RESUMO
Two Raphidiopsis (=Cylindrospermopsis) raciborskii metagenome-assembled genomes (MAGs) were recovered from two freshwater metagenomic datasets sampled in 2011 and 2012 in Pampulha Lake, a hypereutrophic, artificial, shallow reservoir, located in the city of Belo Horizonte (MG), Brazil. Since the late 1970s, the lake has undergone increasing eutrophication pressure, due to wastewater input, leading to the occurrence of frequent cyanobacterial blooms. The major difference observed between PAMP2011 and PAMP2012 MAGs was the lack of the saxitoxin gene cluster in PAMP2012, which also presented a smaller genome, while PAMP2011 presented the complete sxt cluster and all essential proteins and clusters. The pangenome analysis was performed with all Raphidiopsis/Cylindrospermopsis genomes available at NCBI to date, with the addition of PAMP2011 and PAMP2012 MAGs (All33 subset), but also without the South American strains (noSA subset), and only among the South American strains (SA10 and SA8 subsets). We observed a substantial increase in the core genome size for the 'noSA' subset, in comparison to 'All33' subset, and since the core genome reflects the closeness among the pangenome members, the results strongly suggest that the conservation level of the essential gene repertoire seems to be affected by the geographic origin of the strains being analyzed, supporting the existence of a distinct SA clade. The Raphidiopsis pangenome comprised a total of 7943 orthologous protein clusters, and the two new MAGs increased the pangenome size by 11%. The pangenome based phylogenetic relationships among the 33 analyzed genomes showed that the SA genomes clustered together with 99% bootstrap support, reinforcing the metabolic particularity of the Raphidiopsis South American clade, related to its saxitoxin producing unique ability, while also indicating a different evolutionary history due to its geographic isolation.
Assuntos
Cianobactérias , Cylindrospermopsis , Cylindrospermopsis/genética , Saxitoxina/genética , Saxitoxina/metabolismo , Filogenia , Metagenoma , Cianobactérias/genética , Lagos , BrasilRESUMO
Microcystins (MC) are hepatotoxic for organisms. Liver MC accumulation and structural change are intensely studied, but the functional hepatic enzymes and energy metabolism have received little attention. This study investigated the liver and hepatocyte structures and the activity of key hepatic functional enzymes with emphasis on energetic metabolism changes after subchronic fish exposure to cyanobacterial crude extract (CE) containing MC. The Neotropical erythrinid fish, Hoplias malabaricus, were exposed intraperitoneally to CE containing 100 µg MC-LR eq kg-1 for 30 days and, thereafter, the plasma, liver, and white muscle was sampled for analyses. Liver tissue lost cellular structure organization showing round hepatocytes, hyperemia, and biliary duct obstruction. At the ultrastructural level, the mitochondria and the endoplasmic reticulum exhibited disorganization. Direct and total bilirubin increased in plasma. In the liver, the activity of acid phosphatase (ACP) increased, and the aspartate aminotransferase (AST) decreased; AST increased in plasma. Alkaline phosphatase (ALP) and alanine aminotransferase (ALT) were unchanged in the liver, muscle, and plasma. Glycogen stores and the energetic metabolites as glucose, lactate, and pyruvate decrease in the liver; pyruvate decreased in plasma and lactate decreased in muscle. Ammonia levels increased and protein concentration decreased in plasma. CE alters liver morphology by causing hepatocyte intracellular disorder, obstructive cholestasis, and dysfunction in the activity of key liver enzymes. The increasing energy demand implies glucose mobilization and metabolic adjustments maintaining protein preservation and lipid recruitment to supply the needs for detoxification allowing fish survival.
Assuntos
Caraciformes , Cianobactérias , Hepatopatias , Fosfatase Ácida/metabolismo , Alanina Transaminase/metabolismo , Fosfatase Alcalina/metabolismo , Amônia , Animais , Aspartato Aminotransferases/metabolismo , Bilirrubina/metabolismo , Misturas Complexas/metabolismo , Misturas Complexas/toxicidade , Cianobactérias/metabolismo , Glucose/metabolismo , Glicogênio/metabolismo , Lactatos , Lipídeos , Fígado/metabolismo , Hepatopatias/metabolismo , Microcistinas/metabolismo , Microcistinas/toxicidade , Piruvatos/metabolismoRESUMO
The neurotoxic alkaloid ß-N-methyl-amino-l-alanine (BMAA) and related isomers, including N-(2-aminoethyl glycine) (AEG), ß-amino-N-methyl alanine (BAMA), and 2,4-diaminobutyric acid (DAB), have been reported previously in cyanobacterial samples. However, there are conflicting reports regarding their occurrence in surface waters. In this study, we evaluated the impact of amending lake water samples with trichloroacetic acid (0.1 M TCA) on the detection of BMAA isomers, compared with pre-existing protocols. A sensitive instrumental method was enlisted for the survey, with limits of detection in the range of 5−10 ng L−1. Higher detection rates and significantly greater levels (paired Wilcoxon's signed-rank tests, p < 0.001) of BMAA isomers were observed in TCA-amended samples (method B) compared to samples without TCA (method A). The overall range of B/A ratios was 0.67−8.25 for AEG (up to +725%) and 0.69−15.5 for DAB (up to +1450%), with absolute concentration increases in TCA-amended samples of up to +15,000 ng L−1 for AEG and +650 ng L−1 for DAB. We also documented the trends in the occurrence of BMAA isomers for a large breadth of field-collected lakes from Brazil, Canada, France, Mexico, and the United Kingdom. Data gathered during this overarching campaign (overall, n = 390 within 45 lake sampling sites) indicated frequent detections of AEG and DAB isomers, with detection rates of 30% and 43% and maximum levels of 19,000 ng L−1 and 1100 ng L−1, respectively. In contrast, BAMA was found in less than 8% of the water samples, and BMAA was not found in any sample. These results support the analyses of free-living cyanobacteria, wherein BMAA was often reported at concentrations of 2−4 orders of magnitude lower than AEG and DAB. Seasonal measurements conducted at two bloom-impacted lakes indicated limited correlations of BMAA isomers with total microcystins or chlorophyll-a, which deserves further investigation.
Assuntos
Diamino Aminoácidos , Cianobactérias , Alanina , Diamino Aminoácidos/análise , Brasil , Lagos/microbiologia , México , Neurotoxinas/análise , Água/análiseRESUMO
Raphidiopsis (=Cylindrospermopsis) raciborskii was described as a subtropical-tropical cyanobacterium, later reported expanding into temperate regions. Heterocyte presence used to distinguish Cylindrospermopsis from the very similar Raphidiopsis, but recently the two genera were recognized as one and unified. This study aimed to investigate how heterocyte production is related to nitrogen (N) limitation in heterocytous and non-heterocytous strains of R.raciborskii. High N-concentrations did not inhibit heterocyte development in some strains, while prolonged N-starvation periods never stimulated production in others. RT-qPCR was used to examine the genetic background, through the expression patterns of nifH, ntcA and hetR. While gene expression increased under N-restriction, N-sufficiency did not suppress nifH transcripts as previously observed in other diazotrophyc cyanobacteria, suggesting that heterocyte production in R. raciborskii is not regulated by N-availability. Heterocytous and non-heterocytous strains were genotypically characterized to assess their phylogenetic relationships. In the phylogenetic tree, clusters were intermixed and confirmed Raphidiopsis and Cylindrospermopsis as the same genus. The tree supported previous findings of earlier splitting of American strains, while contesting the African origin hypothesis. The existence of two lines of Chinese strains, with distinct evolutionary patterns, is a significant addition that could lead to new hypotheses of the species biogeography.
Assuntos
Cianobactérias , Cylindrospermopsis , Cianobactérias/genética , Expressão Gênica , Filogenia , FilogeografiaRESUMO
RESUMO O estudo teve como objetivo o desenvolvimento e a validação de um método analítico para detecção e quantificação de ácidos haloacéticos por meio da extração líquido-líquido e da análise por cromatografia gasosa acoplada à espectrometria de massas. Para a validação, consideraram-se parâmetros como linearidade, precisão, limites de detecção e quantificação e seletividade. Adicionalmente, aplicou-se o método para avaliar a formação de ácidos haloacéticos em ensaios de cloração de células de Cylindrospermopsis raciborskii com o oxidante hipoclorito de cálcio, simulando situações em estações de tratamento de água. O método apresentou baixo tempo de análise, excelente seletividade, precisão, repetitividade e sensibilidade, com possibilidade de aplicação para análises de rotina em substituição à cromatografia a gás por captura de elétrons. Observou-se a formação de ácidos haloacéticos durante os ensaios com doses de 2,5 e 5,0 mg.L-1 do oxidante, com destaque para os ácidos dicloroacético e tricloroacético.
ABSTRACT The objective of the study was to develop and validate an analytical method for the detection and quantification of haloacetic acids through liquid-liquid extraction and gas chromatography-mass spectrometry analysis. For validation, parameters such as linearity, precision, detection and quantification limits, and selectivity were considered. Additionally, the method was applied to evaluate the formation of haloacetic acids in in Cylindrospermopsis raciborskii cell chlorination assays with the calcium hypochlorite oxidant, simulating full scale situations in water treatment plants. The method presented low analysis time, excellent selectivity, precision, repeatability, and sensitivity, with possibility of application for routine analysis in substitution gas chromatography by electron capture. The formation of haloacetic acids was observed during the tests with 2.5 and 5.0 mg.L-1 doses of the oxidant, with emphasis on dichloroacetic and trichloroacetic acids.
RESUMO
There is growing evidence that cyanobacterial blooms are becoming more common in different parts of the world; within this context, predictive cyanobacteria models have an essential role in lake management. Several models have been successfully used in temperate systems to describe the main drivers of cyanobacterial blooms, but relatively less work has been conducted in the Tropics. We analyzed data from six Brazilian reservoirs and from five Canadian lakes using a combination of regression tree analyses and variation partitioning to evaluate the similarities and differences between regions. Our results, together with a synthesis of the literature from different latitudes, showed that trophic state (i.e. nutrients), climatic variables (e.g., temperature and/or precipitation) and hydrodynamic regimes (i.e. water residence time) are significant drivers of cyanobacteria biomass over several scales. Nutrients came out as the primary predictor in both regions, followed by climate, but when all systems were pooled together, water residence time came out as most important. The consistency in variables identified between regions suggests that these drivers are widely important and cyanobacteria responded quite similarly in different geographical settings and waterbody types (i.e. lakes or reservoirs). However, more work is needed to identify key thresholds across latitudinal gradients. Taken together, these results suggest that multi-region syntheses can help identify drivers that predict broad-scale patterns of cyanobacteria biomass.
Assuntos
Cianobactérias , Eutrofização , Biomassa , Brasil , CanadáRESUMO
Radiocystis fernandoi, a microcystin (MC) producer, has been common in cyanobacterial blooms in tropical regions. Microcystin is a hepatotoxin that causes tissue damage and even death in animals, including humans; its detoxification process may involve biotransformation and activation of the antioxidant defense system. We evaluated the detoxification pathway, examined the antioxidant defense system responses, and determined the alterations and the organ histopathological indexes in the liver of the tropical fish Hoplias malabaricus after acute and subchronic intraperitoneal exposure to microcystin. The crude microcystin extract of R. fernandoi had predominantly MC-RR and MC-YR. The detoxification process was activated by increasing ethoxyresorufin-O-deethylase activity, whereas glutathione S-transferase was inhibited. The activity of the antioxidant defense enzymes superoxide dismutase (SOD) and glutathione peroxidase decreased after acute exposure; the SOD-catalase system and the glutathione level increased after subchronic exposure. The carbonyl protein level, lipid peroxidation (LPO), and DNA damage were unchanged after acute exposure, whereas protein carbonyl was unchanged, LPO decreased, and DNA damage increased after subchronic exposure. Histopathological alteration indexes differed between acute and subchronic exposure, but the histopathological organ indexes indicate liver dysfunction in both exposure periods. We conclude that MC-RR and MC-YR induce different liver responses depending on the time of exposure, and the antioxidant defense responses after subchronic exposure may help to partially restore the liver function. Environ Toxicol Chem 2020;39:1041-1051. © 2020 SETAC.
Assuntos
Antioxidantes/metabolismo , Caraciformes/fisiologia , Cianobactérias/química , Exposição Ambiental , Fígado/metabolismo , Fígado/patologia , Microcistinas/toxicidade , Animais , Biotransformação/efeitos dos fármacos , Ensaio Cometa , Glutationa/metabolismo , Glutationa Peroxidase/metabolismo , Glutationa Transferase/metabolismo , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/efeitos dos fármacos , Mutagênicos/toxicidadeRESUMO
Understanding how ecological traits have changed over evolutionary time is a fundamental question in biology. Specifically, the extent to which more closely related organisms share similar ecological preferences due to phylogenetic conservation - or if they are forced apart by competition - is still debated. Here, we explored the co-occurrence patterns of freshwater cyanobacteria at the sub-genus level to investigate whether more closely related taxa share more similar niches and to what extent these niches were defined by abiotic or biotic variables. We used deep 16S rRNA gene amplicon sequencing and measured several abiotic environmental parameters (nutrients, temperature, etc.) in water samples collected over time and space in Furnas Reservoir, Brazil. We found that relatively more closely related Synechococcus (in the continuous range of 93%-100% nucleotide identity in 16S) had an increased tendency to co-occur with one another (i.e. had similar realized niches). This tendency could not be easily explained by shared preferences for measured abiotic niche dimensions. Thus, commonly measured abiotic parameters might not be sufficient to characterize, nor to predict community assembly or dynamics. Rather, co-occurrence between Synechococcus and the surrounding community (whether or not they represent true biological interactions) may be a more sensitive measure of realized niches. Overall, our results suggest that realized niches are phylogenetically conserved, at least at the sub-genus level and at the resolution of the 16S marker. Determining how these results generalize to other genera and at finer genetic resolution merits further investigation.
Assuntos
Evolução Biológica , Synechococcus/fisiologia , Brasil , Ecossistema , Água Doce/microbiologia , Filogenia , RNA Ribossômico 16S , Synechococcus/classificação , Synechococcus/genéticaRESUMO
RESUMO Estudos demonstram que a utilização do cloro em estações de tratamento de água (ETA) pode contribuir para a formação de subprodutos orgânicos halogenados indesejados, tais como os trialometanos (TAM), quando há presença de matéria orgânica algogênica, composta de algas e cianobactérias. A Microcystis aeruginosa é uma espécie de cianobactéria com frequentes registros em eventos de florações no país e é relacionada com a formação de TAM durante a cloração da água. Desse modo, este estudo teve como objetivo o desenvolvimento e a validação do método analítico por extração líquido-líquido para detecção e quantificação de TAM por cromatografia gasosa acoplada à espectrometria de massas (ELL-CG-EM), bem como a aplicação deste para avaliar a formação de TAM em ensaios de cloração de células de Microcystis aeruginosa, simulando situações em ETA. O método obteve baixo tempo de análise (< 12 minutos), excelente seletividade, precisão, repetitividade e sensibilidade, com possibilidade de aplicação para análises de rotina em detrimento de outras técnicas consideradas mais automatizadas. Foram observadas alta demanda de cloro durante os ensaios e elevada concentração dos subprodutos quando submetida à dose de cloro gasoso (Cl2) de 2,5 e 5 mg.L-1, com destaque para o triclorometano, sendo outras espécies de monitoramento obrigatório não detectadas ou não formadas, o que pode ser justificado pela ausência de bromo.
ABSTRACT Studies have shown that the use of chlorine in water treatment plants (WTPs) can contribute to formation of undesirable halogenated organic by-products, such as trihalomethanes (THMs), when algae and cyanobacteria are present. Microcystis aeruginosa is a cyanobacteria specie with frequent recordings of flowering events in the country and is related to the formation of THMs during water chlorination. Thus, the objective of this study was to develop and validate Liquid-Liquid Extraction the analytical method for detection and quantification of THMs by gas chromatography coupled to mass spectrometry (LLE-GC-MS), as well as the application of the method to evaluate the formation of TAMs from Microcystis aeruginosa cells chlorination tests, simulating situations in WTPs. The method obtained low time of analysis (< 12 minutes), excellent selectivity, precision, repeatability and sensitivity, with possibility of application for routine analysis to the detriment of other techniques considered more automated. High chlorine demand was observed during the tests and high concentration of by-products when submitted to the chlorine gas (Cl2) dose of 2.5 and 5 mg.L-1, with emphasis on trichloromethane. Other species of mandatory monitoring were not detected or not formed, justified by the absence of bromine.
RESUMO
Blooms of cyanobacteria, a common event in eutrophic environments, result in the release of potentially toxic substances into the water. The cyanobacterium Radiocystis fernandoi produces microcystin (MC) and other peptides that may disturb homeostasis. This study evaluated the effect of intraperitoneal injections containing the crude extract (CE) of R. fernandoi strain R28 on the gills and kidneys of neotropical fish, Piaractus mesopotamicus, 3, 6 and 24â¯h post-injection. CE contained MC-RR, MC-YR and minor other oligopeptides. Plasma ions and the activities of the enzymes PP1 and PP2A, Na+/K+-ATPase (NKA), H+-ATPase (HA) and carbonic anhydrase (CA) were determined and morphological changes in both the gills and kidneys were characterized. Compared to controls, the concentration of Na+ within the plasma of P. mesopotamicus decreased after treatment with CE 3â¯h post treatment and increased after 24â¯h; the concentration of K+ decreased after 6â¯h. The activity of the endogenous PP1 and PP2A was unchanged in the gills and was inhibited in the kidneys 6â¯h after i.p. injection. In the gills, NKA activity increased after 3â¯h and decreased 6â¯h post i.p. exposure. Further, NKA activity did not differ from the controls 24-h post injection. In the kidneys, NKA, HA and CA activities were unaffected by treatment. The mitochondria-rich cell (MRC) density in the gills decreased after 3â¯h in the filament and 3 and 6â¯h in the lamellae and was restored to the control levels 24â¯h post-exposure. Filament epithelial hyperplasia and hypertrophy, lamellar atrophy and rupture of the lamellar epithelium were the most common effects of treatment in the gills. No histopathological changes occurred in the kidneys. This study demonstrates that a single dose of toxic CE from R. fernandoi can cause a transitory ion imbalance in P. mesopotamicus which is related to the changes in MRC levels and NKA activity. Ionic balance was recovered 24â¯h post i.p. injection, however, morphological changes that occurred in the gills took a longer amount of time to return to normal. To conclude, the effects of components contained within the CE of R. fernandoi may be harmful to P. mesopotamicus. In particular, the recovery of ionic regulation depends on MRC responses and histopathological changes produced by CE may affect gas exchange and other gill functions.
Assuntos
Caraciformes/fisiologia , Misturas Complexas/toxicidade , Cianobactérias/metabolismo , Exposição Ambiental , Osmorregulação , Animais , Caraciformes/sangue , Cloretos/sangue , Creatinina/sangue , Brânquias/efeitos dos fármacos , Brânquias/enzimologia , Brânquias/patologia , Íons/sangue , Rim/efeitos dos fármacos , Rim/enzimologia , Rim/patologia , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Osmorregulação/efeitos dos fármacos , Potássio/sangue , ATPases Translocadoras de Prótons/metabolismo , Sódio/sangue , ATPase Trocadora de Sódio-Potássio/metabolismo , Poluentes Químicos da Água/toxicidadeRESUMO
Microcystis is a genus of freshwater cyanobacteria, which causes harmful blooms in ecosystems worldwide. Some Microcystis strains produce harmful toxins such as microcystin, impacting drinking water quality. Microcystis colony morphology, rather than genetic similarity, is often used to classify Microcystis into morphospecies. Yet colony morphology is a plastic trait, which can change depending on environmental and laboratory culture conditions, and is thus an inadequate criterion for species delineation. Furthermore, Microcystis populations are thought to disperse globally and constitute a homogeneous gene pool. However, this assertion is based on relatively incomplete characterization of Microcystis genomic diversity. To better understand these issues, we performed a population genomic analysis of 33 newly sequenced genomes mainly from Canada and Brazil. We identified 17 Microcystis clusters of genomic similarity, five of which correspond to monophyletic clades containing at least three newly sequenced genomes. Four out of these five clades match to named morphospecies. Notably, M. aeruginosa is paraphyletic, distributed across 12 genomic clusters, suggesting it is not a coherent species. A few clades of closely related isolates are specific to a unique geographic location, suggesting biogeographic structure over relatively short evolutionary time scales. Higher homologous recombination rates within than between clades further suggest that monophyletic groups might adhere to a Biological Species-like concept, in which barriers to gene flow maintain species distinctness. However, certain genes-including some involved in microcystin and micropeptin biosynthesis-are recombined between monophyletic groups in the same geographic location, suggesting local adaptation.
Assuntos
Microcystis/genética , Microcystis/isolamento & purificação , Brasil , Canadá , Ecossistema , Evolução Molecular , Água Doce/microbiologia , Genoma Bacteriano , Metagenômica , Microcistinas/metabolismo , Microcystis/classificação , Microcystis/metabolismo , FilogeniaRESUMO
The cyanobacterium Radiocystis fernandoi has been frequently identified in cyanobacterial blooms in Brazil. Recently, R. fernandoi strain R28, which produces microcystin (MC)-RR and MC-YR, was isolated from the Furnas reservoir, Minas Gerais, Brazil. The present study evaluated the hematological variables and erythrocyte antioxidant responses, lipid peroxidation (LPO), and genotoxicity in a neotropical fish (Hoplias malabaricus) after acute and subchronic exposure to a crude extract (CE) of R. fernandoi strain R28. Acute exposure (12 or 96â¯h) consisted of a single intraperitoneal (i.p.) CE injection, and subchronic exposure consisted of one i.p. CE injection every 72â¯h for 30 days. After acute exposure, fish exhibited macrocytic anemia (12â¯h post-injection) followed by normocytic anemia (96â¯h post-injection). The increased activity of superoxide dismutase, glutathione peroxidase, glutathione-S-transferase, and the glutathione level in the erythrocytes did not prevent oxidative stress, manifested as lipid peroxidation and elevated DNA damage after acute exposure. After subchronic exposure, the hematological variables recovered, and the absence of erythrocyte oxidative stress suggests possible modulation by other biological factors, including a possible decrease in MC uptake by the cells and/or increasing detoxification efficiency that precludes erythrocyte damage.
Assuntos
Misturas Complexas/toxicidade , Cianobactérias/química , Eritrócitos/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Animais , Misturas Complexas/química , Misturas Complexas/isolamento & purificação , Dano ao DNA/efeitos dos fármacos , Peixes , Peroxidação de Lipídeos/efeitos dos fármacos , Testes de ToxicidadeRESUMO
An analytical liquid-liquid extraction-gas chromatography-mass spectrometry (LLE-GC-MS) method was developed and validated for the determination of trihalomethanes (THMs) in environmental samples. The compounds studied were trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM). The calibration curves for the THMs showed high linearity in the range of 1-1000 µg L-1. Studies of intra-day and inter-day precision, limit of detection (LOD), limit of quantification (LOQ), accuracy, and recovery were performed with low (10 µg L-1), medium (40 µg L-1), and high (200 µg L-1) concentrations of THMs. The intra-day and inter-day precision RSD varied in the ranges of 0.17-6.95% and 0.26-15.70%, respectively. No statistical differences were observed between the analysis of the concentration of certified reference materials (CRM 4M8140-U) and the values reported by CRM, indicating the good accuracy of the proposed method. The recovery was 88.75-119.21%. The LOD and LOQ were smaller than 0.13 and 0.40 µg L-1. Compared with reported LLE-GC-MS methods, the validated method had similar LOD and enhanced LOQ, precision, accuracy, and recovery. Also, the method is robust, selective to THMs, and the total time for the extraction and GC separation of THMs is about 18 min. The method was useful for detecting and quantifying low concentrations of TCM (40-80 µg L-1) formed by water chlorination in the presence of Microcystis aeruginosa cyanobacteria, thus demonstrating its applicability for monitoring THMs in real samples.
Assuntos
Monitoramento Ambiental/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Extração Líquido-Líquido/métodos , Trialometanos/análise , Poluentes Químicos da Água/análise , Clorofórmio/análise , Halogenação , Microcystis/metabolismo , Água/químicaRESUMO
Aquatic ecosystems have been severely altered by invasive species and a connection has been observed between bivalve invasions and an increase in frequency of cyanobacteria toxic blooms. In South America, the invasive golden mussel, Limnoperna fortunei, has caused serious environmental and economic impacts, because of its high filtration rates, high population densities and rapid dispersion. Changes in the plankton community have been detected at sites invaded by this species. The aim of the present study was to investigate the possible effects of this mussel on the growth of the bloom-forming cyanobacterium Microcystis aeruginosa, in laboratory experiments under controlled light and temperature conditions. The cyanobacterium M. aeruginosa and a chlorophyte (Pseudokirchneriella sp.) were used either together or alone as food for the mussels. Density measurements of M. aeruginosa and Pseudokirchneriella sp. growing in vessels with and without mussels were performed daily, and nutrient concentrations in the water were assessed at the beginning and end of the experiment. The results indicated that Pseudokirchneriella sp. acted as a competitor, contributing to reduce densities and growth rates of M. aeruginosa. These effects, however, did not occur in the presence of the golden mussel, when the densities of Pseudokirchneriella sp. were significantly lower, possibly due to selective grazing. Phosphate and nitrate concentrations were always higher in the presence of the bivalves. As previously observed for other invasive mollusks, our results suggest that the golden mussel may have a positive effect on M. aeruginosa by the exclusion of potential competitors as well as by increasing nutrient supply.
Assuntos
Bivalves/fisiologia , Microcystis/fisiologia , Animais , Dinâmica Populacional , Fatores de TempoRESUMO
Cyanobacterial proliferation in river and lakes is the result of eutrophication. The cyanobacterium Radiocystis fernandoi strain R28 produces mostly two MC variants MC-RR and MC-YR and small amounts of other oligopeptides, but does not produce MC-LR. The present study investigated the hepatotoxic potential of the crude extract of the R. fernandoi strain R28 on the Neotropical fish, Piaractus mesopotamicus, at 3, 6, and 24 h after intraperitoneal injection (100 µg MC-LR equivalent per kg-1 body mass) using biochemical and morphological biomarkers of liver damage. Although the protein phosphatases PP1 and PP2A were not inhibited during the 24-h treatment, liver parenchyma and hepatocyte structure were disrupted. Alkaline phosphatase increased at 3 h post-injection and decreased after 24 h; alanine aminotransferase and aspartate aminotransferase increased in a time-dependent manner up to 24 h indicating impaired liver function. Progressive histopathological changes were consistent with biochemical results demonstrating alterations in liver structure and function. In conclusion, the crude extract of R. fernandoi strain R28 has high hepatotoxic potential and can severely compromise fish health.
Assuntos
Alanina Transaminase/metabolismo , Fosfatase Alcalina/metabolismo , Aspartato Aminotransferases/metabolismo , Biomarcadores/metabolismo , Cianobactérias/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Microcistinas/metabolismo , Alanina Transaminase/química , Fosfatase Alcalina/química , Animais , Aspartato Aminotransferases/química , Peixes , Injeções Intraperitoneais , Lagos , HepatopatiasRESUMO
The toxicological effect of cellular extract of cyanobacterium Radiocystis fernandoi strain R28 containing RR and YR microcystins was analyzed in the fish Hoplias malabaricus with emphasis on the liver structure and energetic metabolism, after short-term exposure. Fish were intraperitoneally (i.p.) injected with 100 µg of equivalent MC-LR kg-1 body mass containing in the cellular extract of R. fernandoi strain R28. Twelve and 96 h post-injection, the plasma, liver and white muscle were sampled for biochemical analyses and liver was also sampled for morphological analyses. After i.p. injection, the activity of acid phosphatase (ACP), alanine aminotransferase (ALT) and direct bilirubin increased in the plasma, while ALT and aspartate aminotransferase (AST) decreased in the liver. Glucose, lactate and pyruvate increased while protein decreased in the plasma; glycogen, pyruvate and lactate decreased in the liver; and glycogen and glucose increased in the muscle. Ammonia increased in the plasma, liver and muscle. The hepatocyte cell shape changed from polyhedral to round after cellular extract injection; there was loss of biliary canaliculus organization, but the biliary duct morphology was conserved in the liver parenchyma. In conclusion, microcystins present in the cellular extract of R. fernandoi strain R28 affect the liver structure of H. malabaricus, but the liver was able to continuously produce energy by adjusting its intermediate metabolism; glycogenolysis and gluconeogenesis maintained glucose homeostasis and energy supply.
Assuntos
Caraciformes/metabolismo , Cianobactérias/química , Metabolismo Energético/efeitos dos fármacos , Fígado/efeitos dos fármacos , Microcistinas/toxicidade , Alanina Transaminase/sangue , Animais , Aspartato Aminotransferases/sangue , Bilirrubina/sangue , Caraciformes/sangue , Glicogênio/metabolismo , Hepatócitos/efeitos dos fármacos , Hepatócitos/enzimologia , Hepatócitos/ultraestrutura , Fígado/enzimologia , Fígado/ultraestrutura , Toxinas Marinhas , Microcistinas/isolamento & purificação , Músculos/efeitos dos fármacos , Músculos/metabolismoRESUMO
RESUMO No processo de urbanização, o aumento na proporção de superfícies impermeabilizadas e as mudanças no uso do solo são responsáveis por maiores volumes e velocidades do escoamento superficial, refletindo em uma maior capacidade de arraste e em um maior aporte de nutrientes nos corpos d'água receptores. O objetivo deste trabalho foi implementar uma ferramenta matemática capaz de reproduzir o impacto de mudanças na bacia hidrográfica sobre a dinâmica do fitoplâncton em um lago urbano. Neste artigo são apresentados o desenvolvimento e os resultados de um modelo integrado constituído de um modelo hidrológico, para simular vazões escoadas em uma bacia hidrográfica, e de um modelo hidrodinâmico e ecológico, para simular a biomassa fitoplanctônica em um corpo d'água urbano. A Lagoa da Pampulha (Belo Horizonte, Minas Gerais), escolhida como estudo de caso, foi intensamente monitorada, assim como sua bacia de drenagem, entre outubro de 2011 e junho de 2013. Os dados obtidos foram utilizados para calibrar e validar ambos os modelos. Os resultados obtidos com o modelo hidrológico mostraram-se coerentes com as medidas realizadas em campo (o coeficiente de Nash variou entre 0,70 e 0,88). O modelo da lagoa representou corretamente a evolução da comunidade fitoplanctônica (erro médio absoluto normalizado: 0,25-0,42 e o coeficiente de Pearson: 0,82-0,89; p<0,0001). O monitoramento e a modelagem da lagoa mostraram que a proliferação de cianobactérias é bastante perturbada pelas desestratificações térmicas que ocorrem na lagoa em virtude de eventos meteorológicos. A ferramenta de simulação desenvolvida possui potencial para avaliar diferentes cenários de mudança das condições climáticas e das características da bacia, podendo auxiliar na gestão dos corpos d'água situados em meio urbano.
ABSTRACT In urban areas the increasing imperviousness is responsible for rising runoff volume and speed, leading to a greater capacity to load nutrients and pollutants into reservoirs. In order to study the impacts of catchment changes on the phytoplankton dynamics in urban lakes, a modelling approach in which a hydrological model is connected to an ecological lake model is proposed for Lake Pampulha (Brazil). In this paper we present the methodology used to link both models. Lake Pampulha and its catchment area were intensively monitored between October 2011 and June 2013 in order to provide data for the calibration and validation of both models. The results of the hydrologic model showed good agreement with the in situ measurements, and the Nash coefficient ranged from 0.70 to 0.88. The lake ecological model have successfully represented the cyanobacteria dynamics (normalized mean average error: 0.25-0.42, Pearson coefficient: 0.82-0.89, p<0.0001). Monitoring and modelling showed that cyanobacteria blooms are quite disturbed by water column mixing caused by rain events. The mathematical tool developed here can be used to assess different scenarios of climate changes or catchment area changes and can be very helpful for the management of urban water resources.
RESUMO
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.
Assuntos
Microcistinas/metabolismo , Microcystis/fisiologia , Estresse Fisiológico , Meios de Cultura/química , Perfilação da Expressão Gênica , Genes Bacterianos , Microcystis/metabolismo , Nitrogênio/metabolismo , Estresse Oxidativo , Fósforo/metabolismo , Reação em Cadeia da Polimerase em Tempo Real , Transcrição GênicaRESUMO
Cyanobacteria can form blooms and in these situations they dominate the phytoplanktonic community, reaching extremely high densities. In the domain Bacteria, high population densities can stimulate a phenomenon known as quorum sensing, which may produce several modifications in the cell physiology. Very little is known about quorum sensing in Cyanobacteria. Because of their planktonic way of life, quorum sensing should be more evident during a bloom event. In this work, we tested whether cell density could shape the production of bioactive compounds produced by Cyanobacteria. The experiments consisted of two treatments, where cultures of Cyanobacteria were maintained at low and high cellular densities through a semi-continuous set-up. Analyses were performed by HPLC-PDA and MALDI-TOF MS. Seventeen peptides were detected and 14 identified, including microcystins, aeruginosins, cyanopeptolins and microviridins. The results showed that cellular density seems to have a significant effect on the peptides production. Most of the compounds had significantly higher cellular quotas in the higher-density treatment, although microviridins and an unknown peptide were produced only at low density. These results may hint at a possible role for quorum sensing in triggering the production of several cyanobacterial peptides.
Assuntos
Proteínas de Bactérias/biossíntese , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/metabolismo , Água Doce/microbiologia , Microcistinas/biossíntese , Oligopeptídeos/biossíntese , Proteínas de Bactérias/química , Brasil , Cromatografia Líquida de Alta Pressão , Cianobactérias/química , Cianobactérias/citologia , Eutrofização , Microcistinas/química , Oligopeptídeos/química , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
Cyanobacteria produce a high variety of bioactive oligopeptides, which function, ecological, physiological roles and responses to environmental changes are still unclear. The influence of light intensity on the cell quota and the diversity of oligopeptides of two strains of the cyanobacterium Radiocystis fernandoii were experimentally tested. The peptides were quantified by HPLC and identified by a MALDI-TOF-TOF. Microcystins (MC) were generally more abundant in the treatment with low light. A compensatory mechanism was observed for the different variants of microcystin, whereby MC-RR responses were contrary to those observed for the other three variants and showed higher concentration in the treatment with intermediate light. Two microviridins were also produced at higher amounts at intermediate irradiance. For cyanopeptolins and a third microviridin no significant difference among treatments was found. The absence of a similar response for all peptides suggests that these compounds may have unique cellular functions, which better understanding could help explaining changes in toxicity. Finally, we observed that each chemical profile reflected in physiological differences between strains, strengthening the idea that chemotypes may act as distinct ecotypes in nature.