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Zhang X, Liu Z, Xin Z, Zhang C, Song C. Tracing Nitrogen Sources and Transformation Characteristics in a Large Basin with Spatially Heterogeneous Pollution Distribution. ENVIRONMENTAL RESEARCH 2024; 262:119859. [PMID: 39208978 DOI: 10.1016/j.envres.2024.119859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2024] [Revised: 08/18/2024] [Accepted: 08/26/2024] [Indexed: 09/04/2024]
Abstract
This study used dual stable isotope analysis to examine nitrate sources and geographical distribution in the Liao River Basin (LRB), one of China's seven major river basins. During a normal hydrological season in April 2021, water samples were taken from the main streams of the Liao River (MLR), Shuangtaizi River (STR), Hun River (HR), Taizi River (TZR), and Daliao River (DLR). Monitoring results indicated that 93% of the water samples had a total nitrogen level exceeding the Class IV limit (1.5 mg/L) of the 'Environmental Quality Standards (EQS) for surface water', indicating a serious nitrogen pollution status. 71.3% of the total nitrogen on average was in the form of nitrate. The scatterplots of δD-H2O and δ18O-H2O showed that water in TZR and DLR were mainly affected by precipitation, while MLR, STR and HR were additionally impacted by evaporation and groundwater. The overall δ15N and δ18O of NO3- varied from 7.7‰ to 17.9‰ and 0.6‰ to 11.2‰, respectively. The correlations between δ15N-NO3- and δ18O-NO3-, along with attribution results from the Bayesian isotopic mixing model, indicated a predominant role of manure/sewage (MS) pollution in affecting river nitrate, accounting for 78% of total nitrate in MLR and 72% in DLR. A positive correlation between δ15N-NO3- and δ18O-NO3- in MLR indicated the occurrence of denitrification process. Overall, attribution results showed that the primary nitrate sources varied in different river systems within such a large basin, mainly due to spatially varied land use and human activities. Tailored nitrogen management strategies should be implemented to address the main anthropogenic pressures.
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Affiliation(s)
- Xiaojing Zhang
- School of Infrastruct Engineering, Dalian University of Technology, Dalian 116024, China
| | - Zhihong Liu
- School of Infrastruct Engineering, Dalian University of Technology, Dalian 116024, China; Ningbo Institute of Dalian University of Technology, Ningbo 315000, China
| | - Zhuohang Xin
- School of Infrastruct Engineering, Dalian University of Technology, Dalian 116024, China; Ningbo Institute of Dalian University of Technology, Ningbo 315000, China.
| | - Chi Zhang
- School of Infrastruct Engineering, Dalian University of Technology, Dalian 116024, China
| | - Changchun Song
- School of Infrastruct Engineering, Dalian University of Technology, Dalian 116024, China
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Muñoz-Marín MDC, López-Lozano A, Moreno-Cabezuelo JÁ, Díez J, García-Fernández JM. Mixotrophy in cyanobacteria. Curr Opin Microbiol 2024; 78:102432. [PMID: 38325247 DOI: 10.1016/j.mib.2024.102432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 02/09/2024]
Abstract
Cyanobacteria evolved the oxygenic photosynthesis to generate organic matter from CO2 and sunlight, and they were responsible for the production of oxygen in the Earth's atmosphere. This made them a model for photosynthetic organisms, since they are easier to study than higher plants. Early studies suggested that only a minority among cyanobacteria might assimilate organic compounds, being considered mostly autotrophic for decades. However, compelling evidence from marine and freshwater cyanobacteria, including toxic strains, in the laboratory and in the field, has been obtained in the last decades: by using physiological and omics approaches, mixotrophy has been found to be a more widespread feature than initially believed. Furthermore, dominant clades of marine cyanobacteria can take up organic compounds, and mixotrophy is critical for their survival in deep waters with very low light. Hence, mixotrophy seems to be an essential trait in the metabolism of most cyanobacteria, which can be exploited for biotechnological purposes.
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Affiliation(s)
- María Del Carmen Muñoz-Marín
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Universitario ceiA3, Universidad de Córdoba, Edificio Severo Ochoa, planta 1, ala Este, Campus de Rabanales, 14071 Córdoba, Spain
| | - Antonio López-Lozano
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Universitario ceiA3, Universidad de Córdoba, Edificio Severo Ochoa, planta 1, ala Este, Campus de Rabanales, 14071 Córdoba, Spain
| | - José Ángel Moreno-Cabezuelo
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Universitario ceiA3, Universidad de Córdoba, Edificio Severo Ochoa, planta 1, ala Este, Campus de Rabanales, 14071 Córdoba, Spain
| | - Jesús Díez
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Universitario ceiA3, Universidad de Córdoba, Edificio Severo Ochoa, planta 1, ala Este, Campus de Rabanales, 14071 Córdoba, Spain.
| | - José Manuel García-Fernández
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Universitario ceiA3, Universidad de Córdoba, Edificio Severo Ochoa, planta 1, ala Este, Campus de Rabanales, 14071 Córdoba, Spain.
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3
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Kramer BJ, Hem R, Gobler CJ. Elevated CO 2 significantly increases N 2 fixation, growth rates, and alters microcystin, anatoxin, and saxitoxin cell quotas in strains of the bloom-forming cyanobacteria, Dolichospermum. HARMFUL ALGAE 2022; 120:102354. [PMID: 36470609 DOI: 10.1016/j.hal.2022.102354] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 11/02/2022] [Accepted: 11/11/2022] [Indexed: 06/17/2023]
Abstract
The effect of rising CO2 levels on cyanobacterial harmful algal blooms (CHABs) is an emerging concern, particularly within eutrophic ecosystems. While elevated pCO2 has been associated with enhanced growth rates of some cyanobacteria, few studies have explored the effect of CO2 and nitrogen availability on diazotrophic (N2-fixing) cyanobacteria that produce cyanotoxins. Here, the effects of elevated CO2 and fixed nitrogen (NO3-) availability on the growth rates, toxin production, and N2 fixation of microcystin, saxitoxin, and anatoxin-a - producing strains of the genus Dolichospermum were quantified. Growth rates of all Dolichospermum spp. were significantly increased by CO2 or both CO2 and NO3- with rates being highest in treatments with the highest levels of CO2 and NO3-for all strains. While NO3- suppressed N2 fixation, diazotrophy significantly increased when NO3--enriched Dolichospermum spp. were supplied with higher CO2 compared to cultures grown under lower CO2 levels. This suggests that diazotrophy will play an increasingly important role in N cycling in CO2-enriched, eutrophic lentic systems. NO3- significantly increased quotas of the N-rich cyanotoxins, microcystin and saxitoxin, at ambient and enriched CO2 levels, respectively. In contrast, elevated CO2 significantly decreased cell quotas of microcystin and saxitoxin, but significantly increased cell quotas of the N-poor cyanotoxin, anatoxin. N2 fixation was significantly negatively and positively correlated with quotas of N-rich and N-poor cyanotoxins, respectively. Findings suggest cellular quotas of N-rich toxins (microcystin and saxitoxin) may be significantly reduced, or cellular quotas of N-poor toxins (anatoxin) may be significantly enhanced, under elevated CO2 conditions during diazotrophic cyanobacterial blooms. Finally, in the future, ecosystems that experience combinations of excessive N loading and CO2 enrichment may become more prone to toxic blooms of Dolichospermum.
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Affiliation(s)
- Benjamin J Kramer
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968
| | - Ronojoy Hem
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968
| | - Christopher J Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, 239 Montauk Highway, Southampton, NY, United States, 11968.
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Kramer BJ, Jankowiak JG, Nanjappa D, Harke MJ, Gobler CJ. Nitrogen and phosphorus significantly alter growth, nitrogen fixation, anatoxin-a content, and the transcriptome of the bloom-forming cyanobacterium, Dolichospermum. Front Microbiol 2022; 13:955032. [PMID: 36160233 PMCID: PMC9490380 DOI: 10.3389/fmicb.2022.955032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 08/19/2022] [Indexed: 11/27/2022] Open
Abstract
While freshwater cyanobacteria are traditionally thought to be limited by the availability of phosphorus (P), fixed nitrogen (N) supply can promote the growth and/or toxin production of some genera. This study characterizes how growth on N2 (control), nitrate (NO3 -), ammonium (NH4 +), and urea as well as P limitation altered the growth, toxin production, N2 fixation, and gene expression of an anatoxin-a (ATX-A) - producing strain of Dolichospermum sp. 54. The transcriptomes of fixed N and P-limited cultures differed significantly from those of fixed N-deplete, P-replete (control) cultures, while the transcriptomes of P-replete cultures amended with either NH4 + or NO3 - were not significantly different relative to those of the control. Growth rates of Dolichospermum (sp. 54) were significantly higher when grown on fixed N relative to without fixed N; growth on NH4 + was also significantly greater than growth on NO3 -. NH4 + and urea significantly lowered N2 fixation and nifD gene transcript abundance relative to the control while cultures amended with NO3 - exhibited N2 fixation and nifD gene transcript abundance that was not different from the control. Cultures grown on NH4 + exhibited the lowest ATX-A content per cell and lower transcript abundance of genes associated ATX-A synthesis (ana), while the abundance of transcripts of several ana genes were highest under fixed N and P - limited conditions. The significant negative correlation between growth rate and cellular anatoxin quota as well as the significantly higher number of transcripts of ana genes in cultures deprived of fixed N and P relative to P-replete cultures amended with NH4 + suggests ATX-A was being actively synthesized under P limitation. Collectively, these findings indicate that management strategies that do not regulate fixed N loading will leave eutrophic water bodies vulnerable to more intense and toxic (due to increased biomass) blooms of Dolichospermum.
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Affiliation(s)
- Benjamin J. Kramer
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States
| | | | - Deepak Nanjappa
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States
| | - Matthew J. Harke
- Gloucester Marine Genomics Institute, Gloucester, MA, United States
| | - Christopher J. Gobler
- School of Marine and Atmospheric Sciences, Stony Brook University, Southampton, NY, United States
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Lu Z, Ye J, Chen Z, Xiao L, Lei L, Han BP, Paerl HW. Cyanophycin accumulated under nitrogen-fluctuating and high-nitrogen conditions facilitates the persistent dominance and blooms of Raphidiopsis raciborskii in tropical waters. WATER RESEARCH 2022; 214:118215. [PMID: 35228039 DOI: 10.1016/j.watres.2022.118215] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 02/16/2022] [Accepted: 02/20/2022] [Indexed: 06/14/2023]
Abstract
Nutrient storage is considered a critical strategy for algal species to adapt to a fluctuating nutrient supply. Luxury phosphorus (P) uptake into storage of polyphosphate extends the duration of cyanobacterial dominance and their blooms under P deficiency. However, it is unclear whether nitrogen (N) storage in the form of cyanophycin supports persistent cyanobacterial dominance or blooms in the tropics where N deficiency commonly occurs in summer. In this study, we examined genes for cyanophycin synthesis and degradation in Raphidiopsis raciborskii, a widespread and dominant cyanobacterium in tropical waters; and detected the cyanophycin accumulation under fluctuating N concentrations and its ecological role in the population dynamics of the species. The genes for cyanophycin synthesis (cphA) and degradation (cphB) were highly conserved in 21 out of 23 Raphidiopsis strains. This suggested that the synthesis and degradation of cyanophycin are evolutionarily conserved to support the proliferation of R. raciborskii in N-fluctuating and/or deficient conditions. Isotope 15N-NaNO3 labeling experiments showed that R. raciborskii QDH7 always commenced to synthesize and accumulate cyanophycin under fluctuating N conditions, regardless of whether exogenous N was deficient. When the NO3--N concentration exceeded 1.2 mg L-1, R. raciborskii synthesized cyanophycin primarily through uptake of 15N-NaNO3. However, when the NO3--N concentration was below 1.0 mg L-1, cyanophycin-based N was derived from unlabeled N2, as evidenced by increased dinitrogenase activity. Cells grown under NO3--N < 1.0 mg L-1 had lower cyanophycin accumulation rates than cells grown under NO3--N > 1.2 mg L-1. Our field investigation in a large tropical reservoir underscored the association between cyanophycin content and the population dynamics of R. raciborskii. The cyanophycin content was high in N-sufficient (NO3--N > 0.45 mg L-1) periods, and decreased in N-deficient summer. In summer, R. raciborskii sustained a relatively high biomass and produced few heterocysts (< 1%). These findings indicated that cyanophycin-released N, rather than fixed N, supported persistent R. raciborskii blooms in N-deficient seasons. Our study suggests that the highly adaptive strategy in a N2-fixing cyanobacterial species makes mitigating its bloom more difficult than previously assumed.
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Affiliation(s)
- Zhe Lu
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China
| | - Jinmei Ye
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China
| | - Zhijiang Chen
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China
| | - Lijuan Xiao
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China
| | - Lamei Lei
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China.
| | - Bo-Ping Han
- Department of Ecology and Institute of Hydrobiology, Jinan University, Guangzhou, China
| | - Hans W Paerl
- Institute of Marine Sciences, The University of North Carolina at Chapel Hill, Morehead City, United States of America
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6
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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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Zhang P, Xin Y, Zhong X, Yan Z, Jin Y, Yan M, Liu T. Integrated effects of Ulva prolifera bloom and decay on nutrients inventory and cycling in marginal sea of China. CHEMOSPHERE 2021; 264:128389. [PMID: 33038757 DOI: 10.1016/j.chemosphere.2020.128389] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 09/02/2020] [Accepted: 09/17/2020] [Indexed: 06/11/2023]
Abstract
Ulva prolifera blooms occur annually in the Yellow Sea. Most studies focus on how U. prolifera blooming is influenced by nitrogen chemical forms and concentrations, while little concern goes to how U. prolifera bloom-decay cycle would impact local seawater nutrients structure. Therefore, we use 15N-labeled NO3 tracers and transcriptome analysis to determine N uptake, metabolism, and interconversion during U. prolifera growth and decay, so that we can quantify the conversions rate and fluxes of different nitrogen chemical forms. U. prolifera absorbes 17.37 μmol g-1·d-1 NO3-N during growth. NO3-N predominates (73.75-92.15%) in the dissolved inorganic nitrogen (DIN) in U. prolifera. During decay, NH4-N accountes for 60.87-92.13% of the in-cell DIN. The decomposing U. prolifera releases considerable amounts of NH4-N and dissolved organic nitrogen (DON) (63.8-98.2% < 1 kDa fraction and 1.8-36.2% is > 1 kDa fraction) into the ambient environment. The high DON release rate (59.57 μmol g-1 d-1) indicates active DON biosynthesis in U. prolifera. The isotope 15NO3-N tracer showes that 73.6% of the 15NO3-N is transformed to DON. The <1 kDa and the >1 kDa fractions account for 67.46-90.86% and 9.14-32.54% of the DON, respectively. The high efficiency of U. prolifera in utilizing NO3-N is explained by the responsive nitrate/nitrite transporter in cell membrane, and the DON biosynthesized capability is attributed to the up-regulated glutamine synthetase. Our study highlights the unique role of U. prolifera as a "Nitrogen-Pump" in converting nitrogen chemical forms during its bloom-decay cycle and quantifies its impacts on local N-nutrients inventory.
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Affiliation(s)
- Pengyan Zhang
- College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China.
| | - Yu Xin
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
| | - Xiaosong Zhong
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
| | - Zhenwei Yan
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
| | - Yuemei Jin
- College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China.
| | - Maojun Yan
- Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao, 266100, China.
| | - Tao Liu
- College of Marine Life Sciences, Ocean University of China, 5 Yushan Road, Qingdao, 266005, China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000, China.
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Hobbs WO, Dreher TW, Davis EW, Vinebrooke RD, Wong S, Weissman T, Dawson M. Using a lake sediment record to infer the long-term history of cyanobacteria and the recent rise of an anatoxin producing Dolichospermum sp. HARMFUL ALGAE 2021; 101:101971. [PMID: 33526187 DOI: 10.1016/j.hal.2020.101971] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 12/09/2020] [Accepted: 12/11/2020] [Indexed: 06/12/2023]
Abstract
Lakes that experience recurrent toxic cyanobacterial harmful algae blooms (cyanoHABS) are often subject to cultural eutrophication, where landscape development and upland activities increase the nutrient inputs to the water column and fuel cyanoHABS. Few studies have focused on the response of a lake to nutrient inputs for which the natural geomorphic setting predisposes a nutrient-rich water column to already support abundant cyanobacteria. Here, we present a sediment core record from a lake surrounded by parkland that experiences recurrent cyanoHABs which produce dangerous levels of the neurotoxin, anatoxin-a, impacting the recreational use of the lake and park. Using photoautotrophic pigments in the sediment record, we establish cyanobacteria have long been part of the diverse and abundant phytoplankton community within the lake. Despite this long record, shotgun metagenome and other DNA analyses of the sediment record suggest that the current anatoxin-a producer Dolichospermum sp. WA102 only emerged to dominate the cyanobacterial community in the mid-1990s. A period of lakeshore farming that finished in the 1950s-1960s and possibly the stocking of rainbow trout fry (1970-2016) coincide with a progressive shift in primary production, together with a change in bacterial communities. Based on the history of the lake and contemporary ecology of Dolichospermum, we propose that the legacy of nutrient inputs and changes in nutrient cycling within the lake has encouraged the development of an ecosystem where the toxin producing Dolichospermum sp WA102 is highly competitive. Understanding the historical presence of cyanobacteria in the lake provides a context for current-day management strategies of cyanoHABs.
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Affiliation(s)
- William O Hobbs
- Washington State Department of Ecology, PO Box 47600, Olympia, WA 98502 United States.
| | - Theo W Dreher
- Department of Microbiology, Oregon State University, Corvallis, Oregon 97331 United States; Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon 97331 United States
| | - Edward W Davis
- Center for Genome Research and Biocomputing, Oregon State University, Corvallis, Oregon 97331 United States
| | - Rolf D Vinebrooke
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9 Canada
| | - Siana Wong
- Washington State Department of Ecology, PO Box 47600, Olympia, WA 98502 United States
| | - Tim Weissman
- Jefferson County Public Health, 615 Sheridan St, Port Townsend, Washington 98368 United States
| | - Michael Dawson
- Jefferson County Public Health, 615 Sheridan St, Port Townsend, Washington 98368 United States
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Understanding the Differences in the Growth and Toxin Production of Anatoxin-Producing Cuspidothrix issatschenkoi Cultured with Inorganic and Organic N Sources from a New Perspective: Carbon/Nitrogen Metabolic Balance. Toxins (Basel) 2020; 12:toxins12110724. [PMID: 33228063 PMCID: PMC7699347 DOI: 10.3390/toxins12110724] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/14/2020] [Accepted: 11/17/2020] [Indexed: 11/22/2022] Open
Abstract
Cyanotoxins are the underlying cause of the threat that globally pervasive Cyanobacteria Harmful algal blooms (CyanoHABs) pose to humans. Major attention has been focused on the cyanobacterial hepatotoxin microcystins (MCs); however, there is a dearth of studies on cyanobacterial neurotoxin anatoxins. In this study, we explored how an anatoxin-producing Cuspidothrix issatschenkoi strain responded to culture with inorganic and organic nitrogen sources in terms of growth and anatoxins production. The results of our study revealed that ʟ- alanine could greatly boost cell growth, and was associated with the highest cell productivity, while urea significantly stimulated anatoxin production with the maximum anatoxin yield reaching 25.86 μg/mg dry weight, which was 1.56-fold higher than that in the control group (BG11). To further understand whether the carbon/nitrogen balance in C. issatschenkoi would affect anatoxin production, we explored growth and toxin production in response to different carbon/nitrogen ratios (C/N). Anatoxin production was mildly promoted when the C/N ratio was within low range, and significantly inhibited when the C/N ratio was within high range, showing approximately a three-fold difference. Furthermore, the transcriptional profile revealed that anaC gene expression was significantly up-regulated over 2–24 h when the C/N ratio was increased, and was significantly down-regulated after 96 h. Overall, our results further enriched the evidence that urea can stimulate cyanotoxin production, and ʟ-alanine could boost C. issatschenkoi proliferation, thus providing information for better management of aquatic systems. Moreover, by focusing on the intracellular C/N metabolic balance, this study explained the anatoxin production dynamics in C. issatschenkoi in response to different N sources.
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10
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Christensen VG, Khan E. Freshwater neurotoxins and concerns for human, animal, and ecosystem health: A review of anatoxin-a and saxitoxin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 736:139515. [PMID: 32485372 DOI: 10.1016/j.scitotenv.2020.139515] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/15/2020] [Accepted: 05/16/2020] [Indexed: 05/06/2023]
Abstract
Toxic cyanobacteria are a concern worldwide because they can adversely affect humans, animals, and ecosystems. However, neurotoxins produced by freshwater cyanobacteria are understudied relative to microcystin. Thus, the objective of this critical review was to provide a comprehensive examination of the modes of action, production, fate, and occurrence of the freshwater neurotoxins anatoxin-a and saxitoxin as they relate to human, animal, and ecosystem health. Literature on freshwater anatoxin-a and saxitoxin was obtained and reviewed for both laboratory and field studies. Current (2020) research identifies as many as 41 anatoxin-a producing species and 15 saxitoxin-producing species of freshwater cyanobacteria. Field studies indicate that anatoxin-a and saxitoxin have widespread distribution, and examples are given from every continent except Antarctica. Human and animal health concerns can range from acute to chronic. However, few researchers studied chronic or sublethal effects of freshwater exposures to anatoxin-a or saxitoxin. Ecosystem health also is a concern, as the effects of toxicity may be far reaching and include consequences throughout the food web. Several gaps in knowledge were identified for anatoxin-a and saxitoxin, including triggers of production and release, environmental fate and degradation, primary and secondary exposure routes, diel variation, food web effects, effects of cyanotoxin mixtures, and sublethal health effects on individual organisms and populations. Despite the gaps, this critical review facilitates our current understanding of freshwater neurotoxins and thus can serve to `` guide future research on anatoxin-a, saxitoxin, and other cyanotoxins.
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Affiliation(s)
- Victoria G Christensen
- U.S. Geological Survey, Upper Midwest Water Science Center, Mounds View, MN, USA; North Dakota State University, Environmental and Conservation Sciences Program, Fargo, ND, USA.
| | - Eakalak Khan
- Civil and Environmental Engineering and Construction Department, University of Nevada - Las Vegas, Las Vegas, NV, USA
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11
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Qian ZY, Chen X, Zhu HT, Shi JZ, Gong TT, Xian QM. Study on the cyanobacterial toxin metabolism of Microcystis aeruginosa in nitrogen-starved conditions by a stable isotope labelling method. JOURNAL OF HAZARDOUS MATERIALS 2019; 373:558-564. [PMID: 30952000 DOI: 10.1016/j.jhazmat.2019.03.127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 03/16/2019] [Accepted: 03/30/2019] [Indexed: 06/09/2023]
Abstract
In this study, the biosynthesis of microcystins (MCs) was investigated after long-term nitrogen-starved conditions in cyanobacterium Microcystis aeruginosa. The results demonstrated that the algal cells were able to survive in a non-growing state with nitrogen starvation for more than one month. The physiological properties of the algal cells were studied to elucidate the mechanisms of viability under nitrogen-deprivation conditions. After the state of nitrogen chlorosis, new toxins could be resynthesized and tracked using 15N-stable isotope-labelled nitrogen. Nitrogen starvation of nutritionally replete cells resulted in a significant increase of microcystin-LY (MC-LY), thereby suggesting that MC-LY may undergo catabolism to provide nitrogen or that MC-LY may be produced to play an important role in the cell in response to nitrogen deprivation. The rank order of different types of nitrogen in algal cells assimilation was N-ammonium > N-urea > N-nitrate > N-alanine. The relationship between the production of toxin variants and various environmental conditions is an interesting issue for future research and may help improve the understanding of the ecological role of cyanobacterial toxins.
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Affiliation(s)
- Zong-Yao Qian
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
| | - Xiao Chen
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
| | - He-Te Zhu
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
| | - Jun-Zhe Shi
- Wuxi Environmental Monitoring Central Station, Wuxi, 214121, China
| | - Ting-Ting Gong
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China
| | - Qi-Ming Xian
- State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
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Zhou Y, Zhang X, Li X, Jia P, Dai R. Evaluation of changes in Microcystis aeruginosa growth and microcystin production by urea via transcriptomic surveys. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 655:181-187. [PMID: 30469064 DOI: 10.1016/j.scitotenv.2018.11.100] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Revised: 11/02/2018] [Accepted: 11/07/2018] [Indexed: 06/09/2023]
Abstract
The freshwater cyanobacteria, Microcystis aeruginosa (M. aeruginosa), is well known to produce microcystins (MCs) and induce the formation of harmful algal blooms (HABs) in aquatic environments, but the effects that urea fertilizer has on cyanobacterial growth and toxin production from a molecular biology perspective remain poorly understood. We evaluated changes in the growth and toxicity of M. aeruginosa cultured under different conditions of nitrogen (N) starvation (NN), low nitrogen (LN), and high nitrogen (HN). Cell density and chlorophyll-a concentrations decreased in cyanobacteria exposed to N starvation and increased following the addition of urea, whereas MCs content increased to a peak and then decreased after urea addition. Transcriptomic analysis confirmed that most genes encoding MCs and genes involved in N metabolic pathways were upregulated under N starvation and LN conditions, whereas these genes were downregulated under HN conditions. Our results offer important insights into the exploring N in controlling the formation of HABs and toxin production based on both physiological and molecular response.
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Affiliation(s)
- Yanping Zhou
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China
| | - Xufeng Zhang
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China
| | - Xuan Li
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China
| | - Peili Jia
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China
| | - Ruihua Dai
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China.
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Cho Y, Tsuchiya S, Omura T, Koike K, Oikawa H, Konoki K, Oshima Y, Yotsu-Yamashita M. Metabolomic study of saxitoxin analogues and biosynthetic intermediates in dinoflagellates using 15N-labelled sodium nitrate as a nitrogen source. Sci Rep 2019; 9:3460. [PMID: 30837523 PMCID: PMC6401167 DOI: 10.1038/s41598-019-39708-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 01/30/2019] [Indexed: 12/27/2022] Open
Abstract
A stable-isotope-labelling method using 15N-labelled sodium nitrate as a nitrogen source was developed for the toxic dinoflagellate Alexandrium catenella. The labelled saxitoxin analogues (STXs), their precursor, and the biosynthetic intermediates were analyzed by column-switching high-resolution hydrophilic interaction liquid chromatography with mass spectrometry. The low contents on Day 0, high 15N incorporation % of Int-C'2 and Int-E' suggested that their turn-over rates are high and that the sizes of the pool of these compounds are smaller than those of the other intermediates. The experimentally determined isotopomer distributions showed that arginine, Int-C'2, 11-hydroxy-Int-C'2, Int-E', GTX5, GTX4, C1, and C2, each existed as a combination of three populations that consisted of the non-labelled molecules and the labelled isotopomers representing molecules newly synthesized by incorporation of 15N assimilated from the medium with two different incorporation rates. The order of 15N incorporation % values of the labelled populations predicted by this model largely agreed with the proposed biosynthetic route. The stable-isotope-labelling method will be useful for understanding the complex mechanism of nitrogen flux in STX-producing dinoflagellates.
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Affiliation(s)
- Yuko Cho
- Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan.
| | - Shigeki Tsuchiya
- Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
| | - Takuo Omura
- Laboratory of Aquatic Science Consultant Co., LTD., 2-30-17, Higashikamata, Ota-ku, Tokyo, 144-0031, Japan
| | - Kazuhiko Koike
- Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528, Japan
| | - Hiroshi Oikawa
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648, Japan
| | - Keiichi Konoki
- Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
| | - Yasukatsu Oshima
- Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan
| | - Mari Yotsu-Yamashita
- Graduate School of Agricultural Science, Tohoku University, 468-1 Aramaki Aza Aoba, Aoba-ku, Sendai, Miyagi, 980-8572, Japan
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