Papers by Blahoslav Maršálek
Limnology and Oceanography, 2007
The various oligopeptides produced by individual Microcystis clones enable the classification of ... more The various oligopeptides produced by individual Microcystis clones enable the classification of individual colonies of Microcystis in distinct peptide chemotypes. The dynamics and diversity of coexisting chemotypes are regarded as major factors influencing the microcystin-content of blooms of this potentially toxic cyanobacterial genus. We compared the chemotype composition in planktonic and benthic Microcystis communities in Brno reservoir (Czech Republic) from July to November 2004 by single-colony mass spectrometry (n 5 783). Ninetytwo peptides were selected to characterize 37 chemotypes as revealed by K-means clustering. In the course of the season the Microcystis community became significantly less diverse (linear regression of Shannon indices, p , 0.001) in the pelagic, and in November two chemotypes-both of which did not contain microcystins-accounted for nearly 80% of the colonies. In contrast, other chemotypes that were dominant in the pelagic in July were no longer encountered after August, whereas some chemotypes that never accounted for high relative abundances were encountered throughout the season. The shift to some few dominant chemotypes in the pelagic was also reflected by changes in the benthic community where the same chemotypes increased in relative abundances. Nonetheless, chemotypes were identified in the sediment in July and November that were never found in plankton samples. A principal component analysis revealed that communities in the pelagial and the benthal were very different in July but converged during the season because of the deposition of dominant planktonic chemotypes in the sediment. In accordance with the declining percentage of toxin-producing Microcystis colonies, the microcystin content of seston samples decreased significantly from 0.9 mg g 21 dry weight to levels below the detection limit (linear regression, p , 0.001).
Acta hydrochimica et hydrobiologica, 2005
Algological Studies, 2004
ABSTRACT Ingestion of cyanobacterial biomass by silver carp is frequently considered as one of th... more ABSTRACT Ingestion of cyanobacterial biomass by silver carp is frequently considered as one of the biological methods for the water bloom formation control. We measured the photosynthetic activity of Microcystis (maximal quantum yield of photosystem II determined by PAM fluorimeter FluorCam 700) before and after the gut passage of silver carp. Viability of digested Microcystis was nearly identical with control and no serious damage in metabolic activity was observed. Moreover microscopic observation of Microcystis colonies after digestion proved that larger colonies (more than 1000 cells) were disintegrated to smaller colonies up to 50–100 cells/colony. These smaller colonies were viable and actively growing. Seven days after excretion by silver carp the photosynthetic activity of Microcystis was comparable or slightly higher than the control population. Our results provide an experimental evidence that Microcystis is not damaged by silver carp digestion. That is probably one of the reasons why silver carp is not efficient in Microcystis bloom removal.
Interdisciplinary Toxicology, 2009
Cyanobacterial blooms in freshwaters represent a major ecological and human health problem worldw... more Cyanobacterial blooms in freshwaters represent a major ecological and human health problem worldwide. This paper briefly summarizes information on major cyanobacterial toxins (hepatotoxins, neurotoxins etc.) with special attention to microcystins -cyclic heptapeptides with high acute and chronic toxicities. Besides discussion of human health risks, microcystin ecotoxicology and consequent ecological risks are also highlighted. Although significant research attention has been paid to microcystins, cyanobacteria produce a wide range of currently unknown toxins, which will require research attention. Further research should also address possible additive, synergistic or antagonistic effects among different classes of cyanobacterial metabolites, as well as interactions with other toxic stressors such as metals or persistent organic pollutants.
Embryotoxicity of several persistent organic polutants (POPs) is documented from laboratory exper... more Embryotoxicity of several persistent organic polutants (POPs) is documented from laboratory experiments and field studies. However, biochemical and cellular events involved in the POPs-induced effects (e.g. changes in retinoid concentrations) are not characterized in details. In the present study we introduce a novel in vitro bioassay with embryonal P19 cells (clone P19/A15) stably transfected with firefly luciferase gene under control of RARE (Retinoic Acid Responsive Element). Expression of the reporter luciferase activity is induced after exposure of the cells to retinoic acid (ATRA; 10 -9 mol.l -1 concentrations). Simultaneous treatments by ATRA (20 nM) and picomolar concentrations of 2,3,7,8tetrachlorodibenzo-p-dioxin (TCDD) resulted in the substantial decrease of luciferase activity indicating selective disruption of retinoid signalling. Additional experiments with DELOR106 (commercial mixture of polychlorinated biphenyls, PCBs) and Nibrenwax (mixture of polychlorinated naphthalenes, PCNs) reveal a suitability of the bioassay for rapid screening and detection of xenobiotic-induced biochemical effects directly related to cellular differentiation, embryotoxicity and developmental toxicity.
Acta Veterinaria Brno, 2006
Water Research, 2004
Standard ISO method for chlorophyll a quantification (extraction into ethanol, spectrophotometric... more Standard ISO method for chlorophyll a quantification (extraction into ethanol, spectrophotometrical quantification at 665 and 750 nm), spectrofluorometry (reader for 96 wells, excitation 410 nm, emission 670 nm), and a submersible fluorescence probe for in situ phytoplankton quantification (excitation 410, 525, 570, 590, and 610 nm, emission 685 nm) were compared in different freshwater environments-reservoirs and rivers. The ISO method is accepted as a standard method but requires sample handling and transport to the laboratory. Spectrofluorometry is a sensitive method, even for natural phytoplankton populations. Nevertheless, it cannot be recommended for the quantification of cyanobacterial water blooms because colonial and filamentous species such as Microcystis, Anabaena, or Aphanizomenon display unacceptable variability (18-33%). The submersible probe featured high correlation with a standard ISO method (r=0.97, P&lt;0.05). This probe can provide the selective measurement of technologically important phytoplankton groups like cyanobacteria, diatoms, green algae, and cryptophytes in lake vertical profiles of up to 100 m. The limitation of this instrument is the possible reabsorption of the light signal, e.g. in the presence of humic substances, or dense algal blooms. The use of submersible probes for in situ phytoplankton quantification can be recommended as a sensitive tool for water management, especially in the case of drinking water resources.
Water Research, 2007
In vivo fluorescence methods have been accepted as a quick, simple, and useful tool for quantific... more In vivo fluorescence methods have been accepted as a quick, simple, and useful tool for quantification of phytoplankton organisms. In this paper, we present a case study in which fluorescence methods were employed for the selective detection of potentially toxic cyanobacteria in raw water at the drinking water treatment plant. The occurrence of cyanobacteria in the drinking water reservoir and in raw water was monitored by phycocyanin fluorescence measurements and by standard methods for phytoplankton quantification (cell counts, chlorophyll a). A special attention was paid to the most critical parts of the season -- spring recruitment of cyanobacteria from sediment to water column and autumn bloom collapse. All methods showed similar patterns within the season. Phycocyanin fluorescence was found to be a simple and sensitive indicator of cyanobacteria in water and can serve as a tool that can provide an early warning about the presence of potentially toxic cyanobacterial metabolites in water.
Toxicon, 2009
Cylindrospermopsin (CYN) is a newly emerging carcinogenic alkaloid originally identified in tropi... more Cylindrospermopsin (CYN) is a newly emerging carcinogenic alkaloid originally identified in tropical cyanobacteria Cylindrospermopsis raciborskii. Some recent studies reported production of this toxin also by other cyanobacteria in European countries. Here we report comparison of the immunochemical ELISA determination with the liquid chromatography/mass spectrometry (LC/MS) method for CYN analyses in the samples from the Czech Republic, Central Europe. We have analysed 56 samples of raw lake waters collected from 32 localities. CYN was found at 3 localities with Aphanizomenon sp. sub-dominated water blooms. Results of the ELISA and LC/MS showed good qualitative agreement. However, concentrations determined by ELISA (0.4-4 microg/L) were systematically higher than concentrations determined by LC/MS (0.01-0.3 microg/L). Differences between methods could be attributed to matrix effects (both in ELISA and LC/MS) or ELISA cross-reactivity with other unidentified derivatives of CYN. Our study demonstrates for the first time occurrence of CYN in the Central Europe. With respect to its suspected carcinogenicity, further research on distribution, concentrations and risks of this cyanobacterial toxin is needed.
Toxicon, 2007
Mortality of wild aquatic birds has recently been attributed to cyanobacterial toxins. Despite th... more Mortality of wild aquatic birds has recently been attributed to cyanobacterial toxins. Despite this, no experimental studies on the effects of defined doses of microcystins administered orally to birds exist. In this experiment, four groups of male Japanese quails daily ingesting 10ml of Microcystis biomass containing 0.045, 0.459, 4.605 or 46.044mug of microcystins, respectively, for 10 and 30 days, showed no mortality. Histopathological hepatic changes in birds after the biomass exposure included cloudy swelling of hepatocytes, vacuolar dystrophy, steatosis and hyperplasia of lymphatic centres. On subcellular level, shrunken nuclei of hepatocytes containing ring-like nucleoli, cristolysis within mitochondria and vacuoles with pseudomyelin structures were present. Vacuolar degeneration of the testicular germinative epithelium was found in two exposed males. Statistically significant differences in biochemical parameters were on day 10 of exposure only. They comprised increased activities of lactate dehydrogenase and a drop in blood glucose in birds receiving the highest dose of the biomass. Principal component analysis revealed a pattern of responses in biochemical parameters on day 10 that clearly separated the two greatest exposure groups from the controls and lower exposures. The results indicate that diagnosis of microcystin intoxication solely based on clinical biochemical and haematological parameters is hardly possible in birds.
Toxicon, 2014
Toxic cyanobacterial blooms are a global threat to human health and aquatic biota. While the ecot... more Toxic cyanobacterial blooms are a global threat to human health and aquatic biota. While the ecotoxicity of cyanobacterial toxins such as microcystins has been studied extensively, little is known about the risks they pose in the wild, i.e. within complex biomasses. In this work, crustaceans (Daphnia magna) were exposed to varying concentrations (0-405 mg d.w L(-1)) of eight complex cyanobacterial water bloom samples in a series of acute (48 h) and chronic (21 day) toxicity experiments. Further acute and chronic exposure assays were performed using aqueous extracts of the crude biomass samples and two fractions prepared by solid phase extraction (SPE) of the aqueous extracts. The cyanobacterial biomasses differed with respect to their dominant cyanobacterial species and microcystin contents. High acute toxicity was observed for 6 of the 8 crude biomass samples. Chronic exposure assays were performed using one complex biomass sample and its various subsamples/fractions. The complex biomass, the crude aqueous extract, and the microcystin-free SPE permeate all elicited similar and significant lethal effects, with LC50 values of around 35.6 mg biomass d.w L(-1) after 21 days. The cyanobacterial biomass samples also affected reproductive health, significantly increasing the time to the first brood (LOEC = 45 mg d.w L(-1) exposure) and inhibiting fecundity by 50% at 15 mg d.w L(-1). Conversely, the microcystin-containing C18-SPE eluate fraction had only weak effects in the chronic assay. These results indicate that cyanobacterial water blooms are highly toxic to zooplankton (both acutely and chronically) at environmentally relevant concentrations. However, the effects observed in the acute and chronic assays were independent of the samples&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; microcystin contents. Our results thus point out the importance of other cyanobacterial components such as lipopolysaccharides, various peptides and depsipeptides, polar alkaloid metabolites or other unidentified metabolites in the overall ecotoxicity of complex cyanobacterial blooms.
Science of The Total Environment, 2010
Under environmental conditions, wild birds can be exposed to multiple stressors including natural... more Under environmental conditions, wild birds can be exposed to multiple stressors including natural toxins, anthropogenic pollutants and infectious agents at the same time. This experimental study was successful in testing the hypothesis that adverse effects of cyanotoxins, heavy metals and a non-pathogenic immunological challenge combine to enhance avian toxicity. Mortality occurred in combined exposures to naturally occurring cyanobacterial biomass and lead shots, lead shots and Newcastle vaccination as well as in single lead shot exposure. Mostly acute effects around day 10 were observed. On day 30 of exposure, there were no differences in the liver accumulation of lead in single and combined exposure groups. Interestingly, liver microcystin levels were elevated in birds co-exposed to cyanobacterial biomass together with lead or lead and the Newcastle virus. Significant differences in body weights between all Pb-exposed and Pb-non-exposed birds were found on days 10 and 20. Single exposure to cyanobacterial biomass resulted in hepatic vacuolar dystrophy, whereas co-exposure with lead led to more severe granular dystrophy. Haematological changes were associated with lead exposure, in particular. Biochemical analysis revealed a decrease in glucose and an increase in lactate dehydrogenase in single and combined cyanobacterial and lead exposures, which also showed a decreased antibody response to vaccination. The combined exposure of experimental birds to sub-lethal doses of individual stressors is ecologically realistic. It brings together new pieces of knowledge on avian health. In light of this study, investigators of wild bird die-offs should be circumspect when evaluating findings of low concentrations of contaminants that would not result in mortality on a separate basis. As such it has implications for wildlife biologists, veterinarians and conservationists of avian biodiversity.
Science of The Total Environment, 2008
The cyanobacterial exposure has been implicated in mass mortalities of wild birds, but informatio... more The cyanobacterial exposure has been implicated in mass mortalities of wild birds, but information on the actual effects of cyanobacteria on birds in controlled studies is missing. Effects on detoxification and antioxidant parameters as well as bioaccumulation of microcystins (MCs) were studied in birds after sub-lethal exposure to natural cyanobacterial biomass. Four treatment groups of model species Japanese quail (Coturnix coturnix japonica) were exposed to controlled doses of cyanobacterial bloom during acute (10 days) and sub-chronic (30 days) experiment. The daily doses of cyanobacterial biomass corresponded to 0.2-224.6 ng MCs/g body weight. Significant accumulation of MCs was observed in the liver for both test durations and slight accumulation also in the muscles of the highest treatment group from acute test. The greatest accumulation was observed in the liver of the highest treatment group in the acute test reaching average concentration of 43.7 ng MCs/g fresh weight. The parameters of detoxification metabolism and oxidative stress were studied in the liver, heart and brain. The cyanobacterial exposure caused an increase of activity of cytochrome P-450-dependent 7-ethoxyresorufin O-deethylase representing the activation phase of detoxification metabolism. Also the conjugation phase of detoxification, namely the activity of glutathione-S-transferase, was altered. Cyanobacterial exposure also modulated oxidative stress responses including the level of glutathione and activities of glutathione-related enzymes and caused increase in lipid peroxidation. The overall pattern of detoxification parameters and oxidative stress responses clearly separated the control and the lowest exposure group from all the higher exposed groups. This is the first controlled study documenting the induction of oxidative stress along with MCs accumulation in birds exposed to natural cyanobacterial biomass. The data also suggest that increased activities of detoxification enzymes could lead to greater biotransformation and elimination of the MCs at the longer exposure time.
Phycologia, 2007
ABSTRACT Effects of cyanobacterial toxins microcystin-LR and -RR on growth of five representative... more ABSTRACT Effects of cyanobacterial toxins microcystin-LR and -RR on growth of five representatives of Chlorophyta (Chlamydomonas reinhardtii, Chlorella kesslerii, Pediastrum duplex, Pseudokirchneriella subcapitata, Scenedesmus quadricauda) and cyanobacterium Microcystis aeruginosa (Cyanophyta) were investigated in the concentration range 1-25,000 mu g l(-1) using microplate assays (evaluated after 4, 7 and I I days). Our results demostrate different susceptibility of several planktonic organisms to microcystins. In some species (C. reinhardtii, C. kesslerii, P. duplex, M. aeruginosa), microcystin-RR induced more pronounced effects on growth than structural variant microcystin-LR. However, environmentally relevant concentrations of microcystins (1-10 mu g l(-1)) did not cause significant growth alterations. Also, concentrations 100-5000 mu g l(-1) were ineffective in most tested species with the exception of P. subcapitata. Growth of P. subcapitata was strongly inhibited at concentrations of microcystin-LR or -RR &gt;= 1000 mu g l(-1) after 4 days of exposure, whereas S. quadricauda was affected only at concentration 25,000 mu g l(-1). C. reinhardtii and C. kesslerii responded to both microcystins at the highest experimental concentration, but effects of microcystin-LR were weak and apparent only after I I days of exposure, while microcystin-RR inhibited alga growth from day 4. Growth of P. duplex was also reduced at 25,000 mu g l(-1) of microcystin-RR from day 4, but only slightly inhibited by microcystin-LR (after 4 and 7 days of exposure). Growth of M. aeruginosa was only slightly affected by microcystin-LR (inhibition at 25,000 mu g l(-1) on day 7) and inhibited by microcystin-RR especially at the highest experimental concentration. Our results suggest that microcystin effects on phytoplankton are species specific and congener specific. However, microcystins are not likely to affect proliferation of planktonic photoautotrophs at environmentally occurring conditions. These findings do not support a hypothesis of possible direct allelopathic natural function of microcystins, at least as far as growth inhibition effects are concerned.
Peptides, 2006
Cyanobacteria and particularly Microcystis sp. (Chroococcales) are known to produce a multitude o... more Cyanobacteria and particularly Microcystis sp. (Chroococcales) are known to produce a multitude of peptide metabolites. Here we report on the mass spectral analysis of cyanobacterial peptides in individual colonies of Microcystis sp. collected in a drinking water reservoir. A total number of more than 90 cyanopeptides could be detected, 61 of which could be identified either as known peptides or new structural variants of known peptide classes. For 18 new peptides flat structures are proposed. New congeners differed from known ones mainly in chlorination (aeruginosins), methylation (microginins), or amino acid sequences (cyanopeptolins). The high number of peptides and especially the new peptides underline the capability of Microcystis strains as producers of a high diversity of potentially bioactive compounds.
Journal of Phycology, 2006
... Vallisneria natans (Lour.) Hara, MC-RR, 0.1–10,000, 30 days, Inhibition of growth, reduction ... more ... Vallisneria natans (Lour.) Hara, MC-RR, 0.1–10,000, 30 days, Inhibition of growth, reduction of fresh weight (≥10 μg·L −1 ), other parameters such as length of leaves, cotyledon or roots affected at ≥100 μg·L −1 , weak non-significant reduction in germination rate (≥0.1 μg·L −1 ...
Journal of Photochemistry and Photobiology B: Biology, 2014
We analyzed antibacterial effects of several novel phthalocyanines against Escherichia coli and e... more We analyzed antibacterial effects of several novel phthalocyanines against Escherichia coli and evaluated the suitability of flow cytometry for the detection of antibacterial effects of phthalocyanines in comparison with routinely used cultivation. After 3h of exposure under cool white light eight cationic phthalocyanines showed very high antibacterial activity in the concentration of 2.00 mg L(-1) and four of them were even efficient in the concentration of 0.20 mg L(-1). Antibacterial activity of neutral and anionic compounds was considerably lower or even negligible. No antibacterial effect was detected when bacteria were exposed without illumination. Binding affinity to bacterial cells was found to represent an important parameter influencing phthalocyanine antibacterial activity that can be modified by total charge of peripheral substituents and by the presence of suitable functional groups inside them. Agglomeration of cells observed in suspensions treated with a higher concentration of certain cationic phthalocyanines (the strongest binders to bacterial membrane) affected cytometric measurements of total cell counts, thus without appropriate pretreatment of the sample before analysis this parameter seems not to be fully valid in the evaluation of phthalocyanine antibacterial activity. Cytometric measurement of cell membrane integrity appears to be a suitable and even more sensitive parameter than cultivation.
Hydrobiologia, 2005
A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups ... more A submersible in situ spectrofluorometer, which permits the differentiation of four algal groups (green algae, diatoms, cryptophytes and cyanobacteria), was used for phytoplankton monitoring in five reservoirs with varying levels of eutrophication and composition of their phytoplankton communities. Data obtained in situ were compared to standard laboratory methods for phytoplankton quantification; concentration of chlorophyll a and microscopy analysis. A high
Archiv für Hydrobiologie, 2003
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Papers by Blahoslav Maršálek