To assess uncertainty of determination of MC-LR in environmental samples by solid phase extraction- ultra performance liquid chromatography- tandem mass spectrometry,the sources of the uncertainty were evaluated first...To assess uncertainty of determination of MC-LR in environmental samples by solid phase extraction- ultra performance liquid chromatography- tandem mass spectrometry,the sources of the uncertainty were evaluated firstly,and the expanded uncertainty was calculated finally.The results show that when MC-LR concentration in the water samples was 0.50 μg/L,the expanded uncertainty was 0.00628 μg/L(k=2).展开更多
Aeration induced turbulence was considered as an important measure to control the occurrence of cyanobacterial blooms in many lakes.Different aeration intensities were set for the culture of Microcystis aeruginosa bas...Aeration induced turbulence was considered as an important measure to control the occurrence of cyanobacterial blooms in many lakes.Different aeration intensities were set for the culture of Microcystis aeruginosa based on the formation of Microcystis colony at high iron concentrations.The turbulent dissipation rate was calculated using a computational fluid dynamics(CFD)model to evaluate the intensity of turbulence.The effects of turbulence on the formation of Microcystis colony and the release of microcystin were analyzed.Results show that turbulence produced by aeration promoted the growth of Microcystis compared to that in stagnant water.Low intensity turbulence(4×10^(-8)-1×10^(-7) m2/s3)promoted the formation of Microcystis colonies,but high intensity turbulence(1.28×10^(-6)-1.8×10^(-5) m^(2)/s^(3))did not.The increase in the number of cells per colony was slower than that in total biomass,indicating that the low intensity turbulence induced colony formation via cell division,while the high level turbulence disaggregated colonies formed by both cell division and cell adhesion.Low aeration intensity induced more production of reactive oxygen species(ROS)and malondialdehyde(MDA)in the cells of Microcystis than those in high aeration intensity.In addition,the content of microcystin(MC)-LR in the cells was positively correlated with turbulence intensity,showing that turbulence affected not only the growth and aggregation of Microcystis colonies but also their toxin production.These findings provide a better understanding of the cyanobacterial bloom formation mechanisms and help to propose feasible methods to prevent the formation of Microcystis colonies in a natural environment.展开更多
Using the Widdel medium with extracted microcystin(MC)as the sole carbon and nitrogen sources,the MC-degrading bacteria community S_6 was enriched from the sediment of Litopenaeus vannamei pond,and a novel MC-degradin...Using the Widdel medium with extracted microcystin(MC)as the sole carbon and nitrogen sources,the MC-degrading bacteria community S_6 was enriched from the sediment of Litopenaeus vannamei pond,and a novel MC-degrading bacteria strain was isolated from S_6.According to 16S rDNA gene sequence and biochemical characteristics,the isolated strain was identified and named Nitratireductor aquimarinus D_(1).Fulvic acid(FA),as a widely existing photosensitizer involved in MC photodegradation,coexists with MC-degrading bacteria in natural water.The synergistic effects of N.aquimarinus D_(1) and FA on MC degradation were evaluated via comparing the degradation rate of MC induced by N.aquimarinus D_(1) and FA alone and in combination under natural light conditions.Compared with the control group,the supplementation of N.aquimarinus D_(1) and FA alone or in combination could significantly increase the degradation rate of MC(P<0.05).In the first 36 h,the degradation effect of FA on MC was better than that of N.aquimarinus D_(1),but the degradation effect was opposite at 48 h.N.aquimarinus D_(1) and FA did not show synergistic effect on MC degradation until 48 h.In the application of N.aquimarinus and FA to degrade MC in aquaculture pond,there might be a time-lag effect in the synergistic degradation.展开更多
Microcystinase(MlrA)is a key endopeptidase that catalyzes microcystin degradation without generating harmful byproduct.However,the application of MlrA in the field is primarily impeded by its limited productivity and ...Microcystinase(MlrA)is a key endopeptidase that catalyzes microcystin degradation without generating harmful byproduct.However,the application of MlrA in the field is primarily impeded by its limited productivity and short lifespan.Therefore,the MlrA's function was studied by modelling its structure,which subsequently increased its heterologous expression and high-temperature stability.Results demonstrate that after the irregular sequence at the C-terminus of MlrA was removed,enzyme solubility was significantly decreased.In addition,three fusion tags,namely maltose-binding protein,glutathione S-transferase(GST),and N-utilization substance A(NusA)were used to enhance the overexpression of soluble recombinant MlrA,among which NusA-MlrA exhibited the highest solubility.Moreover,NusA-MlrA was active in pH 4-10 at 20-80℃;even at 80℃,approximately 35.8%of fusion protein remained active.NusA-MlrA retained 89%of MlrA's activity even after 7 d of storage at 50℃;and on day 7,the protein retained>90%of its activity at pH 7.Finally,a stable,soluble,and long-lasting heterologous MlrA was successfully constructed that could eliminate microcystins in Escherichia coli C43(DE3).This study enriched the comprehension of MlrA's structure and enzymatic properties,by particularly addressing the endopeptidase's low expression and short lifespan,which improved its suitability for future applications.展开更多
[Objective] The relationship between three isomers of microcystins and environmental factors were studied in the fields.[Method] Three isomers of microcystins （MC-LR,RR and YR） from water of five sampling spots in a...[Objective] The relationship between three isomers of microcystins and environmental factors were studied in the fields.[Method] Three isomers of microcystins （MC-LR,RR and YR） from water of five sampling spots in a northern reservoir were observed for one year with High Performance Liquid Chromatography analytical method in order to study the relationship between three isomers and environmental factors.[Result] The three isomers of microcystins showed positive correlation with chlorophyll a;LR and YR isomers all had significant linear positive correlations with the water temperature,but the RR isomer showed no significant correlation with the water temperature;LR and YR isomers had relatively significantly correlativities with the contents of total nitrogen,nitrate nitrogen and organic nitrogen,while the RR isomer only showed a significant negative correlation with the content of nitrate nitrogen;LR and RR isomers both showed significant positive correlations with the contents of total phosphorus and organic phosphorus,while the phosphorus hardly affected the YR isomer and showed no evident correlation.[Conclusion] The relationship between three isomers of microcystins and environmental factors such as chlorophyll a,water temperature,nitrogen,phosphorus were studied and investigated the reasons,which might offered a reference for controlling the growth of blue algae in water and toxin synthesis.展开更多
文摘To assess uncertainty of determination of MC-LR in environmental samples by solid phase extraction- ultra performance liquid chromatography- tandem mass spectrometry,the sources of the uncertainty were evaluated firstly,and the expanded uncertainty was calculated finally.The results show that when MC-LR concentration in the water samples was 0.50 μg/L,the expanded uncertainty was 0.00628 μg/L(k=2).
基金Supported by the National Natural Science Foundation of China(No.51979236)。
文摘Aeration induced turbulence was considered as an important measure to control the occurrence of cyanobacterial blooms in many lakes.Different aeration intensities were set for the culture of Microcystis aeruginosa based on the formation of Microcystis colony at high iron concentrations.The turbulent dissipation rate was calculated using a computational fluid dynamics(CFD)model to evaluate the intensity of turbulence.The effects of turbulence on the formation of Microcystis colony and the release of microcystin were analyzed.Results show that turbulence produced by aeration promoted the growth of Microcystis compared to that in stagnant water.Low intensity turbulence(4×10^(-8)-1×10^(-7) m2/s3)promoted the formation of Microcystis colonies,but high intensity turbulence(1.28×10^(-6)-1.8×10^(-5) m^(2)/s^(3))did not.The increase in the number of cells per colony was slower than that in total biomass,indicating that the low intensity turbulence induced colony formation via cell division,while the high level turbulence disaggregated colonies formed by both cell division and cell adhesion.Low aeration intensity induced more production of reactive oxygen species(ROS)and malondialdehyde(MDA)in the cells of Microcystis than those in high aeration intensity.In addition,the content of microcystin(MC)-LR in the cells was positively correlated with turbulence intensity,showing that turbulence affected not only the growth and aggregation of Microcystis colonies but also their toxin production.These findings provide a better understanding of the cyanobacterial bloom formation mechanisms and help to propose feasible methods to prevent the formation of Microcystis colonies in a natural environment.
基金Supported by the National Natural Science Foundation of China(Nos.32172978,31772857)the Natural Science Foundation of Tianjin(No.22JCYBJC00430)+2 种基金the Tianjin Science and Technology Planning Project(No.22ZYCGSN00050)the Fundamental Research Funds of Tianjin Universities(Nos.2020ZD06,2021KJ110)the Gansu Science and Technology Project(Nos.21CX6NP223,2023ZZ1NC006)。
文摘Using the Widdel medium with extracted microcystin(MC)as the sole carbon and nitrogen sources,the MC-degrading bacteria community S_6 was enriched from the sediment of Litopenaeus vannamei pond,and a novel MC-degrading bacteria strain was isolated from S_6.According to 16S rDNA gene sequence and biochemical characteristics,the isolated strain was identified and named Nitratireductor aquimarinus D_(1).Fulvic acid(FA),as a widely existing photosensitizer involved in MC photodegradation,coexists with MC-degrading bacteria in natural water.The synergistic effects of N.aquimarinus D_(1) and FA on MC degradation were evaluated via comparing the degradation rate of MC induced by N.aquimarinus D_(1) and FA alone and in combination under natural light conditions.Compared with the control group,the supplementation of N.aquimarinus D_(1) and FA alone or in combination could significantly increase the degradation rate of MC(P<0.05).In the first 36 h,the degradation effect of FA on MC was better than that of N.aquimarinus D_(1),but the degradation effect was opposite at 48 h.N.aquimarinus D_(1) and FA did not show synergistic effect on MC degradation until 48 h.In the application of N.aquimarinus and FA to degrade MC in aquaculture pond,there might be a time-lag effect in the synergistic degradation.
基金Supported by the National Key R&D Program of China(No.2018YFA0903100)the National Natural Science Foundation of China(No.32071601)。
文摘Microcystinase(MlrA)is a key endopeptidase that catalyzes microcystin degradation without generating harmful byproduct.However,the application of MlrA in the field is primarily impeded by its limited productivity and short lifespan.Therefore,the MlrA's function was studied by modelling its structure,which subsequently increased its heterologous expression and high-temperature stability.Results demonstrate that after the irregular sequence at the C-terminus of MlrA was removed,enzyme solubility was significantly decreased.In addition,three fusion tags,namely maltose-binding protein,glutathione S-transferase(GST),and N-utilization substance A(NusA)were used to enhance the overexpression of soluble recombinant MlrA,among which NusA-MlrA exhibited the highest solubility.Moreover,NusA-MlrA was active in pH 4-10 at 20-80℃;even at 80℃,approximately 35.8%of fusion protein remained active.NusA-MlrA retained 89%of MlrA's activity even after 7 d of storage at 50℃;and on day 7,the protein retained>90%of its activity at pH 7.Finally,a stable,soluble,and long-lasting heterologous MlrA was successfully constructed that could eliminate microcystins in Escherichia coli C43(DE3).This study enriched the comprehension of MlrA's structure and enzymatic properties,by particularly addressing the endopeptidase's low expression and short lifespan,which improved its suitability for future applications.
基金Supported by Technical Innovation Project of Ministry of Water Conservancy(SCX2002-04)National Nature Science Foundation of China(50579015)~~
文摘[Objective] The relationship between three isomers of microcystins and environmental factors were studied in the fields.[Method] Three isomers of microcystins （MC-LR,RR and YR） from water of five sampling spots in a northern reservoir were observed for one year with High Performance Liquid Chromatography analytical method in order to study the relationship between three isomers and environmental factors.[Result] The three isomers of microcystins showed positive correlation with chlorophyll a;LR and YR isomers all had significant linear positive correlations with the water temperature,but the RR isomer showed no significant correlation with the water temperature;LR and YR isomers had relatively significantly correlativities with the contents of total nitrogen,nitrate nitrogen and organic nitrogen,while the RR isomer only showed a significant negative correlation with the content of nitrate nitrogen;LR and RR isomers both showed significant positive correlations with the contents of total phosphorus and organic phosphorus,while the phosphorus hardly affected the YR isomer and showed no evident correlation.[Conclusion] The relationship between three isomers of microcystins and environmental factors such as chlorophyll a,water temperature,nitrogen,phosphorus were studied and investigated the reasons,which might offered a reference for controlling the growth of blue algae in water and toxin synthesis.
