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Jacquemin SJ, Doll JC, Johnson LT, Newell SE. Exploring long-term trends in microcystin toxin values associated with persistent harmful algal blooms in Grand Lake St Marys. HARMFUL ALGAE 2023; 122:102374. [PMID: 36754460 DOI: 10.1016/j.hal.2023.102374] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 12/27/2022] [Accepted: 01/02/2023] [Indexed: 06/18/2023]
Abstract
High external nutrient loads from agricultural runoff have led to persistent and highly toxic algal blooms in Grand Lake St Marys (GLSM) for decades. These pervasive blooms are concurrent with long-term (2009 - 2021) toxin and environmental monitoring, providing a robust weekly dataset for modeling microcystins. Median weekly microcystin concentrations (23.2 µg/L) routinely exceeded World Health Organization recreational limits (20 µg/L) for the study period (ranged 0.03 - 185.0 µg/L). Here, we used a Bayesian hierarchical dynamic linear model to hindcast weekly microcystin toxins using external nutrient loads from tributary data as well as internal lake nutrient and physicochemical concentrations. Overall, lake TN was the biggest driver of microcystin concentration in GLSM. Likewise, TN:TP was a strong negative driver of microcystin (i.e. low N:P ratios align with lower total microcystins), suggesting that N availability directly impacts toxins. External nutrient loading was positively related to microcystin during winter and spring; however, there was no relationship detected between toxin and external loading during summer or fall (particulate phosphorus exhibited the strongest signal but all external nutrients were unsurprisingly correlated). This lack of direct correlation on a weekly timescale between external loads and cyanobacterial toxins during the summer months likely results from nutrient saturation and reflects the importance of internal loading for bloom maintenance as supported by the correlation between in-lake TN and microcystin. Thus, management goals to reduce the highest biomass and toxins in the summer should focus on reduction of winter and spring external nutrient loads. Supporting this, both 2010 and 2021 had lower rain in the first half of the year (winter/spring), resulting in less loading, and experienced smaller/later low toxicity blooms. This suggests that, although internal nutrient loads are important for bloom maintenance, reduced external loads are an effective management strategy even in nutrient saturated systems such as GLSM.
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Affiliation(s)
- Stephen J Jacquemin
- Wright State University - Lake Campus, Department of Biological Sciences, Agriculture and Water Quality Education Center, Celina, Ohio 45822, United States.
| | - Jason C Doll
- Francis Marion University, Department of Biology, Florence, South Carolina 29502, United States
| | - Laura T Johnson
- Heidelberg University, National Center for Water Quality Research, Tiffin, Ohio 44883, United States
| | - Silvia E Newell
- Wright State University, Department of Earth and Environmental Sciences, Dayton, Ohio 45435, United States
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2
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Zhou Y, Li X, Xia Q, Dai R. Transcriptomic survey on the microcystins production and growth of Microcystis aeruginosa under nitrogen starvation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 700:134501. [PMID: 31689655 DOI: 10.1016/j.scitotenv.2019.134501] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 09/15/2019] [Accepted: 09/15/2019] [Indexed: 06/10/2023]
Abstract
Cyanobacteria are a vital component of freshwater phytoplankton, and many species are recognized for their ability to produce toxins and harmful algal blooms (HABs). Nitrogen is an essential element of all the complex macromolecules in algal cells. However, the underlying molecular mechanism of the changes in transcriptomic patterns and physiological responses in response to N starvation is poorly understood. The transcriptomes were generated via RNA-sequencing (RNA-Seq) technology to study the major metabolic pathway under N starvation. The results shed light on the mechanism of toxin production and physiological adaptations in Microcystis aeruginosa (M. aeruginosa). The cell density gradually increased during the first two days then declined over time and was finally stable at (15.50 ± 0.5) × 105 cell mL-1 after 6 days. The chlorophyll-a content and phycocyanin content of M. aeruginosa increased during the first two days and subsequently decreased markedly over time under N starvation. The variable to maximum chlorophyll fluorescence ratio (Fv/Fm ratio) decreased with time under N starvation. Most photosynthesis genes have similarity decreasing trends with growth physiological changes. The microcystins (MCs) levels generally increased first, reaching a peak value with 1.35 pg cell-1 on the fifth day, and then remained roughly constant. The genes involved in N metabolism-related gene expression were upregulated to maintain normal biological activity, while the genes involved in photosynthesis-related gene expression were downregulated to save energy. All genes encoding algae toxin synthesis were upregulated under N starvation. The observed expression patterns demonstrate that all MCs genes respond similarly to MCs production within the cell. Our results indicate the response mechanism of M. aeruginosa under N starvation and provide a comprehensive understanding of N-controlling cyanobacteria and MCs synthesis.
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Affiliation(s)
- Yanping Zhou
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Xuan Li
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China
| | - Qiongqiong Xia
- North China Municipal Engineering Design & Research Institute Co. Ltd., Tianjin 300074, China
| | - Ruihua Dai
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China.
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3
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Su X, Steinman AD, Oudsema M, Hassett M, Xie L. The influence of nutrients limitation on phytoplankton growth and microcystins production in Spring Lake, USA. CHEMOSPHERE 2019; 234:34-42. [PMID: 31203039 DOI: 10.1016/j.chemosphere.2019.06.047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/22/2019] [Accepted: 06/06/2019] [Indexed: 06/09/2023]
Abstract
Due to excessive loadings of nitrogen (N) and phosphorus (P), frequent blooms of harmful cyanobacteria and their associated cyanotoxins pose serious threats to recreational usage and human health. However, whether cyanobacteria growth and toxin production are limited by N, P, or both N + P is still not clear. Thus, we conducted a nutrient enrichment bioassay in situ in Spring Lake, a eutrophic lake in west Michigan, USA, to examine the influence of nutrient limitation on the proliferation of algal blooms and the production of microcystins (MC). N or P addition alone resulted in a slight increase in the concentration of chlorophyll-a (Chl-a), suggesting a positive effect on phytoplankton growth, but alone, neither were sufficient to induce algal blooms. In contrast, the combination of N and P had a significant and positive influence on phytoplankton growth and MC production. Compared to controls, the N + P treatment resulted in high concentrations of Chl-a and MC, as well as high pH and dissolved oxygen. In addition, significant increases were observed in different MC analogues for each treatment; the highest concentrations of intracellular MC-LR, -RR, -YR, and TMC (total MC) were found in the N + P treatment with values of 9.16, 6.10, 2.57, and 17.82 μg/L, respectively. This study suggests that at least in this temperate coastal lake, cyanobacterial blooms and associated MC are influenced more by combined N and P enrichment than by N or P alone, indicating that managing both nutrients is important for effectively reducing algal blooms and MC production.
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Affiliation(s)
- Xiaomei Su
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; Jiangsu Provincial Key Laboratory of Environmental Engineering, Jiangsu Provincial Academy of Environmental Sciences, Nanjing, 210036, China
| | - Alan D Steinman
- Annis Water Resources Institute, Grand Valley State University, Muskegon, MI, 49441, USA
| | - Maggie Oudsema
- Annis Water Resources Institute, Grand Valley State University, Muskegon, MI, 49441, USA
| | - Michael Hassett
- Annis Water Resources Institute, Grand Valley State University, Muskegon, MI, 49441, USA
| | - Liqiang Xie
- State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
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4
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Chen Q, Wang M, Zhang J, Shi W, Mynett AE, Yan H, Hu L. Physiological effects of nitrate, ammonium, and urea on the growth and microcystins contamination of Microcystis aeruginosa: Implication for nitrogen mitigation. WATER RESEARCH 2019; 163:114890. [PMID: 31351354 DOI: 10.1016/j.watres.2019.114890] [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: 03/28/2019] [Revised: 07/18/2019] [Accepted: 07/19/2019] [Indexed: 05/03/2023]
Abstract
The effects of three commonly bioavailable nitrogen (N) sources (nitrate, ammonium, and urea) on regulating the growth and microcystins (MCs) production of Microcystis aeruginosa (M. aeruginosa) at environmentally relevant concentrations were investigated from a physiological perspective. Changes in amino acid quotas as well as the transcripts of target genes associated with N metabolism (ntcA, pipX and glnB) and toxin formation (mcyA and mcyD) were determined. Results indicated that increases in nitrate and urea concentrations enhanced M. aeruginosa growth, but high ammonium concentration (7 mg-N/L) suppressed the growth. The total intracellular MCs (IMCs) content was well correlated (0.65, p < 0.001) to amino acids (the sum of methionine, leucine, serine, alanine, arginine, glutamic acid, and aspartic acid) associated with MCs production. Ammonium favors amino acid synthesis in M. aeruginosa, thus cells grown under high concentrations of ammonium (7 mg-N/L) had sufficient precursors for MCs production, which might lead to higher IMCs. Both high and low ammonium concentration resulted in high total extracellular MCs (EMCs) level in water, despite of their different mechanisms. These results indicated that mitigation of nitrogen in eutrophic waters should be very cautious of unexpected risks, as the reduction of ammonium may have the risk of stimulating M. aeruginosa growth or increasing EMCs levels.
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Affiliation(s)
- Qiuwen Chen
- State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing, 210029, China; Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China.
| | - Min Wang
- State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing, 210029, China; Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
| | - Jianyun Zhang
- State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing, 210029, China.
| | - Wenqing Shi
- State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing Hydraulic Research Institute, Nanjing, 210029, China; Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
| | - Arthur E Mynett
- Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
| | - Hanlu Yan
- Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
| | - Liuming Hu
- Center for Eco-Environmental Research, Nanjing Hydraulic Research Institute, Nanjing, 210029, China
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5
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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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6
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Newell SE, Davis TW, Johengen TH, Gossiaux D, Burtner A, Palladino D, McCarthy MJ. Reduced forms of nitrogen are a driver of non-nitrogen-fixing harmful cyanobacterial blooms and toxicity in Lake Erie. HARMFUL ALGAE 2019; 81:86-93. [PMID: 30638502 DOI: 10.1016/j.hal.2018.11.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 11/05/2018] [Accepted: 11/06/2018] [Indexed: 06/09/2023]
Abstract
Western Lake Erie (WLE) experiences anthropogenic eutrophication and annual, toxic cyanobacterial blooms of non-nitrogen (N) fixing Microcystis. Numerous studies have shown that bloom biomass is correlated with an increased proportion of soluble reactive phosphorus loading from the Maumee River. Long term monitoring shows that the proportion of the annual Maumee River N load of non-nitrate N, or total Kjeldahl nitrogen (TKN), has also increased significantly (Spearman's ρ = 0.68, p = 0.001) over the last few decades and is also significantly correlated to cyanobacterial bloom biomass (Spearman's ρ = 0.64, p = 0.003). The ratio of chemically reduced N to oxidized N (TKN:NO3) concentrations was also compared to extracted chlorophyll and phycocyanin concentrations from all weekly sampling stations within WLE from 2009 to 2015. Both chlorophyll (Spearman's ρ = 0.657, p < 0.0001) and phycocyanin (Spearman's ρ = 0.714, p < 0.0001) were significantly correlated with TKN:NO3. This correlation between the increasing fraction of chemically reduced N from the Maumee River and increasing bloom biomass demonstrates the urgent need to control N loading, in addition to current P load reductions, to WLE and similar systems impacted by non-N-fixing, toxin-producing cyanobacteria.
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Affiliation(s)
- Silvia E Newell
- Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45458, USA.
| | - Timothy W Davis
- NOAA GLERL, 4840 South State Rd., Ann Arbor, MI, 48108, USA; Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Thomas H Johengen
- NOAA GLERL, 4840 South State Rd., Ann Arbor, MI, 48108, USA; Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Duane Gossiaux
- NOAA GLERL, 4840 South State Rd., Ann Arbor, MI, 48108, USA
| | - Ashley Burtner
- Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Danna Palladino
- Cooperative Institute for Great Lakes Research, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Mark J McCarthy
- Wright State University, 3640 Colonel Glenn Highway, Dayton, OH, 45458, USA
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7
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Esteves-Ferreira AA, Inaba M, Fort A, Araújo WL, Sulpice R. Nitrogen metabolism in cyanobacteria: metabolic and molecular control, growth consequences and biotechnological applications. Crit Rev Microbiol 2018. [DOI: 10.1080/1040841x.2018.1446902] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Alberto A. Esteves-Ferreira
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
- CAPES Foundation, Ministry of Education of Brazil, Brasilia, Brazil
| | - Masami Inaba
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Antoine Fort
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Wagner L. Araújo
- Max-Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Brazil
| | - Ronan Sulpice
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
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8
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Chaffin JD, Davis TW, Smith DJ, Baer MM, Dick GJ. Interactions between nitrogen form, loading rate, and light intensity on Microcystis and Planktothrix growth and microcystin production. HARMFUL ALGAE 2018; 73:84-97. [PMID: 29602509 DOI: 10.1016/j.hal.2018.02.001] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 02/02/2018] [Accepted: 02/02/2018] [Indexed: 05/26/2023]
Abstract
The toxin-producing, bloom-forming cyanobacterial genera Microcystis and Planktothrix require fixed nitrogen (N), such as nitrate, ammonium, or organic N (e.g., urea) for growth and production of microcystins (MC). Bioavailable N can enter lakes in pulses via tributary discharge and through in-lake recycling, which can maintain low N concentrations. Additionally, light intensity has been suggested to play a role in MC production. This study examined how three forms of N (nitrate, ammonium, and urea) interacted with N loading rate (one large pulse vs. many small pulses) and light intensity to stimulate Microcystis and Planktothrix growth and MC production using nutrient enrichment experiments. Enrichments of nitrate, ammonium, and urea resulted in greater cyanobacterial biovolumes and MC concentrations than phosphorus-only enrichments, and there was no difference between pulse (100 μmol/L) and press treatments (8.3 μmol/L every 4 h). Analysis of mcyD transcripts showed significant up-regulation within 4 h of ammonium and urea enrichment. High light intensities (300 μmol photons/m2/s) with N enrichment resulted in greater cyanobacterial biovolumes and MC concentrations than lower light intensities (30 and 3 μmol photons/m2/s). Overall, the results suggest Microcystis and Planktothrix can use many forms of N and that high light intensities enhance MC production during elevated N concentrations. Moreover, the results here further demonstrate the importance of considering N, as well as P, in management strategies aimed at mitigating cyanobacterial blooms.
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Affiliation(s)
- Justin D Chaffin
- F.T. Stone Laboratory and Ohio Sea Grant, The Ohio State University, 878 Bayview Ave, P.O. Box 119, Put-in-Bay, OH 43456-0119, USA.
| | - Timothy W Davis
- NOAA Great Lakes Environmental Research Laboratory, 4840 S. State Road, Ann Arbor, MI 48108-9719, USA
| | - Derek J Smith
- Department of Earth & Environmental Sciences, University of Michigan, 1100 N. University Ave, Ann Arbor, MI 48109-1005, USA
| | - Mikayla M Baer
- F.T. Stone Laboratory and Ohio Sea Grant, The Ohio State University, 878 Bayview Ave, P.O. Box 119, Put-in-Bay, OH 43456-0119, USA
| | - Gregory J Dick
- Department of Earth & Environmental Sciences, University of Michigan, 1100 N. University Ave, Ann Arbor, MI 48109-1005, USA
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9
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Domínguez-Martín MA, López-Lozano A, Clavería-Gimeno R, Velázquez-Campoy A, Seidel G, Burkovski A, Díez J, García-Fernández JM. Differential NtcA Responsiveness to 2-Oxoglutarate Underlies the Diversity of C/N Balance Regulation in Prochlorococcus. Front Microbiol 2018; 8:2641. [PMID: 29375510 PMCID: PMC5767323 DOI: 10.3389/fmicb.2017.02641] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 12/19/2017] [Indexed: 11/29/2022] Open
Abstract
Previous studies showed differences in the regulatory response to C/N balance in Prochlorococcus with respect to other cyanobacteria, but no information was available about its causes, or the ecological advantages conferred to thrive in oligotrophic environments. We addressed the changes in key enzymes (glutamine synthetase, isocitrate dehydrogenase) and the ntcA gene (the global nitrogen regulator) involved in C/N metabolism and its regulation, in three model Prochlorococcus strains: MED4, SS120, and MIT9313. We observed a remarkable level of diversity in their response to azaserine, a glutamate synthase inhibitor which increases the concentration of the key metabolite 2-oxoglutarate, used to sense the C/N balance by cyanobacteria. Besides, we studied the binding between the global nitrogen regulator (NtcA) and the promoter of the glnA gene in the same Prochlorococcus strains, and its dependence on the 2-oxoglutarate concentration, by using isothermal titration calorimetry, surface plasmon resonance, and electrophoretic mobility shift. Our results show a reduction in the responsiveness of NtcA to 2-oxoglutarate in Prochlorococcus, especially in the MED4 and SS120 strains. This suggests a trend to streamline the regulation of C/N metabolism in late-branching Prochlorococcus strains (MED4 and SS120), in adaptation to the rather stable conditions found in the oligotrophic ocean gyres where this microorganism is most abundant.
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Affiliation(s)
- María A Domínguez-Martín
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CeiA3, Universidad de Córdoba, Córdoba, Spain
| | - Antonio López-Lozano
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CeiA3, Universidad de Córdoba, Córdoba, Spain
| | - Rafael Clavería-Gimeno
- Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units BIFI-IQFR-CSIC and GBsC-BIFI-CSIC, Universidad de Zaragoza, Zaragoza, Spain.,Aragon Institute for Health Research (IIS Aragon), Zaragoza, Spain.,Instituto Aragonés de Ciencias de la Salud, Zaragoza, Spain
| | - Adrián Velázquez-Campoy
- Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Units BIFI-IQFR-CSIC and GBsC-BIFI-CSIC, Universidad de Zaragoza, Zaragoza, Spain.,Aragon Institute for Health Research (IIS Aragon), Zaragoza, Spain.,Centro de Investigación Biomédica en Red en el Área Temática de Enfermedades Hepáticas y Digestivas, Barcelona, Spain.,Fundación ARAID, Gobierno de Aragón, Zaragoza, Spain
| | - Gerald Seidel
- Professur für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Andreas Burkovski
- Professur für Mikrobiologie, Department Biologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Jesús Díez
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CeiA3, Universidad de Córdoba, Córdoba, Spain
| | - José M García-Fernández
- Departamento de Bioquímica y Biología Molecular, Campus de Excelencia Internacional Agroalimentario CeiA3, Universidad de Córdoba, Córdoba, Spain
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10
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Banerjee S, Subramanian A, Chattopadhyay J, Sarkar RR. Exploring the role of GS-GOGAT cycle in microcystin synthesis and regulation - a model based analysis. MOLECULAR BIOSYSTEMS 2017; 13:2603-2614. [PMID: 29034927 DOI: 10.1039/c7mb00342k] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Toxic cyanobacteria blooms populate water bodies by consuming external nutrients and releasing cyanotoxins that are detrimental for other aquatic species, producing a significant impact on the plankton ecosystem and food web. To exercise population-level control of toxin production, understanding the biochemical mechanisms that explain cyanotoxin regulation within a bacterial cell is of utmost importance. In this study, we explore the mechanistic events to investigate the dependence of toxin microcystin on external nitrogen, a known regulator of the toxin, and for the first time, propose a kinetic model that analyzes the intracellular conditions required to ensure nitrogen dependence on microcystin. We hypothesize that the GS-GOGAT cycle is manipulated by variable influx of different intracellular metabolites that can either disturb or promote the balance between the enzyme microcystin synthetase and substrate glutamate to produce variable microcystin levels. As opposed to the popular notion that nitrogen starvation increases microcystin synthesis, our analyses suggest that under certain intracellular metabolite regimes, this relationship can either be completely lost or reversed. External nitrogen can only complement the conditions fixed by intracellular glutamate, glutamine and 2-oxoglutarate. This mechanistic understanding can provide an experimentally testable hypothesis for exploring the less-known biology of microcystin synthesis and designing specific interventions.
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Affiliation(s)
- Swarnendu Banerjee
- Agricultural and Ecological Research Unit, Indian Statistical Institute, 203, B. T. Road, Kolkata 700108, India
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11
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Omidi A, Esterhuizen-Londt M, Pflugmacher S. Still challenging: the ecological function of the cyanobacterial toxin microcystin – What we know so far. TOXIN REV 2017. [DOI: 10.1080/15569543.2017.1326059] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Azam Omidi
- Institute of Biotechnology, Chair Ecological Impact Research and Ecotoxicology, Technische Universität Berlin, Berlin, Germany and
| | - Maranda Esterhuizen-Londt
- Institute of Biotechnology, Chair Ecological Impact Research and Ecotoxicology, Technische Universität Berlin, Berlin, Germany and
| | - Stephan Pflugmacher
- Institute of Biotechnology, Chair Ecological Impact Research and Ecotoxicology, Technische Universität Berlin, Berlin, Germany and
- Joint laboratory of Applied Ecotoxicology, Korea Institute of Science and Technology Europe (KIST), Saarbrücken, Germany
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12
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Paerl HW, Scott JT, McCarthy MJ, Newell SE, Gardner WS, Havens KE, Hoffman DK, Wilhelm SW, Wurtsbaugh WA. It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:10805-10813. [PMID: 27667268 DOI: 10.1021/acs.est.6b02575] [Citation(s) in RCA: 230] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Preventing harmful algal blooms (HABs) is needed to protect lakes and downstream ecosystems. Traditionally, reducing phosphorus (P) inputs was the prescribed solution for lakes, based on the assumption that P universally limits HAB formation. Reduction of P inputs has decreased HABs in many lakes, but was not successful in others. Thus, the "P-only" paradigm is overgeneralized. Whole-lake experiments indicate that HABs are often stimulated more by combined P and nitrogen (N) enrichment rather than N or P alone, indicating that the dynamics of both nutrients are important for HAB control. The changing paradigm from P-only to consideration of dual nutrient control is supported by studies indicating that (1) biological N fixation cannot always meet lake ecosystem N needs, and (2) that anthropogenic N and P loading has increased dramatically in recent decades. Sediment P accumulation supports long-term internal loading, while N may escape via denitrification, leading to perpetual N deficits. Hence, controlling both N and P inputs will help control HABs in some lakes and also reduce N export to downstream N-sensitive ecosystems. Managers should consider whether balanced control of N and P will most effectively reduce HABs along the freshwater-marine continuum.
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Affiliation(s)
- Hans W Paerl
- Institute of Marine Sciences, University of North Carolina at Chapel Hill , 3431 Arendell Street, Morehead City, North Carolina 28557, United States
| | - J Thad Scott
- Department of Biology, Baylor University , One Bear Place #97388, Waco, Texas 76798, United States
| | - Mark J McCarthy
- Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States
| | - Silvia E Newell
- Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States
| | - Wayne S Gardner
- Marine Science Institute, The University of Texas at Austin , 750 Channel View Drive, Port Aransas, Texas 78373, United States
| | - Karl E Havens
- University of Florida Institute of Food and Agricultural Sciences, and Florida Sea Grant College Program, Gainesville, Florida 32608, United States
| | - Daniel K Hoffman
- Dept. of Earth and Environmental Sciences, Wright State University , Dayton, Ohio 45435, United States
| | - Steven W Wilhelm
- Department of Microbiology, The University of Tennessee , Knoxville, Tennessee 37996-0845, United States
| | - Wayne A Wurtsbaugh
- Watershed Sciences Department and the Ecology Center, Utah State University , Logan, Utah 84322-5210, United States
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13
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Harke MJ, Steffen MM, Gobler CJ, Otten TG, Wilhelm SW, Wood SA, Paerl HW. A review of the global ecology, genomics, and biogeography of the toxic cyanobacterium, Microcystis spp. HARMFUL ALGAE 2016; 54:4-20. [PMID: 28073480 DOI: 10.1016/j.hal.2015.12.007] [Citation(s) in RCA: 511] [Impact Index Per Article: 63.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 12/22/2015] [Indexed: 05/03/2023]
Abstract
This review summarizes the present state of knowledge regarding the toxic, bloom-forming cyanobacterium, Microcystis, with a specific focus on its geographic distribution, toxins, genomics, phylogeny, and ecology. A global analysis found documentation suggesting geographic expansion of Microcystis, with recorded blooms in at least 108 countries, 79 of which have also reported the hepatatoxin microcystin. The production of microcystins (originally "Fast-Death Factor") by Microcystis and factors that control synthesis of this toxin are reviewed, as well as the putative ecophysiological roles of this metabolite. Molecular biological analyses have provided significant insight into the ecology and physiology of Microcystis, as well as revealed the highly dynamic, and potentially unstable, nature of its genome. A genetic sequence analysis of 27 Microcystis species, including 15 complete/draft genomes are presented. Using the strictest biological definition of what constitutes a bacterial species, these analyses indicate that all Microcystis species warrant placement into the same species complex since the average nucleotide identity values were above 95%, 16S rRNA nucleotide identity scores exceeded 99%, and DNA-DNA hybridization was consistently greater than 70%. The review further provides evidence from around the globe for the key role that both nitrogen and phosphorus play in controlling Microcystis bloom dynamics, and the effect of elevated temperature on bloom intensification. Finally, highlighted is the ability of Microcystis assemblages to minimize their mortality losses by resisting grazing by zooplankton and bivalves, as well as viral lysis, and discuss factors facilitating assemblage resilience.
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Affiliation(s)
- Matthew J Harke
- Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, United States
| | - Morgan M Steffen
- James Madison University, Department of Biology, 951 Carrier Dr., Harrisonburg, VA 22807, United States.
| | - Christopher J Gobler
- Stony Brook University, School of Marine and Atmospheric Sciences, 239 Montauk Hwy, Southampton, NY 11968, United States
| | - Timothy G Otten
- Oregon State University, Department of Microbiology, Nash Hall 226, Corvallis, OR 97331, United States
| | - Steven W Wilhelm
- University of Tennessee, Department of Microbiology, 1414 West Cumberland Ave., Knoxville, TN 37996, United States
| | - Susanna A Wood
- Cawthron Institute, Private Bag 2, Nelson, New Zealand and Environmental Research Institute, University of Waikato, Hamilton, New Zealand
| | - Hans W Paerl
- University of North Carolina at Chapel Hill, Institute of Marine Sciences, 3431 Arendell Street, Morehead City, NC 28557, United States
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14
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γ-Lindane Increases Microcystin Synthesis in Microcystis aeruginosa PCC7806. Mar Drugs 2015; 13:5666-80. [PMID: 26404326 PMCID: PMC4584347 DOI: 10.3390/md13095666] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 07/20/2015] [Accepted: 07/29/2015] [Indexed: 11/17/2022] Open
Abstract
HCH factories, and the waste dumpsites associated to its production, have become a global environmental concern, and their runoff could pollute ground and surface waters with high levels of the pollutant. In this study, the influence of lindane (γ-HCH) on microcystin production has been investigated in Microcystis aeruginosa PCC7806. This toxic cyanobacterium is highly tolerant to γ-lindane (20 mg/L), and produces more toxin (microcystin) in the presence of the pollutant. Microcystis degrades γ-lindane and presence of γ-lindane induces genes involved in its own degradation (nirA). RT-PCRsq has been used to monitor changes in levels of transcripts encoded by the mcy operon (mcyD, mcyH and mcyJ), responsible for the microcystin synthesis machinery, as well as other genes involved in its transcriptional regulation, such as ntcA and fur family members. The presence of lindane in the culture media induces mcyD expression, as well as ntcA gene transcription, while other genes, such as mcyH, (putative ABC transporter), are downregulated. The amount of microcystin found in the cells and the culture media is higher when M. aeruginosa is treated with γ-lindane than in control cells. The results suggest that in a lindane polluted environment, Microcystis toxic strains may enhance their microcystin synthesis.
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15
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Regulation of the scp Genes in the Cyanobacterium Synechocystis sp. PCC 6803--What is New? Molecules 2015; 20:14621-37. [PMID: 26274949 PMCID: PMC6331805 DOI: 10.3390/molecules200814621] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 08/05/2015] [Accepted: 08/07/2015] [Indexed: 11/18/2022] Open
Abstract
In the cyanobacterium Synechocystis sp. PCC 6803 there are five genes encoding small CAB-like (SCP) proteins, which have been shown to be up-regulated under stress. Analyses of the promoter sequences of the scp genes revealed the existence of an NtcA binding motif in two scp genes, scpB and scpE. Binding of NtcA, the key transcriptional regulator during nitrogen stress, to the promoter regions was shown by electrophoretic mobility shift assay. The metabolite 2-oxoglutarate did not increase the affinity of NtcA for binding to the promoters of scpB and scpE. A second motif, the HIP1 palindrome 5ʹ GGCGATCGCC 3ʹ, was detected in the upstream regions of scpB and scpC. The transcription factor encoded by sll1130 has been suggested to recognize this motif to regulate heat-responsive genes. Our data suggest that HIP1 is not a regulatory element within the scp genes. Further, the presence of the high light regulatory (HLR1) motif was confirmed in scpB-E, in accordance to their induced transcriptions in cells exposed to high light. The HLR1 motif was newly discovered in eight additional genes.
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16
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Beversdorf LJ, Miller TR, McMahon KD. Long-term monitoring reveals carbon-nitrogen metabolism key to microcystin production in eutrophic lakes. Front Microbiol 2015; 6:456. [PMID: 26029192 PMCID: PMC4428211 DOI: 10.3389/fmicb.2015.00456] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 04/27/2015] [Indexed: 02/04/2023] Open
Abstract
The environmental drivers contributing to cyanobacterial dominance in aquatic systems have been extensively studied. However, understanding of toxic vs. non-toxic cyanobacterial population dynamics and the mechanisms regulating cyanotoxin production remain elusive, both physiologically and ecologically. One reason is the disconnect between laboratory and field-based studies. Here, we combined 3 years of temporal data, including microcystin (MC) concentrations, 16 years of long-term ecological research, and 10 years of molecular data to investigate the potential factors leading to the selection of toxic Microcystis and MC production. Our analysis revealed that nitrogen (N) speciation and inorganic carbon (C) availability might be important drivers of Microcystis population dynamics and that an imbalance in cellular C: N ratios may trigger MC production. More specifically, precipitous declines in ammonium concentrations lead to a transitional period of N stress, even in the presence of high nitrate concentrations, that we call the “toxic phase.” Following the toxic phase, temperature and cyanobacterial abundance remained elevated but MC concentrations drastically declined. Increases in ammonium due to lake turnover may have led to down regulation of MC synthesis or a shift in the community from toxic to non-toxic species. While total phosphorus (P) to total N ratios were relatively low over the time-series, MC concentrations were highest when total N to total P ratios were also highest. Similarly, high C: N ratios were also strongly correlated to the toxic phase. We propose a metabolic model that corroborates molecular studies and reflects our ecological observations that C and N metabolism may regulate MC production physiologically and ecologically. In particular, we hypothesize that an imbalance between 2-oxoglutarate and ammonium in the cell regulates MC synthesis in the environment.
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Affiliation(s)
- Lucas J Beversdorf
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison Madison, WI, USA ; Joseph J. Zilber School of Public Health, University of Wisconsin-Milwaukee Milwaukee, WI, USA
| | - Todd R Miller
- Joseph J. Zilber School of Public Health, University of Wisconsin-Milwaukee Milwaukee, WI, USA
| | - Katherine D McMahon
- Department of Civil and Environmental Engineering, University of Wisconsin-Madison Madison, WI, USA ; Department of Bacteriology, University of Wisconsin-Madison Madison, WI, USA
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17
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Bai S, Dai J, Xia M, Ruan J, Wei H, Yu D, Li R, Jing H, Tian C, Song L, Qiu D. Effects of intermediate metabolite carboxylic acids of TCA cycle on Microcystis with overproduction of phycocyanin. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:5531-5537. [PMID: 25342454 DOI: 10.1007/s11356-014-3730-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 10/14/2014] [Indexed: 06/04/2023]
Abstract
Toxic Microcystis species are the main bloom-forming cyanobacteria in freshwaters. It is imperative to develop efficient techniques to control these notorious harmful algal blooms (HABs). Here, we present a simple, efficient, and environmentally safe algicidal way to control Microcystis blooms, by using intermediate carboxylic acids from the tricarboxylic acid (TCA) cycle. The citric acid, alpha-ketoglutaric acid, succinic acid, fumaric acid, and malic acid all exhibited strong algicidal effects, and particularly succinic acid could cause the rapid lysis of Microcystis in a few hours. It is revealed that the Microcystis-lysing activity of succinic acid and other carboxylic acids was due to their strong acidic activity. Interestingly, the acid-lysed Microcystis cells released large amounts of phycocyanin, about 27-fold higher than those of the control. On the other hand, the transcription of mcyA and mcyD of the microcystin biosynthesis operon was not upregulated by addition of alpha-ketoglutaric acid and other carboxylic acids. Consider the environmental safety of intermediate carboxylic acids. We propose that administration of TCA cycle organic acids may not only provide an algicidal method with high efficiency and environmental safety but also serve as an applicable way to produce and extract phycocyanin from cyanobacterial biomass.
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Affiliation(s)
- Shijie Bai
- Institute of Hydrobiology, The Chinese Academy of Sciences and University of Chinese Academy of Sciences, Wuhan, 430072, China
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18
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Microcystin production and regulation under nutrient stress conditions in toxic microcystis strains. Appl Environ Microbiol 2014; 80:5836-43. [PMID: 25038094 DOI: 10.1128/aem.01009-14] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microcystin is a common and well-known cyanobacterial toxin whose intracellular role is still under investigation. Increasing knowledge on microcystin gene expression and regulation can contribute to the understanding of its putative cellular function. In this work, reverse transcription-quantitative PCR (RT-qPCR) was used to investigate the transcriptional response of the mcyD gene to nitrogen (nitrate and ammonium) and phosphorus limitation in two toxic Microcystis strains. The existence of a direct correlation between transcripts of mcyD and ntcA genes was also identified. In previous studies, NtcA (global nitrogen regulator) has been described as a potential component in the control of microcystin biosynthesis. This research showed that stress agents linked to nutrient deprivation could lead to a significant increase of microcystin production in both strains studied. The more toxic strain proved to be more resistant to nutrient limitation. The similar outcomes of mcyD regulation observed for all nutrients suggest that this response can be linked to oxidative stress of cells undergoing adverse growth conditions.
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Kiyota H, Hirai MY, Ikeuchi M. NblA1/A2-Dependent Homeostasis of Amino Acid Pools during Nitrogen Starvation in Synechocystis sp. PCC 6803. Metabolites 2014; 4:517-31. [PMID: 24983765 PMCID: PMC4192677 DOI: 10.3390/metabo4030517] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 06/14/2014] [Accepted: 06/23/2014] [Indexed: 01/21/2023] Open
Abstract
Nutrient balance is important for photosynthetic growth and biomass production in microalgae. Here, we investigated and compared metabolic responses of amino acid pools to nitrogen and sulfur starvation in a unicellular model cyanobacterium, Synechocystis sp. PCC 6803, and its mutant nblA1/A2. It is known that NblA1/A2-dependent and -independent breakdown of abundant photosynthetic phycobiliproteins and other cellular proteins supply nutrients to the organism. However, the contribution of the NblA1/A2-dependent nutrient supply to amino acid pool homeostasis has not been studied. Our study demonstrates that changes in the pool size of many amino acids during nitrogen starvation can be categorized as NblA1/A2-dependent (Gln, Glu, glutathione, Gly, Ile, Leu, Met, Phe, Pro, Ser, Thr, Tyr and Val) and NblA1/A2-independent (Ala, Asn, Lys, and Trp). We also report unique changes in amino acid pool sizes during sulfur starvation in wild type and the mutant and found a generally marked increase in the Lys pool in cyanobacteria during nutrient starvation. In conclusion, the NblA1/A2-dependent protein turnover contributes to the maintenance of many amino acid pools during nitrogen starvation.
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Affiliation(s)
- Hiroshi Kiyota
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
| | - Masami Yokota Hirai
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
| | - Masahiko Ikeuchi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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20
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Boopathi T, Ki JS. Impact of environmental factors on the regulation of cyanotoxin production. Toxins (Basel) 2014; 6:1951-78. [PMID: 24967641 PMCID: PMC4113735 DOI: 10.3390/toxins6071951] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 06/06/2014] [Accepted: 06/17/2014] [Indexed: 11/25/2022] Open
Abstract
Cyanobacteria are capable of thriving in almost all environments. Recent changes in climatic conditions due to increased human activities favor the occurrence and severity of harmful cyanobacterial bloom all over the world. Knowledge of the regulation of cyanotoxins by the various environmental factors is essential for effective management of toxic cyanobacterial bloom. In recent years, progress in the field of molecular mechanisms involved in cyanotoxin production has paved the way for assessing the role of various factors on the cyanotoxin production. In this review, we present an overview of the influence of various environmental factors on the production of major group of cyanotoxins, including microcystins, nodularin, cylindrospermopsin, anatoxins and saxitoxins.
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Affiliation(s)
| | - Jang-Seu Ki
- Department of Life Science, Sangmyung University, Seoul 110-743, Korea.
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21
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Gehringer MM, Wannicke N. Climate change and regulation of hepatotoxin production in Cyanobacteria. FEMS Microbiol Ecol 2014; 88:1-25. [PMID: 24490596 DOI: 10.1111/1574-6941.12291] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 01/20/2014] [Accepted: 01/20/2014] [Indexed: 01/04/2023] Open
Abstract
Harmful, bloom-forming cyanobacteria (CyanoHABs) are occurring with increasing regularity in freshwater and marine ecosystems. The most commonly occurring cyanobacterial toxins are the hepatotoxic microcystin and nodularin. These cyclic hepta- and pentapeptides are synthesised nonribosomally by the gene products of the toxin gene clusters mcy and nda, respectively. Understanding of the regulation of hepatotoxin production is incomplete, although there is strong evidence supporting the roles of iron, light, higher nitrate availability and inorganic carbon in modulating microcystin levels. The majority of these studies have focused on the unicellular freshwater, microcystin-producing strain of Microcystis aeruginosa, with little attention being paid to terrestrial or marine toxin producers. This review intends to investigate the regulation of microcystin and nodularin production in unicellular and filamentous diazotrophic cyanobacteria against the background of changing climate conditions. Special focus is given to diazotrophic filamentous cyanobacteria, for example Nodularia spumigena, capable of regulating their nitrogen levels by actively fixing dinitrogen. By combining data from significant studies, an overall scheme of the regulation of toxin production is presented, focussing specifically on nodularin production in diazotrophs against the background of increasing carbon dioxide concentrations and temperatures envisaged under current climate change models. Furthermore, the risk of sustaining and spreading CyanoHABs in the future ocean is evaluated.
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Affiliation(s)
- Michelle M Gehringer
- Department of Plant Ecology and Systematics, Technical University of Kaiserslautern, Kaiserslautern, Germany
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22
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Kuniyoshi TM, Sevilla E, Bes MT, Fillat MF, Peleato ML. Phosphate deficiency (N/P 40:1) induces mcyD transcription and microcystin synthesis in Microcystis aeruginosa PCC7806. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 65:120-124. [PMID: 23481586 DOI: 10.1016/j.plaphy.2013.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/15/2013] [Indexed: 06/01/2023]
Abstract
A real-time RT-PCR analysis of the transcriptional response to phosphate availability of the mcyD gene and microcystin-LR synthesis in Microcystis aeruginosa PCC7806 revealed that no significant changes were observed in the relative quantification of mcyD under excess phosphate (N/P = 1:1), whereas in deficiency of this nutrient (N/P = 40:1), a steady increase of mcyD during the exponential growth phase was detected, showing a maximal level on the 7th day of growth with a 6.8-fold increase over the control cells. The microcystin content in phosphate deficient cells correlates with the trend of mcyD transcription observed. Also, in this work we demonstrate that under phosphate deficiency conditions with a ratio of 40:1 N/P, the growth of M. aeruginosa PCC7806 was not affected when compared to control and phosphate excess samples. When blooms occur, the nutrients become exhausted and therefore phosphate availability will be scarce. In such a complex scenario, microcystin synthesis could be a response to phosphate deficiency, among other stress parameters.
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Affiliation(s)
- Taís M Kuniyoshi
- Departamento de Bioquimica y Biologia Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
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Jin MM, Wang P, Li X, Zhao XY, Xu L, Song P, Zhu GP. Biochemical characterization of NADP⁺-dependent isocitrate dehydrogenase from Microcystis aeruginosa PCC7806. Mol Biol Rep 2012; 40:2995-3002. [PMID: 23264072 DOI: 10.1007/s11033-012-2371-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 12/17/2012] [Indexed: 11/30/2022]
Abstract
Microcystis aeruginosa is the key symptom of water eutrophication and produces persistent microcystins. Our special attention was paid to the isocitrate dehydrogenase (IDH) of M. aeruginosa (MaIDH) because it plays important roles in energy and biosynthesis metabolisms and its catalytic product 2-oxoglutarate provides the carbon skeleton for ammonium assimilation and also constitutes a signaling molecule of nitrogen starvation in cyanobacteria. Sequence alignment showed that MaIDH shared significant sequence identity with IDHs from other cyanobacteria (>80 %) and other bacteria (>45 %). The subunit molecular weight of MaIDH was determined to be 52.6 kDa by filtration chromatography, suggesting MaIDH is a typical homodimer. The purified recombinant MaIDH was completely NADP(+)-dependent and no NAD(+)-linked activity was detectable. The K m values for NADP(+) were 32.24 and 71.71 μM with Mg(2+) and Mn(2+) as a sole divalent cation, and DL-isocitrate linked K m values were 32.56 μM (Mg(2+)) and 124.3 μM (Mn(2+)), respectively. As compared with Mn(2+), MaIDH showed about 2.5-times and 4-times higher affinities (1/K m) to NADP(+) and DL-isocitrate with Mg(2+). The optimum activity of MaIDH was found at pH 7.5, and its optimum temperature was 45 °C (Mn(2+)) and 50 °C (Mg(2+)). Heat-inactivation studies showed that heat treatment for 20 min at 45 °C caused a 50 % loss of enzyme activity. MaIDH was completely divalent cation dependent as other typical dimeric IDHs and Mn(2+) was its best activator. Our study is expected to give a better understanding of primary metabolic enzymes in M. aeruginosa. This would provide useful basic information for the research of controlling the blue-green algae blooms through biological techniques.
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Affiliation(s)
- Ming-Ming Jin
- Key Laboratory of Molecular Evolution and Biodiversity and Institute of Molecular Biology and Biotechnology, College of Life Sciences, Anhui Normal University, No.1 Beijing East Road, Wuhu 241000, Anhui, People's Republic of China
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