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Yang S, Zuo J, Grossart HP, Dai G, Liu J, Song L, Gan N. Evaluating microcystinase A-based approach on microcystins degradation during harvested cyanobacterial blooms. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 348:123878. [PMID: 38548158 DOI: 10.1016/j.envpol.2024.123878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Revised: 03/21/2024] [Accepted: 03/25/2024] [Indexed: 04/07/2024]
Abstract
Addressing notorious and worldwide Microcystis blooms, mechanical algae harvesting is an effective emergency technology for bloom mitigation and removal of nutrient loads in waterbodies. However, the absence of effective methods for removal of cyanobacterial toxins, e.g., microcystins (MCs), poses a challenge to recycle the harvested Microcystis biomass. In this study, we therefore introduced a novel approach, the "captured biomass-MlrA enzymatic MC degradation", by enriching microcystinase A (MlrA) via fermentation and spraying it onto salvaged Microcystis slurry to degrade all MCs. After storing the harvested Microcystis slurry, a rapid release of extracellular MCs occurred within the initial 8 h, reaching a peak concentration of 5.33 μg/mL at 48 h during the composting process. Upon spraying the recombinant MlrA crude extract (about 3.36 U) onto the Microcystis slurry in a ratio of 0.1% (v/v), over 95% of total MCs were degraded within a 24-h period. Importantly, we evaluated the reliability and safety of using MlrA extracts to degrade MCs. Results showed that organic matter/nutrient contents, e.g. soluble proteins, polysaccharides, phycocyanin and carotenoids, were not significantly altered. Furthermore, the addition of MlrA extracts did not significantly change the bacterial community composition and diversity in the Microcystis slurry, indicating that the MlrA extracts did not increase the risk of pathogenic bacteria. Our study provides an effective and promising method for the pre-treatment of harvested Microcystis biomass, highlighting an ecologically sustainable framework for addressing Microcystis blooms.
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Affiliation(s)
- Siyu Yang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China; University of Chinese Academy of Sciences, Beijing, 100190, China
| | - Jun Zuo
- National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Zhejiang Provincial Key Lab for Water Environment and Marine Biological Resources Protection, Institute for Eco-Environmental Research of Sanyang Wetland, Wenzhou University, Wenzhou, 325035, China.
| | - Hans-Peter Grossart
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries IGB, Stechlin, Germany; Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Guofei Dai
- Jiangxi Academy of Water Science and Engineering, Nanchang, 330029, China
| | - Jin Liu
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Lirong Song
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China
| | - Nanqin Gan
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, 430072, China.
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Piel T, Sandrini G, Weenink EFJ, Qin H, Herk MJV, Morales-Grooters ML, Schuurmans JM, Slot PC, Wijn G, Arntz J, Zervou SK, Kaloudis T, Hiskia A, Huisman J, Visser PM. Shifts in phytoplankton and zooplankton communities in three cyanobacteria-dominated lakes after treatment with hydrogen peroxide. HARMFUL ALGAE 2024; 133:102585. [PMID: 38485435 DOI: 10.1016/j.hal.2024.102585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 12/22/2023] [Accepted: 01/18/2024] [Indexed: 03/19/2024]
Abstract
Cyanobacteria can reach high densities in eutrophic lakes, which may cause problems due to their potential toxin production. Several methods are in use to prevent, control or mitigate harmful cyanobacterial blooms. Treatment of blooms with low concentrations of hydrogen peroxide (H2O2) is a promising emergency method. However, effects of H2O2 on cyanobacteria, eukaryotic phytoplankton and zooplankton have mainly been studied in controlled cultures and mesocosm experiments, while much less is known about the effectiveness and potential side effects of H2O2 treatments on entire lake ecosystems. In this study, we report on three different lakes in the Netherlands that were treated with average H2O2 concentrations ranging from 2 to 5 mg L-1 to suppress cyanobacterial blooms. Effects on phytoplankton and zooplankton communities, on cyanotoxin concentrations, and on nutrient availability in the lakes were assessed. After every H2O2 treatment, cyanobacteria drastically declined, sometimes by more than 99%, although blooms of Dolichospermum sp., Aphanizomenon sp., and Planktothrix rubescens were more strongly suppressed than a Planktothrix agardhii bloom. Eukaryotic phytoplankton were not significantly affected by the H2O2 additions and had an initial advantage over cyanobacteria after the treatment, when ample nutrients and light were available. In all three lakes, a new cyanobacterial bloom developed within several weeks after the first H2O2 treatment, and in two lakes a second H2O2 treatment was therefore applied to again suppress the cyanobacterial population. Rotifers strongly declined after most H2O2 treatments except when the H2O2 concentration was ≤ 2 mg L-1, whereas cladocerans were only mildly affected and copepods were least impacted by the added H2O2. In response to the treatments, the cyanotoxins microcystins and anabaenopeptins were released from the cells into the water column, but disappeared after a few days. We conclude that lake treatments with low concentrations of H2O2 can be a successful tool to suppress harmful cyanobacterial blooms, but may negatively affect some of the zooplankton taxa in lakes. We advise pre-tests prior to the treatment of lakes to define optimal treatment concentrations that kill the majority of the cyanobacteria and to minimize potential side effects on non-target organisms. In some cases, the pre-tests may discourage treatment of the lake.
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Affiliation(s)
- Tim Piel
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands; Agendia NV, 1043 NT Amsterdam, The Netherlands
| | - Giovanni Sandrini
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands; Department of Technology & Sources, Evides Water Company, 3006 AL Rotterdam, The Netherlands
| | - Erik F J Weenink
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
| | - Hongjie Qin
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands; Guangdong Provincial Key Lab of Ornamental Plant Germplasm Innovation and Utilization, Environmental Horticulture Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China; Institute of Agricultural Resources and Environment, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Maria J van Herk
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
| | - Mariël Léon Morales-Grooters
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands; Department of Biomedical Engineering, Erasmus MC University Rotterdam, Office Ee2302, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - J Merijn Schuurmans
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
| | - Pieter C Slot
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
| | - Geert Wijn
- Arcadis Nederland B.V., P.O. Box 264, 6800 AG Arnhem, The Netherlands
| | - Jasper Arntz
- Arcadis Nederland B.V., P.O. Box 264, 6800 AG Arnhem, The Netherlands
| | - Sevasti-Kiriaki Zervou
- Photo-Catalytic Processes and Environmental Chemistry, Institute of Nanoscience and Nanotechnology, National Centre for Scientific Research, "Demokritos", Patriarchou Gregoriou E & 27 Neapoleos Str, 15341 Athens, Greece
| | - Triantafyllos Kaloudis
- Photo-Catalytic Processes and Environmental Chemistry, Institute of Nanoscience and Nanotechnology, National Centre for Scientific Research, "Demokritos", Patriarchou Gregoriou E & 27 Neapoleos Str, 15341 Athens, Greece; Laboratory of Organic Micropollutants, Water Quality Control Department, Athens Water Supply & Sewerage Company (EYDAP SA), Athens, Greece
| | - Anastasia Hiskia
- Photo-Catalytic Processes and Environmental Chemistry, Institute of Nanoscience and Nanotechnology, National Centre for Scientific Research, "Demokritos", Patriarchou Gregoriou E & 27 Neapoleos Str, 15341 Athens, Greece
| | - Jef Huisman
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
| | - Petra M Visser
- Department of Freshwater and Marine Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240,1090 GE Amsterdam, The Netherlands
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Zheng Y, Xue C, Chen H, Jia A, Zhao L, Zhang J, Zhang L, Wang Q. Reconstitution and expression of mcy gene cluster in the model cyanobacterium Synechococcus 7942 reveals a role of MC-LR in cell division. THE NEW PHYTOLOGIST 2023; 238:1101-1114. [PMID: 36683448 DOI: 10.1111/nph.18766] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 01/12/2023] [Indexed: 06/17/2023]
Abstract
Cyanobacterial blooms pose a serious threat to public health due to the presence of cyanotoxins. Microcystin-LR (MC-LR) produced by Microcystis aeruginosa is the most common cyanotoxins. Due to the limitation of isolation, purification, and genetic manipulation techniques, it is difficult to study and verify in situ the biosynthetic pathways and molecular mechanisms of MC-LR. We reassembled the biosynthetic gene cluster (mcy cluster) of MC-LR in vitro by synthetic biology, designed and constructed the strong bidirectional promoter biPpsbA2 , transformed it into Synechococcus 7942, and successfully expressed MC-LR at a level of 0.006-0.018 fg cell-1 d-1 . We found the expression of MC-LR led to abnormal cell division and cellular filamentation, further using various methods proved that by irreversibly competing its GTP-binding site, MC-LR inhibits assembly of the cell division protein FtsZ. The study represents the first reconstitution and expression of the mcy cluster and the autotrophic production of MC-LR in model cyanobacterium, which lays the foundation for resolving the microcystins biosynthesis pathway. The discovered role of MC-LR in cell division reveals a mechanism of how blooming cyanobacteria gain a competitive edge over their nonblooming counterparts.
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Affiliation(s)
- Yanli Zheng
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Chunling Xue
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Hui Chen
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Anqi Jia
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Liang Zhao
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Junli Zhang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
| | - Lixin Zhang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
- Academy for Advanced Interdisciplinary Studies, Henan University, Kaifeng, 475004, China
| | - Qiang Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China
- Academy for Advanced Interdisciplinary Studies, Henan University, Kaifeng, 475004, China
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Microcystin-Detoxifying Recombinant Saccharomyces cerevisiae Expressing the mlrA Gene from Sphingosinicella microcystinivorans B9. Microorganisms 2023; 11:microorganisms11030575. [PMID: 36985150 PMCID: PMC10058252 DOI: 10.3390/microorganisms11030575] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 03/03/2023] Open
Abstract
Contamination of water by microcystins is a global problem. These potent hepatotoxins demand constant monitoring and control methods in potable water. Promising approaches to reduce contamination risks have focused on natural microcystin biodegradation led by enzymes encoded by the mlrABCD genes. The first enzyme of this system (mlrA) linearizes microcystin structure, reducing toxicity and stability. Heterologous expression of mlrA in different microorganisms may enhance its production and activity, promote additional knowledge on the enzyme, and support feasible applications. In this context, we intended to express the mlrA gene from Sphingosinicella microcystinivorans B9 in an industrial Saccharomyces cerevisiae strain as an innovative biological alternative to degrade microcystins. The mlrA gene was codon-optimized for expression in yeast, and either expressed from a plasmid or through chromosomal integration at the URA3 locus. Recombinant and wild yeasts were cultivated in medium contaminated with microcystins, and the toxin content was analyzed during growth. Whereas no difference in microcystins content was observed in cultivation with the chromosomally integrated strain, the yeast strain hosting the mlrA expression plasmid reduced 83% of toxins within 120 h of cultivation. Our results show microcystinase A expressed by industrial yeast strains as a viable option for practical applications in water treatment.
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Anam GB, Guda DR, Ahn YH. Impact of melatonin on the hydrogen peroxide treatment efficacy in Microcystis aeruginosa: Cell growth, oxidative stress response, and gene transcription. CHEMOSPHERE 2022; 307:136036. [PMID: 36007744 DOI: 10.1016/j.chemosphere.2022.136036] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 07/22/2022] [Accepted: 08/08/2022] [Indexed: 06/15/2023]
Abstract
A study was conducted to determine how melatonin (MLT), a growth regulator, affects Microcystis aeruginosa cell behaviour and how MLT exposed cells respond to hydrogen peroxide (H2O2) treatment. MLT promotes the growth, chl-a content, Fv/Fm values, and microcystins (MCs) production of M. aeruginosa at low concentrations of 1-2.5 μmol/L but suppresses the growth at high concentrations (5-10 μmol/L). The cellular and genetic responses of MLT pre-treated cells to H2O2 treatment were examined further. Further research found that the cells pre-treated with MLT were susceptible to a range of growth-promoting, inhibiting and lethal effects when exposed to higher levels of H2O2. A dose-dependent pattern was observed under conditions of 0.05-0.2 mmol/L H2O2 with 0.5-2.5 μmol/L MLT concentrations to different degrees. High doses of H2O2 (0.2 and 0.3 mmol/L) typically lead to cell lysis and release of MCs in 5.0 and 10 μmol/L MLT pre-treated cells. A decrease in SOD/CAT activities and an increase in MDA levels validated the growth reduction. Furthermore, higher cell lysis and release of intracellular MCs were observed when H2O2 was increased for 5-10 μmol/L MLT pre-treated cells. This led to a higher accumulation of extracellular MCs. The results provide insight into how MLT influences H2O2 damage and assist in identifying situations where H2O2 treatment of cyanobacterial blooms is most appropriate.
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Affiliation(s)
- Giridhar Babu Anam
- Department of Civil Engineering, Yeungnam University, Gyeongsan, 38541, Gyeongbuk, Republic of Korea
| | - Dinneswara Reddy Guda
- Korea Center for Artificial Photosynthesis and Center for Nanomaterial, Sogang University, Seoul, 121-742, Republic of Korea
| | - Young-Ho Ahn
- Department of Civil Engineering, Yeungnam University, Gyeongsan, 38541, Gyeongbuk, Republic of Korea.
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Liu J, Chen L, Zhang X. Current research scenario for biological effect of exogenous factors on microcystin synthesis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:26190-26201. [PMID: 35089514 DOI: 10.1007/s11356-021-18256-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 12/17/2021] [Indexed: 06/14/2023]
Abstract
In natural water bodies, numerous cyanobacteria have the potential to intracellularly synthesize cyanotoxins, among which microcystin (MC) is the ubiquitous toxin that has been well known to be carcinogenic for hepatocytes. MC synthesis is a complex process, which involves about 10 non-ribosomal proteins encoded by the mcy gene cluster. In the natural environments containing MC-producing cyanobacteria, a variety of external factors can affect the generation of MC by mediating the expression of synthesizing genes. These factors can be generally divided into biotic factors (e.g., daphnia, virioplankton, MC-degrading bacteria, algicidal bacteria) and abiotic factors (e.g., nutrients, physical factors, chemicals, phytochemicals, essential trace elements), which are of great significance to the effective reduction of MC. Furthermore, comparison of MC-synthesizing genes in different cyanobacterial strains was performed, and the related factors affecting MC synthesis were summarized. Then, the problems and gaps regarding the biological effect of exogenous factors on microcystin synthesis were discussed. This review article may provide new ideas for addressing the challenges and bottlenecks of MC management.
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Affiliation(s)
- Jiahui Liu
- Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, Changsha, China
| | - Lv Chen
- Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, Changsha, China
| | - Xian Zhang
- Department of Occupational and Environmental Health, Xiangya School of Public Health, Central South University, Changsha, China.
- Hunan Provincial Key Laboratory of Clinical Epidemiology, Central South University, Changsha, China.
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Fionah A, Hackett C, Aljewari H, Brady L, Alqhtani F, Escobar IC, Thompson AK. Microcystin-LR Removal from Water via Enzymatic Linearization and Ultrafiltration. Toxins (Basel) 2022; 14:toxins14040231. [PMID: 35448840 PMCID: PMC9024530 DOI: 10.3390/toxins14040231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 03/14/2022] [Accepted: 03/18/2022] [Indexed: 02/05/2023] Open
Abstract
Microcystin-LR (MC-LR) is a toxin produced by cyanobacteria that can bloom in freshwater supplies. This study describes a new strategy for remediation of MC-LR that combines linearization of the toxin using microcystinase A, MlrA, enzyme with rejection of linearized byproducts using membrane filtration. The MlrA enzyme was expressed in Escherichia coli (E. coli) and purified via a His-tag with 95% purity. Additionally, composite membranes made of 95% polysulfone and 5% sulfonated polyether ether ketone (SPEEK) were fabricated and used to filter a solution containing cyclic and linearized MC-LR. Tests were also performed to measure the adsorption and desorption of MC-LR on polysulfone/SPEEK membranes. Liquid chromatography-mass spectrometry (LC-MS) was used to characterize the progress of linearization and removal of MC-LR. Results indicate that the MlrA was successful at linearizing MC-LR. Membrane filtration tests showed rejection of 97% of cyclic MC-LR and virtually all linearized MC-LR, with adsorption to the membranes being the main rejection mechanism. Adsorption/desorption tests indicated that methanol could be used to strip residual MC-LR from membranes to regenerate them. This study demonstrates a novel strategy of remediation of microcystin-tainted water, combining linearization of MC-LR to a low-toxicity byproduct along with removal by membrane filtration.
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Affiliation(s)
- Abelline Fionah
- Department of Chemistry, University of Kentucky, Lexington, KY 40506, USA;
| | - Cannon Hackett
- Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA; (C.H.); (H.A.); (F.A.)
| | - Hazim Aljewari
- Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA; (C.H.); (H.A.); (F.A.)
| | - Laura Brady
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, USA; (L.B.); (I.C.E.)
| | - Faisal Alqhtani
- Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA; (C.H.); (H.A.); (F.A.)
| | - Isabel C. Escobar
- Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, USA; (L.B.); (I.C.E.)
| | - Audie K. Thompson
- Ralph E. Martin Department of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701, USA; (C.H.); (H.A.); (F.A.)
- Correspondence:
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Biodegradation of Nodularin by a Microcystin-Degrading Bacterium: Performance, Degradation Pathway, and Potential Application. Toxins (Basel) 2021; 13:toxins13110813. [PMID: 34822597 PMCID: PMC8618024 DOI: 10.3390/toxins13110813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 11/15/2021] [Accepted: 11/15/2021] [Indexed: 01/19/2023] Open
Abstract
Currently, studies worldwide have comprehensively recognized the importance of Sphingomonadaceae bacteria and the mlrCABD gene cluster in microcystin (MC) degradation. However, knowledge about their degradation of nodularin (NOD) is still unclear. In this study, the degradation mechanism of NOD by Sphingopyxis sp. m6, an efficient MC degrader isolated from Lake Taihu, was investigated in several aspects, including degradation ability, degradation products, and potential application. The strain degraded NOD of 0.50 mg/L with a zero-order rate constant of 0.1656 mg/L/d and a half-life of 36 h. The average degradation rate of NOD was significantly influenced by the temperature, pH, and initial toxin concentrations. Moreover, four different biodegradation products, linear NOD, tetrapeptide H-Glu-Mdhb-MeAsp-Arg-OH, tripeptide H-Mdhb-MeAsp-Arg-OH, and dipeptide H-MeAsp-Arg-OH, were identified, of which the latter two are the first reported. Furthermore, the four mlr genes were upregulated during NOD degradation. The microcystinase MlrA encoded by the mlrA gene hydrolyzes the Arg-Adda bond to generate linear NOD as the first step of NOD biodegradation. Notably, recombinant MlrA showed higher degradation activity and stronger environmental adaptability than the wild strain, suggesting future applications in NOD pollution remediation. This research proposes a relatively complete NOD microbial degradation pathway, which lays a foundation for exploring the mechanisms of NOD degradation by MC-degrading bacteria.
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Simultaneous Removal of the Freshwater Bloom-Forming Cyanobacterium Microcystis and Cyanotoxin Microcystins via Combined Use of Algicidal Bacterial Filtrate and the Microcystin-Degrading Enzymatic Agent, MlrA. Microorganisms 2021; 9:microorganisms9081594. [PMID: 34442673 PMCID: PMC8401626 DOI: 10.3390/microorganisms9081594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 07/19/2021] [Accepted: 07/20/2021] [Indexed: 11/16/2022] Open
Abstract
Freshwater cyanobacterial blooms (e.g., Microcystis blooms) constitute a major global environmental problem because of their risks to public health and aquatic ecological systems. Current physicochemical treatments of toxic cyanobacteria cause the significant release of cyanotoxin microcystins from damaged cells. Biological control is a promising eco-friendly technology to manage harmful cyanobacteria and cyanotoxins. Here, we demonstrated an efficient biological control strategy at the laboratory scale to simultaneously remove Microcystis and microcystins via the combined use of the algicidal bacterial filtrate and the microcystin-degrading enzymatic agent. The algicidal indigenous bacterium Paenibacillus sp. SJ-73 was isolated from the sediment of northern Lake Taihu, China, and the microcystin-degrading enzymatic agent (MlrA) was prepared via the heterologous expression of the mlrA gene in the indigenous microcystin-degrading bacterium Sphingopyxis sp. HW isolated from Lake Taihu. The single use of a fermentation filtrate (5%, v/v) of Paenibacillus sp. SJ-73 for seven days removed the unicellular Microcystis aeruginosa PCC 7806 and the native colonial Microcystis strain TH1701 in Lake Taihu by 84% and 92%, respectively, whereas the single use of MlrA removed 85% of microcystins. Used in combination, the fermentation filtrate and MlrA removed Microcystis TH1701 and microcystins by 92% and 79%, respectively. The present biological control thus provides an important technical basis for the further development of safe, efficient, and effective measures to manage Microcystis blooms and microcystins in natural waterbodies.
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Are Bacterio- and Phytoplankton Community Compositions Related in Lakes Differing in Their Cyanobacteria Contribution and Physico-Chemical Properties? Genes (Basel) 2021; 12:genes12060855. [PMID: 34199405 PMCID: PMC8227929 DOI: 10.3390/genes12060855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 05/24/2021] [Accepted: 05/28/2021] [Indexed: 12/05/2022] Open
Abstract
Bacterioplankton community composition has become the center of research attention in recent years. Bacteria associated with toxic cyanobacteria blooms have attracted considerable interest. However, little is known about the environmental factors driving the bacteria community, including the impact of invasive cyanobacteria. Therefore, our aim has been to determine the relationships between heterotrophic bacteria and phytoplankton community composition across 24 Polish lakes with different contributions of cyanobacteria including the invasive species Raphidiopsis raciborskii. This analysis revealed that cyanobacteria were present in 16 lakes, while R. raciborskii occurred in 14 lakes. Our results show that bacteria communities differed between lakes dominated by cyanobacteria and lakes with minor contributions of cyanobacteria but did not differ between lakes with R. raciborskii and other lakes. Physical factors, including water and Secchi depth, were the major drivers of bacteria and phytoplankton community composition. However, in lakes dominated by cyanobacteria, bacterial community composition was also influenced by biotic factors such as the amount of R. raciborskii, chlorophyll-a and total phytoplankton biomass. Thus, our study provides novel evidence on the influence of environmental factors and R. raciborskii on lake bacteria communities.
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11
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Lürling M, Mucci M, Waajen G. Removal of Positively Buoyant Planktothrix rubescens in Lake Restoration. Toxins (Basel) 2020; 12:toxins12110700. [PMID: 33167347 PMCID: PMC7694384 DOI: 10.3390/toxins12110700] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/02/2020] [Accepted: 11/03/2020] [Indexed: 01/31/2023] Open
Abstract
The combination of a low-dose coagulant (polyaluminium chloride—‘Floc’) and a ballast able to bind phosphate (lanthanum modified bentonite, LMB—‘Sink/Lock’) have been used successfully to manage cyanobacterial blooms and eutrophication. In a recent ‘Floc and Lock’ intervention in Lake de Kuil (the Netherlands), cyanobacterial chlorophyll-a was reduced by 90% but, surprisingly, after one week elevated cyanobacterial concentrations were observed again that faded away during following weeks. Hence, to better understand why and how to avoid an increase in cyanobacterial concentration, experiments with collected cyanobacteria from Lakes De Kuil and Rauwbraken were performed. We showed that the Planktothrix rubescens from Lake de Kuil could initially be precipitated using a coagulant and ballast but, after one day, most of the filaments resurfaced again, even using a higher ballast dose. By contrast, the P. rubescens from Lake Rauwbraken remained precipitated after the Floc and Sink/Lock treatment. We highlight the need to test selected measures for each lake as the same technique with similar species (P. rubescens) yielded different results. Moreover, we show that damaging the cells first with hydrogen peroxide before adding the coagulant and ballast (a ‘Kill, Floc and Lock/Sink’ approach) could be promising to keep P. rubescens precipitated.
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Affiliation(s)
- Miquel Lürling
- Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, The Netherlands;
- Correspondence: ; Tel.: +31-317-489-838
| | - Maíra Mucci
- Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, The Netherlands;
| | - Guido Waajen
- Water Authority Brabantse Delta, Team Knowledge, P.O. Box 5520, 4801 DZ Breda, The Netherlands;
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Ding Q, Liu K, Song Z, Sun R, Zhang J, Yin L, Pu Y. Effects of Microcystin-LR on Metabolic Functions and Structure Succession of Sediment Bacterial Community under Anaerobic Conditions. Toxins (Basel) 2020; 12:toxins12030183. [PMID: 32183408 PMCID: PMC7150748 DOI: 10.3390/toxins12030183] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Revised: 03/05/2020] [Accepted: 03/14/2020] [Indexed: 01/02/2023] Open
Abstract
Microcystins (MCs), which are produced by harmful cyanobacteria blooms, pose a serious threat to environmental health. However, the effect of MCs on the bacterial community under anaerobic conditions is still unclear. This study examined the dynamic changes of MC-degrading capacity, metabolic activity, and structure of the bacterial community in lake sediment repeatedly treated with 1 mg/L microcystin-LR (MC-LR) under anaerobic conditions. The results showed that the MC-degrading capacity of the bacterial community was increased nearly three-fold with increased treatment frequency. However, the metabolic profile behaved in exactly opposite trend, in which the overall carbon metabolic activity was inhibited by repeated toxin addition. Microbial diversity was suppressed by the first addition of MC-LR and then gradually recovered. The 16S amplicon sequencing showed that the dominant genera were changed from Exiguobacterium and Acinetobacter to Prosthecobacter, Dechloromonas, and Agrobacterium. Furthermore, the increase in the relative abundance of Dechloromonas, Pseudomonas, Hydrogenophaga, and Agrobacterium was positively correlated with the MC-LR treatment times. This indicates that they might be responsible for MC degradation under anaerobic conditions. Our findings reveal the relationship between MC-LR and the sediment bacterial community under anaerobic conditions and indicate that anaerobic biodegradation is an effective and promising method to remediate MCs pollution.
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Affiliation(s)
- Qin Ding
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
| | - Kaiyan Liu
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
| | - Zhiquan Song
- Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697, USA
| | - Rongli Sun
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
| | - Juan Zhang
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
| | - Lihong Yin
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
| | - Yuepu Pu
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education of China, School of Public Health, Southeast University, Nanjing 210009, China; (Q.D.)
- Correspondence: ; Tel.: +86-25-83272582
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13
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Protected Freshwater Ecosystem with Incessant Cyanobacterial Blooming Awaiting a Resolution. WATER 2019. [DOI: 10.3390/w12010129] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
For 50 years persistent cyanobacterial blooms have been observed in Lake Ludoš (Serbia), a wetland area of international significance listed as a Ramsar site. Cyanobacteria and cyanotoxins can affect many organisms, including valuable flora and fauna, such as rare and endangered bird species living or visiting the lake. The aim was to carry out monitoring, estimate the current status of the lake, and discuss potential resolutions. Results obtained showed: (a) the poor chemical state of the lake; (b) the presence of potentially toxic (genera Dolichospermum, Microcystis, Planktothrix, Chroococcus, Oscillatoria, Woronichinia and dominant species Limnothrix redekei and Pseudanabaena limnetica) and invasive cyanobacterial species Raphidiopsis raciborskii; (c) the detection of microcystin (MC) and saxitoxin (STX) coding genes in biomass samples; (d) the detection of several microcystin variants (MC-LR, MC-dmLR, MC-RR, MC-dmRR, MC-LF) in water samples; (e) histopathological alterations in fish liver, kidney and gills. The potential health risk to all organisms in the ecosystem and the ecosystem itself is thus still real and present. Although there is still no resolution in sight, urgent remediation measures are needed to alleviate the incessant cyanobacterial problem in Lake Ludoš to break this ecosystem out of the perpetual state of limbo in which it has been trapped for quite some time.
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14
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Piel T, Sandrini G, White E, Xu T, Schuurmans JM, Huisman J, Visser PM. Suppressing Cyanobacteria with Hydrogen Peroxide Is More Effective at High Light Intensities. Toxins (Basel) 2019; 12:toxins12010018. [PMID: 31906135 PMCID: PMC7020451 DOI: 10.3390/toxins12010018] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/18/2019] [Accepted: 12/20/2019] [Indexed: 12/01/2022] Open
Abstract
Hydrogen peroxide (H2O2) can be used as an emergency method to selectively suppress cyanobacterial blooms in lakes and drinking water reservoirs. However, it is largely unknown how environmental parameters alter the effectiveness of H2O2 treatments. In this study, the toxic cyanobacterial strain Microcystis aeruginosa PCC 7806 was treated with a range of H2O2 concentrations (0 to 10 mg/L), while being exposed to different light intensities and light colors. H2O2 treatments caused a stronger decline of the photosynthetic yield in high light than in low light or in the dark, and also a stronger decline in orange than in blue light. Our results are consistent with the hypothesis that H2O2 causes major damage at photosystem II (PSII) and interferes with PSII repair, which makes cells more sensitive to photoinhibition. Furthermore, H2O2 treatments caused a decrease in cell size and an increase in extracellular microcystin concentrations, indicative of leakage from disrupted cells. Our findings imply that even low H2O2 concentrations of 1–2 mg/L can be highly effective, if cyanobacteria are exposed to high light intensities. We therefore recommend performing lake treatments during sunny days, when a low H2O2 dosage is sufficient to suppress cyanobacteria, and may help to minimize impacts on non-target organisms.
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