Pseudomonas aeruginosa causes severe and persistent infections in immune compromised individuals and cystic fibrosis sufferers. The infection is hard to eradi- cate as P. aeruginosa has developed strong resistance to ...Pseudomonas aeruginosa causes severe and persistent infections in immune compromised individuals and cystic fibrosis sufferers. The infection is hard to eradi- cate as P. aeruginosa has developed strong resistance to most conventional antibiotics. The problem is further compounded by the ability of the pathogen to form biofilm matrix, which provides bacterial cells a protected environment withstanding various stresses including antibiotics. Quorum sensing （QS）, a cell density-based intercellular communication system, which plays a key role in regulation of the bacterial virulence and biofilm formation, could be a promising target for developing new strategies against P. aeruginosa infection. The QS network of P. aeruginosa is organized in a multi-layered hierarchy consisting of at least four interconnected signaling mechanisms. Evidence is accumulating that the QS regulatory network not only responds to bacte- rial population changes but also could react to envi- ronmental stress cues. This plasticity should be taken into consideration during exploration and development of anti-QS therapeutics.展开更多
Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria （and fungi） are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-pro...Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria （and fungi） are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA. Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity and increased doubling times. These more or less dormant cells are therefore responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations. Bacteria in biofilms communicate by means of molecules, which activates certain genes responsible for production of virulence factors and, to some extent, biofilm structure. This phenomenon is called quorum sensing and depends upon the concentration of the quorum sensing molecules in a certain niche, which depends on the number of the bacteria. Biofilms can be prevented by antibiotic prophylaxis or early aggressive antibiotic therapy and they can be treated by chronic suppressive antibiotic therapy. Promising strategies may include the use of compounds which can dissolve the biofilm matrix and quorum sensing inhibitors, which increases biofilm susceptibility to antibiotics and phagocytosis.展开更多
Objective To isolate and identify the bioactive phytochemicals from the leaves of Camellia nitidissima. Methods The chemical constituents were isolated and purified by repeated silica gel, Sephadex LH-20, MCI gel colu...Objective To isolate and identify the bioactive phytochemicals from the leaves of Camellia nitidissima. Methods The chemical constituents were isolated and purified by repeated silica gel, Sephadex LH-20, MCI gel columns, recrystallization, and semi-preparative HPLC techniques. The chemicl structures of these compounds were identified on the basis of spectral data including NMR and MS. Then quorum sensing inhibition （QSI） activities of these compounds were tested using Chromobacterium violaceum CV026 as the bioindicator strain. The antitumor activities of these compounds were measured using SGC7901 as cell proliferation and cytotoxicity. Results cx-Spinasteryl-I^-D-glucopyranoside （1）, stigmasta-7,22-diene-3-O-[c^-L-arabinopyranosyl （1 -2）]-β-D-galactopyranoside （2）, kaempferol 3-O-[2-O-（trans-p-coumaroyl）-3-O-α -D-glucopyranosyl]-α-D-glucopyranoside （3）, aromadendrin （4）, catechin （5）, phlorizin 4＇-O-β-D-glucopyranoside （6）, （3R,6R,7Lg-3-hydroxy-4,7-megastigmadien- 9-one （7）, dodecanoic acid （8）, 3α-acetoxy-20-1upanol （9）, and 3β,6α- trihydroxyolean- 7-one （1 0） were successively isolated from the leaves of C. nitidissima. Unfortunately, these compounds had no QSI activity. Based on Cell Counting Kit-8 （CCK-8） assay, compound 10 showed the best anti-tumor activity or all compounds （ICs0 = 91.7 μg/mL）. Conclusion Apart from compounds 4 and 5, other eight compounds are reported in this plant for the first time. All compounds show no QSI activity, compound 10 shows potential cytotoxic activity on SGC7901 cells in vitro.展开更多
Quorum sensing(QS)regulation of the composition of ammonia-oxidising archaea(AOA)and ammonia-oxidising bacteria(AOB)communities and functions in wastewater treatment was investigated.Specifically,we explored the role ...Quorum sensing(QS)regulation of the composition of ammonia-oxidising archaea(AOA)and ammonia-oxidising bacteria(AOB)communities and functions in wastewater treatment was investigated.Specifically,we explored the role of N-acyl-L-homoserine lactones(AHLs)in microbial community dynamics in activated sludge.On average,the specific ammoniaoxidising-rate increased from 1.6 to 2.8 mg NH_4^+-N/g MLSS/hr after treatment with long-chain AHLs for 16 days,and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes.Significant differences were observed in the AOA communities of control and AHL-treated cultures,but not the AOB community.Furthermore,the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition.These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment.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
Quorum sensing(QS)is a regulatory system that regulates the behavior of microbial populations by sensing the concentration of signal molecules that are spontaneously produced and released by bacteria.The strategy of b...Quorum sensing(QS)is a regulatory system that regulates the behavior of microbial populations by sensing the concentration of signal molecules that are spontaneously produced and released by bacteria.The strategy of blocking the QS system and inhibiting the production of virulence factors is termed as quorum quenching(QQ).This strategy attenuates virulence without killing the pathogens,thereby weakening the selective pressure on pathogens and postponing the evolution of QQ-mediated drug resistance.In recent years,there have been significant theoretical and practical developments in the field of QS and QQ.In particular,with the development and utilization of marine resources,more and more marine microbial species have been found to be regulated by these two mechanisms,further promoting the research progress of QS and QQ.In this review,we described the diversity of QS signals and QS-related regulatory systems,and then introduced mechanisms related to QS interference,with particular emphasis on the description of natural QQ enzymes and chemicals acting as QS inhibitors.Finally,the exploitation of quorum sensing quenchers and the practical application of QQ were introduced,while some QQ strategies were proposed as promising tools in different fields such as medicine,aquaculture,agriculture and biological pollution prevention areas.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
N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL...N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL-containing AGSR supernatant into the continuously stirred tank reactors reduced the start-up time of the anammox process from80 to 66 days.Moreover,the nitrogen loading rate was also enhanced to 1.6 times that of the control reactor.AHLs could increase the secretion of extracellular polymeric substances and anammox obtained better enrichment with the addition of AHLs-containing AGSR supernatant.Denaturing gradient gel electrophoresis analysis further revealed that AHLs played a role in mediating microbial community parameters.In conclusion,adding AHL-containing supernatant could be an effective and economical way to accelerate the start-up of anammox.展开更多
The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in ...The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in PAO1. After induction by IPTG for 6 h and 18 h, expression of the aiiA gene in PAO1 completely degraded the quorum sensing autoinducers N-acylhomoserine lactones (AHLs): N-oxododecanoyl-L-homoserine lactone (OdDHL) and N-butyryl-L-homoserine lactone (BHL). The re- duced amount of AHLs in PAO1 was also correlated with decreased expression and production of several virulence factors such as elastase and pyocyanin. AiiA expression also influenced bacterial swarming motility. Most importantly, our studies indicated that aiiA played significant roles in P. aeruginosa biofilm formation and dispersion, as observed by the differences of the biofilm formation on liquid and solid surfaces, and biofilm structures under a scanning electron microscope.展开更多
N-acyl-homoserine lactones（AHLs） serve as quorum-sensing signals, which control a number of bacterial processes in many proteobacteria. Here we report the effects of exogenous short-chain AHL on the denitrifying pro...N-acyl-homoserine lactones（AHLs） serve as quorum-sensing signals, which control a number of bacterial processes in many proteobacteria. Here we report the effects of exogenous short-chain AHL on the denitrifying process of Paracoccus denitrificans, which are capable of aerobic and anaerobic growth by utilizing nitrate. The denitrification activity of these cells was monitored by measuring denitrification products（including nitrate, nitrite,and nitrous oxide）, and the individual messenger ribonucleic acid（m RNA） levels of nitrate,nitrite, nitric oxide and nitrous oxide reductases. The results indicated that 2 μmol/L C6-homoserine lactone（HSL） has little effect on cell density under either anaerobic or aerobic culture conditions, and the nitrate reduction activity appeared slightly affected by N-hexanoyl-DL-homoserine lactone（C6-HSL）. However, exogenous C6-HSL significantly affected the transcription of nitrite reductase and nitric oxide reductase genes in P.denitrificans regardless of the presence of oxygen, and N2O accumulation activity in P. denitrificans was suppressed by C6-HSL under aerobic condition. In contrast, exogenous C6-HSL stimulated the production of N2O under anaerobic condition, suggesting that the regulation of denitrification by quorum sensing may be important in N2O release.展开更多
The aim of this study was to investigate antibacterial activity of Origanum compactum essential oils collected at three phenological stages on Escherichia coli and Bacillus subtilis. The antibacterial activity was eva...The aim of this study was to investigate antibacterial activity of Origanum compactum essential oils collected at three phenological stages on Escherichia coli and Bacillus subtilis. The antibacterial activity was evaluated using the agar-well diffusion assay. The MIC and MBC values were determined using the micro-dilution assay. The investigation of the antibacterial action was carried out by the evaluation of the effect of O. compactum essential oils on the antibacterial kinetic growth, the integrity of cell membrane and permeability of the cell membrane. The anti-quorum sensing activity was tested by the inhibition of the biofilm formation. The findings of this study showed that O. compactum essential oil has potent antibacterial activities against E. coli and B. subtilis. The lowest inhibition value against B. subtilis was obtained with O. compactum essential oil at the post-flowering stage (MIC=MBC=0.0312%(v/v)). The antibacterial mechanisms of O. compactum essential oils are related to the disturbing of the cell membrane integrity and the increasing of the membrane permeability, which leads to the leakage of genetic materials (DNA and RNA). Moreover, O. compactum essential oils inhibited the formation of the biofilms, a phenotype that has been known to be quorum sensing regulated.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
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
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
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
基金This work was funded by the Biomedical Research Council, Agency for Science, Technology and Research （A＇STAR）, Singapore, and by the National Natural Science Foundation of China （Grant No. 31330002）. We apologize to the scientists who made contributionsto the field, but their works have not been cited due to space limitations.
文摘Pseudomonas aeruginosa causes severe and persistent infections in immune compromised individuals and cystic fibrosis sufferers. The infection is hard to eradi- cate as P. aeruginosa has developed strong resistance to most conventional antibiotics. The problem is further compounded by the ability of the pathogen to form biofilm matrix, which provides bacterial cells a protected environment withstanding various stresses including antibiotics. Quorum sensing （QS）, a cell density-based intercellular communication system, which plays a key role in regulation of the bacterial virulence and biofilm formation, could be a promising target for developing new strategies against P. aeruginosa infection. The QS network of P. aeruginosa is organized in a multi-layered hierarchy consisting of at least four interconnected signaling mechanisms. Evidence is accumulating that the QS regulatory network not only responds to bacte- rial population changes but also could react to envi- ronmental stress cues. This plasticity should be taken into consideration during exploration and development of anti-QS therapeutics.
文摘Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria （and fungi） are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA. Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity and increased doubling times. These more or less dormant cells are therefore responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations. Bacteria in biofilms communicate by means of molecules, which activates certain genes responsible for production of virulence factors and, to some extent, biofilm structure. This phenomenon is called quorum sensing and depends upon the concentration of the quorum sensing molecules in a certain niche, which depends on the number of the bacteria. Biofilms can be prevented by antibiotic prophylaxis or early aggressive antibiotic therapy and they can be treated by chronic suppressive antibiotic therapy. Promising strategies may include the use of compounds which can dissolve the biofilm matrix and quorum sensing inhibitors, which increases biofilm susceptibility to antibiotics and phagocytosis.
基金National High Technology Research and Development Program of China(863 Program)(2014AA022208)National Natural Science Foundation of China(31170131 and 31070312)Jiangsu Qinglan Project
文摘Objective To isolate and identify the bioactive phytochemicals from the leaves of Camellia nitidissima. Methods The chemical constituents were isolated and purified by repeated silica gel, Sephadex LH-20, MCI gel columns, recrystallization, and semi-preparative HPLC techniques. The chemicl structures of these compounds were identified on the basis of spectral data including NMR and MS. Then quorum sensing inhibition （QSI） activities of these compounds were tested using Chromobacterium violaceum CV026 as the bioindicator strain. The antitumor activities of these compounds were measured using SGC7901 as cell proliferation and cytotoxicity. Results cx-Spinasteryl-I^-D-glucopyranoside （1）, stigmasta-7,22-diene-3-O-[c^-L-arabinopyranosyl （1 -2）]-β-D-galactopyranoside （2）, kaempferol 3-O-[2-O-（trans-p-coumaroyl）-3-O-α -D-glucopyranosyl]-α-D-glucopyranoside （3）, aromadendrin （4）, catechin （5）, phlorizin 4＇-O-β-D-glucopyranoside （6）, （3R,6R,7Lg-3-hydroxy-4,7-megastigmadien- 9-one （7）, dodecanoic acid （8）, 3α-acetoxy-20-1upanol （9）, and 3β,6α- trihydroxyolean- 7-one （1 0） were successively isolated from the leaves of C. nitidissima. Unfortunately, these compounds had no QSI activity. Based on Cell Counting Kit-8 （CCK-8） assay, compound 10 showed the best anti-tumor activity or all compounds （ICs0 = 91.7 μg/mL）. Conclusion Apart from compounds 4 and 5, other eight compounds are reported in this plant for the first time. All compounds show no QSI activity, compound 10 shows potential cytotoxic activity on SGC7901 cells in vitro.
基金supported by the National Natural Science Foundation of China (No. 41501250)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB15030101)the National Key Research and Development Program of China (Nos. 2016YFC0500401 and 2017YFC050580301)
文摘Quorum sensing(QS)regulation of the composition of ammonia-oxidising archaea(AOA)and ammonia-oxidising bacteria(AOB)communities and functions in wastewater treatment was investigated.Specifically,we explored the role of N-acyl-L-homoserine lactones(AHLs)in microbial community dynamics in activated sludge.On average,the specific ammoniaoxidising-rate increased from 1.6 to 2.8 mg NH_4^+-N/g MLSS/hr after treatment with long-chain AHLs for 16 days,and the addition of AHLs to sludge resulted in an increased number of AOA/AOB amoA genes.Significant differences were observed in the AOA communities of control and AHL-treated cultures,but not the AOB community.Furthermore,the dominant functional AOA strains of the Crenarchaeota altered their ecological niche in response to AHL addition.These results provide evidence that AHLs play an important role in mediating AOA/AOB microbial community parameters and demonstrate the potential for application of QS to the regulation of nitrogen compound metabolism in wastewater treatment.
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.
基金supported by the Young Elite Scientists Sponsorship Program by China Association for Science and Technology (CAST) (No. YESS20160009)the National Natural Science Foundation of China (Nos. 31870023, 31571970 and 41506160)
文摘Quorum sensing(QS)is a regulatory system that regulates the behavior of microbial populations by sensing the concentration of signal molecules that are spontaneously produced and released by bacteria.The strategy of blocking the QS system and inhibiting the production of virulence factors is termed as quorum quenching(QQ).This strategy attenuates virulence without killing the pathogens,thereby weakening the selective pressure on pathogens and postponing the evolution of QQ-mediated drug resistance.In recent years,there have been significant theoretical and practical developments in the field of QS and QQ.In particular,with the development and utilization of marine resources,more and more marine microbial species have been found to be regulated by these two mechanisms,further promoting the research progress of QS and QQ.In this review,we described the diversity of QS signals and QS-related regulatory systems,and then introduced mechanisms related to QS interference,with particular emphasis on the description of natural QQ enzymes and chemicals acting as QS inhibitors.Finally,the exploitation of quorum sensing quenchers and the practical application of QQ were introduced,while some QQ strategies were proposed as promising tools in different fields such as medicine,aquaculture,agriculture and biological pollution prevention areas.
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 the Major State Science and Technology Water Projects (No. 2013ZX07202010)
文摘N-dodecanoyl homoserine lactone（C（12）-HSL）was detected in the supernatant of an anammox granular sludge reactor（AGSR）.C（12）-HSL could enhance the specific anammox activity of anammox biomass.Adding C（12）-HSL-containing AGSR supernatant into the continuously stirred tank reactors reduced the start-up time of the anammox process from80 to 66 days.Moreover,the nitrogen loading rate was also enhanced to 1.6 times that of the control reactor.AHLs could increase the secretion of extracellular polymeric substances and anammox obtained better enrichment with the addition of AHLs-containing AGSR supernatant.Denaturing gradient gel electrophoresis analysis further revealed that AHLs played a role in mediating microbial community parameters.In conclusion,adding AHL-containing supernatant could be an effective and economical way to accelerate the start-up of anammox.
基金the National Natural Science Foundation of China (Grant No. 30570020)Natural Science Foundation of Hubei Province of China (Grant No. 2004ABA120)
文摘The aiiA gene from Bacillus thuringiensis was cloned into the Pseudomonas/E. coli shuttle vector and transformed into Pseudomonas aeruginosa strain PAO1. Western blotting showed that the AiiA protein was expressed in PAO1. After induction by IPTG for 6 h and 18 h, expression of the aiiA gene in PAO1 completely degraded the quorum sensing autoinducers N-acylhomoserine lactones (AHLs): N-oxododecanoyl-L-homoserine lactone (OdDHL) and N-butyryl-L-homoserine lactone (BHL). The re- duced amount of AHLs in PAO1 was also correlated with decreased expression and production of several virulence factors such as elastase and pyocyanin. AiiA expression also influenced bacterial swarming motility. Most importantly, our studies indicated that aiiA played significant roles in P. aeruginosa biofilm formation and dispersion, as observed by the differences of the biofilm formation on liquid and solid surfaces, and biofilm structures under a scanning electron microscope.
基金supported by the National Natural Science Foundation of China(Nos.41371266,41501250,21377157)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB15030101)
文摘N-acyl-homoserine lactones（AHLs） serve as quorum-sensing signals, which control a number of bacterial processes in many proteobacteria. Here we report the effects of exogenous short-chain AHL on the denitrifying process of Paracoccus denitrificans, which are capable of aerobic and anaerobic growth by utilizing nitrate. The denitrification activity of these cells was monitored by measuring denitrification products（including nitrate, nitrite,and nitrous oxide）, and the individual messenger ribonucleic acid（m RNA） levels of nitrate,nitrite, nitric oxide and nitrous oxide reductases. The results indicated that 2 μmol/L C6-homoserine lactone（HSL） has little effect on cell density under either anaerobic or aerobic culture conditions, and the nitrate reduction activity appeared slightly affected by N-hexanoyl-DL-homoserine lactone（C6-HSL）. However, exogenous C6-HSL significantly affected the transcription of nitrite reductase and nitric oxide reductase genes in P.denitrificans regardless of the presence of oxygen, and N2O accumulation activity in P. denitrificans was suppressed by C6-HSL under aerobic condition. In contrast, exogenous C6-HSL stimulated the production of N2O under anaerobic condition, suggesting that the regulation of denitrification by quorum sensing may be important in N2O release.
基金the "Centre National pour la Recherche Scientifique et Technique" (CNRST) "Agence Nationale des Plantes Medicinales et Aromatiques" (ANPMA) for their funding supports
文摘The aim of this study was to investigate antibacterial activity of Origanum compactum essential oils collected at three phenological stages on Escherichia coli and Bacillus subtilis. The antibacterial activity was evaluated using the agar-well diffusion assay. The MIC and MBC values were determined using the micro-dilution assay. The investigation of the antibacterial action was carried out by the evaluation of the effect of O. compactum essential oils on the antibacterial kinetic growth, the integrity of cell membrane and permeability of the cell membrane. The anti-quorum sensing activity was tested by the inhibition of the biofilm formation. The findings of this study showed that O. compactum essential oil has potent antibacterial activities against E. coli and B. subtilis. The lowest inhibition value against B. subtilis was obtained with O. compactum essential oil at the post-flowering stage (MIC=MBC=0.0312%(v/v)). The antibacterial mechanisms of O. compactum essential oils are related to the disturbing of the cell membrane integrity and the increasing of the membrane permeability, which leads to the leakage of genetic materials (DNA and RNA). Moreover, O. compactum essential oils inhibited the formation of the biofilms, a phenotype that has been known to be quorum sensing regulated.
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 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.
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.
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.
