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Peng T, Tang Y, Cai D, Gu Y, Wei J, Zhang J, Ni J, Liu J, Ren X, Pan J, Long X, Wang H, Yang F. Insights into the interaction mechanisms between Microcystin-degrading bacteria and Microcystis aeruginosa. WATER RESEARCH 2024; 265:122241. [PMID: 39154396 DOI: 10.1016/j.watres.2024.122241] [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: 03/01/2024] [Revised: 06/03/2024] [Accepted: 08/08/2024] [Indexed: 08/20/2024]
Abstract
Interactions between bacteria and cyanobacteria influence the occurrence and development of harmful cyanobacterial blooms (HCBs). Bloom-forming cyanobacteria and cyanotoxin-degrading bacteria are essential in HCBs, nonetheless, their interactions and the underlying mechanisms remain unclear. To address this gap, a typical microcystin-LR (MC-LR)-degrading bacterium and a toxic Microcystis aeruginosa strain were co-cultivated to investigate their interactions. The cyanobacterial growth was enhanced by 24.8 %-44.3 % in the presence of the bacterium in the first 7 days, and the cyanobacterium enhanced the bacterial growth by 59.2 %-117.5 % throughout the growth phases, suggesting a mutualistic relationship between them. The presence of the bacterium increased cyanobacterial intracellular MC-LR content on days 4, 8, and 10 while reducing the extracellular MC-LR concentration, revealing the dual roles of the bacterium in enhancing cyanotoxin production and degrading cyanotoxins. The bacterium alleviated the oxidative stress, which may be crucial in promoting cyanobacterial growth. Critical functional genes related to cyanobacterial photosynthesis and MC-LR synthesis, and bacterial MC-LR degradation were up-regulated in the presence of the bacterium and cyanobacterium, respectively. Moreover, extracellular polymeric substances (EPS) were produced at the cell interface, implying EPS play a role in cyanobacterial-bacterial interactions. This study is the first to unveil the interaction mechanisms between cyanotoxin-degrading bacteria and bloom-forming cyanobacteria, shedding light on the dynamics of HCBs.
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Affiliation(s)
- Tangjian Peng
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Yanqing Tang
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Danping Cai
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Yuqing Gu
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Jia Wei
- Hunan Provincial Key Laboratory of Clinical Epidemiology, Xiangya School of Public Health, Central South University, Changsha, Hunan 410078, PR China
| | - Jiajia Zhang
- Hunan Provincial Key Laboratory of Clinical Epidemiology, Xiangya School of Public Health, Central South University, Changsha, Hunan 410078, PR China
| | - Juan Ni
- Department of Cell Biology and Genetics, Institute of Cytology and Genetics, Key Laboratory of Ecological Environment and Critical Human Diseases Prevention of Hunan Province Department of Education, School of Basic Medical Sciences, Hengyang Medical School, University of South China, PR China
| | - Jun Liu
- Department of Cell Biology and Genetics, Institute of Cytology and Genetics, Key Laboratory of Ecological Environment and Critical Human Diseases Prevention of Hunan Province Department of Education, School of Basic Medical Sciences, Hengyang Medical School, University of South China, PR China
| | - Xiaoya Ren
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Jiafeng Pan
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Xizi Long
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Hui Wang
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China
| | - Fei Yang
- Hunan Province Key Laboratory of Typical Environmental Pollution and Health Hazards, School of Public Health, Hengyang Medical School, University of South China, Hengyang 421001, PR China.
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2
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Wang L, Yi Z, Zhang P, Xiong Z, Zhang G, Zhang W. Comprehensive strategies for microcystin degradation: A review of the physical, chemical, and biological methods and genetic engineering. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 365:121707. [PMID: 38968883 DOI: 10.1016/j.jenvman.2024.121707] [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: 02/22/2024] [Revised: 06/02/2024] [Accepted: 07/02/2024] [Indexed: 07/07/2024]
Abstract
Addressing the threat of harmful cyanobacterial blooms (CyanoHABs) and their associated microcystins (MCs) is crucial for global drinking water safety. In this review, we comprehensively analyze and compares the physical, chemical, and biological methods and genetic engineering for MCs degradation in aquatic environments. Physical methods, such as UV treatments and photocatalytic reactions, have a high efficiency in breaking down MCs, with the potential for further enhancement in performance and reduction of hazardous byproducts. Chemical treatments using chlorine dioxide and potassium permanganate can reduce MC levels but require careful dosage management to avoid toxic by-products and protect aquatic ecosystems. Biological methods, including microbial degradation and phytoremediation techniques, show promise for the biodegradation of MCs, offering reduced environmental impact and increased sustainability. Genetic engineering, such as immobilization of microcystinase A (MlrA) in Escherichia coli and its expression in Synechocystis sp., has proven effective in decomposing MCs such as MC-LR. However, challenges related to specific environmental conditions such as temperature variations, pH levels, presence of other contaminants, nutrient availability, oxygen levels, and light exposure, as well as scalability of biological systems, necessitate further exploration. We provide a comprehensive evaluation of MCs degradation techniques, delving into their practicality, assessing the environmental impacts, and scrutinizing their efficiency to offer crucial insights into the multifaceted nature of these methods in various environmental contexts. The integration of various methodologies to enhance degradation efficiency is vital in the field of water safety, underscoring the need for ongoing innovation.
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Affiliation(s)
- Long Wang
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
| | - Zhuoran Yi
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
| | - Peng Zhang
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
| | - Zhu Xiong
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
| | - Gaosheng Zhang
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
| | - Wei Zhang
- School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, People's Republic of China.
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3
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Mohamed ZA, Elnour RO, Alamri S, Hashem M. Biodegradation of the cyanobacterial toxin anatoxin-a by a Bacillus subtilis strain isolated from a eutrophic lake in Saudi Arabia. Arch Microbiol 2024; 206:348. [PMID: 38990418 DOI: 10.1007/s00203-024-04074-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2024] [Revised: 06/22/2024] [Accepted: 06/24/2024] [Indexed: 07/12/2024]
Abstract
Anatoxin-a (ATX-a) is a neurotoxin produced by some species of cyanobacteria. Due to its water solubility and stability in natural water, it could pose health risks to human, animals, and plants. Conventional water treatment techniques are not only insufficient for the removal of ATX-a, but they also result in cell lysis and toxin release. The elimination of this toxin through biodegradation may be a promising strategy. This study examines for the first time the biodegradation of ATX-a to a non-toxic metabolite (Epoxy-ATX-a) by a strain of Bacillus that has a history of dealing with toxic cyanobacteria in a eutrophic lake. The Bacillus strain AMRI-03 thrived without lag phase in a lake water containing ATX-a. The strain displayed fast degradation of ATX-a, depending on initial toxin concentration. At the highest initial concentrations (50 & 100 µg L- 1), total ATX-a degradation took place in 4 days, but it took 6 & 7 days at lower concentrations (20, 10, and 1 µg L- 1, respectively). The ATX-a biodegradation rate was also influenced by the initial toxin concentration, reaching its maximum value (12.5 µg L- 1 day- 1) at the highest initial toxin concentrations (50 & 100 µg L- 1). Temperature and pH also had an impact on the rate of ATX-a biodegradation, with the highest rates occurring at 25 and 30 ºC and pH 7 and 8. This nontoxic bacterial strain could be immobilized within a biofilm on sand filters and/or sludge for the degradation and removal of ATX-a and other cyanotoxins during water treatment processes, following the establishment of mesocosm experiments to assess the potential effects of this bacterium on water quality.
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Affiliation(s)
- Zakaria A Mohamed
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt.
| | - Rehab O Elnour
- Biology Department, Faculty of Sciences and Arts, King Khalid University, Dahran Al-Janoub, Abha, Saudi Arabia
| | - Saad Alamri
- Department of Biology, College of Science, King Khalid University, Abha, 61413, Saudi Arabia
| | - Mohamed Hashem
- Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut, 71516, Egypt
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Thyssen LA, Martinez I Quer A, Arias CA, Ellegaard-Jensen L, Carvalho PN, Johansen A. Constructed wetland mesocosms improve the biodegradation of microcystin-LR and cylindrospermopsin by indigenous bacterial consortia. HARMFUL ALGAE 2024; 131:102549. [PMID: 38212082 DOI: 10.1016/j.hal.2023.102549] [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: 09/03/2023] [Revised: 11/14/2023] [Accepted: 11/22/2023] [Indexed: 01/13/2024]
Abstract
Cyanobacterial blooms releasing harmful cyanotoxins, such as microcystin (MC) and cylindrospermopsin (CYN), are prominent threats to human and animal health. Constructed wetlands (CW) may be a nature-based solution for bioremediation of lake surface water containing cyanotoxins, due to its low-cost requirement of infrastructure and environmentally friendly operation. There is recent evidence that microcystin-LR (MC-LR) can efficiently be removed in CW microcosms where CYN degradation in CW is unknown. Likewise, the mechanistic background regarding cyanotoxins transformation in CW is not yet elucidated. In the present study, the objective was to compare MC-LR and CYN degradation efficiencies by two similar microbial communities obtained from CW mesocosms, by two different experiments setup: 1) in vitro batch experiment in serum bottles with an introduced CW community, and 2) degradation in CW mesocosms. In experiment 1) MC-LR and CYN were spiked at 100 µg L-1 and in experiment 2) 200 µg L-1 were spiked. Results showed that MC-LR was degraded to ≤1 µg L-1 within seven days in both experiments. However, with a markedly higher degradation rate constant in the CW mesocosms (0.18 day-1 and 0.75 day-1, respectively). No CYN removal was detected in the in vitro incubations, whereas around 50 % of the spiked CYN was removed in the CW mesocosms. The microbial community responded markedly to the cyanotoxin treatment, with the most prominent increase of bacteria affiliated with Methylophilaceae (order: Methylophilales, phylum: Proteobacteria). The results strongly indicate that CWs can develop an active microbial community capable of efficient removal of MC-LR and CYN. However, the CW operational conditions need to be optimized to achieve a full CYN degradation. To the best of our knowledge, this study is the first to report the ability of CW mesocosms to degrade CYN.
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Affiliation(s)
- Lasse Ahrenkiel Thyssen
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Alba Martinez I Quer
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Carlos Alberto Arias
- Department of Biology, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Lea Ellegaard-Jensen
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
| | - Pedro N Carvalho
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark.
| | - Anders Johansen
- Department of Environmental Science, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark; WATEC, Centre for Water Technology, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark
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Wang T, Liu H. Aquatic plant allelochemicals inhibit the growth of microalgae and cyanobacteria in aquatic environments. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:105084-105098. [PMID: 37740161 DOI: 10.1007/s11356-023-29994-5] [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: 04/04/2023] [Accepted: 09/16/2023] [Indexed: 09/24/2023]
Abstract
Excess nitrogen and phosphorus nutrients in the aquatic environment result in the growth of algal cells and water eutrophication, which adversely affect the aquatic environment and human health. Therefore, discovering a safe and efficient algae suppression method is necessary to ensure the ecological safety of water. Recently, the allelopathic effects of aquatic plants on algae have attracted extensive attention from researchers. This review demonstrates the current research hotspot of allelopathic algal inhibition in aquatic plants and lists the common aquatic plant species and allelochemicals. In addition, the inhibition mechanism of allelochemicals from aquatic plants on algae is systematically discussed. Moreover, the key factors affecting the inhibition of allelopathy in algae, such as pH, temperature, algal cell density, and concentration of allelochemicals, are summarized. The present utilization modes of allelochemicals on algae are also presented. Finally, the problems existing in the study of allelopathic algal inhibition of aquatic plants are highlighted, and suggestions for further research are proposed.
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Affiliation(s)
- Tiantian Wang
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 21500, China
| | - Haicheng Liu
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 21500, China.
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Valencia-Cárdenas D, Tavares TS, Silveira R, Brandão CCS, Soares RM, Ginoris YP. Evaluation of the Removal and Effects of Cylindrospermopsin on Ripened Slow Sand Filters. Toxins (Basel) 2023; 15:543. [PMID: 37755969 PMCID: PMC10536468 DOI: 10.3390/toxins15090543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/24/2023] [Accepted: 08/26/2023] [Indexed: 09/28/2023] Open
Abstract
The occurrence of toxic blooms of cyanobacteria has been a matter of public health interest due to the cyanotoxins produced by these microorganisms. Cylindrospermopsin (CYN) is a cyanotoxin of particular concern due to its toxic effects on humans. This study investigated the removal and effects of CYN in ripened slow sand filters (SSFs) treating water from Paranoá Lake, Brasilia, Brazil. Four pilot-scale SSFs were ripened and operated for 74 days. Two contamination peaks with CYN were applied along the filtration run. The improvement of any of the evaluated water quality parameters was not affected by the presence of CYN in the raw water. The SSFs efficiently removed CYN, presenting concentrations lower than 0.8 µg/L in the filtered water. The microbiota of the SSFs were dominated by protozoa of the genus Euglypha and amoebas of the genera Arcella, Centropyxis, and Amoeba, together with some groups of rotifers. These microorganisms played a crucial role in removing total coliforms and E. coli. In addition, CYN was not identified as a determining factor in the microbiota composition.
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Affiliation(s)
- Daniel Valencia-Cárdenas
- Department of Civil and Environmental Engineering, Faculty of Technology, University of Brasilia, Brasilia 70910-900, Brazil; (T.S.T.); (R.S.); (C.C.S.B.); (R.M.S.)
| | | | | | | | | | - Yovanka Pérez Ginoris
- Department of Civil and Environmental Engineering, Faculty of Technology, University of Brasilia, Brasilia 70910-900, Brazil; (T.S.T.); (R.S.); (C.C.S.B.); (R.M.S.)
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7
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Nugumanova G, Ponomarev ED, Askarova S, Fasler-Kan E, Barteneva NS. Freshwater Cyanobacterial Toxins, Cyanopeptides and Neurodegenerative Diseases. Toxins (Basel) 2023; 15:toxins15030233. [PMID: 36977124 PMCID: PMC10057253 DOI: 10.3390/toxins15030233] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 03/13/2023] [Accepted: 03/19/2023] [Indexed: 03/30/2023] Open
Abstract
Cyanobacteria produce a wide range of structurally diverse cyanotoxins and bioactive cyanopeptides in freshwater, marine, and terrestrial ecosystems. The health significance of these metabolites, which include genotoxic- and neurotoxic agents, is confirmed by continued associations between the occurrence of animal and human acute toxic events and, in the long term, by associations between cyanobacteria and neurodegenerative diseases. Major mechanisms related to the neurotoxicity of cyanobacteria compounds include (1) blocking of key proteins and channels; (2) inhibition of essential enzymes in mammalian cells such as protein phosphatases and phosphoprotein phosphatases as well as new molecular targets such as toll-like receptors 4 and 8. One of the widely discussed implicated mechanisms includes a misincorporation of cyanobacterial non-proteogenic amino acids. Recent research provides evidence that non-proteinogenic amino acid BMAA produced by cyanobacteria have multiple effects on translation process and bypasses the proof-reading ability of the aminoacyl-tRNA-synthetase. Aberrant proteins generated by non-canonical translation may be a factor in neuronal death and neurodegeneration. We hypothesize that the production of cyanopeptides and non-canonical amino acids is a more general mechanism, leading to mistranslation, affecting protein homeostasis, and targeting mitochondria in eukaryotic cells. It can be evolutionarily ancient and initially developed to control phytoplankton communities during algal blooms. Outcompeting gut symbiotic microorganisms may lead to dysbiosis, increased gut permeability, a shift in blood-brain-barrier functionality, and eventually, mitochondrial dysfunction in high-energy demanding neurons. A better understanding of the interaction between cyanopeptides metabolism and the nervous system will be crucial to target or to prevent neurodegenerative diseases.
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Affiliation(s)
- Galina Nugumanova
- Department of Biology, School of Sciences and Humanities, Nazarbayev University, Astana 010000, Kazakhstan
| | - Eugene D Ponomarev
- Department of Biology, School of Sciences and Humanities, Nazarbayev University, Astana 010000, Kazakhstan
| | - Sholpan Askarova
- Center for Life Sciences, National Laboratory Astana, Nazarbayev University, Astana 010000, Kazakhstan
| | - Elizaveta Fasler-Kan
- Department of Pediatric Surgery, Children's Hospital, Inselspital Bern, University of Bern, 3010 Bern, Switzerland
| | - Natasha S Barteneva
- Department of Biology, School of Sciences and Humanities, Nazarbayev University, Astana 010000, Kazakhstan
- The Environment & Resource Efficiency Cluster (EREC), Nazarbayev University, Astana 010000, Kazakhstan
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Mutoti MI, Edokpayi J, Mutileni N, Durowoju O, Munyai FL. Cyanotoxins in groundwater; occurrence, potential sources, health impacts and knowledge gap for public health. Toxicon 2023; 226:107077. [PMID: 36893989 DOI: 10.1016/j.toxicon.2023.107077] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 01/27/2023] [Accepted: 03/06/2023] [Indexed: 03/11/2023]
Abstract
Groundwater is a significant source of water across the world and constitutes about 30% of the earth's freshwater. This water source is likely to be contaminated by cyanobacteria that produce secondary metabolites called cyanotoxins. Studies on contamination of groundwater by cyanobacteria have been sketchy with limited information. There is a need for better evidence regarding groundwater contamination by cyanobacteria as their presence in surface water bodies could cause contamination of groundwater via infiltration and percolation during rainfall events or during groundwater-surface water interaction, bank infiltration or water quality exchange. Therefore, this review is aimed at exploring the occurrences and potential sources of cyanotoxins in groundwater. This was achieved by summarising the existing data on the occurrence of cyanobacteria in groundwater and their potential sources across the world. Groundwater cyanobacteria contamination can possibly pose threat to water quality because many of the cyanotoxins produced by cyanobacteria pose a severe threat to human health, animals and the environment. Concentrations of microcystins (MCs) in groundwater have been recorded in China (Chaohu), Saudi Arabia, and China (Huai River Basin), with concentrations of 1.446 μg/L, 1.8 μg/L and 1.07 μg/L, respectively. In humans, exposure to these cyanotoxins can cause symptoms such as vomiting, diarrhea, and skin irritation, to mention a few. This work highlights the importance of providing information or knowledge regarding public health implications of exposure to groundwater contaminated with cyanotoxins and the need to undertake risk management actions through national and international regulation. This review also points out current knowledge gaps, which could lead to future research.
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Affiliation(s)
- Mulalo Isaih Mutoti
- Department of Earth Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Private Bag X5050, University Road, Thohoyandou, Limpopo, South Africa.
| | - Joshua Edokpayi
- Department of Geography and Environmental Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Private Bag X5050, University Road, Thohoyandou, Limpopo, South Africa
| | - Ntwanano Mutileni
- Department of Earth Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Private Bag X5050, University Road, Thohoyandou, Limpopo, South Africa
| | - Olatunde Durowoju
- Department of Earth Sciences, Faculty of Science, Engineering and Agriculture, University of Venda, Private Bag X5050, University Road, Thohoyandou, Limpopo, South Africa
| | - Fhatuwani Linton Munyai
- School of Biology and Environmental Sciences, Faculty of Agriculture and Natural Sciences, University of Mpumalanga, Nelspruit, 1201, South Africa
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Mohamed ZA, Mostafa Y, Alamri S, Hashem M, Alrumman S. Biotransformation and detoxification of saxitoxin by Bacillus flexus in batch experiments. Arch Microbiol 2023; 205:63. [PMID: 36629970 DOI: 10.1007/s00203-022-03397-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 12/17/2022] [Accepted: 12/30/2022] [Indexed: 01/12/2023]
Abstract
Saxitoxins (STXs) are carbamate alkaloid neurotoxins produced by some species of cyanobacteria. They are water soluble and relatively stable in the natural environment, and thereby represent a risk to animal and human health through a long-time exposure. STXs cannot be sufficiently removed by conventional water treatment methods. Therefore, this study investigates the potential STX biodegradation and detoxification by bacteria as a promising method for toxin removal. STX biodegradation experiments were conducted using Bacillus flexus SSZ01 strain in batch cultures. The results revealed that SSZ01 strain grew well and rapidly detoxified STX, with no lag phase observed. STX detoxification by SSZ01 strain was initial-toxin-concentration-dependent. The highest biotransformation rate (10 µg STX L-1 day-1) the pseudo-first-order kinetic constant (0.58 d-1) were obtained at the highest initial toxin concentration (50 µg L-1) and the lowest ones (0.06 µg STX L-1 day-1 and 0.14 d-1, respectively) were recorded at the lowest initial concentration (0.5 µg L-1). STX biotransformation rate increased with temperature, with highest occurred at 30 ºC. This rate was also influenced by pH, with highest obtained at pH8 and lowest at higher and lower pH values. HPLC chromatograms showed that STX biotransformation peak is corresponding to the least toxic STX analog (disulfated sulfocarbamoyl-C1 variant). The Artemia-based toxicity assay revealed that this biotransformation byproduct was nontoxic. This suggests the potential application of this bacterial strain in slow sand filters for cyanotoxin removal in water treatment plants. Being nontoxic, this byproduct needs to be assayed for its therapeutic effects toward neurodegenerative diseases.
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Affiliation(s)
- Zakaria A Mohamed
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt.
| | - Yasser Mostafa
- College of Science, Department of Biology, King Khalid University, Abha, 61413, Saudi Arabia
| | - Saad Alamri
- College of Science, Department of Biology, King Khalid University, Abha, 61413, Saudi Arabia
| | - Mohamed Hashem
- College of Science, Department of Biology, King Khalid University, Abha, 61413, Saudi Arabia.,Faculty of Science, Botany and Microbiology Department, Assiut University, Assiut, 71516, Egypt
| | - Sulaiman Alrumman
- College of Science, Department of Biology, King Khalid University, Abha, 61413, Saudi Arabia
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Mohamed Z, Alamri S, Hashem M. Simultaneous biodegradation of harmful Cylindrospermopsis raciborskii and cylindrospermopsin toxin in batch culture by single Bacillus strain. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:5153-5161. [PMID: 34417702 DOI: 10.1007/s11356-021-16062-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 08/16/2021] [Indexed: 06/13/2023]
Abstract
This study investigates the capability of a Bacillus flexus strain isolated from decayed cyanobacterial blooms for the bioremediation of Cylindrospermopsis raciborskii and cylindrospermopsin (CYN) toxin. The algicidal activity of this strain was tested by co-cultivation with C. raciborskii cultures. CYN biodegradation was investigated in the presence of living and heat-inactivated bacterial cells or bacterial filtrate. Living bacterial cells inhibited C. raciborskii growth after 2 days of incubation with complete cell death at day 5. Bacterial filtrate caused a rapid reduction in C. raciborskii growth at the first day, with complete cell lysis at day 3. Only living cells of SSZ01 caused reduction in CYN released into the medium during the bacterial decay of C. raciborskii cells. The biodegradation rate of CYN by SSZ01 relied on initial toxin concentrations. The highest rate (42 μg CYN L-1 day-1) was obtained at the higher initial concentration (300 μg L-1), and the lowest (4μg CYN L-1 day-1) was at lower concentration (50 μg L-1). These results suggest that this bacterial strain could be employed to bioremediate cyanobacterial blooms in freshwaters. Also, the application of this bacterium in slow sand filters would give possibilities for degradation and bioremediation of cyanotoxins in drinking water treatment plants.
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Affiliation(s)
- Zakaria Mohamed
- Faculty of Science, Department of Botany and Microbiology, Sohag University, Sohag, 82524, Egypt.
| | - Saad Alamri
- Department of Biology, King Khalid University, College of Science, Abha, 61413, Saudi Arabia
| | - Mohamed Hashem
- Department of Biology, King Khalid University, College of Science, Abha, 61413, Saudi Arabia
- Faculty of Science, Botany and Microbiology Department, Assiut University, Assiut, 71516, Egypt
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11
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Martínez-Ruiz EB, Cooper M, Barrero-Canosa J, Haryono MAS, Bessarab I, Williams RBH, Szewzyk U. Genome analysis of Pseudomonas sp. OF001 and Rubrivivax sp. A210 suggests multicopper oxidases catalyze manganese oxidation required for cylindrospermopsin transformation. BMC Genomics 2021; 22:464. [PMID: 34157973 PMCID: PMC8218464 DOI: 10.1186/s12864-021-07766-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 06/03/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cylindrospermopsin is a highly persistent cyanobacterial secondary metabolite toxic to humans and other living organisms. Strain OF001 and A210 are manganese-oxidizing bacteria (MOB) able to transform cylindrospermopsin during the oxidation of Mn2+. So far, the enzymes involved in manganese oxidation in strain OF001 and A210 are unknown. Therefore, we analyze the genomes of two cylindrospermopsin-transforming MOB, Pseudomonas sp. OF001 and Rubrivivax sp. A210, to identify enzymes that could catalyze the oxidation of Mn2+. We also investigated specific metabolic features related to pollutant degradation and explored the metabolic potential of these two MOB with respect to the role they may play in biotechnological applications and/or in the environment. RESULTS Strain OF001 encodes two multicopper oxidases and one haem peroxidase potentially involved in Mn2+ oxidation, with a high similarity to manganese-oxidizing enzymes described for Pseudomonas putida GB-1 (80, 83 and 42% respectively). Strain A210 encodes one multicopper oxidase potentially involved in Mn2+ oxidation, with a high similarity (59%) to the manganese-oxidizing multicopper oxidase in Leptothrix discophora SS-1. Strain OF001 and A210 have genes that might confer them the ability to remove aromatic compounds via the catechol meta- and ortho-cleavage pathway, respectively. Based on the genomic content, both strains may grow over a wide range of O2 concentrations, including microaerophilic conditions, fix nitrogen, and reduce nitrate and sulfate in an assimilatory fashion. Moreover, the strain A210 encodes genes which may convey the ability to reduce nitrate in a dissimilatory manner, and fix carbon via the Calvin cycle. Both MOB encode CRISPR-Cas systems, several predicted genomic islands, and phage proteins, which likely contribute to their genome plasticity. CONCLUSIONS The genomes of Pseudomonas sp. OF001 and Rubrivivax sp. A210 encode sequences with high similarity to already described MCOs which may catalyze manganese oxidation required for cylindrospermopsin transformation. Furthermore, the analysis of the general metabolism of two MOB strains may contribute to a better understanding of the niches of cylindrospermopsin-removing MOB in natural habitats and their implementation in biotechnological applications to treat water.
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Affiliation(s)
- Erika Berenice Martínez-Ruiz
- Chair of Environmental Microbiology, Technische Universität Berlin, Institute of Environmental Technology, Straße des 17. Juni 135, 10623, Berlin, Germany.
| | - Myriel Cooper
- Chair of Environmental Microbiology, Technische Universität Berlin, Institute of Environmental Technology, Straße des 17. Juni 135, 10623, Berlin, Germany.
| | - Jimena Barrero-Canosa
- Chair of Environmental Microbiology, Technische Universität Berlin, Institute of Environmental Technology, Straße des 17. Juni 135, 10623, Berlin, Germany
| | - Mindia A S Haryono
- Singapore Centre for Environmental Life Sciences Engineering, National University of Singapore, Singapore, 119077, Singapore
| | - Irina Bessarab
- Singapore Centre for Environmental Life Sciences Engineering, National University of Singapore, Singapore, 119077, Singapore
| | - Rohan B H Williams
- Singapore Centre for Environmental Life Sciences Engineering, National University of Singapore, Singapore, 119077, Singapore
| | - Ulrich Szewzyk
- Chair of Environmental Microbiology, Technische Universität Berlin, Institute of Environmental Technology, Straße des 17. Juni 135, 10623, Berlin, Germany
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Yang Y, Yu G, Chen Y, Jia N, Li R. Four decades of progress in cylindrospermopsin research: The ins and outs of a potent cyanotoxin. JOURNAL OF HAZARDOUS MATERIALS 2021; 406:124653. [PMID: 33321325 DOI: 10.1016/j.jhazmat.2020.124653] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/19/2020] [Accepted: 11/20/2020] [Indexed: 06/12/2023]
Abstract
The cyanotoxin cylindrospermopsin (CYN), a toxic metabolite from cyanobacteria, is of particular concern due to its cosmopolitan occurrence, aquatic bioaccumulation, and multi-organ toxicity. CYN is the second most often recorded cyanotoxin worldwide, and cases of human morbidity and animal mortality are associated with ingestion of CYN contaminated water. The toxin poses a great challenge for drinking water treatment plants and public health authorities. CYN, with the major toxicity manifested in the liver, is cytotoxic, genotoxic, immunotoxic, neurotoxic and may be carcinogenic. Adverse effects are also reported for endocrine and developmental processes. We present a comprehensive review of CYN over the past four decades since its first reported poisoning event, highlighting its global occurrence, biosynthesis, toxicology, removal, and monitoring. In addition, current data gaps are identified, and future directions for CYN research are outlined. This review is beneficial for understanding the ins and outs of this environmental pollutant, and for robustly assessing health hazards posed by CYN exposure to humans and other organisms.
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Affiliation(s)
- Yiming Yang
- Affiliated Stomatology Hospital of Guangzhou Medical University, Guangzhou Key Laboratory of Basic and Applied Research of Oral Regenerative Medicine, Guangzhou, Guangdong 510182, China
| | - Gongliang Yu
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China
| | - Youxin Chen
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China
| | - Nannan Jia
- Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Renhui Li
- College of Life and Environmental Science, Wenzhou University, Wenzhou, Zhejiang 325035, China.
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Martínez-Ruiz EB, Cooper M, Al-Zeer MA, Kurreck J, Adrian L, Szewzyk U. Manganese-oxidizing bacteria form multiple cylindrospermopsin transformation products with reduced human liver cell toxicity. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 729:138924. [PMID: 32361450 DOI: 10.1016/j.scitotenv.2020.138924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 04/03/2020] [Accepted: 04/21/2020] [Indexed: 06/11/2023]
Abstract
Cylindrospermopsin (CYN) is a toxic alkaloid highly persistent in aquatic environments. Biological removal of CYN was described previously. However, no transformation products formed by biological processes could be identified so far. Here, we describe that various manganese-oxidizing bacteria (MOB) transform CYN completely at an initial mean concentration of 7 mg L-1 (17 μM) within 3 to 34 days. Regardless of the strain, and transformation rate, transformation of CYN by MOB led to the same seven transformation products identified by mass spectrometry, which suggests that the removal of CYN by MOB follows a similar mechanism. Oxidation was the main transformation process, and the uracil moiety was the most susceptible part of the CYN molecule. In vitro cytotoxicity tests with the transformation products of CYN formed by one of the tested strains against the two human liver cell lines HepG2 and HepaRG, revealed that the transformation products were substantially less toxic than pure CYN for both cell lines. The results suggest that incubation with MOB might be an option for water treatment to remove CYN and may allow more detailed studies on the fate of CYN in the environment.
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Affiliation(s)
- Erika Berenice Martínez-Ruiz
- Technische Universität Berlin, Institute of Environmental Technology, Chair of Environmental Microbiology, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Myriel Cooper
- Technische Universität Berlin, Institute of Environmental Technology, Chair of Environmental Microbiology, Straße des 17. Juni 135, 10623 Berlin, Germany.
| | - Munir A Al-Zeer
- Technische Universität Berlin, Institute of Biotechnology, Chair of Applied Biochemistry, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Jens Kurreck
- Technische Universität Berlin, Institute of Biotechnology, Chair of Applied Biochemistry, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Lorenz Adrian
- Helmholtz-Centre for Environmental Research GmbH - UFZ, Department of Isotope Biogeochemistry, Permoserstraße 15, 04318 Leipzig, Germany; Technische Universität Berlin, Institute of Biotechnology, Chair of Geobiotechnology, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Ulrich Szewzyk
- Technische Universität Berlin, Institute of Environmental Technology, Chair of Environmental Microbiology, Straße des 17. Juni 135, 10623 Berlin, Germany
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14
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Martínez-Ruiz EB, Cooper M, Fastner J, Szewzyk U. Manganese-oxidizing bacteria isolated from natural and technical systems remove cylindrospermopsin. CHEMOSPHERE 2020; 238:124625. [PMID: 31466008 DOI: 10.1016/j.chemosphere.2019.124625] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/25/2019] [Accepted: 08/19/2019] [Indexed: 06/10/2023]
Abstract
The cyanotoxin cylindrospermopsin was discovered during a drinking water-related outbreak of human poisoning in 1979. Knowledge about the degradation of cylindrospermopsin in waterbodies is limited. So far, only few cylindrospermopsin-removing bacteria have been described. Manganese-oxidizing bacteria remove a variety of organic compounds. However, this has not been assessed for cyanotoxins yet. We investigated cylindrospermopsin removal by manganese-oxidizing bacteria, isolated from natural and technical systems. Cylindrospermopsin removal was evaluated under different conditions. We analysed the correlation between the amount of oxidized manganese and the cylindrospermopsin removal, as well as the removal of cylindrospermopsin by sterile biogenic oxides. Removal rates in the range of 0.4-37.0 μg L-1 day-1 were observed. When MnCO3 was in the media Pseudomonas sp. OF001 removed ∼100% of cylindrospermopsin in 3 days, Comamonadaceae bacterium A210 removed ∼100% within 14 days, and Ideonella sp. A288 and A226 removed 65% and 80% within 28 days, respectively. In the absence of Mn2+, strain A288 did not remove cylindrospermopsin, while the other strains removed 5-16%. The amount of manganese oxidized by the strains during the experiment did not correlate with the amount of cylindrospermopsin removed. However, the mere oxidation of Mn2+ was indispensable for cylindrospermopsin removal. Cylindrospermopsin removal ranging from 0 to 24% by sterile biogenic oxides was observed. Considering the efficient removal of cylindrospermopsin by the tested strains, manganese-oxidizing bacteria might play an important role in cylindrospermopsin removal in the environment. Besides, manganese-oxidizing bacteria could be promising candidates for biotechnological applications for cylindrospermopsin removal in water treatment plants.
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Affiliation(s)
- Erika Berenice Martínez-Ruiz
- Technische Universität Berlin, Chair of Environmental Microbiology, Ernst-Reuter-Platz 1, 10587, Berlin, Germany.
| | - Myriel Cooper
- Technische Universität Berlin, Chair of Environmental Microbiology, Ernst-Reuter-Platz 1, 10587, Berlin, Germany
| | - Jutta Fastner
- German Environment Agency, Section Drinking Water Treatment and Resource Protection, Schichauweg 58, D-12307, Berlin, Germany
| | - Ulrich Szewzyk
- Technische Universität Berlin, Chair of Environmental Microbiology, Ernst-Reuter-Platz 1, 10587, Berlin, Germany
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15
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Huang IS, Zimba PV. Cyanobacterial bioactive metabolites-A review of their chemistry and biology. HARMFUL ALGAE 2019; 86:139-209. [PMID: 31358273 DOI: 10.1016/j.hal.2019.05.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/14/2018] [Accepted: 11/16/2018] [Indexed: 06/10/2023]
Abstract
Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.
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Affiliation(s)
- I-Shuo Huang
- Center for Coastal Studies, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA.
| | - Paul V Zimba
- Center for Coastal Studies, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA
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16
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Kumar P, Hegde K, Brar SK, Cledon M, Kermanshahi-Pour A. Potential of biological approaches for cyanotoxin removal from drinking water: A review. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 172:488-503. [PMID: 30738231 DOI: 10.1016/j.ecoenv.2019.01.066] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 01/20/2019] [Accepted: 01/22/2019] [Indexed: 05/20/2023]
Abstract
Biological treatment of cyanotoxins has gained much importance in recent decades and holds a promise to work in coordination with various physicochemical treatments. In drinking water treatment plants (DWTPs), effective removal of cyanotoxins with reduced toxicity is a primary concern. Commonly used treatments, such as ozonation, chlorination or activated carbon, undergo significant changes in their operating conditions (mainly dosage) to counter the variation in different environmental parameters, such as pH, temperature, and high cyanotoxin concentration. Presence of metal ions, natural organic matter (NOM), and other chemicals demand higher dosage and hence affect the activation energy to efficiently break down the cyanotoxin molecule. Due to these higher dose requirements, the treatment leads to the formation of toxic metabolites at a concentration high enough to break the guideline values. Biological methods of cyanotoxin removal proceed via enzymatic pathway where the protein-encoding genes are often responsible for the compound breakdown into non-toxic metabolites. However, in contrast to the chemical treatment, the biological processes advance at a much slower kinetic rate, predominantly due to a longer onset period (high lag phase). In fact, more than 90% of the studies reported on the biological degradation of the cyanotoxins attribute the biodegradation to the bacterial suspension. This suspended growth limits the mass transfer kinetics due to the presence of metal ions, NOMs and, other oxidizable matter, which further prolongs the lag phase and makes biological process toxic-free, albeit less efficient. In this context, this review attempts to bring out the importance of the attached growth mechanism, in particular, the biofilm-based treatment approaches which can enhance the biodegradation rate.
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Affiliation(s)
- Pratik Kumar
- INRS-ETE, Université du Québec, 490, Rue de la Couronne, Québec, Canada G1K 9A9
| | | | - Satinder Kaur Brar
- INRS-ETE, Université du Québec, 490, Rue de la Couronne, Québec, Canada G1K 9A9; Department of Civil Engineering, Lassonde School of Engineering, York University, North York, Toronto, Ontario, Canada M3J 1P3.
| | - Maximiliano Cledon
- CIMAS (CONICET, UnComa, Rio Negro), Güemes 1030, San Antonio Oeste, Rio Negro, Argentina
| | - Azadeh Kermanshahi-Pour
- Biorefining and Remediation Laboratory, Department of Process Engineering and Applied Science, Dalhousie University, 1360 Barrington Street, Halifax, Nova Scotia, Canada B3J 1Z1
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17
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Mashile PP, Dimpe MK, Nomngongo PN. Application of waste tyre-based powdered activated carbon for the adsorptive removal of cylindrospermopsin toxins from environmental matrices: Optimization using response surface methodology and desirability function. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2019; 54:679-685. [PMID: 30821608 DOI: 10.1080/10934529.2019.1579538] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/18/2019] [Accepted: 01/28/2019] [Indexed: 06/09/2023]
Abstract
Activated carbon (AC) derived from waste tyre was investigated for the removal of cylindrospermopsin (CYN) from aqueous solutions and spiked real water samples. Response surface methodology based on Box-Behnken design was used for the optimization of experimental conditions. Based on the desirability score of 1.0, the percentage recovery of CYN was optimized at 104% and the optimum conditions were found to be 50.0 mg for the mass of adsorbent, 60 min for contact time and sample pH value of 3. The experimental equilibrium data best fitted Langmuir isotherm model and the maximum monolayer adsorption uptake of the waste tyre-based AC (WTAC) was 107 µg g-1. Kinetic studies demonstrated that the adsorption data were best described by pseudo-second-order. Finally, the optimized adsorption process was applied for the removal of CYN from real samples.
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Affiliation(s)
- Phodiso P Mashile
- a Department of Applied Chemistry , University of Johannesburg , Johannesburg , South Africa
| | - Mogolodi K Dimpe
- a Department of Applied Chemistry , University of Johannesburg , Johannesburg , South Africa
| | - Philiswa N Nomngongo
- a Department of Applied Chemistry , University of Johannesburg , Johannesburg , South Africa
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18
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Huang IS, Zimba PV. Cyanobacterial bioactive metabolites-A review of their chemistry and biology. HARMFUL ALGAE 2019; 83:42-94. [PMID: 31097255 DOI: 10.1016/j.hal.2018.11.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/14/2018] [Accepted: 11/16/2018] [Indexed: 06/09/2023]
Abstract
Cyanobacterial blooms occur when algal densities exceed baseline population concentrations. Cyanobacteria can produce a large number of secondary metabolites. Odorous metabolites affect the smell and flavor of aquatic animals, whereas bioactive metabolites cause a range of lethal and sub-lethal effects in plants, invertebrates, and vertebrates, including humans. Herein, the bioactivity, chemistry, origin, and biosynthesis of these cyanobacterial secondary metabolites were reviewed. With recent revision of cyanobacterial taxonomy by Anagnostidis and Komárek as part of the Süβwasserflora von Mitteleuropa volumes 19(1-3), names of many cyanobacteria that produce bioactive compounds have changed, thereby confusing readers. The original and new nomenclature are included in this review to clarify the origins of cyanobacterial bioactive compounds. Due to structural similarity, the 157 known bioactive classes produced by cyanobacteria have been condensed to 55 classes. This review will provide a basis for more formal procedures to adopt a logical naming system. This review is needed for efficient management of water resources to understand, identify, and manage cyanobacterial harmful algal bloom impacts.
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Affiliation(s)
- I-Shuo Huang
- Center for Coastal Studies, Texas A&M University Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA.
| | - Paul V Zimba
- Center for Coastal Studies, Texas A&M University Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA
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19
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Mohamed ZA, Bakr A. Concentrations of cylindrospermopsin toxin in water and tilapia fish of tropical fishponds in Egypt, and assessing their potential risk to human health. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:36287-36297. [PMID: 30368701 DOI: 10.1007/s11356-018-3581-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 10/23/2018] [Indexed: 06/08/2023]
Abstract
Unlike microcystin, cylindrospermospin (CYN) concentrations in fishpond water and their accumulation in fish tissues have been largely unexplored. This study determined CYN levels in water and tilapia fish organs from three tropical fishponds in southern Egypt. Water and fish samples were collected monthly from fishponds for 12 months (Oct 2012 to Sep 2013). The results revealed that six CYN-producing species of cyanobacteria dominated phytoplankton populations and formed blooms in these fishponds during warm months. Among these species, Anabaena affinis, Planktothrix agardhii, Cylindrospermopsis catemaco, and C. philippinensis were assigned as CYN producers for the first time in the present study. The highest cell densities of CYN-producing species in fishponds were recorded in August and September 2013, correlating with high temperature, pH and nutrient concentrations. Dissolved CYN was found in fishpond waters at levels (0.3-2.76 μg L-1) very close to those of particulate CYN (0.4-2.37 μg L-1). CYN was also estimated in tilapia fish organs at levels up to 417 ng g-1 in the intestines, 1500 ng g-1 in the livers, and 280 ng g-1in edible muscles. Compared to the recommended guideline (0.03 μg kg-1 day-1), the estimated daily intake (EDI) of CYN in our samples of edible muscles exceeded this limit by a factor of 1.3-14 during summer and autumn. This might represent a risk to human health upon consumption of such contaminated fish muscles. Therefore, fishponds worldwide should be monitored for the presence toxic cyanobacteria to protect humans from their potent toxins.
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Affiliation(s)
- Zakaria A Mohamed
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt.
| | - Asmaa Bakr
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt
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20
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Mohamed Z. Cyanobacterial Toxins in Water Sources and Their Impacts on Human Health. PHARMACEUTICAL SCIENCES 2017. [DOI: 10.4018/978-1-5225-1762-7.ch054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Cyanobacteria are a group of phytoplankton of marine and freshwaters. The accelerated eutrophication of water sources by agricultural and industrial run-off has increased the occurrence and intensity of cyanobacterial blooms. They are of particular concern because of their production for potent hepato-, neuro-, and dermatoxins, being hazardous to human health. Dissemination of knowledge about cyanobacteria and their cyanotoxins assists water supply authorities in developing monitoring and management plans, and provides the public with appropriate information to avoid exposure to these toxins. This chapter provides a broad overview and up-to-date information on cyanobacteria and their toxins in terms of their occurrence, chemical and toxicological characteristics, fate in the environment, guideline limits, and effective treatment techniques to remove these toxins from drinking water. Future research directions were also suggested to fill knowledge and research gaps, and advance the abilities of utilities and water treatment plant designers to deal with these toxins.
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21
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Maghsoudi E, Fortin N, Greer C, Maynard C, Pagé A, Duy SV, Sauvé S, Prévost M, Dorner S. Cyanotoxin degradation activity and mlr gene expression profiles of a Sphingopyxis sp. isolated from Lake Champlain, Canada. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2016; 18:1417-1426. [PMID: 27711837 DOI: 10.1039/c6em00001k] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A bacterium capable of degrading five microcystin (MC) variants, microcystin-LR, YR, LY, LW and LF at an initial total concentration of 50 μg l-1 in less than 16 hours was isolated from Missisquoi Bay, in the south of Quebec, Canada. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Sphingopyxis sp., designated strain MB-E. It was shown that microcystin biodegradation activity was reduced at acidic and basic pH values. Even though no biodegradation occurred at pH values of 5.05 and 10.23, strain MB-E was able to degrade MCLR and MCYR at pH 9.12 and all five MCs variants tested at pH 6.1. Genomic sequencing revealed that strain MB-E contained the microcystin degrading gene cluster, including the mlrA, mlrB, mlrC and mlrD genes, and transcriptomic analysis demonstrated that all of these genes were induced during the degradation of MCLR alone or in the mixture of all five MCs. This novel transcriptomic analysis showed that the expression of the mlr gene cluster was similar for MCLR alone, or the mixture of MCs, and appeared to be related to the total concentration of substrate. The results suggested that the bacterium used the same pathway for the degradation of all MC variants.
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Affiliation(s)
- Ehsan Maghsoudi
- Polytechnique Montreal, Civil, Mineral and Mining Engineering Department, P.O. Box 6079, Station Centre-Ville, Montreal, Quebec, Canada H3C 3A7.
| | - Nathalie Fortin
- National Research Council Canada, Energy, Mining and Environment, 6100 Royalmount Ave., Montreal, QC, Canada H4P 2R2
| | - Charles Greer
- National Research Council Canada, Energy, Mining and Environment, 6100 Royalmount Ave., Montreal, QC, Canada H4P 2R2
| | - Christine Maynard
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore, Ste-Anne-de-Bellevue, QC, Canada
| | - Antoine Pagé
- Department of Natural Resource Sciences, McGill University, 21,111 Lakeshore, Ste-Anne-de-Bellevue, QC, Canada
| | - Sung Vo Duy
- Department of Chemistry, Université de Montreal, C.P. 6128, Centre-Ville, Montreal, QC, Canada H3C 3J7
| | - Sébastien Sauvé
- Department of Chemistry, Université de Montreal, C.P. 6128, Centre-Ville, Montreal, QC, Canada H3C 3J7
| | - Michèle Prévost
- Polytechnique Montreal, Civil, Mineral and Mining Engineering Department, P.O. Box 6079, Station Centre-Ville, Montreal, Quebec, Canada H3C 3A7.
| | - Sarah Dorner
- Polytechnique Montreal, Civil, Mineral and Mining Engineering Department, P.O. Box 6079, Station Centre-Ville, Montreal, Quebec, Canada H3C 3A7.
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22
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Li H, Ai H, Kang L, Sun X, He Q. Simultaneous Microcystis Algicidal and Microcystin Degrading Capability by a Single Acinetobacter Bacterial Strain. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:11903-11911. [PMID: 27712061 DOI: 10.1021/acs.est.6b03986] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Measures for removal of toxic harmful algal blooms often cause lysis of algal cells and release of microcystins (MCs). In this study, Acinetobacter sp. CMDB-2 that exhibits distinct algal lysing activity and MCs degradation capability was isolated. The physiological response and morphological characteristics of toxin-producing Microcystis aeruginosa, the dynamics of intra- and extracellular MC-LR concentration were studied in an algal/bacterial cocultured system. The results demonstrated that Acinetobacter sp. CMDB-2 caused thorough decomposition of algal cells and impairment of photosynthesis within 24 h. Enhanced algal lysis and MC-LR release appeared with increasing bacterial density from 1 × 103 to 1 × 107 cells/mL; however, the MC-LR was reduced by nearly 94% within 14 h irrespective of bacterial density. Measurement of extracellular and intracellular MC-LR revealed that the toxin was decreased by 92% in bacterial cell incubated systems relative to control and bacterial cell-free filtrate systems. The results confirmed that the bacterial metabolite caused 92% lysis of Microcystis aeruginosa cells, whereas the bacterial cells were responsible for approximately 91% reduction of MC-LR. The joint efforts of the bacterium and its metabolite accomplished the sustainable removal of algae and MC-LR. This is the first report of a single bacterial strain that achieves these dual actions.
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Affiliation(s)
- Hong Li
- Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University , Chongqing 400044, China
| | - Hainan Ai
- Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University , Chongqing 400044, China
| | - Li Kang
- Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University , Chongqing 400044, China
| | - Xingfu Sun
- Xiamen Municipal Engineering Design Institute CO., LTD, Chongqing 401122, China
| | - Qiang He
- Key Laboratory of Eco-Environment of Three Gorges Region of Ministry of Education, Chongqing University , Chongqing 400044, China
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Characterization of cylindrospermopsin decomposition products formed under irradiation conditions. ALGAL RES 2016. [DOI: 10.1016/j.algal.2016.05.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Zhou S, Yin H, Tang S, Peng H, Yin D, Yang Y, Liu Z, Dang Z. Physiological responses of Microcystis aeruginosa against the algicidal bacterium Pseudomonas aeruginosa. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2016; 127:214-221. [PMID: 26866757 DOI: 10.1016/j.ecoenv.2016.02.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 02/02/2016] [Accepted: 02/02/2016] [Indexed: 06/05/2023]
Abstract
Proliferation of cyanobacteria in aquatic ecosystems has caused water security problems throughout the world. Our preliminary study has showed that Pseudomonas aeruginosa can inhibit the growth of cyanobacterium, Microcystis aeruginosa. In order to explore the inhibitory mechanism of P. aeruginosa on the cell growth and synthesis of intracellular substances of M. aeruginosa, concentrations of Chlorophyll-a, intracellular protein, carbohydrate, enzyme activities and ion metabolism of M. aeruginosa, were investigated. The results indicated that 83.84% algicidal efficiency of P. aeruginosa was achieved after treatment for 7 days. The strain inhibited the reproduction of M. aeruginosa by impeding the synthesis of intracellular protein and carbohydrate of cyanobacterium, and only a very small part of intracellular protein and carbohydrate was detected after exposure to P. aeruginosa for 5 days. P. aeruginosa caused the alteration of intracellular antioxidant enzyme activity of M. aeruginosa, such as catalase, peroxidase. The accumulation of malondialdehyde aggravated membrane injury after treatment for 3 days. P. aeruginosa also affected the ion metabolism of cyanobacteria. The release of Na(+) and Cl(-) was significantly enhanced while the uptake of K(+), Ca(2+), Mg(2+), NO3(-) and SO4(2)(-) decreased. Surface morphology and intracellular structure of cyanobacteria and bacterial cells changed dramatically over time as evidenced by electron microscope (SEM) and transmission electron microscope (TEM) analysis. These results revealed that the algicidal activity of P. aeruginosa was primarily due to the fermentation liquid of P. aeruginosa that impeded the synthesis of intracellular protein and carbohydrate, and damaged the cell membrane through membrane lipid peroxidation.
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Affiliation(s)
- Su Zhou
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
| | - Hua Yin
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China.
| | - Shaoyu Tang
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
| | - Hui Peng
- Department of Chemistry, Jinan University, Guangzhou 510632, Guangdong, China
| | - Donggao Yin
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
| | - Yixuan Yang
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
| | - Zehua Liu
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
| | - Zhi Dang
- Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, School of Environment and Energy, South China University of Technology, Guangzhou 510006,Guangdong, China
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Adamski M, Żmudzki P, Chrapusta E, Bober B, Kaminski A, Zabaglo K, Latkowska E, Bialczyk J. Effect of pH and temperature on the stability of cylindrospermopsin. Characterization of decomposition products. ALGAL RES 2016. [DOI: 10.1016/j.algal.2016.02.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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26
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Dziga D, Kokocinski M, Maksylewicz A, Czaja-Prokop U, Barylski J. Cylindrospermopsin Biodegradation Abilities of Aeromonas sp. Isolated from Rusałka Lake. Toxins (Basel) 2016; 8:toxins8030055. [PMID: 26927173 PMCID: PMC4810200 DOI: 10.3390/toxins8030055] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/09/2016] [Accepted: 02/09/2016] [Indexed: 11/16/2022] Open
Abstract
The occurrence of the cyanobacterial toxin cylindrospermopsin (CYN) in freshwater reservoirs is a common phenomenon. However, the biodegradation of this toxin in environmental samples has been observed only occasionally. In this work the biodegradation ability of cylindrospermopsin was investigated based on isolates from lakes with previous cyanotoxin history. Bacterial strains were identified based on the 16S rDNA and rpoD gene comparison. CYN biodegradation was monitored using the HPLC method. The R6 strain identified as Aeromonas sp. was documented as being capable of CYN removal. This biodegradation was dependent on the pH and temperature. Additionally, the stimulation of the growth of the R6 strain in the presence of CYN was indicated. Our discovery supports the hypothesis that (in analogy to the well-known phenomenon of microcystin biodegradation) in lakes dominated by potential CYN-producing cyanobacteria, the processes of microbial utilization of this toxin may occur.
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Affiliation(s)
- Dariusz Dziga
- Department of Plant Physiology and Development, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30387 Krakow, Poland.
| | - Mikolaj Kokocinski
- Department of Hydrobiology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
| | - Anna Maksylewicz
- Department of Plant Physiology and Development, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30387 Krakow, Poland.
| | - Urszula Czaja-Prokop
- Department of Plant Physiology and Development, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30387 Krakow, Poland.
| | - Jakub Barylski
- Department of Molecular Virology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.
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27
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Chen L, Zhao C, Dionysiou DD, O’Shea KE. TiO2 photocatalytic degradation and detoxification of cylindrospermopsin. J Photochem Photobiol A Chem 2015. [DOI: 10.1016/j.jphotochem.2015.03.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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28
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Rzymski P, Poniedziałek B. In search of environmental role of cylindrospermopsin: a review on global distribution and ecology of its producers. WATER RESEARCH 2014; 66:320-337. [PMID: 25222334 DOI: 10.1016/j.watres.2014.08.029] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 06/03/2023]
Abstract
Despite a significant interest in cyanotoxins over recent decades, their biological role is still poorly elucidated. Cylindrospermopsin (CYN) is a cyanobacterial metabolite that is globally identified in surface fresh- and brackish waters and whose producers are observed to spread throughout different climate zones. This paper provides a comprehensive review of the characteristics and global distribution of CYN-producing species, the variety of their chemotypes and the occurrence of strains which, while incapable of toxin synthesis, are able to produce other bioactive compounds including those that are hitherto unknown and yet to be identified. Environmental conditions that can trigger CYN production and promote growth of CYN-producers in aquatic ecosystems are also discussed. Finally, on the basis of existing experimental evidence, potential ecological role(s) of CYN are indicated. It is eventually concluded that CYN can be at least partially responsible for the ecological success of certain cyanobacteria species.
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Affiliation(s)
- Piotr Rzymski
- Department of Biology and Environmental Protection, Poznan University of Medical Sciences, Poznań, Poland.
| | - Barbara Poniedziałek
- Department of Biology and Environmental Protection, Poznan University of Medical Sciences, Poznań, Poland.
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Mohamed ZA, Hashem M, Alamri SA. Growth inhibition of the cyanobacterium Microcystis aeruginosa and degradation of its microcystin toxins by the fungus Trichoderma citrinoviride. Toxicon 2014; 86:51-8. [DOI: 10.1016/j.toxicon.2014.05.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Revised: 03/06/2014] [Accepted: 05/07/2014] [Indexed: 11/26/2022]
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30
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Sharma V, Bhandari P, Singh B, Bhatacharya A, Shanmugam V. Chitinase Expression Due to Reduction in Fusaric Acid Level in an Antagonistic Trichoderma harzianum S17TH. Indian J Microbiol 2014; 53:214-20. [PMID: 24426111 DOI: 10.1007/s12088-012-0335-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 11/06/2012] [Indexed: 11/28/2022] Open
Abstract
To study the effect of reduction in phytotoxin level on fungal chitinases, antagonistic Trichoderma spp. were screened for their ability to reduce the level of fusaric acid (FA), the phytotoxin produced by Fusarium spp. A T. harzianum isolate S17TH was able to tolerate high levels of FA (up to 500 ppm) but was unable to reduce the toxin to a significant level (non-toxic) added to minimal synthetic broth (MSB). However, the isolate was able to reduce 400 ppm FA in the liquid medium after 7 days to a non-toxic level and displayed similar level of antagonism over the control (without FA). In studies of the effect of the reduction in FA (400 ppm) level on chitinase gene expression in PCR assays, nag1 was significantly repressed but ech42 expression was only slightly repressed. Chitinase activity was either reduced or absent in the extracellular proteins of MSB supplemented with 400 ppm FA, which could be attributed to the effect of residual FA or its breakdown products through unknown mechanisms. Selection of S17TH as a toxin insensitive isolate that could commensurate the negative effect on chitinase activity makes it a potential antagonist against Fusarium spp.
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Affiliation(s)
- Vivek Sharma
- Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, 176 061 HP India
| | - Pamita Bhandari
- Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, 176 061 HP India
| | - Bikram Singh
- Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, 176 061 HP India
| | - Amita Bhatacharya
- Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, 176 061 HP India
| | - Veerubommu Shanmugam
- Council of Scientific and Industrial Research-Institute of Himalayan Bioresource Technology, Palampur, 176 061 HP India
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Cyanobacterial toxin degrading bacteria: who are they? BIOMED RESEARCH INTERNATIONAL 2013; 2013:463894. [PMID: 23841072 PMCID: PMC3690202 DOI: 10.1155/2013/463894] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 05/21/2013] [Indexed: 11/17/2022]
Abstract
Cyanobacteria are ubiquitous in nature and are both beneficial and detrimental to humans. Benefits include being food supplements and producing bioactive compounds, like antimicrobial and anticancer substances, while their detrimental effects are evident by toxin production, causing major ecological problems at the ecosystem level. To date, there are several ways to degrade or transform these toxins by chemical methods, while the biodegradation of these compounds is understudied. In this paper, we present a meta-analysis of the currently available 16S rRNA and mlrA (microcystinase) genes diversity of isolates known to degrade cyanobacterial toxins. The available data revealed that these bacteria belong primarily to the Proteobacteria, with several strains from the sphingomonads, and one from each of the Methylobacillus and Paucibacter genera. Other strains belonged to the genera Arthrobacter, Bacillus, and Lactobacillus. By combining the ecological knowledge on the distribution, abundance, and ecophysiology of the bacteria that cooccur with toxic cyanobacterial blooms and newly developed molecular approaches, it is possible not only to discover more strains with cyanobacterial toxin degradation abilities, but also to reveal the genes associated with the degradation of these toxins.
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