The influence of nitrogen and growth phase on the toxicity of the cyanobacterial strain Microcystis PCC 7806

The worldwide occurrence of toxic cyanobacterial blooms and their numerous harmful effects have instigated extensive research into the environmental conditions promoting such events. Among the environmental factors which have been suggested to influence the increase in cyanobacterial proliferation, nutrient levels have been identified as one of the most prominent, affecting the growth and toxic metabolite production of cyano?bacteria in freshwater ecosystems. In the present study, toxicity of the cyanobacterial strain Microcystis PCC 7806 was evaluated after growth in media with three different nitrogen concentrations. The toxicity of intracellular extracts was analyzed during different growth phases (after 7, 21, and 35 days of cultivation) by observing mortality rates in the Artemia salina bioassay after 24h and 48h of exposure. The results have not shown significantly higher mortality levels between the test organisms exposed to extracts obtained from the cultures grown in the presence of higher nitrogen content (1.5 g/l and 0.8 g/l) and those grown in a nitrogen-free medium. A dose dependent effect, however, can be observed in most cases, with the most substantial changes observed in the high-dose groups. Also, the toxic effects and larval mortality increased during the exposure, suggesting the time-dependent toxicity. Extracts obtained after longer periods of cultivation (21 and 35 days) had stronger effects on the test organisms, which indicates that the toxicity of the tested cyanobacterial strain depends on the specific growth phase.

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Impacts of phosphorus loads on the water quality and the proliferation of harmful cyanobacteria in Foum-Gleita Reservoir (Mauritania)

Annales de Limnologie - International Journal of Limnology ◽

10.1051/limn/2020029 ◽

2021 ◽

Vol 57 ◽

pp. 1

Author(s):

Ahmed Sidi Sadegh ◽

Zeinebou Sidoumou ◽

Mamadou Dia ◽

Juan Luis Gomez Pinchetti ◽

Noureddine Bouaïcha

Keyword(s):

Water Quality ◽

High Performance ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Pearson’S Correlation ◽

Biological Variables ◽

Nitrogen Inputs ◽

Harmful Cyanobacteria ◽

Nitrogen Concentrations ◽

Pearson's Correlation

Excess phosphorus and nitrogen inputs into freshwater ecosystems is one of the main causes of expansion of harmful cyanobacterial blooms worldwide. This work was conducted to study the impacts of phosphorus leaching from the exploitation of phosphate mines present in the watershed of Foum-Gleita Reservoir (Mauritania) on the water quality and its major contribution to the proliferation of harmful cyanobacteria throughout the year. The physicochemical parameters, the occurrence and abundance of phytoplankton (including cyanobacteria), and the microcystins concentration were monitored monthly from September 2017 to August 2018. The relationships between limnological and biological variables were explored by using Pearson's correlation and forward stepwise multiple linear regression (MLR) analysis. Microcystins were detected by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Our results showed that this reservoir can be classified as hypereutrophic throughout the year and that Microcystis aeruginosa (M. aeruginosa) and Dolichospermum flos-aquae (D. flos-aquae) were dominant species during the rainy season (July-September), and only the congener microcystin-LR (MC-LR) was detected with a peak at 3.55 µg L−1. Pearson's correlation and MLR analysis showed that water temperature pH, phosphorus, nitrogen, and iron concentrations were the most important variables accounting for M. aeruginosa and D. flos-aquae abundance and MC-LR concentration. Our study provides new insight into the effects of moderate nitrogen concentrations on phytoplankton community composition with dominance of the cyanobacteria phylum in phosphorus-rich freshwater ecosystems.

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Harmful phytoplankton blooms and fish mortality in a eutrophicated reservoir of northeast Brazil

Brazilian Archives of Biology and Technology ◽

10.1590/s1516-89132008000400022 ◽

2008 ◽

Vol 51 (4) ◽

pp. 633-641 ◽

Cited By ~ 23

Author(s):

Naithirithi Tiruvenkatachary Chellappa ◽

Sarah Laxhmi Chellappa ◽

Sathyabama Chellappa

Keyword(s):

Cyanobacterial Bloom ◽

Hplc Method ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Fish Mortality ◽

Cylindrospermopsis Raciborskii ◽

Northeast Brazil ◽

Cyanobacterial Toxin ◽

Bloom Formation ◽

Harmful Effects

The aim of this work was to study the eutrophication in the tropical freshwater ecosystems and the consequent cyanobacterial bloom formation and economical damage to fisheries and harmful effects to public health. Mass fish mortality due to toxin producing cyanobacterial blooms was registered during December 2003 in Marechal Dutra Reservoir, Acari/RN, Northeast Brazil. Phytoplankton and fish samplings were carried out on alternate days during the episode of fish mortality and monthly during January to June 2004. The cyanobacterial toxin was identified and quantified from the seston samples and liver of the dead fishes using the standard HPLC method. The results indicated that the toxic blooms of Cylindrospermopsis raciborskii and Microcystis aeruginosa were persistent for two weeks and represented 90% of the phytoplankton species assemblages. The lethally affected fishes were Oreochromis niloticus, Plagioscion squamosissimus, Cichla monoculus, Prochilodus brevis, Hoplias malabaricus and Leporinus friderici. The microcystin levels varied from 0.07 to 8.73µg L-1 the seston samples and from 0.01 to 2.59µg g-1in the liver samples of the fishes during the bloom period.

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Photosynthetic response to nitrogen source and different ratios of nitrogen and phosphorus in toxic cyanobacteria, Microcystis aeruginosa FACHB-905

Journal of Limnology ◽

10.4081/jlimnol.2016.1458 ◽

2016 ◽

Cited By ~ 3

Author(s):

Guotao Peng ◽

Zhengqiu Fan ◽

Xiangrong Wang ◽

Chen Chen

Keyword(s):

Chlorophyll Fluorescence ◽

Algal Blooms ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Photosynthetic Response ◽

Nitrogen And Phosphorus ◽

Ammonium Toxicity ◽

Chlorophyll Fluorescence Parameters ◽

Fluorescence Parameters ◽

N Assimilation

The frequent outbreak of cyanobacterial blooms has become a worldwide phenomenon in freshwater ecosystems. Studies have elucidated the close relationship between harmful algal blooms and nutrient contents, including the loading of nitrogen and the ratios of nitrogen (N) and phosphorus (P). In this study, the effect of inorganic (nitrate and ammonium) and organic (urea) nitrogen at varied N/P ratios on the Microcystis aeruginosa FACHB-905 accumulation and photosynthesis was investigated. The optimal NO3/P in this study were 30~50 indicated by the cell abundance (4.1×106/mL), pigment concentration (chlorophyll a 3.1 mg/L, phycocyanin 8.3mg/L), and chlorophyll fluorescence parameters (rETR, Ek, α, φPSII and Fv/Fm values), while too high NO3-N (N/P=100:1) would cause an intracellular nitrate inhibition, leading to a decrease of photosynthetic activity. In addition, low concentration of NH4-N (N/P=4:1) would favor the M. aeruginosa growth and photosynthesis, and high NH4/P ratio (>16) would rise the ammonium toxicity of algal cells and affect the N assimilation. In urea treatments, M. aeruginosa responded similarly to the NH4-N treatments both in growth curves and pigment contents, and the favorable N/P ratio was between 16~30, suggested by the chlorophyll fluorescence parameters. The results demonstrated that the various chemical forms of N and N/P ratios have a significant impact on Microcystis abundance and photosynthesis. More work is needed to figure out the mechanism of nitrogen utilization by Microcystis and the photosynthetic response to nutrient stress at the molecular level.

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Anabaenopeptins from Cyanobacteria in Freshwater Bodies of Greece

Toxins ◽

10.3390/toxins14010004 ◽

2021 ◽

Vol 14 (1) ◽

pp. 4

Author(s):

Sevasti-Kiriaki Zervou ◽

Triantafyllos Kaloudis ◽

Spyros Gkelis ◽

Anastasia Hiskia ◽

Hanna Mazur-Marzec

Keyword(s):

Mass Spectra ◽

Cyanobacterial Blooms ◽

Bioactive Metabolites ◽

Cyanobacterial Strain ◽

Structural Variety ◽

Freshwater Bodies ◽

Photosynthetic Microorganisms ◽

Time Periods ◽

Favorable Conditions ◽

Of Greece

Cyanobacteria are photosynthetic microorganisms that are able to produce a large number of secondary metabolites. In freshwaters, under favorable conditions, they can rapidly multiply, forming blooms, and can release their toxic/bioactive metabolites in water. Among them, anabaenopeptins (APs) are a less studied class of cyclic bioactive cyanopeptides. The occurrence and structural variety of APs in cyanobacterial blooms and cultured strains from Greek freshwaters were investigated. Cyanobacterial extracts were analyzed with LC–qTRAP MS/MS using information-dependent acquisition in enhanced ion product mode in order to obtain the fragmentation mass spectra of APs. Thirteen APs were detected, and their possible structures were annotated based on the elucidation of fragmentation spectra, including three novel ones. APs were present in the majority of bloom samples (91%) collected from nine Greek lakes during different time periods. A large variety of APs was observed, with up to eight congeners co-occurring in the same sample. AP F (87%), Oscillamide Y (87%) and AP B (65%) were the most frequently detected congeners. Thirty cyanobacterial strain cultures were also analyzed. APs were only detected in one strain (Microcystis ichtyoblabe). The results contribute to a better understanding of APs produced by freshwater cyanobacteria and expand the range of structurally characterized APs.

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Effects of Cyanobacteria on Phosphorus Cycling and Other Aquatic Organisms in Simulated Eutrophic Ecosystems

Water ◽

10.3390/w12082265 ◽

2020 ◽

Vol 12 (8) ◽

pp. 2265

Author(s):

Peng Gu ◽

Qi Li ◽

Hao Zhang ◽

Xin Luo ◽

Weizhen Zhang ◽

...

Keyword(s):

Nutrient Management ◽

Lake Taihu ◽

Cyanobacterial Bloom ◽

Aquatic Organisms ◽

Pilot Scale ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Eutrophic Lakes ◽

P Concentration ◽

Bloom Formation

Cyanobacterial blooms caused by eutrophication in Lake Taihu have led to ecological threats to freshwater ecosystems. A pilot scale experiment was implemented to investigate the relationship between cyanobacteria and other aquatic plants and animals in simulated eutrophic ecosystems under different phosphorus (P) regimes. The results of this study showed that cyanobacteria had two characteristics favorable for bloom formation in eutrophic ecosystems. One is the nutrient absorption. The presence of alkaline phosphatase was beneficial for algal cells in nutrition absorption under low P concentration. Cyanobacteria exhibited a stronger ability to absorb and store P compared to Vallisneria natans, which contributed to the fast growth of algal cells between 0.2 and 0.5 mg·L−1 of P (p < 0.05). However, P loads affected only the maximum biomass, but not the growth phases. The growth cycle of cyanobacteria remained unchanged and was not related to P concentration. P cycling indicated that 43.05–69.90% of the total P existed in the form of sediment, and P content of cyanobacteria showed the highest increase among the organisms. The other is the release of microcystin. Toxic microcystin-LR was released into the water, causing indirectly the growth inhibition of Carassius auratus and Bellamya quadrata and the reduction of microbial diversity. These findings are of importance in exploring the mechanism of cyanobacterial bloom formation and the nutrient management of eutrophic lakes.

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Inhibition of Extracellular Enzymes Exposed to Cyanopeptides

CHIMIA International Journal for Chemistry ◽

10.2533/chimia.2020.122 ◽

2020 ◽

Vol 74 (3) ◽

pp. 122-128

Author(s):

Christine M. Egli ◽

Regiane S. Natumi ◽

Martin R. Jones ◽

Elisabeth M.-L. Janssen

Keyword(s):

Extracellular Enzymes ◽

Heterotrophic Bacteria ◽

Hydrolytic Enzymes ◽

Aquatic Organisms ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Biologically Relevant ◽

Metabolic Functions ◽

Harmful Cyanobacterial Blooms ◽

Quality Assessments

Harmful cyanobacterial blooms in freshwater ecosystems produce bioactive secondary metabolites including cyanopeptides that pose ecological and human health risks. Only adverse effects of one class of cyanopeptides, microcystins, have been studied extensively and have consequently been included in water quality assessments. Inhibition is a commonly observed effect for enzymes exposed to cyanopeptides and has mostly been investigated for human biologically relevant model enzymes. Here, we investigated the inhibition of ubiquitous aquatic enzymes by cyanobacterial metabolites. Hydrolytic enzymes are utilized in the metabolism of aquatic organisms and extracellularly by heterotrophic bacteria to obtain assimilable substrates. The ubiquitous occurrence of hydrolytic enzymes leads to the co-occurrence with cyanopeptides especially during cyanobacterial blooms. Bacterial leucine aminopeptidase and alkaline phosphatase were exposed to cyanopeptide extracts of different cyanobacterial strains ( Microcystis aeruginosa wild type and microcystin-free mutant, Planktothrix rubescens) and purified cyanopeptides. We observed inhibition of aminopeptidase and phosphatase upon exposure, especially to the apolar fractions of the cyanobacterial extracts. Exposure to the dominant cyanopeptides in these extracts confirmed that purified microcystins, aerucyclamide A and cyanopeptolin A inhibit the aminopeptidase in the low mg L–1 range while the phosphatase was less affected. Inhibition of aquatic enzymes can reduce the turnover of nutrients and carbon substrates and may also impair metabolic functions of grazing organisms.

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Spatiotemporal Variations in Microcystin Concentrations and in the Proportions of Microcystin-Producing Cells in Several Microcystis aeruginosa Populations

Applied and Environmental Microbiology ◽

10.1128/aem.02531-09 ◽

2010 ◽

Vol 76 (14) ◽

pp. 4750-4759 ◽

Cited By ~ 71

Author(s):

M. Sabart ◽

D. Pobel ◽

E. Briand ◽

B. Combourieu ◽

M. J. Salençon ◽

...

Keyword(s):

Microcystis Aeruginosa ◽

Environmental Conditions ◽

Real Time Pcr ◽

Geographical Area ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Spatiotemporal Variations ◽

Potential Toxicity ◽

Genotype Composition ◽

Over Time

ABSTRACT With the aim of explaining the variations in microcystin (MC) concentrations during cyanobacterial blooms, we studied several Microcystis aeruginosa populations blooming in different freshwater ecosystems located in the same geographical area. As assessed by real-time PCR, it appeared that the potentially MC-producing cells (mcyB +) were predominant (70 to 100%) in all of these M. aeruginosa populations, with the exception of one population in which non-MC-producing cells always dominated. Apart from the population in the Grangent Reservoir, we found that the proportions of potentially MC-producing and non-MC-producing cells varied little over time, which was consistent with the fact that according to a previous study of the same populations, the intergenic transcribed spacer (ITS) genotype composition did not change (38). In the Grangent Reservoir, the MC-RR variant was the dominant microcystin variant throughout the bloom season, despite changes in the ITS composition and in the proportions of mcyB + cells. Finally, the variations in total MC concentrations (0.3 to 15 μg liter−1) and in the MC cellular quotas (0.01 to 3.4 pg cell−1) were high both between and within sites, and no correlation was found between the MC concentrations and the proportion of mcyB + cells. All of these findings demonstrate that very different results can be found for the proportions of potentially MC-producing and non-MC-producing cells and MC concentrations, even in M. aeruginosa populations living in more or less connected ecosystems, demonstrating the importance of the effect of very local environmental conditions on these parameters and also the difficulty of predicting the potential toxicity of Microcystis blooms.

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Efficacy of Fludarabine and Cytarabine Combination for Salvage Treatment of Refractory/Relapsed Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML): Promising Results from a Single Center Experience.

Blood ◽

10.1182/blood.v106.11.4622.4622 ◽

2005 ◽

Vol 106 (11) ◽

pp. 4622-4622

Author(s):

M. Tassara ◽

F. Ciceri ◽

A. Crotta ◽

J. Peccatori ◽

P. Servida ◽

...

Keyword(s):

Stem Cell ◽

Stem Cell Transplantation ◽

Cell Transplantation ◽

Fungal Infections ◽

Salvage Treatment ◽

High Dose ◽

Toxic Metabolite ◽

Refractory Disease ◽

Hematopoietic Stem ◽

Relapsed Disease

Abstract Background: response of refractory or relapsed MDS/AML to current standard chemotherapy (CHT) is unsatisfactory; high dose CHT without hematopoietic stem cell support is often unsuccessful because of its high toxicity. As the only curative chance for these patients (pts) is to receive an allogeneic stem cell transplantation (AlloSCT) in a complete remission (CR) or in a minimal residual disease status, a salvage treatment with the highest efficacy and lowest toxicity is warranted; if no donor is available, consolidation with intensified-dose CHT and autologous stem cell transplantation (ASCT) is the preferable alternative. Fludarabine+cytarabine (FLA) containing regimens have shown promising results in CR induction of poor prognosis MDS/AML at diagnosis. Fludarabine has no direct activity on myeloid malignancies but improves cytotoxicity of cytarabine by increasing intracellular concentration of its toxic metabolite, ara-CTP, in leukemic blasts; priming of myeloid precursors with G-CSF increases the sensibility of leukemic blasts to cytarabine by committing them to phase S of the cell-cycle. Aim: we retrospectively evaluated the efficacy and toxicity of FLA regimens in pts with refractory or relapsed MDS/AML, treated at our Center. Patients and Methods: 25 pts in the period 6/1999–6/2005; median age 55 (18–72), 11 pts > 60 years. Diagnosis (FAB): AML 20, sAML 4, AREB 1 (IPSS: INT-2), no therapy-related AML/MDS. Cytogenetics: normal 15, poor 3, good 1, intermediate 6. Eight pts (32%) had refractory disease to standard induction CHT and 17 pts (68%) had relapsed disease after a median of 3 CHT cycles (range 1–4); 11 of them relapsed after ASCT. Median CR duration (17 pts): 10 months (range 1–59). Salvage treatment: 20 FLAG-Ida regimen, 4 FLAG, 1 FLAG+liposomal dauno. Results: overall response rate (RR) was 68%: 15 CR (60%), 2 PR (8%), 7 NR (28%); 1 pt not evaluable for prolonged marrow hypoplasia. RR for refractory and relapsed disease was 37.5% (CR 25%) and 88.2% (CR 82.3%) respectively. RR for <60 and ≥60 years-old pts was 67.4% (CR 57.1%) and 63.6% (CR 63.6%), respectively. RR for AML and sAML was 76% (CR 65%) and 80% (CR 80%), respectively. Toxicities: no treatment related deaths; FUO/sepsis 96% (24 pts); invasive fungal infections 8% (2 pts). No further major toxicities. Nine patients received further CHT after salvage with FLA, 8 for CR consolidation, 1 for reinduction: 5 FLAG, 3 high dose cytarabine, 1 gentuzumab-ozogamicine. Fourteen patients (56%) received a SCT: 2 ASCT, 12 AlloSCT. At transplant 10 pts (71%) were in CR, 3 (21%) had overt disease, 1 had an hypoplastic marrow. Relapses in pts who obtained a CR were 5 (33%), 2 before transplant and 3 after transplant (1 ASCT, 2 AlloSCT). After a median follow-up of 7 months (range 2–72) from the beginning of rescue treatment, 16 pts have died (64%), 12 with progressive/refractory disease, 4 in CR (1 sepsis after CHT, 2 transplant related toxicity, 1 Guillain-Barrè syndrome); 9 patients (36%) are alive, all in CR; six of them after SCT (1 ASCT, 5 AlloSCT). Median OS is 209 days (44–1993) 7 months (range 2–72), median DFS is 163 days (13–922) 5 months (range 1–30). Conclusions: FLA regimens induced a significant rate of responses in relapsed pts, with tolerable toxicity, also in the elderly subgroup. Consolidation with high dose CHT and ASCT or with AlloSCT could induce prolonged OS and DFS. Response and outcome of refractory diseases seem to have a worse trend.

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Biological Species and Environment Study in Microsystins Causing Apotosis in Heart

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.886.341 ◽

2014 ◽

Vol 886 ◽

pp. 341-344

Author(s):

Tong Qiu

Keyword(s):

Caspase 3 ◽

Apoptotic Cell ◽

Cell Number ◽

Biological Species ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Caspase 9 ◽

Gene Expressions ◽

Genes Expression ◽

Environment Study

The occurrence of heavy cyanobacterial blooms in eutrophic freshwater ecosystems has been a worldwide problem. Microcystins, the predominant toxins of cyanobacterial blooms, are associated with mortality and illness in both animals and human. In present study, we monitored the apoptosis of heart from MCs intoxication, and evaluated the roles of main apoptosis-related genes expression in cardiotoxic effects. The results revealed that MCs exposure led to the gradually rise in apoptotic cell number. Meanwhile, Bax, Bcl-2, p53, Caspase-3 and Caspase-9 gene expressions were significantly elevated simultaneously with the extension of the time. It suggested that MCs can cause damage to heart directly.

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Development of photosynthetic carbon fixation model using multi-excitation wavelength fast repetition rate fluorometry in Lake Biwa

PLoS ONE ◽

10.1371/journal.pone.0238013 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0238013

Author(s):

Takehiro Kazama ◽

Kazuhide Hayakawa ◽

Victor S. Kuwahara ◽

Koichi Shimotori ◽

Akio Imai ◽

...

Keyword(s):

Repetition Rate ◽

Carbon Fixation ◽

Lake Biwa ◽

Freshwater Ecosystems ◽

Cyanobacterial Blooms ◽

Excitation Wavelength ◽

Freshwater Ecosystem ◽

Fixation Rate ◽

Excitation Light ◽

Fast Repetition Rate Fluorometry

Direct measurements of gross primary productivity (GPP) in the water column are essential, but can be spatially and temporally restrictive. Fast repetition rate fluorometry (FRRf) is a bio-optical technique based on chlorophyll a (Chl-a) fluorescence that can estimate the electron transport rate (ETRPSII) at photosystem II (PSII) of phytoplankton in real time. However, the derivation of phytoplankton GPP in carbon units from ETRPSII remains challenging because the electron requirement for carbon fixation (Фe,C), which is mechanistically 4 mol e− mol C−1 or above, can vary depending on multiple factors. In addition, FRRf studies are limited in freshwater lakes where phosphorus limitation and cyanobacterial blooms are common. The goal of the present study is to construct a robust Фe,C model for freshwater ecosystems using simultaneous measurements of ETRPSII by FRRf with multi-excitation wavelengths coupled with a traditional carbon fixation rate by the 13C method. The study was conducted in oligotrophic and mesotrophic parts of Lake Biwa from July 2018 to May 2019. The combination of excitation light at 444, 512 and 633 nm correctly estimated ETRPSII of cyanobacteria. The apparent range of Фe,C in the phytoplankton community was 1.1–31.0 mol e− mol C−1 during the study period. A generalised linear model showed that the best fit including 12 physicochemical and biological factors explained 67% of the variance in Фe,C. Among all factors, water temperature was the most significant, while photosynthetically active radiation intensity was not. This study quantifies the in situ FRRf method in a freshwater ecosystem, discusses core issues in the methodology to calculate Фe,C, and assesses the applicability of the method for lake GPP prediction.

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