We assessed the quorum sensing(QS)inhibitory impact of sesamol against the foodborne bacterium Pseudomonas aeruginosa.At concentrations ranging from 50 to 200μg/mL,sesamol significantly inhibited the production of vi...We assessed the quorum sensing(QS)inhibitory impact of sesamol against the foodborne bacterium Pseudomonas aeruginosa.At concentrations ranging from 50 to 200μg/mL,sesamol significantly inhibited the production of virulence factors such as protease,elastase,pyocyanin,rhamnolipid,and chemotaxis,and improved the susceptibility of bacterial and biofilm cells to colistin.Integrated transcriptomics,metabolomics,and docking analyses indicated that exposure to sesamol destroyed the QS system and down-regulated the expressions of genes encoding virulence and antioxidant enzymes.The down-regulation of genes encoding antioxidant enzymes intensified oxidative stress,as demonstrated by the enhancement of reactive oxygen species and H_(2)O_(2).The enhanced oxidative stress changed the components of the cell membrane,improved its permeability,and ultimately enhanced the susceptibility of bacterial and biofilm cells to colistin.Moreover,exposure to sesamol also led to the disorder of amino acid metabolism and energy metabolism,eventually attenuating the pathogenicity of P.aeruginosa.These findings indicated that sesamol can function as a potent anti-virulence agent to defend against food spoilage caused by P.aeruginosa.展开更多
Background:Over the past 50 years,the incidence of obesity has gradually increased,necessitating investigation into the multifactorial contributors to this disease,including the gut microbiota.Bacteria within the huma...Background:Over the past 50 years,the incidence of obesity has gradually increased,necessitating investigation into the multifactorial contributors to this disease,including the gut microbiota.Bacteria within the human gut microbiome communicate using a density-dependent process known as quorum sensing(QS),in which autoinducer(AI)molecules(e.g.,N-acyl-homoserine lactones[AHLs])are produced to enable bacterial interactions and regulate gene expression.Methods:We aimed to disrupt QS using quorum quenching(QQ)lactonases GcL and SsoPox,which cleave AHL signaling molecules in a taxa-specific manner based on differing enzyme affinities for different substrates.We hypothesized that QQ hinders signals from obesity-associated pathobionts,thereby slowing or preventing obesity.Results:In a murine model of dietinduced obesity,we observed GcL and SsoPox treatments have separate sex-dependent and dose-dependent effects on intestinal community composition and diversity.Notably,male mice given 2 mg/mL SsoPox exhibited significant changes in the relative abundances of gram-negative taxa,including Porphyromonadaceae,Akkermansiaceae,Muribaculaceae,and Bacteroidales(Kruskal-Wallis p<0.001).Additionally,we used covariance matrix network analysis to model bacterial taxa co-occurrence due to QQ enzyme administration.There were more associations among taxa in control mice,particularly among gram-negative bacteria,whereas mice receiving SsoPox had the fewest associations.Conclusions:Overall,our study establishes proof of concept that QQ is a targetable strategy for microbial control in vivo.Further characterization and dosage optimization of QQ enzymes are necessary to harness their therapeutic capability for the treatment of chronic microbial-associated diseases.展开更多
Quorum sensing(QS)represents a mechanism through which bacteria engage in communication via chemical signals,a phenomenon prevalent across diverse bacterial species.Recent investigations have elucidated that QS signal...Quorum sensing(QS)represents a mechanism through which bacteria engage in communication via chemical signals,a phenomenon prevalent across diverse bacterial species.Recent investigations have elucidated that QS signaling pathways are pivotal in governing bacterial physiological processes,collective behaviors,and the emergence of drug resistance.Escherichia coli(E.coli),a prominent pathogenic bacterium,is increasingly exhibiting severe drug resistance issues,posing substantial hurdles for clinical interventions.Presently,a burgeoning body of research is exploring the connection between QS signaling pathways and the drug resistance mechanisms in E.coli,unveiling the coordinating function of QS within bacterial communities and its influence on antibiotic resistance.Despite some research advancements,the precise mechanisms underlying the QS signaling pathway remain ambiguous,and its potential applications are somewhat constrained.This article endeavors to systematically review the research progress concerning the QS signaling pathway in the context of clinical drug resistance mechanisms in E.coli,delving into its potential clinical applications and future research avenues,with the aim of offering novel insights and strategies to counteract drug resistance.展开更多
Pseudomonas aeruginosa,recognized for its biofilm production and secretion of virulence factors,posing a severe threat in areas such as clinical infections,food contamination,and marine biofouling.To address this,a ne...Pseudomonas aeruginosa,recognized for its biofilm production and secretion of virulence factors,posing a severe threat in areas such as clinical infections,food contamination,and marine biofouling.To address this,a new type of zinc-binding peptide(CSSP-Zn)was prepared from crimson snapper scales peptides(CSSP)and goslarite,and its antibacterial and anti-quorum-sensing activities toward P.aeruginosa PAO1 were exploited.Results indicated that CSSP-Zn induced planktonic strain PAO1 membrane injury via inhibiting expression levels of cell integrity genes,targeting microbial-specific membrane constituents,disrupting proton motive force,and causing metabolic disturbances.Meanwhile,CSSP-Zn decreased virulence factors pyocyanin,protease and rhamnolipid secretion,while considerably inhibiting quorum sensing-related genes(las,pqs and rhl)expression and decreasing bacterial abundance and pathogenicity in fish models.Moreover,CSSP-Zn not only effectively hindered biofilm formation but also disassembled preformed ones,thus disrupting biofilm topology.Taken together,utilizing food byproducts to obtain CSSP-Zn could help recycle food resources and provide insight into controlling planktonic and biofilm strain PAO1 contamination.展开更多
Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated thr...Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated three novel QQ strains (Bacillus sp.QX01 and QX03,Delftia sp.QX14) from the activated sludge of an actual MBR.They can degrade 11 N-acylhomoserine lactones (AHLs) with high efficiencies and rates through intracellular QQ pathways involving putative acylases and lactonases.Running two lab-scale MBRs,we found that introducing antibiotics (sulfamethoxazole,azithromycin,and ciprofloxacin,each at100μg/L) shortened the fouling cycle by 71.4%.However,the immobilized inoculation of QX01 into one MBR extended the fouling cycle by 1.5-2.0 times.Quantitative detection revealed that QX01 significantly reduced the concentrations of two AHLs (C4-HSL and C8-HSL),which were positively correlated with the contents of extracellular polymeric substances(EPS)(Pearson’s r=0.62-0.83,P<0.01).This suggests that QX01 could perform its QQ activity robustly under antibiotic stress,thereby inhibiting EPS production (proteins especially) and biofilm formation.Moreover,QX01 notably altered the succession patterns of both sludge and fouling communities,with more pronounced effects on abundant taxa.Genera associated with AHL synthesis and EPS production,such as Terrimonas and Rhodobacter,were significantly depleted,contributing to the mitigated biofouling.Additionally,QX01 increased the bacterial community diversity (evenness especially),which was inhibited by antibiotics.Overall,we demonstrate that the novel QQ bacteria could be effective for biofouling control in antibiotic-stressed MBRs,though future work is needed to develop practical approaches for prolonging QQ activity.展开更多
The communication system known as quorum sensing (QS) in gram-negative bacteria regulates biofilm formation and many other functions. The particularity of Pseudoalteromonas ulvae TC14 seems to be the absence of a LuxI...The communication system known as quorum sensing (QS) in gram-negative bacteria regulates biofilm formation and many other functions. The particularity of Pseudoalteromonas ulvae TC14 seems to be the absence of a LuxI inducer, and therefore the lack of production of small molecules of Acyl homoserine lactone (AHL). Previous studies had shown that it does not harbor the inducer of the regulatory molecule (AHL). Nevertheless, it is able to regulate these same functions (biofilm, violacein) via AHLs. This could mean the presence of specific receptors for these induction molecules, belonging to the LuxR family. The aim of this study was to test these hypotheses using molecular analysis. Genome sequencing of the P. ulvae TC14 strain was carried out by Molecular Research LP (MR DNA), using the Illumina Hiseq 2500 method. The results revealed the presence of 2,293,242 base pairs, i.e. 100% of the genomic volume. The number of coding gene sequences was 1983, and the Guanine + Cytosine (G+C) percentage of the base number was 41.55%, revealing stability in the sequenced genome. In order to verify the identity of the sequenced genome, a phylogenetic analysis based on RNA16S was carried out. This analysis resulted in 93% homology with the previously sequenced and characterized species Pseudoalteromonas tunicata, showing that it belongs to the genus Pseudoalteromonas. To these comparative results should be added those derived from genome analysis based on nucleotide percentage using the tools available at https://img.jgi.doe.gov/. The results showed that Pseudoalteromonas tunicata D2 has the highest percentage nucleotide identity (ANI) (75.7913%), followed by Pseudoalteromonas flavipulchra NCIMB2033 (72.2736%) and Pseudoalteromonas phenolica KCTC 12086 (71.6685%). Next, the search for the various genes involved in QS was carried out using sequence comparisons via the BLAST method. For LuxI, sequence templates from the genomes of Vibrio, Chromobacterium, Shewanella or even other Pseudoalteromonas species were screened against the TC14 genome. This yielded no conclusive results synonymous with the non-presence of LuxI in TC14 as assumed by previous research. The search for LuxR, on the other hand, gave rise to the presence of eight presumptive sequences. Molecular characterization of the presumptive LuxR sequences was carried out to assess their gene expression. This characterization showed expression of these LuxR homologous sequences in a range from o.11 to 5.33 picograms (pg). Even if these sequences were not analyzed in depth, the retro-transcription technique nevertheless showed a minimum of activity, which could enable us to distinguish them from inactive sequences. The next step was to compare the LuxRs found in TC14 with the so-called Solo LuxRs, which act autonomously. This study shows that P. ulvae TC14 is a bacterium with a particular LuxR-based communication system.展开更多
Background:To investigate the effect of flavaspidic acid BB(BB)on biofilms and quorum sensing-related genes of drug-resistant Staphylococcus epidermidis(SE)and to provide a theoretical basis for the development of BB ...Background:To investigate the effect of flavaspidic acid BB(BB)on biofilms and quorum sensing-related genes of drug-resistant Staphylococcus epidermidis(SE)and to provide a theoretical basis for the development of BB as a new type of quorum sensing inhibitor.Methods:The microdilution method was applied to screen 15 clinical isolates of S.epidermidis for drug-resistant S.epidermidis to be used as the test strain.The effects of BB on the biofilms of drug-resistant S.epidermidis at different growth stages were studied using the cell counting kit-8 assay and scanning electron microscopy.The gene expression of sigB,sarA,and luxS,regulators involved in quorum sensing of biofilm formation,was measured by PCR.Results:The minimum inhibitory concentrations of BB against 15 clinical strains of S.epidermidis ranged 11.67-66.67μg/mL.BB significantly inhibited biofilm formation by drug-resistant SE06 in the aggregation and maturation stages,with an activity superior to those of mupirocin and fusidic acid(P<0.05).At 40μg/mL,BB reduced the secretion of extracellular polymers and promoted the disruption of biofilm structure.At 80μg/mL,BB specifically interfered with the quorum sensing system of drug-resistant SE06 by downregulating sarA and luxS,thereby inhibiting this microbe’s biofilm formation.Conclusion:BB exhibited strong inhibitory activity against SE06 by suppressing biofilm formation and downregulating quorum sensing-related genes and was identified as a new potential quorum sensing inhibitor against S.epidermidis.展开更多
在无线传感器网络中,异步低占空比技术可以极大地降低能耗,但是由于节点的低占空比唤醒会造成极大的端到端数据时延。针对这个问题提出一种基于Quorum的异步自适应低占空比路由算法ORDA(Optimal-Reliable delay routing algorithm for l...在无线传感器网络中,异步低占空比技术可以极大地降低能耗,但是由于节点的低占空比唤醒会造成极大的端到端数据时延。针对这个问题提出一种基于Quorum的异步自适应低占空比路由算法ORDA(Optimal-Reliable delay routing algorithm for low duty cycle WSNs based on Quorum),将异步占空比网络和实际链路模型相结合,在异步占空比网络中节点在不同时刻的邻居发现延迟也在不断变化。首先为每个节点根据网络负载选择自身的Quorum类型,并利用Quorum特性来计算邻居节点的重叠时隙个数;然后根据链路质量进一步计算出这一跳范围内邻居节点间的成功转发预期值,并在即将唤醒的节点中选择更可靠的节点转发数据。仿真实验证明,该算法不仅能够降低端到端延迟,而且能获得很好的转发成功率。展开更多
针对无线传感器网络占空比MAC协议在链路或节点失效环境下易导致严重的能量浪费问题,提出了一种基于Grid Quorum的异步低占空比M AC协议-AGQ-M AC(Asynchronous Grid Quorum M AC).AGQ-M AC采用Grid Quorum组分配信道,通过动态调配Quoru...针对无线传感器网络占空比MAC协议在链路或节点失效环境下易导致严重的能量浪费问题,提出了一种基于Grid Quorum的异步低占空比M AC协议-AGQ-M AC(Asynchronous Grid Quorum M AC).AGQ-M AC采用Grid Quorum组分配信道,通过动态调配Quorum比率得到了节点的最优占空比,并在邻节点发现过程中采用双前导序文抽样来监测信道状态,以减少节点唤醒时间从而达到能量高效.仿真实验结果表明,与其他占空比MAC协议相比,AGQ-MAC延长了网络生存时间,降低了网络能耗,提高了邻发现数据传输率,同时保持较低的平均邻发现延迟.展开更多
Interference with quorum sensing(QS)represents an antivirulence strategy with a significant promise for the treatment of bacterial infections and a new approach to restoring antibiotic tolerance.Over the past two deca...Interference with quorum sensing(QS)represents an antivirulence strategy with a significant promise for the treatment of bacterial infections and a new approach to restoring antibiotic tolerance.Over the past two decades,a novel series of studies have reported that quorum quenching approaches and the discovery of quorum sensing inhibitors(QSIs)have a strong impact on the discovery of anti-infective drugs against various types of bacteria.The discovery of QSI was demonstrated to be an appropriate strategy to expand the anti-infective therapeutic approaches to complement classical antibiotics and antimicrobial agents.For the discovery of QSIs,diverse approaches exist and develop in-step with the scale of screening as well as specific QS systems.This review highlights the latest findings in strategies and methodologies for QSI screening,involving activity-based screening with bioassays,chemical methods to seek bacterial QS pathways for QSI discovery,virtual screening for QSI screening,and other potential tools for interpreting QS signaling,which are innovative routes for future efforts to discover additional QSIs to combat bacterial infections.展开更多
Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activi...Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activity of ethanol extract of Syzygium cumini L.and Pimenta dioica L.were screened using C.violaceum CV026 biosensor bioassay.By bioassay guided fractionation of 5.cumini and P.dioica,ethyl acetate fraction(EAF)with strong anti-QS activity was separated.Inhibition of QS regulated violacein production in C.violaceum ATCC12472 by EAF was assessed at different concentrations.The effect of EAF on the synthesis of autoinducer like N-acyl homoserine lactone(AHL)was studied in C.violaceum ATCC31532 using its mutant C.violaceum CV026 by standard methods.Results:EAF inhibited violacein production in C.violaceum ATCC12472 in a concentration dependent manner without significant reduction in bacterial growth.Complete inhibition of violacein production was evidenced in 0.75-1.0 mg/mL concentration of EAF without inhibiting the synthesis of the AHL.TLC biosensor overlay profile of EAF revealed two translucent spots in 5.cumini and P.dioica that inhibited C_6-AHL mediated violacein production in C.violaceum CV026.Conclusions:This study indicates the anti-QS activity of the tested medicinal plants against C.violaceum.展开更多
Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is trig- gered via auto inducers which passively diffuse across the bacterial envelope and therefore intracell...Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is trig- gered via auto inducers which passively diffuse across the bacterial envelope and therefore intracellulaly accumulate only at higher bacterial densities to regulate specialized processes such as genetic competence, bioluminescence, virulence and sporulation. N-acyl homoserine lactones are the most common type of signal molecules. Aquaculture is one of the fastest-growing food-producing indus- tries, but disease outbreaks caused by pathogenic bacteria are a significant constraint on the development of the sector worldwide. Many of these pathogens have been found to be controlled by their quorum sensing systems. As there is relevance between the pathogenic bacteria＇s virulence factor expression and their auto inducers, quorum quenching is a new effective anti-infective strategy to control infections caused by bacterial pathogens in aquaculture. The techniques used to do this mainly include the following： （1） the inhibition of signal molecule biosynthesis, （2） blocking signal transduction, and （3） chemical inactivation and biodegradation of signal molecules. To provide a basis for finding alternative means of controlling aquatic diseases by quorum quenching instead of treatment by antibiotics and disinfectants, we will discuss the examination, purification and identification of auto inducers in this paper.展开更多
Bacterial cells rely on signaling molecules to communicate with others from the same species and induce certain genes in a process known as quorum sensing (QS). A common molecule is N-acyl homoserine lactone (AHL) whi...Bacterial cells rely on signaling molecules to communicate with others from the same species and induce certain genes in a process known as quorum sensing (QS). A common molecule is N-acyl homoserine lactone (AHL) which is responsible for the expression of virulence and other factors that allow the organisms to compete in a given environment. On the other hand, other bacteria produce certain enzymes such as AHL-lactonase that break down AHL molecules and prevent gene expression of these factors. The aim of this work was to examine the level of degradation of AHL molecules by AHL-lactonase in 62 Bacillus thuringiensis (Bt) strains isolated from Middle Tennessee, Mississippi, and Alabama. N-hexanoyl-homoserine lactone (C<sub>6</sub>-HSL) and N-3-oxo-hexanoyl homoserine lactone (3-oxo-C<sub>6</sub>-HSL), which cause Chromobacterium violaceum (CV026) to produce a purple pigment were tested at different concentrations to view the Bt lactonase activity. In addition, PCR was used to test for the presence of the lactonase gene. The results showed that among the 62 Bt strains, there were 58 that possessed the AHL-lactonase (aiiA) gene and 48 strains were able to degrade C<sub>6</sub>-HSL. At high concentrations of AHL, only 13 strains were able to completely degrade C6-HSL. In addition, degradation of 3-oxo-C<sub>6</sub>-HSL was weak compared to C<sub>6</sub>-HSL. The results also revealed that AHL lactonase was thermostable, and it was concluded that the level of degradation varies in Bt strains. Only 13 of the strains studied have potent inhibitory activity against C<sub>6</sub>-HSL, which may be good to be used in field applications to control agricultural pest.展开更多
基金supported by grants from the National Natural Science Foundation of China(32000091)General Projects of Natural Science Research in Universities of Jiangsu Province(20KJB180019)Jiangsu Youth Talent Promotion Project(TJ-2021-066)。
文摘We assessed the quorum sensing(QS)inhibitory impact of sesamol against the foodborne bacterium Pseudomonas aeruginosa.At concentrations ranging from 50 to 200μg/mL,sesamol significantly inhibited the production of virulence factors such as protease,elastase,pyocyanin,rhamnolipid,and chemotaxis,and improved the susceptibility of bacterial and biofilm cells to colistin.Integrated transcriptomics,metabolomics,and docking analyses indicated that exposure to sesamol destroyed the QS system and down-regulated the expressions of genes encoding virulence and antioxidant enzymes.The down-regulation of genes encoding antioxidant enzymes intensified oxidative stress,as demonstrated by the enhancement of reactive oxygen species and H_(2)O_(2).The enhanced oxidative stress changed the components of the cell membrane,improved its permeability,and ultimately enhanced the susceptibility of bacterial and biofilm cells to colistin.Moreover,exposure to sesamol also led to the disorder of amino acid metabolism and energy metabolism,eventually attenuating the pathogenicity of P.aeruginosa.These findings indicated that sesamol can function as a potent anti-virulence agent to defend against food spoilage caused by P.aeruginosa.
基金Biotechnology Institute and the MnDrive initiative(to MHE)。
文摘Background:Over the past 50 years,the incidence of obesity has gradually increased,necessitating investigation into the multifactorial contributors to this disease,including the gut microbiota.Bacteria within the human gut microbiome communicate using a density-dependent process known as quorum sensing(QS),in which autoinducer(AI)molecules(e.g.,N-acyl-homoserine lactones[AHLs])are produced to enable bacterial interactions and regulate gene expression.Methods:We aimed to disrupt QS using quorum quenching(QQ)lactonases GcL and SsoPox,which cleave AHL signaling molecules in a taxa-specific manner based on differing enzyme affinities for different substrates.We hypothesized that QQ hinders signals from obesity-associated pathobionts,thereby slowing or preventing obesity.Results:In a murine model of dietinduced obesity,we observed GcL and SsoPox treatments have separate sex-dependent and dose-dependent effects on intestinal community composition and diversity.Notably,male mice given 2 mg/mL SsoPox exhibited significant changes in the relative abundances of gram-negative taxa,including Porphyromonadaceae,Akkermansiaceae,Muribaculaceae,and Bacteroidales(Kruskal-Wallis p<0.001).Additionally,we used covariance matrix network analysis to model bacterial taxa co-occurrence due to QQ enzyme administration.There were more associations among taxa in control mice,particularly among gram-negative bacteria,whereas mice receiving SsoPox had the fewest associations.Conclusions:Overall,our study establishes proof of concept that QQ is a targetable strategy for microbial control in vivo.Further characterization and dosage optimization of QQ enzymes are necessary to harness their therapeutic capability for the treatment of chronic microbial-associated diseases.
基金Research on the Resistance Mechanism of Carbapenem-Resistant Escherichia coli in Patients with Urosepsis Based on Bacterial Droplet Single-Cell RNA Sequencing(Project No.:MTyk2024-34,2024.01-2026-12)。
文摘Quorum sensing(QS)represents a mechanism through which bacteria engage in communication via chemical signals,a phenomenon prevalent across diverse bacterial species.Recent investigations have elucidated that QS signaling pathways are pivotal in governing bacterial physiological processes,collective behaviors,and the emergence of drug resistance.Escherichia coli(E.coli),a prominent pathogenic bacterium,is increasingly exhibiting severe drug resistance issues,posing substantial hurdles for clinical interventions.Presently,a burgeoning body of research is exploring the connection between QS signaling pathways and the drug resistance mechanisms in E.coli,unveiling the coordinating function of QS within bacterial communities and its influence on antibiotic resistance.Despite some research advancements,the precise mechanisms underlying the QS signaling pathway remain ambiguous,and its potential applications are somewhat constrained.This article endeavors to systematically review the research progress concerning the QS signaling pathway in the context of clinical drug resistance mechanisms in E.coli,delving into its potential clinical applications and future research avenues,with the aim of offering novel insights and strategies to counteract drug resistance.
文摘Pseudomonas aeruginosa,recognized for its biofilm production and secretion of virulence factors,posing a severe threat in areas such as clinical infections,food contamination,and marine biofouling.To address this,a new type of zinc-binding peptide(CSSP-Zn)was prepared from crimson snapper scales peptides(CSSP)and goslarite,and its antibacterial and anti-quorum-sensing activities toward P.aeruginosa PAO1 were exploited.Results indicated that CSSP-Zn induced planktonic strain PAO1 membrane injury via inhibiting expression levels of cell integrity genes,targeting microbial-specific membrane constituents,disrupting proton motive force,and causing metabolic disturbances.Meanwhile,CSSP-Zn decreased virulence factors pyocyanin,protease and rhamnolipid secretion,while considerably inhibiting quorum sensing-related genes(las,pqs and rhl)expression and decreasing bacterial abundance and pathogenicity in fish models.Moreover,CSSP-Zn not only effectively hindered biofilm formation but also disassembled preformed ones,thus disrupting biofilm topology.Taken together,utilizing food byproducts to obtain CSSP-Zn could help recycle food resources and provide insight into controlling planktonic and biofilm strain PAO1 contamination.
基金supported by the National Natural Science Foundation of China (Nos.51938001 and 52300073)。
文摘Quorum quenching (QQ)-based strategies are efficient for biofouling control.However,the feasibility of using QQ bacteria in antibiotic-stressed membrane bioreactors (MBRs) remains unknown.In this study,we isolated three novel QQ strains (Bacillus sp.QX01 and QX03,Delftia sp.QX14) from the activated sludge of an actual MBR.They can degrade 11 N-acylhomoserine lactones (AHLs) with high efficiencies and rates through intracellular QQ pathways involving putative acylases and lactonases.Running two lab-scale MBRs,we found that introducing antibiotics (sulfamethoxazole,azithromycin,and ciprofloxacin,each at100μg/L) shortened the fouling cycle by 71.4%.However,the immobilized inoculation of QX01 into one MBR extended the fouling cycle by 1.5-2.0 times.Quantitative detection revealed that QX01 significantly reduced the concentrations of two AHLs (C4-HSL and C8-HSL),which were positively correlated with the contents of extracellular polymeric substances(EPS)(Pearson’s r=0.62-0.83,P<0.01).This suggests that QX01 could perform its QQ activity robustly under antibiotic stress,thereby inhibiting EPS production (proteins especially) and biofilm formation.Moreover,QX01 notably altered the succession patterns of both sludge and fouling communities,with more pronounced effects on abundant taxa.Genera associated with AHL synthesis and EPS production,such as Terrimonas and Rhodobacter,were significantly depleted,contributing to the mitigated biofouling.Additionally,QX01 increased the bacterial community diversity (evenness especially),which was inhibited by antibiotics.Overall,we demonstrate that the novel QQ bacteria could be effective for biofouling control in antibiotic-stressed MBRs,though future work is needed to develop practical approaches for prolonging QQ activity.
文摘The communication system known as quorum sensing (QS) in gram-negative bacteria regulates biofilm formation and many other functions. The particularity of Pseudoalteromonas ulvae TC14 seems to be the absence of a LuxI inducer, and therefore the lack of production of small molecules of Acyl homoserine lactone (AHL). Previous studies had shown that it does not harbor the inducer of the regulatory molecule (AHL). Nevertheless, it is able to regulate these same functions (biofilm, violacein) via AHLs. This could mean the presence of specific receptors for these induction molecules, belonging to the LuxR family. The aim of this study was to test these hypotheses using molecular analysis. Genome sequencing of the P. ulvae TC14 strain was carried out by Molecular Research LP (MR DNA), using the Illumina Hiseq 2500 method. The results revealed the presence of 2,293,242 base pairs, i.e. 100% of the genomic volume. The number of coding gene sequences was 1983, and the Guanine + Cytosine (G+C) percentage of the base number was 41.55%, revealing stability in the sequenced genome. In order to verify the identity of the sequenced genome, a phylogenetic analysis based on RNA16S was carried out. This analysis resulted in 93% homology with the previously sequenced and characterized species Pseudoalteromonas tunicata, showing that it belongs to the genus Pseudoalteromonas. To these comparative results should be added those derived from genome analysis based on nucleotide percentage using the tools available at https://img.jgi.doe.gov/. The results showed that Pseudoalteromonas tunicata D2 has the highest percentage nucleotide identity (ANI) (75.7913%), followed by Pseudoalteromonas flavipulchra NCIMB2033 (72.2736%) and Pseudoalteromonas phenolica KCTC 12086 (71.6685%). Next, the search for the various genes involved in QS was carried out using sequence comparisons via the BLAST method. For LuxI, sequence templates from the genomes of Vibrio, Chromobacterium, Shewanella or even other Pseudoalteromonas species were screened against the TC14 genome. This yielded no conclusive results synonymous with the non-presence of LuxI in TC14 as assumed by previous research. The search for LuxR, on the other hand, gave rise to the presence of eight presumptive sequences. Molecular characterization of the presumptive LuxR sequences was carried out to assess their gene expression. This characterization showed expression of these LuxR homologous sequences in a range from o.11 to 5.33 picograms (pg). Even if these sequences were not analyzed in depth, the retro-transcription technique nevertheless showed a minimum of activity, which could enable us to distinguish them from inactive sequences. The next step was to compare the LuxRs found in TC14 with the so-called Solo LuxRs, which act autonomously. This study shows that P. ulvae TC14 is a bacterium with a particular LuxR-based communication system.
文摘Background:To investigate the effect of flavaspidic acid BB(BB)on biofilms and quorum sensing-related genes of drug-resistant Staphylococcus epidermidis(SE)and to provide a theoretical basis for the development of BB as a new type of quorum sensing inhibitor.Methods:The microdilution method was applied to screen 15 clinical isolates of S.epidermidis for drug-resistant S.epidermidis to be used as the test strain.The effects of BB on the biofilms of drug-resistant S.epidermidis at different growth stages were studied using the cell counting kit-8 assay and scanning electron microscopy.The gene expression of sigB,sarA,and luxS,regulators involved in quorum sensing of biofilm formation,was measured by PCR.Results:The minimum inhibitory concentrations of BB against 15 clinical strains of S.epidermidis ranged 11.67-66.67μg/mL.BB significantly inhibited biofilm formation by drug-resistant SE06 in the aggregation and maturation stages,with an activity superior to those of mupirocin and fusidic acid(P<0.05).At 40μg/mL,BB reduced the secretion of extracellular polymers and promoted the disruption of biofilm structure.At 80μg/mL,BB specifically interfered with the quorum sensing system of drug-resistant SE06 by downregulating sarA and luxS,thereby inhibiting this microbe’s biofilm formation.Conclusion:BB exhibited strong inhibitory activity against SE06 by suppressing biofilm formation and downregulating quorum sensing-related genes and was identified as a new potential quorum sensing inhibitor against S.epidermidis.
文摘在无线传感器网络中,异步低占空比技术可以极大地降低能耗,但是由于节点的低占空比唤醒会造成极大的端到端数据时延。针对这个问题提出一种基于Quorum的异步自适应低占空比路由算法ORDA(Optimal-Reliable delay routing algorithm for low duty cycle WSNs based on Quorum),将异步占空比网络和实际链路模型相结合,在异步占空比网络中节点在不同时刻的邻居发现延迟也在不断变化。首先为每个节点根据网络负载选择自身的Quorum类型,并利用Quorum特性来计算邻居节点的重叠时隙个数;然后根据链路质量进一步计算出这一跳范围内邻居节点间的成功转发预期值,并在即将唤醒的节点中选择更可靠的节点转发数据。仿真实验证明,该算法不仅能够降低端到端延迟,而且能获得很好的转发成功率。
文摘针对无线传感器网络占空比MAC协议在链路或节点失效环境下易导致严重的能量浪费问题,提出了一种基于Grid Quorum的异步低占空比M AC协议-AGQ-M AC(Asynchronous Grid Quorum M AC).AGQ-M AC采用Grid Quorum组分配信道,通过动态调配Quorum比率得到了节点的最优占空比,并在邻节点发现过程中采用双前导序文抽样来监测信道状态,以减少节点唤醒时间从而达到能量高效.仿真实验结果表明,与其他占空比MAC协议相比,AGQ-MAC延长了网络生存时间,降低了网络能耗,提高了邻发现数据传输率,同时保持较低的平均邻发现延迟.
基金funded by the National Natural Science Foundation of China (Grant No.: 81803812)
文摘Interference with quorum sensing(QS)represents an antivirulence strategy with a significant promise for the treatment of bacterial infections and a new approach to restoring antibiotic tolerance.Over the past two decades,a novel series of studies have reported that quorum quenching approaches and the discovery of quorum sensing inhibitors(QSIs)have a strong impact on the discovery of anti-infective drugs against various types of bacteria.The discovery of QSI was demonstrated to be an appropriate strategy to expand the anti-infective therapeutic approaches to complement classical antibiotics and antimicrobial agents.For the discovery of QSIs,diverse approaches exist and develop in-step with the scale of screening as well as specific QS systems.This review highlights the latest findings in strategies and methodologies for QSI screening,involving activity-based screening with bioassays,chemical methods to seek bacterial QS pathways for QSI discovery,virtual screening for QSI screening,and other potential tools for interpreting QS signaling,which are innovative routes for future efforts to discover additional QSIs to combat bacterial infections.
基金Supported by the Department of Biotechnology.Govt.of India,under Rapid Grant for Young Investigator scheme(Grant no.BT/PR13242/CBD/27/226/2009)
文摘Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activity of ethanol extract of Syzygium cumini L.and Pimenta dioica L.were screened using C.violaceum CV026 biosensor bioassay.By bioassay guided fractionation of 5.cumini and P.dioica,ethyl acetate fraction(EAF)with strong anti-QS activity was separated.Inhibition of QS regulated violacein production in C.violaceum ATCC12472 by EAF was assessed at different concentrations.The effect of EAF on the synthesis of autoinducer like N-acyl homoserine lactone(AHL)was studied in C.violaceum ATCC31532 using its mutant C.violaceum CV026 by standard methods.Results:EAF inhibited violacein production in C.violaceum ATCC12472 in a concentration dependent manner without significant reduction in bacterial growth.Complete inhibition of violacein production was evidenced in 0.75-1.0 mg/mL concentration of EAF without inhibiting the synthesis of the AHL.TLC biosensor overlay profile of EAF revealed two translucent spots in 5.cumini and P.dioica that inhibited C_6-AHL mediated violacein production in C.violaceum CV026.Conclusions:This study indicates the anti-QS activity of the tested medicinal plants against C.violaceum.
文摘Quorum sensing, or auto induction, as a cell density dependent signaling mechanism in many microorganisms, is trig- gered via auto inducers which passively diffuse across the bacterial envelope and therefore intracellulaly accumulate only at higher bacterial densities to regulate specialized processes such as genetic competence, bioluminescence, virulence and sporulation. N-acyl homoserine lactones are the most common type of signal molecules. Aquaculture is one of the fastest-growing food-producing indus- tries, but disease outbreaks caused by pathogenic bacteria are a significant constraint on the development of the sector worldwide. Many of these pathogens have been found to be controlled by their quorum sensing systems. As there is relevance between the pathogenic bacteria＇s virulence factor expression and their auto inducers, quorum quenching is a new effective anti-infective strategy to control infections caused by bacterial pathogens in aquaculture. The techniques used to do this mainly include the following： （1） the inhibition of signal molecule biosynthesis, （2） blocking signal transduction, and （3） chemical inactivation and biodegradation of signal molecules. To provide a basis for finding alternative means of controlling aquatic diseases by quorum quenching instead of treatment by antibiotics and disinfectants, we will discuss the examination, purification and identification of auto inducers in this paper.
文摘Bacterial cells rely on signaling molecules to communicate with others from the same species and induce certain genes in a process known as quorum sensing (QS). A common molecule is N-acyl homoserine lactone (AHL) which is responsible for the expression of virulence and other factors that allow the organisms to compete in a given environment. On the other hand, other bacteria produce certain enzymes such as AHL-lactonase that break down AHL molecules and prevent gene expression of these factors. The aim of this work was to examine the level of degradation of AHL molecules by AHL-lactonase in 62 Bacillus thuringiensis (Bt) strains isolated from Middle Tennessee, Mississippi, and Alabama. N-hexanoyl-homoserine lactone (C<sub>6</sub>-HSL) and N-3-oxo-hexanoyl homoserine lactone (3-oxo-C<sub>6</sub>-HSL), which cause Chromobacterium violaceum (CV026) to produce a purple pigment were tested at different concentrations to view the Bt lactonase activity. In addition, PCR was used to test for the presence of the lactonase gene. The results showed that among the 62 Bt strains, there were 58 that possessed the AHL-lactonase (aiiA) gene and 48 strains were able to degrade C<sub>6</sub>-HSL. At high concentrations of AHL, only 13 strains were able to completely degrade C6-HSL. In addition, degradation of 3-oxo-C<sub>6</sub>-HSL was weak compared to C<sub>6</sub>-HSL. The results also revealed that AHL lactonase was thermostable, and it was concluded that the level of degradation varies in Bt strains. Only 13 of the strains studied have potent inhibitory activity against C<sub>6</sub>-HSL, which may be good to be used in field applications to control agricultural pest.
