Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety.However,the suppression efficiency is affected inevitably by the extracellular polymeric sub...Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety.However,the suppression efficiency is affected inevitably by the extracellular polymeric substances(EPS)produced by cyanobacteria,and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce.For the study,two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa.Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae,especially in stabilizing the metabolism and photosynthetic activity of algal cells.The aggregation rate of algal cells increased with the increase of EPS secretion,which alleviated the stress of allelopathy.Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals,and the EPS-allelochemicals complex were formed by chemical bonding.This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.展开更多
Dolichospermum,a typical model filamentous of cyanobacteria,has the potential to cause severely bloom.Extracellular polymeric substances(EPSs)are considered to influence the aggregation of the algae,and temperature is...Dolichospermum,a typical model filamentous of cyanobacteria,has the potential to cause severely bloom.Extracellular polymeric substances(EPSs)are considered to influence the aggregation of the algae,and temperature is a significant factor affecting EPSs secretion.However,the mechanism of how EPSs affects the aggregation of Dolichospermum is still unclear because the structure and composition of EPSs are complex.In this study,the effects of EPSs on the aggregation of Dolichospermum during the rise of temperature(7-37℃)were determined.The results showed that the concentration of extracellular polysaccharides and proteins changed significantly with increasing temperature(P<0.01).Firstly,during the increasing temperature,the polysaccharide content of EPSs increased from 20.34 to 54.64 mg/L,and the polysaccharides in the soluble EPS(S-EPS)layer changed significantly.The protein content reached maximum value at 21℃(14.52 mg/L)and varied significantly in S-EPS and loosely bound EPS(LB-EPS).In the EPSs matrix,humus substances and protein were main components of S-EPS and LB-EPS,and protein was the main component of tightly bound EPS(TB-EPS).Secondly,the cell density of Dolichospermum increased during the temperature rise while the aggregation ratio decreased.Moreover,zeta potential and surface thermodynamic analysis of Dolichospermum revealed that the interfacial free energy and electrostatic repulsion increased gradually with increasing temperature,which further reduced the aggregation of Dolichospermum.Finally,principal component analysis(PCA)analysis showed the aggregation of Dolichospermum was directly related to the changes of protein in EPSs(especially S-EPS and LB-EPS)and zeta potential,and polysaccharides in EPSs inhibited the aggregation of Dolichospermum.Based on these results,it was illustrated that the composition and concentration of EPSs affected the cell surface properties of Dolichospermum with the change of temperature and thus affected the aggregation of Dolichospermum.展开更多
Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not...Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established.Six cyanobacterial Microcystis strains(including both unicellular and colonial ones)were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances(EPS)on colony or aggregate formation.Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies of Microcystis to produce excess EPS enhancing colony formation.Tightly bound EPS(T-EPS)was responsible for colony formation,which approximately accounted for 50%of the total amount of EPS.Five fluorescent components(protein-,tryptophan-,and tyrosine-like components and two humic-like components)were found in the T-EPS,although the amounts of these components varied with strains.Importantly,colonial strains contained much higher tyrosine-like substances than unicellular ones.We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS(e.g.,proteins or polysaccharides)for colony formation.Our findings identified key physiological traits and chemical components of EPS for colony formation in Microcystis,which can contribute to a better understanding on the formation of Microcystis blooms.展开更多
Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production wh...Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production which reduced arsenic(As)availability.The main component of EPS secreted by iron-oxidizing bacteria(Ochrobactrum EEELCW01)was composed of polysaccharides(150.76-165.33 mg/g DW)followed by considerably smaller amounts of proteins(12.98–16.12 mg/g DW).Low concentrations of As(100 or 500μmol/L)promoted the amount of EPS secretion.FTIR results showed that EPS was composed of polysaccharides,proteins,and a miniscule amount of nucleic acids.The functional groups including-COOH,-OH,-NH,-C=O,and-C-O played an important role in the adsorption of As.XPS results showed that As was bound to EPS in the form of As3+.With increasing As concentration,the proportion of As3+adsorbed on EPS increased.Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp.At day 8,the minerals were composed of goethite,galena,and siderite.With the increasing mineralization time,the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite(FeCO_(3))or goethite(α-FeOOH),and the specific surface area and active sites of minerals were reduced.It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals.This study is potential to understand the biomineralizationmechanism of iron-oxidizing bacteria and As remediation in the environment.展开更多
Antibiotics,the most frequently prescribed drugs,have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment syst...Antibiotics,the most frequently prescribed drugs,have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems,a hotspot where the occurrence and transformation of antibiotic resistance take place.Extracellular polymeric substances(EPS),biopolymers secreted via microbial activity,play an important role in cell adhesion,nutrient retention,and toxicity resistance.However,the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear.This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS,highlights the critical role of EPS in antibiotics removal,evaluates their defense performances under different antibiotics exposures,and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics.Next,interactions between microbial EPS and antibiotic resistance genes are analyzed.Future perspectives,especially the engineering application of microbial EPS for antibiotics toxicity detection and defense,are also emphatically stressed.展开更多
Aluminum ions produced by aluminum mining,electrolytic industry and aluminum-based coagulants can enter wastewater treatment plants and interact with activated sludge.They can subsequently contribute to the removal of...Aluminum ions produced by aluminum mining,electrolytic industry and aluminum-based coagulants can enter wastewater treatment plants and interact with activated sludge.They can subsequently contribute to the removal of suspended solids and affect activated sludge flocculation,as well as nitrogen and phosphorus removal.In this study,the effects of Al^3+on pollutant removal,sludge flocculation and the composition and structure of extracellular polymeric substances(EPS)were investigated under anaerobic,anoxic and oxic conditions.Results demonstrated that the highest chemical oxygen demand(COD)and total nitrogen(TN)removal efficiencies were detected for an Al^3+concentration of 10 mg/L.In addition,the maximal dehydrogenase activity and sludge flocculation were also observed at this level of Al^3+.The highest removal efficiency of total phosphorus(TP)was achieved at an Ar+concentration of30 mg/L.The flocculability of sludge in the anoxic zone was consistently higher than that in the anaerobic and oxic zones.The addition of Al^3+promoted the secretion of EPS.Tryptophan-like fluorescence peaks were detected in each EPS layer in the absence of Al^3+.At the Al^3+concentration of 10 mg/L,fulvic acid and tryptophan fluorescence peaks began to appear while the majority of protein species and the highest microbial activity were also detected.Low Al^3+concentrations(<10 mg/L)could promote the removal efficiencies of COD and TN,yet excessive Al^3+levels(>10 mg/L)weakened microbial activity.Higher Al^3+concentrations(>30 mg/L)also inhibited the release of phosphorus in the anaerobic zone by reacting with PO4^3-.展开更多
Extracellular polymeric substances(EPS)in activated sludge from wastewater treatment plants(WWTPs)could affect interactions between nanoparticles and alter their migration behavior.The influence mechanisms of silver n...Extracellular polymeric substances(EPS)in activated sludge from wastewater treatment plants(WWTPs)could affect interactions between nanoparticles and alter their migration behavior.The influence mechanisms of silver nanoparticles(Ag NPs)and silver sulfide nanoparticles(Ag_(2)S NPs)aggregated by active EPS sludge were studied in monovalent or divalent cation solutions.The aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek(DLVO)theory.The counterions aggravated the aggregation of both NPs,and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive force.Through extended DLVO(EDLVO)model analysis,in NaNO3 and low-concentration Ca(NO_(3))_(2)(<10 mmol/L)solutions,EPS could alleviate the aggregation behaviors of Cit-Ag NPs and Ag_(2)S NPs due to the enhancement of steric repulsive forces.At high concentrations of Ca(NO_(3))_(2)(10‒100 mmol/L),exopolysaccharide macromolecules could promote the aggregation of Cit-Ag NPs and Ag_(2)S NPs by interparticle bridging.As the final transformation form of Ag NPs in water environments,Ag_(2)S NPs had better stability,possibly due to their small van der Waals forces and their strong steric repulsive forces.It is essential to elucidate the surface mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.展开更多
Extracellular polymeric substances(EPS),produced by microorganisms,establish the functional and structural integrity of microbial biofilms.In biological wastewater treatments,the transformation of pollutants largely r...Extracellular polymeric substances(EPS),produced by microorganisms,establish the functional and structural integrity of microbial biofilms.In biological wastewater treatments,the transformation of pollutants largely relies on microbial electron transfer.As a bridge between the microbial cytomembrane/cytoderm and terminal electron acceptors,the role of EPS in microbial electron transfer cannot be ignored.However,due to the complexity of its composition,the in situ function of EPS in extracellular electron transfer is still unclear.In this work,we constructed an epsH gene knockout mutant of Methylomonas sp.LW13 with significantly reduced EPS formation.The content of protein and polysaccharide,two major components of EPS,of theΔepsH mutant and wild-type during different growth stages were compared.The redox signal and in situ Au reduction of theΔepsH mutant were obviously stronger than those of the wild-type,which suggested that EPS can hinder extracellular electron transfer in this system.Although redox activity was detected in EPS,high faradaic resistance of EPS was demonstrated.Our results enlighten the in situ role of EPS in extracellular electron transfer with the help of molecular manipulations and provide insights into how to regulate the microbial process of wastewater treatments.展开更多
Biochemical, chemical, and mechanical, techniques have been employed to enhance soil resilience for decades. While the use of mechanical techniques requires transporting huge amounts of soil materials, the cement used...Biochemical, chemical, and mechanical, techniques have been employed to enhance soil resilience for decades. While the use of mechanical techniques requires transporting huge amounts of soil materials, the cement used in chemical techniques may lead to increase atmospheric carbon dioxide. Numerous studies indicate that biochemical techniques may be less expensive, cost effective, and environmentally friendly. Biopolymers and enzymes derived from microorganisms have been suggested as biological enhancers in strengthening and fortifying soils used for earthen structures. Lime and other treatment techniques used as biobased materials have been shown to be less effective for stabilizing soils. Here, we review biochemical processes and techniques involved in the interactions of soil enzymes, microorganisms, microbial extracellular polymeric substances, and other biopolymers with soil particles, and the challenges and strategies of their use as biobased materials for stabilizing soils. This review provides their impacts on various soil properties and the growth potentials of agricultural crops. .展开更多
Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of ph...Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances(EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs(PFS) by Shewanella oneidensis MR-1(S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite.EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(Ⅲ). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(Ⅱ) was 107.9, 111.0,and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail.展开更多
Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence e...Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence excitation-emission matrix(3D-EEM)spectroscopy and zeta potentiometer were used to characterize the loosely bound EPS(LB-EP S)and tightly bound EPS(TB-EPS)from two dominant Microcystis morphospecies from Taihu Lake(China)at different light intensities.Physiochemical analysis showed that the growth and TB-EPS or bEPS contents in Microcystis aeruginosa were higher than those in Microcystisfl os-aquae at each light intensity.The 3D-EEM contour demonstrated that the intensities of peak B(tryptophan-like substances)in the TB-EPS from M.aeruginosa were stronger than those from M.flosaquae when the light intensity was higher than 10μE/(m^(2)·s).Zeta potential analysis showed that the absolute values of the zeta potential of TB-EPS in the two species both increased with rising light intensity,except those of TB-EPS in M.aeruginosa at 105μE/(m^(2)·s).Moreover,the absolute values of the zeta potential of M.aeruginosa were higher than tho se of M.flos-aquae at each light intensity.All these re sults indicated that M.aeruginosa may more quickly proliferate than M.flos-aquae through increased negative charges,bEPS contents.growth.and tryptophan-like substance contents at certain light intensities.展开更多
In this study,nitrogen removal performance of the denitrifying ammonium oxidation(DAO)process was investigated when treating sulfamethoxazole(SMX)-laden secondary wastewater effluent.The influent SMX concentration sho...In this study,nitrogen removal performance of the denitrifying ammonium oxidation(DAO)process was investigated when treating sulfamethoxazole(SMX)-laden secondary wastewater effluent.The influent SMX concentration showed negligible effect on efficiencies for removal of nitrate and COD.However,the ammonium ions removal rate was moderately reduced,when the influent SMX concentration in wastewater reached 6 mg/L.Total nitrogen removal efficiency remained as high as 76.77%towards the day 158 at the end of experiment.Candidatus_Brocadia and Candidatus_Kuenenia were the functional anammox strains.The unclassified_f__Rhodobacteraceae sp.was predominant heterotrophic denitrifying strain in the studied reactor.The concentrations of soluble extracellular polymeric substances in sludge obviously increased from 16.76 mg/g VSS to 32.31 mg/g VSS,which might protect the nitrogen removal strains from high-concentration SMX.This result provides a theoretical and technical foundation for the application of denitrifying ammonium oxidation process in treating sulfamethoxazole-laden secondary wastewater effluent.展开更多
Biofilms are being engineered in-vitro to produce numerous commodities like biofertilizers, pharmaceuticals, biofuels and electricity, the efficacies of which rely on the biochemicals secreted by the biofilms i.e. ext...Biofilms are being engineered in-vitro to produce numerous commodities like biofertilizers, pharmaceuticals, biofuels and electricity, the efficacies of which rely on the biochemicals secreted by the biofilms i.e. extracellular polymeric substances (EPS). It has been shown that once EPS-biochemicals of developed biofilms are applied to an ecosystem, they can restore degraded complex ecosystem networks for improved ecosystem functioning and sustainability. Identification of the EPS biochemicals and understanding their contributions to the network interactions in particular, are at initial stage. In the present study, using Aspergillus niger, Nostoc sp., and gram (-) Stenotrophomonas maltophilia & gram (+) Bacillus subtilis as test fungal (F), cyanobacterial (C), and bacterial (B) counterparts, respectively we analyzed morphology and biochemical parameters of fungal-bacterial (FBBs), fungal-cyanobacterial (FCBs), cyanobacterial-bacterial (CBBs), and fungal-cyanobacterial-bacterial biofilms (FCBBs). Results revealed that the FCBBs produced the highest concentrations of lipids, proteins, and polysaccharides whereas FBBs generated the highest diversity of biochemicals. Bacterial type (i.e. gram + or -) and microbial composition in the biofilm affected the biochemical production. Ecologically and industrially important diverse biochemicals which are used individually as medicines, bioremediating agents and industrial chemicals in human society with certain adverse and beneficial effects were detected in the biofilm-EPS. However, in the nature, simultaneous action of those diverse biochemicals applied as biofertilizers has already shown a huge potential to restore the entire agroecosystems degraded due to farmers’ detrimental practices. This striking difference in utilization of the biochemicals and their enhanced effect when they act simultaneously needs further investigations for their better applications.展开更多
[Objective] The aim was to study the influence factors of membrane fouling in A/O-MBR system,so as to control membrane fouling better,prolong the service life of membrane,further reduce the cost of water treatment and...[Objective] The aim was to study the influence factors of membrane fouling in A/O-MBR system,so as to control membrane fouling better,prolong the service life of membrane,further reduce the cost of water treatment and promote the popularization of membrane bioreactor(MBR) effectively.[Method] Based on small A/O-MBR device,an orthogonal test with three factors(including aeration intensity,pump-stop ratio and mixed liquor suspended solid) and three levels was designed to optimize three parameters,and the effects of factors on membrane fouling and their mechanisms were studied through single-factor analysis.[Result] The order of operation parameters affecting membrane fouling in A/O-MBR was aeration intensity>pump-stop ratio>mixed liquor suspended solid(MLSS),and the optimum operating parameters were composed of 1.6 m3/h of aeration intensity,4 500 mg/L of MLSS and 9:2 of pump-stop ratio.With the increase of running time,soluble microbial product(SMP) and extracellular polymeric substance(EPS) accumulated gradually in the reactor,and EPS accumulated more rapidly than SMP;meanwhile,membrane fouling was accelerated.Therefore,EPS was the priority factor for membrane fouling compared with SMP.In addition,membrane fouling was accelerated gradually with the increase of protein content in EPS,while the variation of polysaccharides content in EPS had no obvious effect on membrane fouling,so protein content in EPS was the main factor for membrane fouling.[Conclusion] The study could provide theoretical references for the choice of parameters,operation and running in practical engineering.展开更多
Surfaces submerged in seawater are colonized by various microorganisms,resulting in the formation of heterogenic marine biofilms.This work aims to evaluate the biofilm formation by Cobetia marina alex and doing a comp...Surfaces submerged in seawater are colonized by various microorganisms,resulting in the formation of heterogenic marine biofilms.This work aims to evaluate the biofilm formation by Cobetia marina alex and doing a comparative study between this promising strain with the two bacterial strains isolated previously from the Mediterranean seawater,Alexandria,Egypt.Three strains;Cobetia marina alex,Pseudoalteromonas sp.alex,and Pseudoalteromonas prydzensis alex were screened for biofilm formation using the crystal violet(CV)quantification method in a single culture.The values of biofilm formed were OD600=3.0,2.7,and 2.6,respectively leading to their selection for further evaluation.However,factors affecting biofilm formation by C.marina alex were investigated.Biofilm formation was evaluated in single and multispecies consortia.Synergistic and antagonistic interactions proved in this work lead to the belief that these bacteria have the capability to produce some interesting signal molecules N-acyl Homoserine Lactones(AHLs).展开更多
Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect protein...Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.展开更多
The wide application of CdSe quantum dots(QDs)increases its stress risk to sewage treatment systems.This study evaluated the response of nitrification performance,floc characteristics and microbial community of nitrif...The wide application of CdSe quantum dots(QDs)increases its stress risk to sewage treatment systems.This study evaluated the response of nitrification performance,floc characteristics and microbial community of nitrifying sludge under long-term exposure to CdSe QDs.Results showed CdSe QDs(≥1 mg/L)would decrease the activity of ammonia monooxygenase(AMO).Under the stress of 30 mg/L CdSe QDs,the activity of AMO was reduced by 66%,while the activities of hydroxylamine oxidase and nitrite oxidoreductase were enhanced by 19.1%and 26%,respectively.Thus,the final nitrification effects were not adversely affected,and the production rates of NO_(2)^(-)-N and NO_(3)^(-)-N were accelerated.Additionally,CdSe QDs improved biomass concentration in sludge and maintained the stability of sludge settleability.High throughput sequencing analysis showed that CdSe QDs evidently reduced the abundance and diversity of microbial community in nitrifying sludge.The abundances of amino acid metabolism and lipid metabolism were enriched.Moreover,CdSe QDs decreased the fluorescence intensity of tryptophan-like protein from 2,326 to 1,179 a.u.in loosely bound extracellular polymeric substances(EPSs)and from 3,792 to 3,117 a.u.in tightly bound EPSs.To relieve CdSe QD stress,the polysaccharide content increased from0.31 to 0.61 mg/g MLSS and intracellular antioxidant defense was activated.With CdSe QD level increasing to 30 mg/L,the total antioxygenic capacity and the activities of catalase were enhanced up to 411%and 143.2%,respectively.Thereby,CdSe QDs had little adverse effects on cell membrane integrity,microbial metabolism and the abundance of Nitrospirae.展开更多
The effect of nanoplastics(NPs)on nitrite oxidation bacteria(NOB)community in treating high-strength wastewater remains unclear,which seriously affects the stability of nitrogen removal process.In this study,highly ac...The effect of nanoplastics(NPs)on nitrite oxidation bacteria(NOB)community in treating high-strength wastewater remains unclear,which seriously affects the stability of nitrogen removal process.In this study,highly active nitrifying sludge was enriched and exposed to 50nm polystyrene NPs(PS-NPs)for short-term(1,100,500,and 1000 mg/L,1.5 hr)and long-term(1,10,100 mg/L,40 days)at high nitrite concentration.In contrast to previous studies,our results showed that the exposures to PS-NPs had little effect on nitrifying performances.After long-term exposure,the protein/polysaccharide ratios in extracellular polymeric substances(EPS)were positively correlated with PS-NPs concentrations(0.78–0.99).The produced reactive oxygen species(ROS)were gradually removed,and PS-NPs higher than 10 mg/L caused damage to membrane integrity.Long-term exposure for 40 days increased the community diversity and caused significant differences between the control and exposed communities.The control group were dominated by Nitrobacter and Exiguobacterium,while the exposure group was dominated by Bacillus,Mycobacterium,and Nitrospira.A noticeable shift in the NOB community from Nitrobacter(26.5%to 3.4%)to Nitrospira(1.61%to 14.27%)was observed.A KEGG analysis indicated a decrease in cell growth and death,cell motility and energy metabolism.It appeared that NOB could adapt to PS-NPs stress through enhanced secretion and removal of oxidative damage.Overall,this study provided new insights into the response mechanism of NOB to PS-NPs exposure.展开更多
Recently, the use of microalgae for bioremediation of pharmaceuticals(Ph As) has attracted increasing interest. However, most studies focused more on microalgae removal performance, its defensive response to the Ph As...Recently, the use of microalgae for bioremediation of pharmaceuticals(Ph As) has attracted increasing interest. However, most studies focused more on microalgae removal performance, its defensive response to the Ph As during wastewater treatment remains unexplored. Herein, microalgal three defensive systems have been investigated in synthetic wastewater, with six Ph As as the typical drug. Results show that Ph As could bind to EPS, and this action in turn could help to alleviate the direct toxicity of Ph As to microalgae. Subsequently, the physiological analyses revealed the increase of superoxide dismutase(SOD), catalase(CAT), and peroxidase(POD) activities, potentially reducing the oxidative stress induced by Ph As. Furthermore, the enzyme activities of cytochrome P450(CYP450) and glutathione-S-transferase(GST) were significantly upregulated after exposure to SMX, CIP and BPA, followed by a significant decrease in biodegradation rates after the addition of CYP450 inhibitors, suggesting that the biotransformation and detoxification of Ph As occurred. Meanwhile, molecular docking further revealed that CYP450 could bind with Ph As via hydrogen bond and hydrophobic interaction, which proved their abilities to be metabolized and form transformation products in microalgae. These findings provide an advancing understanding of microalgae technologies to improve the treatment of wastewater contaminated with Ph As.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.51979137,51779079,41931292)。
文摘Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety.However,the suppression efficiency is affected inevitably by the extracellular polymeric substances(EPS)produced by cyanobacteria,and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce.For the study,two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa.Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae,especially in stabilizing the metabolism and photosynthetic activity of algal cells.The aggregation rate of algal cells increased with the increase of EPS secretion,which alleviated the stress of allelopathy.Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals,and the EPS-allelochemicals complex were formed by chemical bonding.This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.
基金Supported by the National Natural Science Foundation of China(Nos.41877336,41907202,91951112,41773077)the China Postdoctoral Science Foundation(No.2019M651877)+2 种基金the Natural Science Foundation of Jiangsu Province(No.SBK2019043965)the Yancheng Fishery High Quality Development Project(No.YCSCYJ2021030)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_1581)。
文摘Dolichospermum,a typical model filamentous of cyanobacteria,has the potential to cause severely bloom.Extracellular polymeric substances(EPSs)are considered to influence the aggregation of the algae,and temperature is a significant factor affecting EPSs secretion.However,the mechanism of how EPSs affects the aggregation of Dolichospermum is still unclear because the structure and composition of EPSs are complex.In this study,the effects of EPSs on the aggregation of Dolichospermum during the rise of temperature(7-37℃)were determined.The results showed that the concentration of extracellular polysaccharides and proteins changed significantly with increasing temperature(P<0.01).Firstly,during the increasing temperature,the polysaccharide content of EPSs increased from 20.34 to 54.64 mg/L,and the polysaccharides in the soluble EPS(S-EPS)layer changed significantly.The protein content reached maximum value at 21℃(14.52 mg/L)and varied significantly in S-EPS and loosely bound EPS(LB-EPS).In the EPSs matrix,humus substances and protein were main components of S-EPS and LB-EPS,and protein was the main component of tightly bound EPS(TB-EPS).Secondly,the cell density of Dolichospermum increased during the temperature rise while the aggregation ratio decreased.Moreover,zeta potential and surface thermodynamic analysis of Dolichospermum revealed that the interfacial free energy and electrostatic repulsion increased gradually with increasing temperature,which further reduced the aggregation of Dolichospermum.Finally,principal component analysis(PCA)analysis showed the aggregation of Dolichospermum was directly related to the changes of protein in EPSs(especially S-EPS and LB-EPS)and zeta potential,and polysaccharides in EPSs inhibited the aggregation of Dolichospermum.Based on these results,it was illustrated that the composition and concentration of EPSs affected the cell surface properties of Dolichospermum with the change of temperature and thus affected the aggregation of Dolichospermum.
基金Supported by the National Natural Science Foundation of China(No.32071569)the Scientific Instruments and Equipment Development Project+2 种基金Chinese Academy of Sciences,2020(No.YJKYYQ20200048)the Fundamental Research Funds for the Central Universities(No.B210202010)the China Postdoctoral Foundation(No.2020M681472)。
文摘Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established.Six cyanobacterial Microcystis strains(including both unicellular and colonial ones)were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances(EPS)on colony or aggregate formation.Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies of Microcystis to produce excess EPS enhancing colony formation.Tightly bound EPS(T-EPS)was responsible for colony formation,which approximately accounted for 50%of the total amount of EPS.Five fluorescent components(protein-,tryptophan-,and tyrosine-like components and two humic-like components)were found in the T-EPS,although the amounts of these components varied with strains.Importantly,colonial strains contained much higher tyrosine-like substances than unicellular ones.We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS(e.g.,proteins or polysaccharides)for colony formation.Our findings identified key physiological traits and chemical components of EPS for colony formation in Microcystis,which can contribute to a better understanding on the formation of Microcystis blooms.
基金supported by the National Natural Science Foundation of China(No.42177392)the Dean’s Research Fund 2020/21(No.04626)of the Education University of Hong Kong.
文摘Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production which reduced arsenic(As)availability.The main component of EPS secreted by iron-oxidizing bacteria(Ochrobactrum EEELCW01)was composed of polysaccharides(150.76-165.33 mg/g DW)followed by considerably smaller amounts of proteins(12.98–16.12 mg/g DW).Low concentrations of As(100 or 500μmol/L)promoted the amount of EPS secretion.FTIR results showed that EPS was composed of polysaccharides,proteins,and a miniscule amount of nucleic acids.The functional groups including-COOH,-OH,-NH,-C=O,and-C-O played an important role in the adsorption of As.XPS results showed that As was bound to EPS in the form of As3+.With increasing As concentration,the proportion of As3+adsorbed on EPS increased.Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp.At day 8,the minerals were composed of goethite,galena,and siderite.With the increasing mineralization time,the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite(FeCO_(3))or goethite(α-FeOOH),and the specific surface area and active sites of minerals were reduced.It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals.This study is potential to understand the biomineralizationmechanism of iron-oxidizing bacteria and As remediation in the environment.
基金supported by the funding from the National Key Research and Development Program of China(2019YFC1803802)the National Natural Science Foundation of China(No.51878213)+1 种基金the State Key Laboratory of Urban Water Resource and Environment(No.2020TS01)the Heilongjiang Nature Science Foundation(YQ2020E022).
文摘Antibiotics,the most frequently prescribed drugs,have been widely applied to prevent or cure human and veterinary diseases and have undoubtedly led to massive releases into sewer networks and wastewater treatment systems,a hotspot where the occurrence and transformation of antibiotic resistance take place.Extracellular polymeric substances(EPS),biopolymers secreted via microbial activity,play an important role in cell adhesion,nutrient retention,and toxicity resistance.However,the potential roles of sludge EPS related to the resistance and removal of antibiotics are still unclear.This work summarizes the composition and physicochemical characteristics of state-of-the-art microbial EPS,highlights the critical role of EPS in antibiotics removal,evaluates their defense performances under different antibiotics exposures,and analyzes the typical factors that could affect the sorption and biotransformation behavior of antibiotics.Next,interactions between microbial EPS and antibiotic resistance genes are analyzed.Future perspectives,especially the engineering application of microbial EPS for antibiotics toxicity detection and defense,are also emphatically stressed.
基金This research was financially supported by the National Natural Science Foundation of China(Grant Nos.51678119 and 51808254)the Science and Technology Development Program of Jilin Province(Nos.20180201016SF and 20180101079JC)the Scientific Research Foundation from Education Department of Jilin Province(Nos.JJKH20180453KJ and JJKH20180454KJ).
文摘Aluminum ions produced by aluminum mining,electrolytic industry and aluminum-based coagulants can enter wastewater treatment plants and interact with activated sludge.They can subsequently contribute to the removal of suspended solids and affect activated sludge flocculation,as well as nitrogen and phosphorus removal.In this study,the effects of Al^3+on pollutant removal,sludge flocculation and the composition and structure of extracellular polymeric substances(EPS)were investigated under anaerobic,anoxic and oxic conditions.Results demonstrated that the highest chemical oxygen demand(COD)and total nitrogen(TN)removal efficiencies were detected for an Al^3+concentration of 10 mg/L.In addition,the maximal dehydrogenase activity and sludge flocculation were also observed at this level of Al^3+.The highest removal efficiency of total phosphorus(TP)was achieved at an Ar+concentration of30 mg/L.The flocculability of sludge in the anoxic zone was consistently higher than that in the anaerobic and oxic zones.The addition of Al^3+promoted the secretion of EPS.Tryptophan-like fluorescence peaks were detected in each EPS layer in the absence of Al^3+.At the Al^3+concentration of 10 mg/L,fulvic acid and tryptophan fluorescence peaks began to appear while the majority of protein species and the highest microbial activity were also detected.Low Al^3+concentrations(<10 mg/L)could promote the removal efficiencies of COD and TN,yet excessive Al^3+levels(>10 mg/L)weakened microbial activity.Higher Al^3+concentrations(>30 mg/L)also inhibited the release of phosphorus in the anaerobic zone by reacting with PO4^3-.
基金We sincerely thank the National Natural Science Foundation of China(No.51878092 and No.52070029)for their support.
文摘Extracellular polymeric substances(EPS)in activated sludge from wastewater treatment plants(WWTPs)could affect interactions between nanoparticles and alter their migration behavior.The influence mechanisms of silver nanoparticles(Ag NPs)and silver sulfide nanoparticles(Ag_(2)S NPs)aggregated by active EPS sludge were studied in monovalent or divalent cation solutions.The aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek(DLVO)theory.The counterions aggravated the aggregation of both NPs,and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive force.Through extended DLVO(EDLVO)model analysis,in NaNO3 and low-concentration Ca(NO_(3))_(2)(<10 mmol/L)solutions,EPS could alleviate the aggregation behaviors of Cit-Ag NPs and Ag_(2)S NPs due to the enhancement of steric repulsive forces.At high concentrations of Ca(NO_(3))_(2)(10‒100 mmol/L),exopolysaccharide macromolecules could promote the aggregation of Cit-Ag NPs and Ag_(2)S NPs by interparticle bridging.As the final transformation form of Ag NPs in water environments,Ag_(2)S NPs had better stability,possibly due to their small van der Waals forces and their strong steric repulsive forces.It is essential to elucidate the surface mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.
基金supported by the National Natural Science Foundation of China(Grants No.41907027,22025603 and 41471260)。
文摘Extracellular polymeric substances(EPS),produced by microorganisms,establish the functional and structural integrity of microbial biofilms.In biological wastewater treatments,the transformation of pollutants largely relies on microbial electron transfer.As a bridge between the microbial cytomembrane/cytoderm and terminal electron acceptors,the role of EPS in microbial electron transfer cannot be ignored.However,due to the complexity of its composition,the in situ function of EPS in extracellular electron transfer is still unclear.In this work,we constructed an epsH gene knockout mutant of Methylomonas sp.LW13 with significantly reduced EPS formation.The content of protein and polysaccharide,two major components of EPS,of theΔepsH mutant and wild-type during different growth stages were compared.The redox signal and in situ Au reduction of theΔepsH mutant were obviously stronger than those of the wild-type,which suggested that EPS can hinder extracellular electron transfer in this system.Although redox activity was detected in EPS,high faradaic resistance of EPS was demonstrated.Our results enlighten the in situ role of EPS in extracellular electron transfer with the help of molecular manipulations and provide insights into how to regulate the microbial process of wastewater treatments.
文摘Biochemical, chemical, and mechanical, techniques have been employed to enhance soil resilience for decades. While the use of mechanical techniques requires transporting huge amounts of soil materials, the cement used in chemical techniques may lead to increase atmospheric carbon dioxide. Numerous studies indicate that biochemical techniques may be less expensive, cost effective, and environmentally friendly. Biopolymers and enzymes derived from microorganisms have been suggested as biological enhancers in strengthening and fortifying soils used for earthen structures. Lime and other treatment techniques used as biobased materials have been shown to be less effective for stabilizing soils. Here, we review biochemical processes and techniques involved in the interactions of soil enzymes, microorganisms, microbial extracellular polymeric substances, and other biopolymers with soil particles, and the challenges and strategies of their use as biobased materials for stabilizing soils. This review provides their impacts on various soil properties and the growth potentials of agricultural crops. .
基金supported by the National Natural Science Foundation of China (No. 41673090)the Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control (No. 2017B030301012)the Local Innovation and Entrepreneurship Team Project of Guangdong Special Support Program (No. 2019BT02L218)。
文摘Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances(EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs(PFS) by Shewanella oneidensis MR-1(S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite.EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(Ⅲ). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(Ⅱ) was 107.9, 111.0,and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail.
基金Supported by the National Natural Science Foundation of China(No.31800457)the Natural Science Foundation of Hubei(No.2016CFB355)。
文摘Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence excitation-emission matrix(3D-EEM)spectroscopy and zeta potentiometer were used to characterize the loosely bound EPS(LB-EP S)and tightly bound EPS(TB-EPS)from two dominant Microcystis morphospecies from Taihu Lake(China)at different light intensities.Physiochemical analysis showed that the growth and TB-EPS or bEPS contents in Microcystis aeruginosa were higher than those in Microcystisfl os-aquae at each light intensity.The 3D-EEM contour demonstrated that the intensities of peak B(tryptophan-like substances)in the TB-EPS from M.aeruginosa were stronger than those from M.flosaquae when the light intensity was higher than 10μE/(m^(2)·s).Zeta potential analysis showed that the absolute values of the zeta potential of TB-EPS in the two species both increased with rising light intensity,except those of TB-EPS in M.aeruginosa at 105μE/(m^(2)·s).Moreover,the absolute values of the zeta potential of M.aeruginosa were higher than tho se of M.flos-aquae at each light intensity.All these re sults indicated that M.aeruginosa may more quickly proliferate than M.flos-aquae through increased negative charges,bEPS contents.growth.and tryptophan-like substance contents at certain light intensities.
基金This research was supported by the Natural Science Foundation of Shandong Province(ZR2019MEE038)the Fundamental Research Funds for the Central Universities(19CX02038A).
文摘In this study,nitrogen removal performance of the denitrifying ammonium oxidation(DAO)process was investigated when treating sulfamethoxazole(SMX)-laden secondary wastewater effluent.The influent SMX concentration showed negligible effect on efficiencies for removal of nitrate and COD.However,the ammonium ions removal rate was moderately reduced,when the influent SMX concentration in wastewater reached 6 mg/L.Total nitrogen removal efficiency remained as high as 76.77%towards the day 158 at the end of experiment.Candidatus_Brocadia and Candidatus_Kuenenia were the functional anammox strains.The unclassified_f__Rhodobacteraceae sp.was predominant heterotrophic denitrifying strain in the studied reactor.The concentrations of soluble extracellular polymeric substances in sludge obviously increased from 16.76 mg/g VSS to 32.31 mg/g VSS,which might protect the nitrogen removal strains from high-concentration SMX.This result provides a theoretical and technical foundation for the application of denitrifying ammonium oxidation process in treating sulfamethoxazole-laden secondary wastewater effluent.
文摘Biofilms are being engineered in-vitro to produce numerous commodities like biofertilizers, pharmaceuticals, biofuels and electricity, the efficacies of which rely on the biochemicals secreted by the biofilms i.e. extracellular polymeric substances (EPS). It has been shown that once EPS-biochemicals of developed biofilms are applied to an ecosystem, they can restore degraded complex ecosystem networks for improved ecosystem functioning and sustainability. Identification of the EPS biochemicals and understanding their contributions to the network interactions in particular, are at initial stage. In the present study, using Aspergillus niger, Nostoc sp., and gram (-) Stenotrophomonas maltophilia & gram (+) Bacillus subtilis as test fungal (F), cyanobacterial (C), and bacterial (B) counterparts, respectively we analyzed morphology and biochemical parameters of fungal-bacterial (FBBs), fungal-cyanobacterial (FCBs), cyanobacterial-bacterial (CBBs), and fungal-cyanobacterial-bacterial biofilms (FCBBs). Results revealed that the FCBBs produced the highest concentrations of lipids, proteins, and polysaccharides whereas FBBs generated the highest diversity of biochemicals. Bacterial type (i.e. gram + or -) and microbial composition in the biofilm affected the biochemical production. Ecologically and industrially important diverse biochemicals which are used individually as medicines, bioremediating agents and industrial chemicals in human society with certain adverse and beneficial effects were detected in the biofilm-EPS. However, in the nature, simultaneous action of those diverse biochemicals applied as biofertilizers has already shown a huge potential to restore the entire agroecosystems degraded due to farmers’ detrimental practices. This striking difference in utilization of the biochemicals and their enhanced effect when they act simultaneously needs further investigations for their better applications.
基金Supported by Science and Technology Key Project of Water Pollution Control and Management(2008ZX07314-003)
文摘[Objective] The aim was to study the influence factors of membrane fouling in A/O-MBR system,so as to control membrane fouling better,prolong the service life of membrane,further reduce the cost of water treatment and promote the popularization of membrane bioreactor(MBR) effectively.[Method] Based on small A/O-MBR device,an orthogonal test with three factors(including aeration intensity,pump-stop ratio and mixed liquor suspended solid) and three levels was designed to optimize three parameters,and the effects of factors on membrane fouling and their mechanisms were studied through single-factor analysis.[Result] The order of operation parameters affecting membrane fouling in A/O-MBR was aeration intensity>pump-stop ratio>mixed liquor suspended solid(MLSS),and the optimum operating parameters were composed of 1.6 m3/h of aeration intensity,4 500 mg/L of MLSS and 9:2 of pump-stop ratio.With the increase of running time,soluble microbial product(SMP) and extracellular polymeric substance(EPS) accumulated gradually in the reactor,and EPS accumulated more rapidly than SMP;meanwhile,membrane fouling was accelerated.Therefore,EPS was the priority factor for membrane fouling compared with SMP.In addition,membrane fouling was accelerated gradually with the increase of protein content in EPS,while the variation of polysaccharides content in EPS had no obvious effect on membrane fouling,so protein content in EPS was the main factor for membrane fouling.[Conclusion] The study could provide theoretical references for the choice of parameters,operation and running in practical engineering.
文摘Surfaces submerged in seawater are colonized by various microorganisms,resulting in the formation of heterogenic marine biofilms.This work aims to evaluate the biofilm formation by Cobetia marina alex and doing a comparative study between this promising strain with the two bacterial strains isolated previously from the Mediterranean seawater,Alexandria,Egypt.Three strains;Cobetia marina alex,Pseudoalteromonas sp.alex,and Pseudoalteromonas prydzensis alex were screened for biofilm formation using the crystal violet(CV)quantification method in a single culture.The values of biofilm formed were OD600=3.0,2.7,and 2.6,respectively leading to their selection for further evaluation.However,factors affecting biofilm formation by C.marina alex were investigated.Biofilm formation was evaluated in single and multispecies consortia.Synergistic and antagonistic interactions proved in this work lead to the belief that these bacteria have the capability to produce some interesting signal molecules N-acyl Homoserine Lactones(AHLs).
基金National Natural Science Foundations of China(Nos.21477018,21007010)Hunan Province Ministry of Transportation Scientific Research Projects,China(Nos.200908,201105)Ministry of Transport Science and Technology Program,China(No.2010353343290)
文摘Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.
基金supported by the Special Scientific Research Program of Shaanxi Provincial Education Department (No.21JK0716)the Natural Science Basic Research Project of Shaanxi Province (No.2022JM-217)the National Natural Science Foundation of China (No.51878537)。
文摘The wide application of CdSe quantum dots(QDs)increases its stress risk to sewage treatment systems.This study evaluated the response of nitrification performance,floc characteristics and microbial community of nitrifying sludge under long-term exposure to CdSe QDs.Results showed CdSe QDs(≥1 mg/L)would decrease the activity of ammonia monooxygenase(AMO).Under the stress of 30 mg/L CdSe QDs,the activity of AMO was reduced by 66%,while the activities of hydroxylamine oxidase and nitrite oxidoreductase were enhanced by 19.1%and 26%,respectively.Thus,the final nitrification effects were not adversely affected,and the production rates of NO_(2)^(-)-N and NO_(3)^(-)-N were accelerated.Additionally,CdSe QDs improved biomass concentration in sludge and maintained the stability of sludge settleability.High throughput sequencing analysis showed that CdSe QDs evidently reduced the abundance and diversity of microbial community in nitrifying sludge.The abundances of amino acid metabolism and lipid metabolism were enriched.Moreover,CdSe QDs decreased the fluorescence intensity of tryptophan-like protein from 2,326 to 1,179 a.u.in loosely bound extracellular polymeric substances(EPSs)and from 3,792 to 3,117 a.u.in tightly bound EPSs.To relieve CdSe QD stress,the polysaccharide content increased from0.31 to 0.61 mg/g MLSS and intracellular antioxidant defense was activated.With CdSe QD level increasing to 30 mg/L,the total antioxygenic capacity and the activities of catalase were enhanced up to 411%and 143.2%,respectively.Thereby,CdSe QDs had little adverse effects on cell membrane integrity,microbial metabolism and the abundance of Nitrospirae.
基金supported by the Science and Technology Project of Henan Province (No.212102310510)the Doctoral Scientific Research Foundation of Anyang Institute of Technology (No.BSJ2019026)the Anyang Municipal Major Special Project (No.201928)。
文摘The effect of nanoplastics(NPs)on nitrite oxidation bacteria(NOB)community in treating high-strength wastewater remains unclear,which seriously affects the stability of nitrogen removal process.In this study,highly active nitrifying sludge was enriched and exposed to 50nm polystyrene NPs(PS-NPs)for short-term(1,100,500,and 1000 mg/L,1.5 hr)and long-term(1,10,100 mg/L,40 days)at high nitrite concentration.In contrast to previous studies,our results showed that the exposures to PS-NPs had little effect on nitrifying performances.After long-term exposure,the protein/polysaccharide ratios in extracellular polymeric substances(EPS)were positively correlated with PS-NPs concentrations(0.78–0.99).The produced reactive oxygen species(ROS)were gradually removed,and PS-NPs higher than 10 mg/L caused damage to membrane integrity.Long-term exposure for 40 days increased the community diversity and caused significant differences between the control and exposed communities.The control group were dominated by Nitrobacter and Exiguobacterium,while the exposure group was dominated by Bacillus,Mycobacterium,and Nitrospira.A noticeable shift in the NOB community from Nitrobacter(26.5%to 3.4%)to Nitrospira(1.61%to 14.27%)was observed.A KEGG analysis indicated a decrease in cell growth and death,cell motility and energy metabolism.It appeared that NOB could adapt to PS-NPs stress through enhanced secretion and removal of oxidative damage.Overall,this study provided new insights into the response mechanism of NOB to PS-NPs exposure.
基金the support of the National Key Research and Development Program (No. 2019YFC0408503)the Project of Thousand Youth Talents (No. AUGA2160100917)。
文摘Recently, the use of microalgae for bioremediation of pharmaceuticals(Ph As) has attracted increasing interest. However, most studies focused more on microalgae removal performance, its defensive response to the Ph As during wastewater treatment remains unexplored. Herein, microalgal three defensive systems have been investigated in synthetic wastewater, with six Ph As as the typical drug. Results show that Ph As could bind to EPS, and this action in turn could help to alleviate the direct toxicity of Ph As to microalgae. Subsequently, the physiological analyses revealed the increase of superoxide dismutase(SOD), catalase(CAT), and peroxidase(POD) activities, potentially reducing the oxidative stress induced by Ph As. Furthermore, the enzyme activities of cytochrome P450(CYP450) and glutathione-S-transferase(GST) were significantly upregulated after exposure to SMX, CIP and BPA, followed by a significant decrease in biodegradation rates after the addition of CYP450 inhibitors, suggesting that the biotransformation and detoxification of Ph As occurred. Meanwhile, molecular docking further revealed that CYP450 could bind with Ph As via hydrogen bond and hydrophobic interaction, which proved their abilities to be metabolized and form transformation products in microalgae. These findings provide an advancing understanding of microalgae technologies to improve the treatment of wastewater contaminated with Ph As.
