2524-2530
N-Acylhomoserine lactones (AHLs) are used as quorum-sensing signal molecules by many Gram-negative bacteria. We have reported that Microbacterium testaceum StLB037, which was isolated from the leaf surface of potato, has AHL-degrading activity. In this study, we cloned the aiiM gene from the genomic library of StLB037, which has AHL-degrading activity and shows high homology with the α/β hydrolase fold family from Actinobacteria. Purified AiiM as a maltose binding fusion protein showed high degrading activity of AHLs with both short- and long-chain AHLs with or without substitution at carbon 3. High-performance liquid chromatography analysis revealed that AiiM works as an AHL lactonase that catalyzes AHL ring opening by hydrolyzing lactones. In addition, expression of AiiM in the plant pathogen Pectobacterium carotovorum subsp. carotovorum reduced pectinase activity markedly and attenuated soft rot symptoms on potato slices. In conclusion, this study indicated that AiiM might be effective in quenching quorum sensing of P. carotovorum subsp. carotovorum.Quorum sensing is a cell-cell communication mechanism that depends on cell population density in bacteria (3, 7). In many Gram-negative bacteria, several kinds of N-acyl-l-homoserine lactones (AHLs) have been identified as signal compounds involved in this mechanism, and these are termed autoinducers (3, 7). AHL-mediated quorum sensing regulates the expression of many genes, including those responsible for bioluminescence, the production of pigments and antibiotics, and other processes (7). Many Gram-negative plant pathogens produce AHLs and regulate their virulence by AHL-mediated quorum sensing (31). For instance, Pectobacterium carotovorum subsp. carotovorum (formerly Erwinia carotovora), which causes soft rot diseases in many plant species, induces the production of various exoenzymes and plant tissue maceration by AHLs (1). Pantoea stewartii and Pantoea ananatis produce AHLs and regulate exopolysaccharide biosynthesis and the infection of plants (15, 32). In general, AHL-negative mutants show defects in pathogenicity, so it is expected that disrupting or manipulating quorum-sensing signals could inhibit the expression of virulence and infection of host cells.Recently, many AHL-degrading genes have been cloned and characterized from various bacteria. Genes encoding AHL lactonase, which catalyzes AHL ring opening by hydrolyzing lactones, have been cloned from Bacillus sp., Arthrobacter sp., Agrobacterium tumefaciens, and Rhodococcus erythropolis (5, 23, 30, 34). Genes encoding AHL acylase, which hydrolyze the amide bond of AHL, have been cloned from Ralstonia sp., Anabaena sp., Streptomyces sp., Shewanella sp., and Pseudomonas aeruginosa (11, 12, 16, 22, 25). Human and murine paraoxonase degrades AHL by hydrolyzing its lactone ring (21). Novel AHL lactonase genes have been isolated from a metagenomic library which was constructed from environmental soil samples (24, 27). AHL-degrading genes have also been utilized in the biocontrol of plant diseases. Expression of aiiA in transformed P. carotovorum subsp. carotovorum significantly attenuates pathogenicity on some crops (5). Transgenic plants expressing AHL lactonase exhibited significantly enhanced resistance to the infection of P. carotovorum subsp. carotovorum (4).We have reported the isolation of AHL-degrading Microbacterium testaceum StLB037 from the leaf surface of potato (Solanum tuberosum) (17). In coinfections, we found that StLB037 interrupted quorum-sensing-dependent bacterial infection by the plant pathogen P. carotovorum subsp. carotovorum. In this study, we report the cloning and characterization of a novel AHL lactonase gene (aiiM) from the chromosome of StLB037. In addition, we evaluated the potential use of heterologous aiiM gene expression in quenching quorum sensing in the plant pathogen P. carotovorum subsp. carotovorum. 相似文献
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Sesquiterpene lactone stereochemistry influences herbivore resistance and plant fitness in the field
Background and Aims
Stereochemical variation is widely known to influence the bioactivity of compounds in the context of pharmacology and pesticide science, but our understanding of its importance in mediating plant–herbivore interactions is limited, particularly in field settings. Similarly, sesquiterpene lactones are a broadly distributed class of putative defensive compounds, but little is known about their activities in the field.Methods
Natural variation in sesquiterpene lactones of the common cocklebur, Xanthium strumarium (Asteraceae), was used in conjunction with a series of common garden experiments to examine relationships between stereochemical variation, herbivore damage and plant fitness.Key Results
The stereochemistry of sesquiterpene lactone ring junctions helped to explain variation in plant herbivore resistance. Plants producing cis-fused sesquiterpene lactones experienced significantly higher damage than plants producing trans-fused sesquiterpene lactones. Experiments manipulating herbivore damage above and below ambient levels found that herbivore damage was negatively correlated with plant fitness. This pattern translated into significant fitness differences between chemotypes under ambient levels of herbivore attack, but not when attack was experimentally reduced via pesticide.Conclusions
To our knowledge, this work represents only the second study to examine sesquiterpene lactones as defensive compounds in the field, the first to document herbivore-mediated natural selection on sesquiterpene lactone variation and the first to investigate the ecological significance of the stereochemistry of the lactone ring junction. The results indicate that subtle differences in stereochemistry may be a major determinant of the protective role of secondary metabolites and thus of plant fitness. As stereochemical variation is widespread in many groups of secondary metabolites, these findings suggest the possibility of dynamic evolutionary histories within the Asteraceae and other plant families showing extensive stereochemical variation. 相似文献7.
Chakrit Sawasdidoln Suwimol Taweechaisupapong Rasana W. Sermswan Unchalee Tattawasart Sumalee Tungpradabkul Surasakdi Wongratanacheewin 《PloS one》2010,5(2)
Background
Burkholderia pseudomallei, a Gram-negative bacterium that causes melioidosis, was reported to produce biofilm. As the disease causes high relapse rate when compared to other bacterial infections, it therefore might be due to the reactivation of the biofilm forming bacteria which also provided resistance to antimicrobial agents. However, the mechanism on how biofilm can provide tolerance to antimicrobials is still unclear.Methodology/Principal Findings
The change in resistance of B. pseudomallei to doxycycline, ceftazidime, imipenem, and trimethoprim/sulfamethoxazole during biofilm formation were measured as minimum biofilm elimination concentration (MBEC) in 50 soil and clinical isolates and also in capsule, flagellin, LPS and biofilm mutants. Almost all planktonic isolates were susceptible to all agents studied. In contrast, when they were grown in the condition that induced biofilm formation, they were markedly resistant to all antimicrobial agents even though the amount of biofilm production was not the same. The capsule and O-side chains of LPS mutants had no effect on biofilm formation whereas the flagellin-defective mutant markedly reduced in biofilm production. No alteration of LPS profiles was observed when susceptible form was changed to resistance. The higher amount of N-acyl homoserine lactones (AHLs) was detected in the high biofilm-producing isolates. Interestingly, the biofilm mutant which produced a very low amount of biofilm and was sensitive to antimicrobial agents significantly resisted those agents when grown in biofilm inducing condition.Conclusions/Significance
The possible drug resistance mechanism of biofilm mutants and other isolates is not by having biofilm but rather from some factors that up-regulated when biofilm formation genes were stimulated. The understanding of genes related to this situation may lead us to prevent B. pseudomallei biofilms leading to the relapse of melioidosis. 相似文献8.
Background
Intestinal microbes play significant roles in fish and can be possibly used as probiotics in aquaculture. In our previous study, Flaviramulus ichthyoenteri Th78T, a novel species in the family Flavobacteriaceae, was isolated from fish intestine and showed strong quorum quenching (QQ) ability. To identify the QQ enzymes in Th78T and explore the potential roles of Th78T in fish intestine, we sequenced the genome of Th78T and performed extensive genomic analysis.Results
An N-acyl homoserine lactonase FiaL belonging to the metallo-β-lactamase superfamily was identified and the QQ activity of heterologously expressed FiaL was confirmed in vitro. FiaL has relatively little similarity to the known lactonases (25.2 ~ 27.9% identity in amino acid sequence). Various digestive enzymes including alginate lyases and lipases can be produced by Th78T, and enzymes essential for production of B vitamins such as biotin, riboflavin and folate are predicted. Genes encoding sialic acid lyases, sialidases, sulfatases and fucosidases, which contribute to utilization of mucus, are present in the genome. In addition, genes related to response to different stresses and gliding motility were also identified. Comparative genome analysis shows that Th78T has more specific genes involved in carbohydrate transport and metabolism compared to other two isolates in Flavobacteriaceae, both isolated from sediments.Conclusions
The genome of Th78T exhibits evident advantages for this bacterium to survive in the fish intestine, including production of QQ enzyme, utilization of various nutrients available in the intestine as well as the ability to produce digestive enzymes and vitamins, which also provides an application prospect of Th78T to be used as a probiotic in aquaculture.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1275-0) contains supplementary material, which is available to authorized users. 相似文献9.
Background
Differential gel electrophoresis (DIGE) is a technology widely used for protein expression analysis. It is based on labelling with fluorescent Cy dyes. In comparative fluorescence gel electrophoresis experiments, however, unspecific labelling using N-hydroxy-succinimide-ester-based labelling protocols was recently detected. Cross-talk was observed due to failure of the quenching process. Here, the impact of this effect for DIGE experiments was investigated.Methodology/Principal Findings
Experiments to test quenching efficiency were performed in replicate using Escherichia coli lysate. Parameters such as the amount of dye and quencher were varied. Labelling and quenching were reversed in one experiment. Differences in protein spot volumes due to limited quenching were determined. For some spots twice the volume was detected underscoring the importance of proper control of silencing of active dye.Conclusions/Significance
It could be demonstrated that uncontrolled labelling increased protein spot volume, even doubling it in some cases. Moreover, proteins responded differently to the protocol. Such unpredictable and unspecific processes are not acceptable in protein regulation studies so that it is necessary to validate the correct amount of quencher for individual samples before the DIGE experiment is performed. Increase of the concentration of lysine, which is used as quencher, from 10 mM to 2500 mM, was sufficient to silence the dye. Alternatively, active dye molecules can be removed by filtration. 相似文献10.
Gustavo A. Santa Cruz 《Reports of Practical Oncology and Radiotherapy》2016,21(2):135-139
Aim
to present the most important aspects of Microdosimetry, a research field in radiation biophysics.Background
microdosimetry is the branch of radiation biophysics that systematically studies the spatial, temporal and spectral aspects of the stochastic nature of the energy deposition processes in microscopic structures.Materials and Methods
we briefly review its history, the people, the formalism and the theories and devices that allowed researchers to begin to understand the true nature of radiation action on living matter.Results and Conclusions
we outline some of its applications, especially to Boron Neutron Capture Therapy, attempting to explain the biological effectiveness of the boron thermal neutron capture reaction. 相似文献11.
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Background
Despite the high prevalence and major public health ramifications, obstructive sleep apnea syndrome (OSAS) remains underdiagnosed. In many developed countries, because community pharmacists (CP) are easily accessible, they have been developing additional clinical services that integrate the services of and collaborate with other healthcare providers (general practitioners (GPs), nurses, etc.). Alternative strategies for primary care screening programs for OSAS involving the CP are discussed.Objective
To estimate the quality of life, costs, and cost-effectiveness of three screening strategies among patients who are at risk of having moderate to severe OSAS in primary care.Design
Markov decision model.Data Sources
Published data.Target Population
Hypothetical cohort of 50-year-old male patients with symptoms highly evocative of OSAS.Time Horizon
The 5 years after initial evaluation for OSAS.Perspective
Societal.Interventions
Screening strategy with CP (CP-GP collaboration), screening strategy without CP (GP alone) and no screening.Outcomes measures
Quality of life, survival and costs for each screening strategy.Results of base-case analysis
Under almost all modeled conditions, the involvement of CPs in OSAS screening was cost effective. The maximal incremental cost for “screening strategy with CP” was about 455€ per QALY gained.Results of sensitivity analysis
Our results were robust but primarily sensitive to the treatment costs by continuous positive airway pressure, and the costs of untreated OSAS. The probabilistic sensitivity analysis showed that the “screening strategy with CP” was dominant in 80% of cases. It was more effective and less costly in 47% of cases, and within the cost-effective range (maximum incremental cost effectiveness ratio at €6186.67/QALY) in 33% of cases.Conclusions
CP involvement in OSAS screening is a cost-effective strategy. This proposal is consistent with the trend in Europe and the United States to extend the practices and responsibilities of the pharmacist in primary care. 相似文献14.
Background
Retrotransposons have been extensively studied in plants and animals and have been shown to have an impact on human genome dynamics and evolution. Their ability to move within genomes gives retrotransposons to affect genome instability.Methods
we examined the polymorphic inserted AluYa5, evolutionary young Alu, in the progesterone receptor gene to determine the effects of Alu insertion on molecular environment. We used mono-allelic inserted cell lines which carry both Alu-present and Alu-absent alleles. To determine the epigenetic change and gene expression, we performed restriction enzyme digestion, Pyrosequencing, and Chromatin Immunoprecipitation.Results
We observed that the polymorphic insertion of evolutionally young Alu causes increasing levels of DNA methylation in the surrounding genomic area and generates inactive histone tail modifications. Consequently the Alu insertion deleteriously inactivates the neighboring gene expression.Conclusion
The mono-allelic Alu insertion cell line clearly showed that polymorphic inserted repetitive elements cause the inactivation of neighboring gene expression, bringing aberrant epigenetic changes. 相似文献15.
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Vis JC De Bruin-Bon HA Bouma BJ Huisman SA Imschoot L van den Brink K Mulder BJ 《Netherlands heart journal》2012,20(6):264-269
Objective
Physical fitness is reduced in adults with Down syndrome (DS). The present study was conducted to elucidate the exercise response in adults with DS.Design
Case controlled before-after trial.Setting
Residential centre for people with intellectual disabilities.Participants
96 Adults with DS, 25 non-DS adults with an intellectual disability, 33 controls.Interventions
Echocardiography to exclude heart defects and to measure cardiac index (CI) in the supine position, supine position with raised legs, and following ten knee bends.Main outcome measure
Exercise testingResults
At rest, mean CI was not significantly different between persons with DS and controls (2.3 vs. 2.4 l/min/m2, p = 0.3). However, mean CI after exercise was significantly lower in DS (2.9 vs. 3.7 l/min/m2, p < 0.001) and mean CI increase from rest to exercise was more than 50% lower in DS. On the contrary, CI after exercise was similar among controls and non-DS adults with an intellectual disability. Significantly lower stroke volumes in DS were found with insufficient heart rate response.Conclusions
CI at rest was similar in adults with DS and controls; however persons with DS have a diminished cardiac response to exercise. Stroke volumes were significantly lower in DS during exercise and a compensated heightened heart rate was absent. 相似文献17.
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Teresa Cobo Marian Kacerovsky Ctirad Andrys Marcela Drahosova Ivana Musilova Helena Hornychova Bo Jacobsson 《PloS one》2013,8(7)
Objective
To evaluate umbilical cord interleukin (IL)-6 and funisitis as independent predictors of early-onset neonatal sepsis (EONS) in preterm prelabor rupture of membranes (PPROM).Design
Prospective cohort study.Setting
Evaluation of umbilical cord IL-6 and funisitis as predictors of early-onset neonatal sepsis in PPROM.Population
176 women with PPROM between 23+0−36+6 weeks of gestation.Methods
Umbilical cord IL-6 was assayed by ELISA. Funisitis was defined according to the Salafia classification. Data was adjusted by gestational age at delivery and prenatal administration of corticosteroids and antibiotics.Main Outcome Measures
Binary logistic regression was performed to assess the independence of umbilical cord IL-6 and funisitis to predict EONS in women complicated with PPROM.Results
The rate of EONS was 7%. Funisitis was present in 18% of women. Umbilical cord IL-6 was significantly higher in women complicated with EONS than without [median (range) 389.5 pg/mL (13.9–734.8) vs 5.2 (0.1–801–4), p<0.001]. Umbilical cord IL-6 was the only independent predictor of early-onset neonatal sepsis (odds ratio 13.6, p = 0.004).Conclusion
Umbilical cord IL-6 was the only predictor of early-onset neonatal sepsis in PPROM. Contrary to what is reported, funisitis was not. 相似文献19.
Mary Leamy Eleanor Clarke Clair Le Boutillier Victoria Bird Monika Janosik Kai Sabas Genevieve Riley Julie Williams Mike Slade 《PloS one》2014,9(5)
Objective
To investigate staff and trainer perspectives on the barriers and facilitators to implementing a complex intervention to help staff support the recovery of service users with a primary diagnosis of psychosis in community mental health teams.Design
Process evaluation nested within a cluster randomised controlled trial (RCT).Participants
28 interviews with mental health care staff, 3 interviews with trainers, 4 focus groups with intervention teams and 28 written trainer reports.Setting
14 community-based mental health teams in two UK sites (one urban, one semi-rural) who received the intervention.Results
The factors influencing the implementation of the intervention can be organised under two over-arching themes: Organisational readiness for change and Training effectiveness. Organisational readiness for change comprised three sub-themes: NHS Trust readiness; Team readiness; and Practitioner readiness. Training effectiveness comprised three sub-themes: Engagement strategies; Delivery style and Modelling recovery principles.Conclusions
Three findings can inform future implementation and evaluation of complex interventions. First, the underlying intervention model predicted that three areas would be important for changing practice: staff skill development; intention to implement; and actual implementation behaviour. This study highlighted the importance of targeting the transition from practitioners'' intent to implement to actual implementation behaviour, using experiential learning and target setting. Second, practitioners make inferences about organisational commitment by observing the allocation of resources, Knowledge Performance Indicators and service evaluation outcome measures. These need to be aligned with recovery values, principles and practice. Finally, we recommend the use of organisational readiness tools as an inclusion criteria for selecting both organisations and teams in cluster RCTs. We believe this would maximise the likelihood of adequate implementation and hence reduce waste in research expenditure.Trial Registration
Controlled-Trials.com ISRCTN02507940 相似文献20.