Quorum sensing （QS） is a bacterial cell-cell communication process by which bacteria communicate using extracellular signals called autoinducers. Two QS systems have been identified in Escherichia coli K-12, includi...Quorum sensing （QS） is a bacterial cell-cell communication process by which bacteria communicate using extracellular signals called autoinducers. Two QS systems have been identified in Escherichia coli K-12, including an intact QS system 2 that is stimulated by the cyclic AMP （cAMP）-cAMP receptor protein （CRP） complex and a partial QS system 1 that consists of SdiA （suppressor of cell division inhibitor） responding to signals generated by other microbial species. The relationship between QS system 1 and system 2 in E. coli, however, remains obscure. Here, we show that an EAL domain protein, encoded by ydiV, and cAMP are involved in the interaction between the two QS systems in E. coli. Expression of sdiA and ydiV is inhibited by glucose. SdiA binds to the ydiV promoter region in a dose-dependent, but nonspecific, manner; extracellular autoinducer 1 from other species stimulates ydiV expression in an sdiA-depen- dent manner. Furthermore, we discovered that the double sdiA-ydiV mutation, but not the single mutation, causes a 2-fold decrease in intracellular cAMP concentration that leads to the inhibition of QS system 2. These results indicate that signaling pathways that respond to important environmental cues, such as autoinducers and glucose, are linked together for their control in E. coli.展开更多
Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application ...Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application in spoilage microorganism control and aquatic products quality maintenance.Materials and Methods:SHP CN-32 was treated by prepared citral nanoemulsion when the minimal inhibitory concentration(MIC)was verified.The growth curve,membrane integrity,scanning electron microscope(SEM)observation,biofilm formation and quorum sensing(QS)signaling molecule Al-2 content were evaluated in different MIC treatment groups(0 to 1.00 MIC).The gene expression status of SHP CN-32 in O and 0.50 MIC groups were compared using transcriptome sequencing and quantitative polymerase chain reaction(PCR).Results:The in vitro culture revealed that the citral nanoemulsion could inhibit the growth of SHP CN-32 with MIC of approximately 200μg/mL.Images of membrane integrity.SEM and biofilm formation suggested significant biological structure damage in bacteria after treatment.Meanwhile,the Qs signaling molecule Al-2 content showed a decline with increasing treatment concentration.Transcriptome sequencing and quantitative PCR revealed that the majority genes related diversified functional metabolic pathways of SHP CN-32 were downregulated at varying degree.Conclusion:A significant bacteriostasis of citral nanoemulsion against SHP CN-32 was verified via the results of growth inhibition,structural destruction,signal molecular decrease and gene expression downregulation of strains.These synergies significantly affect the characteristic expression of SHP CN-32,revealing the application potential as bacteriostat,QS inhibitor and preservative in aquatic products.展开更多
The detection of acyl homoserine lactones（AHLs） in activated sludge is essential for clarifying their function in wastewater treatment processes. An LC–MS/MS method was developed for the detection of AHLs in both t...The detection of acyl homoserine lactones（AHLs） in activated sludge is essential for clarifying their function in wastewater treatment processes. An LC–MS/MS method was developed for the detection of AHLs in both the aqueous and solid phases of activated sludge. In addition, the effects of proteases and extracellular polymeric substances（EPS） on the detection of AHLs were evaluated by adding protease inhibitors and extracting EPS,respectively. Recoveries of each AHL were improved by adding 50 μL of protease inhibitor,and recoveries were also improved from 0 to 56.9% to 24.2%–105.8% by EPS extraction.Applying the developed method to determine the type and concentration of AHLs showed that C4-HSL, C6-HSL, C8-HSL and 3-oxo-C8-HSL were widely detected in a suspended activated sludge system. The dominant AHL was C8-HSL, with a highest concentration of304.3 ng/L. C4-HSL was mainly distributed in the aqueous phase, whereas C6-HSL, C8-HSL and 3-oxo-C8-HSL were preferentially distributed in the sludge phase.展开更多
Heterotrophic nitrification-aerobic denitrification(HNAD)is essential in diverse nitrogen-transforming processes.How HNAD is modulated by quorum sensing(QS)systems is still ambiguous.The QS system in Pseudomonas aerug...Heterotrophic nitrification-aerobic denitrification(HNAD)is essential in diverse nitrogen-transforming processes.How HNAD is modulated by quorum sensing(QS)systems is still ambiguous.The QS system in Pseudomonas aeruginosa manipulates colony behavior.Here,we described the influence of the Pseudomonas quinolone signal(PQS)and N-acyl-L-homoserine lactone(AHL)on HNAD.The HNAD of P.aeruginosa was inhibited by the oversecretion of PQS.AHL-or PQS-deficient P.aeruginosa mutants had a higher ability for nitrogen removal.QS inhibited heterotrophic nitrification mainly via controlling the activity of nitrite oxidoreductase(NXR)and the depressed aerobic denitrification by regulating the catalytic abilities of nitric oxide reductase(NOR),nitrite reductase(NIR),and nitrate reductase(NAR).The addition of citrate as the sole carbon source increased the nitrogen removal efficiency compared with other carbon sources.Nitrite,as the sole nitrogen source,could be used entirely with only the moderate concentration of PQS contained.AHL and PQS controlled both nitrification and denitrification,suggesting that QS plays an important role in nitrogen cycle under aerobic conditions.展开更多
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
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 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
Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poi...Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poisoning to consumers.The life course of biofilms is generally thought to be regulated by a quorum sensing(QS)system by secreted autoinducing peptides(AIPs).Recent studies have revealed that small non-coding RNA(sRNA)also plays an important role in regulating biofilm formation at the post-transcriptional level.Moreover,sRNA can act as an intermediate regulating hub between the quorum sensing system and biofilm.This review summarizes the latest findings on sRNA in biofilms of common foodborne pathogens and their potential impact.We also highlight the different mechanism of cascade regulation of sRNA and QS system in biofilm formation in several typical foodborne pathogens.In this process,sRNA responds to dynamic external environmental signals finely and accurately,and can feedback information on the bacterial cell environment to modify the QS system.These findings will deepen our understanding of biofilm formation and provide new perspectives for eliminating biofilm of foodborne pathogens based on the cascade regulation of small RNA and QS for developing biofilm-free food-processing systems.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
Autoinducer 2（AI-2）, an important bioactive by-product of the Lux S-catalyzed S-ribosylhomocysteine cleavage reaction in the activated-methyl-cycle, has been suggested to serve as a universal intra- and inter-specie...Autoinducer 2（AI-2）, an important bioactive by-product of the Lux S-catalyzed S-ribosylhomocysteine cleavage reaction in the activated-methyl-cycle, has been suggested to serve as a universal intra- and inter-species signaling molecule. The development of reliable and sensitive methods for quantitative determination of AI-2 is highly desired.However, the chemical properties of AI-2 cause difficulty in its quantitative analysis.Herein, we report a high performance liquid chromatography-tandem mass spectrometric method that enables reproducible and sensitive measurement of AI-2 concentrations in complex matrixes. 4,5-Dimethylbenzene-1,2-diamine（DMBDM）, an easy-to-obtain commercial reagent, was used for the derivatization treatment. The assay was linear in the concentration range of 1.0–1000 ng/m L（R^2= 0.999） and had a lower limit of quantification of0.58 ng/m L. The method exhibited several advantages, e.g., high selectivity, wide linear response range, and good sensitivity. Furthermore, the effectiveness of the method was further validated through measuring AI-2 concentrations in the cell-free culture supernatant from Escherichia coli wild type.展开更多
Quorum sensing(QS) is cell communication that is widely used by bacterial pathogens to coordinate the expression of several collective traits, including the production of multiple virulence factors, biofilm formation,...Quorum sensing(QS) is cell communication that is widely used by bacterial pathogens to coordinate the expression of several collective traits, including the production of multiple virulence factors, biofilm formation, and swarming motility once a population threshold is reached. Several lines of evidence indicate that QS enhances virulence of bacterial pathogens in animal models as well as in human infections; however, its relative importance for bacterial pathogenesis is still incomplete. In this review, we discuss the present evidence from in vitro and in vivo experiments in animal models, as well as from clinical studies, that link QS systems with human infections. We focus on two major QS bacterial models, the opportunistic Gram negative bacteria Pseudomonas aeruginosa and the Gram positive Staphylococcus aureus, which are also two of the main agents responsible of nosocomial and wound infections. In addition, QS communication systems in other bacterial, eukaryotic pathogens, and even immune and cancer cells are also reviewed, and finally, the new approaches proposed to combat bacterial infections by the attenuation of their QS communication systems and virulence are also discussed.展开更多
In quorum sensing （QS） process, bacteria regulate gene expression by utilizing small signaling molecules called autoinducers in response to a variety of environmental cues. Autoinducer 2 （AI-2）, a QS signaling mol...In quorum sensing （QS） process, bacteria regulate gene expression by utilizing small signaling molecules called autoinducers in response to a variety of environmental cues. Autoinducer 2 （AI-2）, a QS signaling molecule proposed to be involved in interspecies communication, is produced by many species of gram-negative and gram-positive bacteria. In Escherichia coil and Salmonella typhimurium, the extracellular AI-2 is imported into the cell by a transporter encoded by the lsr operon. Upstream of the lsr operon, there is a divergently transcribed gene encoding LsrR, which was reported previously to repress the transcription of the lsr operon and itself. Here, we have demonstrated for the first time that LsrR represses the transcription of the lsr operon and itself by directly binding to their promoters using gel shift and DNase I footprinting assays. The β-galactosidase reporter assays further suggest that two motifs in both the lsrR and lsrA promoter regions are crucial for the LsrR binding. Furthermore, in agreement with the conclusion that phosphorylated AI-2 can relieve the repression of LsrR in previous studies, our data show that phospho- AI-2 renders LsrR unable to bind to its own promoter in vitro.展开更多
Traditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. The bacterial resistance against antibiotics is a serious issue for public health. Today, new therapeuti...Traditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. The bacterial resistance against antibiotics is a serious issue for public health. Today, new therapeutic targets other than the bacterial wall were deciphered. Quorum sensing or bacterial pheromones are molecules called auto-inducer secreted by bacteria to regulate some functions such as antibiotic resistance and biofilms formation. This therapeutic target is well-studied worldwide, nevertheless the scientific data are not updated and only recent researches started to look into its potential as a target to fight against infectious diseases. A major concern with this approach is the frequently observed development of resistance to antimicrobial compounds. Therefore, this paper aims to provide a current overview of the quorum sensing system in bacteria by revealing their implication in biofilms formation and the development of antibiotic resistance, and an update on their importance as a potential target for natural substances.展开更多
The present study investigated the relationship between N-acyl-homoserine lactone（AHL）-based quorum sensing（QS） and the physico-chemical properties of aerobic granules.Stable mature granules were observed in SBR2 ...The present study investigated the relationship between N-acyl-homoserine lactone（AHL）-based quorum sensing（QS） and the physico-chemical properties of aerobic granules.Stable mature granules were observed in SBR2 and SBR3 with average diameters of 0.96,and1.49 mm,respectively. The sludge densities of aerobic granules in SBR2 and SBR3 were1.0246,and 1.0201 g/mL,respectively,which were higher than that of flocculent sludge in SBR1（1.0065 g/mL）. The results showed that the activity of AHL-based QS in SBR2 and SBR3 amounted to 2.4- and 2.1-fold induction,however,that in SBR1 with flocculent sludge was1.6-fold induction. In addition,the results also showed that the activity of AHL-based QS in the three reactors rose in the feast condition,and then dropped with the consumption of substrate. However,the activity of AHL-based QS in these three reactors recovered again in prolonged starvation. Furthermore,the results showed that the enhancement of AHL-based QS favored the extracellular polymeric substance production of microorganisms in activated sludge. Thus,it could be concluded that aerobic granules showed higher AHL-based QS than flocculent sludge,which resulted from the higher sludge density of aerobic granules than flocculent sludge. AHL-based QS was related to the metabolism energy in the feast condition; however,in prolonged starvation,microorganisms would emit more AHL-like molecules to protect themselves to resist starvation. Moreover,the enhancement of AHL-based QS favored the EPS component productivity of the microorganisms in activated sludge,which contributed to maintain the aerobic granular structure.展开更多
Bacteria are known to communicate with each other and regulate their activities in social networks by secreting and sensing signaling molecules called autoinducers,a process known as quorum sensing(QS).This is a growi...Bacteria are known to communicate with each other and regulate their activities in social networks by secreting and sensing signaling molecules called autoinducers,a process known as quorum sensing(QS).This is a growing area of research in which we are expanding our understanding of how bacteria collectively modify their behavior but are also involved in the crosstalk between the host and gut microbiome.This is particularly relevant in the case of pathologies associated with dysbiosis or disorders of the intestinal ecosystem.This review will examine the different QS systems and the evidence for their presence in the intestinal ecosystem.We will also provide clues on the role of QS molecules that may exert,directly or indirectly through their bacterial gossip,an influence on intestinal epithelial barrier function,intestinal inflammation,and intestinal carcinogenesis.This review aims to provide evidence on the role of QS molecules in gut physiology and the potential shared by this new player.Better understanding the impact of intestinal bacterial social networks and ultimately developing new therapeutic strategies to control intestinal disorders remains a challenge that needs to be addressed in the future.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
Bioaugmentation of denitrifying bacteria can serve as a promising technique to improve nutrient removal during wastewater treatment. While denitrification inhibition by bacterial quorum sensing(QS) in Pseudomonas aeru...Bioaugmentation of denitrifying bacteria can serve as a promising technique to improve nutrient removal during wastewater treatment. While denitrification inhibition by bacterial quorum sensing(QS) in Pseudomonas aeruginosa has been indicated, the application of bacterial QS disruption to improve nitrate removal from wastewater has not been investigated. In this study, the effect of bioaugmentation of P. aeruginosa SD-1 on nitrate removal in sequencing batch reactors that treat nitrate rich wastewater was assessed. Additionally, the potential of a quorum sensing inhibitor(QSI) to improve denitrification following bacterial bioaugmentation was evaluated. Curcumin, a natural plant extract, was used as a QSI. The chemical oxygen demand(COD) and initial nitrate concentration of the influent were 700 ±20 mg/L and 200 ±10 mg/L respectively, and their respective concentrations in the effluent were 56.9 ±3.2 mg/L and 9.0 ±3.2 mg/L. Thus, the results revealed that bioaugmentation of P. aeruginosa SD-1 resulted in an increased nitrate removal to 82% ±1%. Further, nitrate was almost completely removed following the addition of the QSI, and activities of nitrate reductase and nitrite reductase increased by 88% ±2% and 74% ±2% respectively. The nitrogen mass balance indicated that aerobic denitrification was employed as the main pathway for nitrogen removal in the reactors. The results imply that bioaugmentation and modulation of QS in denitrifying bacteria, through the use of a QSI, can enhance nitrate removal during wastewater treatment.展开更多
Quorum sensing（QS） is a type of microbe-microbe communication system that is widespread among the microbial world, particularly among microorganisms that are symbiotic with plants and animals. Thereby, the cell-cell...Quorum sensing（QS） is a type of microbe-microbe communication system that is widespread among the microbial world, particularly among microorganisms that are symbiotic with plants and animals. Thereby, the cell-cell signalling is likely to occur in an anaerobic rumen environment, which is a complex microbial ecosystem. In this study, using six ruminally fistulated Liuyang black goats as experimental animals, we aimed to detect the activity of quorum sensing autoinducers（AI） both in vivo and in vitro and to clone the lux S gene that encoded autoinducer-2（AI-2） synthase of microbial samples that were collected from the rumen of goats. Neutral detergent fiber（NDF） and soluble starch were the two types of substrates that were used for in vitro fermentation. The fermented fluid samples were collected at 0, 2, 4, 6, 8, 12, 24, 36, and 48 h of incubation. The acyl-homoserine lactones（AHLs） activity was determined using gas chromatography-mass spectrometer（GC-MS） analysis. However, none of the rumen fluid extracts that were collected from the goat rumen showed the same or similar fragmentation pattern to AHLs standards. Meanwhile, the AI-2 activity, assayed using a Vibrio harveyi BB170 bioassay, was negative in all samples that were collected from the goat rumen and from in vitro fermentation fluids. Our results indicated that the activities of AHLs and AI-2 were not detected in the ruminal contents from six goats and in ruminal fluids obtained from in vitro fermentation at different sampling time-points. However, the homologues of lux S in Prevotella ruminicola were cloned from in vivo and in vitro ruminal fluids. We concluded that AHLs and AI-2 could not be detected in in vivo and in vitro ruminal fluids of goats using the current detection techniques under current dietary conditions. However, the microbes that inhabited the goat rumen had the potential ability to secrete AI-2 signaling molecules and to communicate with each other via AI-2-mediated QS because of the presence of lux S.展开更多
Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data...Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular （AI） and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.展开更多
Objective:To investigate anti-quorum sensing(anti-QS)and anti-biofilm formation(antiBF)activities of the ethanol extracts of 388 plants.Methods:The anti-QS activity of the plant extracts was evaluated by disc-diffusio...Objective:To investigate anti-quorum sensing(anti-QS)and anti-biofilm formation(antiBF)activities of the ethanol extracts of 388 plants.Methods:The anti-QS activity of the plant extracts was evaluated by disc-diffusion assays using the bio-reporter strain,Chromobacterium violaceum CV017.Pseudomonas aeruginosa PAO1,Yersinia enterocolitica ATCC 9610,and Agrobacterium tumefaciens C58,which possess QS systems,were used to evaluate the antiBF activity of the plant extracts.Results:Among 388 plant extracts,the Cornus controversa(C.controversa)and Cynanchum wilfordii extracts exhibited the strongest anti-QS activity.The C.controversa extract exhibited anti-BF activity against Pseudomonas aeruginosa,Yersinia enterocolitica and Agrobacterium tumefaciens,whereas the Cynanchum wilfordii extract exhibited no anti-BF activity against Pseudomonas aeruginosa.In addition,the C.controversa extract suppressed soft rot of cabbage.Conclusions:The C.controversa extract inhibits bacterial QS and BF,and is capable of controlling soft rot.Therefore,this extract has potential for the prevention and treatment of bacterial infections and for the development of alternatives to antibiotics.展开更多
文摘Quorum sensing （QS） is a bacterial cell-cell communication process by which bacteria communicate using extracellular signals called autoinducers. Two QS systems have been identified in Escherichia coli K-12, including an intact QS system 2 that is stimulated by the cyclic AMP （cAMP）-cAMP receptor protein （CRP） complex and a partial QS system 1 that consists of SdiA （suppressor of cell division inhibitor） responding to signals generated by other microbial species. The relationship between QS system 1 and system 2 in E. coli, however, remains obscure. Here, we show that an EAL domain protein, encoded by ydiV, and cAMP are involved in the interaction between the two QS systems in E. coli. Expression of sdiA and ydiV is inhibited by glucose. SdiA binds to the ydiV promoter region in a dose-dependent, but nonspecific, manner; extracellular autoinducer 1 from other species stimulates ydiV expression in an sdiA-depen- dent manner. Furthermore, we discovered that the double sdiA-ydiV mutation, but not the single mutation, causes a 2-fold decrease in intracellular cAMP concentration that leads to the inhibition of QS system 2. These results indicate that signaling pathways that respond to important environmental cues, such as autoinducers and glucose, are linked together for their control in E. coli.
基金supported by the Hainan Provincial Natural Science Foundation of China (321CXTD1012)the National Natural Science Foundation of China (NSFC31871868)the Scientific Research Foundation of Hainan Tropical Ocean University (RHDRC202117),China.
文摘Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application in spoilage microorganism control and aquatic products quality maintenance.Materials and Methods:SHP CN-32 was treated by prepared citral nanoemulsion when the minimal inhibitory concentration(MIC)was verified.The growth curve,membrane integrity,scanning electron microscope(SEM)observation,biofilm formation and quorum sensing(QS)signaling molecule Al-2 content were evaluated in different MIC treatment groups(0 to 1.00 MIC).The gene expression status of SHP CN-32 in O and 0.50 MIC groups were compared using transcriptome sequencing and quantitative polymerase chain reaction(PCR).Results:The in vitro culture revealed that the citral nanoemulsion could inhibit the growth of SHP CN-32 with MIC of approximately 200μg/mL.Images of membrane integrity.SEM and biofilm formation suggested significant biological structure damage in bacteria after treatment.Meanwhile,the Qs signaling molecule Al-2 content showed a decline with increasing treatment concentration.Transcriptome sequencing and quantitative PCR revealed that the majority genes related diversified functional metabolic pathways of SHP CN-32 were downregulated at varying degree.Conclusion:A significant bacteriostasis of citral nanoemulsion against SHP CN-32 was verified via the results of growth inhibition,structural destruction,signal molecular decrease and gene expression downregulation of strains.These synergies significantly affect the characteristic expression of SHP CN-32,revealing the application potential as bacteriostat,QS inhibitor and preservative in aquatic products.
基金supported by the National Key Research and Development Program of China for International Science and Innovation Cooperation Major Project between Governments(No.2016YFE0118800)the Shenzhen Science and Technology Development Funding-Fundamental Research Plan(No.JCYJ20150331151358156)
文摘The detection of acyl homoserine lactones（AHLs） in activated sludge is essential for clarifying their function in wastewater treatment processes. An LC–MS/MS method was developed for the detection of AHLs in both the aqueous and solid phases of activated sludge. In addition, the effects of proteases and extracellular polymeric substances（EPS） on the detection of AHLs were evaluated by adding protease inhibitors and extracting EPS,respectively. Recoveries of each AHL were improved by adding 50 μL of protease inhibitor,and recoveries were also improved from 0 to 56.9% to 24.2%–105.8% by EPS extraction.Applying the developed method to determine the type and concentration of AHLs showed that C4-HSL, C6-HSL, C8-HSL and 3-oxo-C8-HSL were widely detected in a suspended activated sludge system. The dominant AHL was C8-HSL, with a highest concentration of304.3 ng/L. C4-HSL was mainly distributed in the aqueous phase, whereas C6-HSL, C8-HSL and 3-oxo-C8-HSL were preferentially distributed in the sludge phase.
基金supported by the National Key Research and Development Program of China(No.2018YFD1100503).
文摘Heterotrophic nitrification-aerobic denitrification(HNAD)is essential in diverse nitrogen-transforming processes.How HNAD is modulated by quorum sensing(QS)systems is still ambiguous.The QS system in Pseudomonas aeruginosa manipulates colony behavior.Here,we described the influence of the Pseudomonas quinolone signal(PQS)and N-acyl-L-homoserine lactone(AHL)on HNAD.The HNAD of P.aeruginosa was inhibited by the oversecretion of PQS.AHL-or PQS-deficient P.aeruginosa mutants had a higher ability for nitrogen removal.QS inhibited heterotrophic nitrification mainly via controlling the activity of nitrite oxidoreductase(NXR)and the depressed aerobic denitrification by regulating the catalytic abilities of nitric oxide reductase(NOR),nitrite reductase(NIR),and nitrate reductase(NAR).The addition of citrate as the sole carbon source increased the nitrogen removal efficiency compared with other carbon sources.Nitrite,as the sole nitrogen source,could be used entirely with only the moderate concentration of PQS contained.AHL and PQS controlled both nitrification and denitrification,suggesting that QS plays an important role in nitrogen cycle under aerobic conditions.
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.
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.
基金This work was supported by National Natural Science Foundation of China(32272424)Guangdong Major Project of Basic and Applied Basic Research(2020B0301030005)+1 种基金Guangdong Provincial Key Laboratory(2020B121201009)Guangdong Academy of Sciences Special Project for Capacity Building of Innovation Driven Development(2020GDASYL-20200401002).
文摘Biofilms containing foodborne pathogens can adhere to food ingredients or food processing equipment.Due to their enhanced resilience to cleaning and chance of cross-contamination,there is an increased risk of food poisoning to consumers.The life course of biofilms is generally thought to be regulated by a quorum sensing(QS)system by secreted autoinducing peptides(AIPs).Recent studies have revealed that small non-coding RNA(sRNA)also plays an important role in regulating biofilm formation at the post-transcriptional level.Moreover,sRNA can act as an intermediate regulating hub between the quorum sensing system and biofilm.This review summarizes the latest findings on sRNA in biofilms of common foodborne pathogens and their potential impact.We also highlight the different mechanism of cascade regulation of sRNA and QS system in biofilm formation in several typical foodborne pathogens.In this process,sRNA responds to dynamic external environmental signals finely and accurately,and can feedback information on the bacterial cell environment to modify the QS system.These findings will deepen our understanding of biofilm formation and provide new perspectives for eliminating biofilm of foodborne pathogens based on the cascade regulation of small RNA and QS for developing biofilm-free food-processing systems.
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.
基金supported by the National Natural Science Foundation of China(Nos.21261160489,21207031 and51538011)the Program for Changjiang Scholars and Innovative Research Team in University,China
文摘Autoinducer 2（AI-2）, an important bioactive by-product of the Lux S-catalyzed S-ribosylhomocysteine cleavage reaction in the activated-methyl-cycle, has been suggested to serve as a universal intra- and inter-species signaling molecule. The development of reliable and sensitive methods for quantitative determination of AI-2 is highly desired.However, the chemical properties of AI-2 cause difficulty in its quantitative analysis.Herein, we report a high performance liquid chromatography-tandem mass spectrometric method that enables reproducible and sensitive measurement of AI-2 concentrations in complex matrixes. 4,5-Dimethylbenzene-1,2-diamine（DMBDM）, an easy-to-obtain commercial reagent, was used for the derivatization treatment. The assay was linear in the concentration range of 1.0–1000 ng/m L（R^2= 0.999） and had a lower limit of quantification of0.58 ng/m L. The method exhibited several advantages, e.g., high selectivity, wide linear response range, and good sensitivity. Furthermore, the effectiveness of the method was further validated through measuring AI-2 concentrations in the cell-free culture supernatant from Escherichia coli wild type.
基金Supported by JSPS grant Challenging Exploratory Research,No.25660062SEP-CONACyT grant,No.152794(García-Contreras R)+3 种基金Fideicomiso COLPOS 167304 and Programa Cátedras-CONACyT 2112(Castillo-Juárez)the Miguel Servet Program(C.H.U.A Coruña and ISCIII)(Tomás M)the CONACyT grant number 441393/269132(Mandujano-Tinoco EA)and the Biotechnology Endowed Chair at the Pennsylvania State University.
文摘Quorum sensing(QS) is cell communication that is widely used by bacterial pathogens to coordinate the expression of several collective traits, including the production of multiple virulence factors, biofilm formation, and swarming motility once a population threshold is reached. Several lines of evidence indicate that QS enhances virulence of bacterial pathogens in animal models as well as in human infections; however, its relative importance for bacterial pathogenesis is still incomplete. In this review, we discuss the present evidence from in vitro and in vivo experiments in animal models, as well as from clinical studies, that link QS systems with human infections. We focus on two major QS bacterial models, the opportunistic Gram negative bacteria Pseudomonas aeruginosa and the Gram positive Staphylococcus aureus, which are also two of the main agents responsible of nosocomial and wound infections. In addition, QS communication systems in other bacterial, eukaryotic pathogens, and even immune and cancer cells are also reviewed, and finally, the new approaches proposed to combat bacterial infections by the attenuation of their QS communication systems and virulence are also discussed.
基金We thank our colleagues J Zang and X Liu for their technical assistance in protein purification. This work was supported by the One Hundred Talent Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China （50738006）.
文摘In quorum sensing （QS） process, bacteria regulate gene expression by utilizing small signaling molecules called autoinducers in response to a variety of environmental cues. Autoinducer 2 （AI-2）, a QS signaling molecule proposed to be involved in interspecies communication, is produced by many species of gram-negative and gram-positive bacteria. In Escherichia coil and Salmonella typhimurium, the extracellular AI-2 is imported into the cell by a transporter encoded by the lsr operon. Upstream of the lsr operon, there is a divergently transcribed gene encoding LsrR, which was reported previously to repress the transcription of the lsr operon and itself. Here, we have demonstrated for the first time that LsrR represses the transcription of the lsr operon and itself by directly binding to their promoters using gel shift and DNase I footprinting assays. The β-galactosidase reporter assays further suggest that two motifs in both the lsrR and lsrA promoter regions are crucial for the LsrR binding. Furthermore, in agreement with the conclusion that phosphorylated AI-2 can relieve the repression of LsrR in previous studies, our data show that phospho- AI-2 renders LsrR unable to bind to its own promoter in vitro.
文摘Traditional treatment of infectious diseases is based on compounds that aim to kill or inhibit bacterial growth. The bacterial resistance against antibiotics is a serious issue for public health. Today, new therapeutic targets other than the bacterial wall were deciphered. Quorum sensing or bacterial pheromones are molecules called auto-inducer secreted by bacteria to regulate some functions such as antibiotic resistance and biofilms formation. This therapeutic target is well-studied worldwide, nevertheless the scientific data are not updated and only recent researches started to look into its potential as a target to fight against infectious diseases. A major concern with this approach is the frequently observed development of resistance to antimicrobial compounds. Therefore, this paper aims to provide a current overview of the quorum sensing system in bacteria by revealing their implication in biofilms formation and the development of antibiotic resistance, and an update on their importance as a potential target for natural substances.
基金supported by the National Natural Science Found of China (No.51078036)
文摘The present study investigated the relationship between N-acyl-homoserine lactone（AHL）-based quorum sensing（QS） and the physico-chemical properties of aerobic granules.Stable mature granules were observed in SBR2 and SBR3 with average diameters of 0.96,and1.49 mm,respectively. The sludge densities of aerobic granules in SBR2 and SBR3 were1.0246,and 1.0201 g/mL,respectively,which were higher than that of flocculent sludge in SBR1（1.0065 g/mL）. The results showed that the activity of AHL-based QS in SBR2 and SBR3 amounted to 2.4- and 2.1-fold induction,however,that in SBR1 with flocculent sludge was1.6-fold induction. In addition,the results also showed that the activity of AHL-based QS in the three reactors rose in the feast condition,and then dropped with the consumption of substrate. However,the activity of AHL-based QS in these three reactors recovered again in prolonged starvation. Furthermore,the results showed that the enhancement of AHL-based QS favored the extracellular polymeric substance production of microorganisms in activated sludge. Thus,it could be concluded that aerobic granules showed higher AHL-based QS than flocculent sludge,which resulted from the higher sludge density of aerobic granules than flocculent sludge. AHL-based QS was related to the metabolism energy in the feast condition; however,in prolonged starvation,microorganisms would emit more AHL-like molecules to protect themselves to resist starvation. Moreover,the enhancement of AHL-based QS favored the EPS component productivity of the microorganisms in activated sludge,which contributed to maintain the aerobic granular structure.
基金by Fondation pour la Recherche Médicale,No.EQU202003010171Association François Aupetit,No.AHLs 2019 and No.AHLs 2021+1 种基金Fondation pour la Recherche Médical FRM,No.ECO201806006843(to Coquant G)and CORDDIM,Ile-de-France Region(to Aguanno D).
文摘Bacteria are known to communicate with each other and regulate their activities in social networks by secreting and sensing signaling molecules called autoinducers,a process known as quorum sensing(QS).This is a growing area of research in which we are expanding our understanding of how bacteria collectively modify their behavior but are also involved in the crosstalk between the host and gut microbiome.This is particularly relevant in the case of pathologies associated with dysbiosis or disorders of the intestinal ecosystem.This review will examine the different QS systems and the evidence for their presence in the intestinal ecosystem.We will also provide clues on the role of QS molecules that may exert,directly or indirectly through their bacterial gossip,an influence on intestinal epithelial barrier function,intestinal inflammation,and intestinal carcinogenesis.This review aims to provide evidence on the role of QS molecules in gut physiology and the potential shared by this new player.Better understanding the impact of intestinal bacterial social networks and ultimately developing new therapeutic strategies to control intestinal disorders remains a challenge that needs to be addressed in the future.
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 Natural Science Foundation of Zhejiang Province (nos. LY17E080001 and LQ18E080005)the China Scholarship Council (no. iCET 2017)。
文摘Bioaugmentation of denitrifying bacteria can serve as a promising technique to improve nutrient removal during wastewater treatment. While denitrification inhibition by bacterial quorum sensing(QS) in Pseudomonas aeruginosa has been indicated, the application of bacterial QS disruption to improve nitrate removal from wastewater has not been investigated. In this study, the effect of bioaugmentation of P. aeruginosa SD-1 on nitrate removal in sequencing batch reactors that treat nitrate rich wastewater was assessed. Additionally, the potential of a quorum sensing inhibitor(QSI) to improve denitrification following bacterial bioaugmentation was evaluated. Curcumin, a natural plant extract, was used as a QSI. The chemical oxygen demand(COD) and initial nitrate concentration of the influent were 700 ±20 mg/L and 200 ±10 mg/L respectively, and their respective concentrations in the effluent were 56.9 ±3.2 mg/L and 9.0 ±3.2 mg/L. Thus, the results revealed that bioaugmentation of P. aeruginosa SD-1 resulted in an increased nitrate removal to 82% ±1%. Further, nitrate was almost completely removed following the addition of the QSI, and activities of nitrate reductase and nitrite reductase increased by 88% ±2% and 74% ±2% respectively. The nitrogen mass balance indicated that aerobic denitrification was employed as the main pathway for nitrogen removal in the reactors. The results imply that bioaugmentation and modulation of QS in denitrifying bacteria, through the use of a QSI, can enhance nitrate removal during wastewater treatment.
基金financially support of the Chinese Academy of Sciences (KZCX2-YW-455)the CAS/SAFEA International Partnership Program for Creative Research Teams,China (KZCX2-YW-T07) and K C Wong Education, Hong Kong
文摘Quorum sensing（QS） is a type of microbe-microbe communication system that is widespread among the microbial world, particularly among microorganisms that are symbiotic with plants and animals. Thereby, the cell-cell signalling is likely to occur in an anaerobic rumen environment, which is a complex microbial ecosystem. In this study, using six ruminally fistulated Liuyang black goats as experimental animals, we aimed to detect the activity of quorum sensing autoinducers（AI） both in vivo and in vitro and to clone the lux S gene that encoded autoinducer-2（AI-2） synthase of microbial samples that were collected from the rumen of goats. Neutral detergent fiber（NDF） and soluble starch were the two types of substrates that were used for in vitro fermentation. The fermented fluid samples were collected at 0, 2, 4, 6, 8, 12, 24, 36, and 48 h of incubation. The acyl-homoserine lactones（AHLs） activity was determined using gas chromatography-mass spectrometer（GC-MS） analysis. However, none of the rumen fluid extracts that were collected from the goat rumen showed the same or similar fragmentation pattern to AHLs standards. Meanwhile, the AI-2 activity, assayed using a Vibrio harveyi BB170 bioassay, was negative in all samples that were collected from the goat rumen and from in vitro fermentation fluids. Our results indicated that the activities of AHLs and AI-2 were not detected in the ruminal contents from six goats and in ruminal fluids obtained from in vitro fermentation at different sampling time-points. However, the homologues of lux S in Prevotella ruminicola were cloned from in vivo and in vitro ruminal fluids. We concluded that AHLs and AI-2 could not be detected in in vivo and in vitro ruminal fluids of goats using the current detection techniques under current dietary conditions. However, the microbes that inhabited the goat rumen had the potential ability to secrete AI-2 signaling molecules and to communicate with each other via AI-2-mediated QS because of the presence of lux S.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10802043 and 10832006, Program for Science ＆ Technology Innovation Talents in Universities of Henan under Grant No. 2009HASTIT033 and Key Disciplines of Shanghai municipality （$30104）
文摘Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular （AI） and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)the Ministry of Education(2015R1A6A1A03031413)Rural Development Administration,Republic of Korea(PJ00743703).
文摘Objective:To investigate anti-quorum sensing(anti-QS)and anti-biofilm formation(antiBF)activities of the ethanol extracts of 388 plants.Methods:The anti-QS activity of the plant extracts was evaluated by disc-diffusion assays using the bio-reporter strain,Chromobacterium violaceum CV017.Pseudomonas aeruginosa PAO1,Yersinia enterocolitica ATCC 9610,and Agrobacterium tumefaciens C58,which possess QS systems,were used to evaluate the antiBF activity of the plant extracts.Results:Among 388 plant extracts,the Cornus controversa(C.controversa)and Cynanchum wilfordii extracts exhibited the strongest anti-QS activity.The C.controversa extract exhibited anti-BF activity against Pseudomonas aeruginosa,Yersinia enterocolitica and Agrobacterium tumefaciens,whereas the Cynanchum wilfordii extract exhibited no anti-BF activity against Pseudomonas aeruginosa.In addition,the C.controversa extract suppressed soft rot of cabbage.Conclusions:The C.controversa extract inhibits bacterial QS and BF,and is capable of controlling soft rot.Therefore,this extract has potential for the prevention and treatment of bacterial infections and for the development of alternatives to antibiotics.
