Martin Bačkor

Pavol Jozef Šafárik University in Košice, Kassa, Košický, Slovakia

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Publications (61)145.46 Total impact

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    ABSTRACT: Epiphytic lichens have been used as indicators of environmental quality around a municipal solid waste landfill in C Italy. An integrated approach, using the diversity of epiphytic lichens, as well as element bioaccumulation and physiological parameters in the lichen Flavoparmelia caperata (L.) Hale was applied along a transect from the facility. The results highlighted the biological effects of air pollution around the landfill. The Index of Lichen Diversity (ILD) increased and the content of heavy metals (Cr, Cd, Cu, Fe, Ni and Zn) decreased with distance from the landfill. Clear stress signals were observed in lichens growing in front of the facility, i.e. discoloration, necrosis, membrane lipid peroxidation, lower ergosterol content, higher dehydrogenase activity. Decreased photosynthetic efficiency, altered chlorophyll integrity and production of secondary metabolites were also found. The results suggested that lichens can be profitably used as bioindicators of environmental quality around landfills.
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    ABSTRACT: In the present work, the phytotoxic effects of secondary metabolites extracted from five lichen species (Cladonia arbuscula var. mitis, Cladonia furcata, Hypogymnia physodes, Evernia prunastri and Ramalina farinacea) on cultures of the aposymbiotically grown lichen photobiont Trebouxia erici were evaluated. Toxicity of single secondary metabolites, as well as their naturally occurred mixtures in the lichens was tested at the two selected doses, 0.1 mg/disk and 0.01 mg/disk. Application of all tested metabolites decreased the growth of photobiont cells in a dose dependent manner. However, based on selected physiological parameters, e.g. composition of assimilation pigments, fluorescence of chlorophyll a, content of soluble proteins, production of TBARS and ROS, differential phytotoxicity of tested compounds and their mixtures was confirmed. It appears that most of the secondary metabolites tested in the present study may be functioning as allelochemicals which are controlling the cell division of the algal partner inside the thallus. The allelochemicals may play a key role in maintaining the balance between the symbionts forming the lichen thallus.
    South African Journal of Botany 07/2014; 93:86–91. DOI:10.1016/j.sajb.2014.03.015 · 1.34 Impact Factor
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    ABSTRACT: A series of lichen secondary metabolites (parietin, atranorin, usnic and gyrophoric acid) and their interactions with calf thymus DNA were investigated using molecular biophysics and biochemical methods. The binding constants K were estimated to range from 4.3 × 10(5) to 2.4 × 10(7) M(-1) and the percentage of hypochromism was found to be 16-34% (from spectral titration). The results of spectral measurement indicate that the compounds act as effective DNA-interacting agents. Electrophoretic separation studies prove that from all the metabolites tested in this study, only gyrophoric acid exhibited an inhibitory effect on Topo I (25 μM).
    Toxicology in Vitro 11/2013; 28(2). DOI:10.1016/j.tiv.2013.11.003 · 3.21 Impact Factor
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    ABSTRACT: Effect of nitric oxide donor (sodium nitroprusside, SNP, 500 μM) or hydrogen peroxide scavenger (dithiothreitol, DTT, 500 μM) on cadmium (Cd) or copper (Cu) uptake (150 μM solutions) and toxicity using Scenedesmus quadricauda was studied. Combined treatments (Cd or Cu + DTT or SNP) usually ameliorated metal-induced toxicity at the level of pigments, proteins, and mineral nutrients in comparison with respective metal alone. Viability tests (MTT and TTC) showed the lowest values preferentially in Cu treatments, indicating higher toxicity in comparison with Cd. Cd showed low impact on amino acids while strong Cu-induced depletion was mitigated by DTT and SNP. Amount of ROS and NO showed the most pronounced responses in SNP variants being rather reciprocal than parallel and regulated ascorbate peroxidase activity. Blot gel analyses of hsp70 protein did not reveal extensive changes after given exposure period. Phenols were elevated by DTT alone while all Cu treatments revealed depletion. Total Cu content decreased while total Cd content increased in metal + SNP or metal + DTT. Subsequent experiment using lower Cd, SNP or DTT doses (10 and 100 μM) revealed concentration-dependent impact on Cd uptake. Overall, DTT was found to be more suitable for the amelioration of metal-induced toxicity.
    Environmental Science and Pollution Research 02/2013; 20(8). DOI:10.1007/s11356-013-1541-0 · 2.76 Impact Factor
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    ABSTRACT: a b s t r a c t The vibrational characterization of the anthraquinone pigment and drug parietin was carried out by means of infrared spectroscopy, Raman and Surface-enhanced Raman scattering (SERS) at different laser excitation lines. The vibrational spectra obtained experimentally were analysed using DFT calculations at the B3LYP/6-31+G** level. The SERS technique was very useful in the vibrational study of parietin, and was proven to be a highly sensitive technique for the detection of low concentrations of the drug. The silver nanoparticles used as SERS substrates were prepared by reduction with hydroxylamine hydrochloride. The adsorption of parietin on the nanoparticles at different surface coverage leaded to the calculation the limit of detection (LOD) and the adsorption constant (K ad) of parietin on the SERS substrate.
    Vibrational Spectroscopy 11/2012; 63:477-484. DOI:10.1016/j.vibspec.2012.09.015 · 1.55 Impact Factor
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    ABSTRACT: Lichens are a known source of approximately 800 unique secondary metabolites, many of which play important ecological roles, including regulating the equilibrium between symbionts. However, only a few of these compounds have been assessed for their effectiveness against various in vitro cancer models. Moreover, the mechanisms of biological activity of lichen secondary metabolites on living cells (including cancer cells) are still almost entirely unknown. In the present study, we investigated the mechanisms of cytotoxicity of four lichen secondary metabolites (parietin, atranorin, usnic acid and gyrophoric acid) on A2780 and HT-29 cancer cell lines. We found that usnic acid and atranorin were more effective anti-cancer compounds when compared to parietin and gyrophoric acid. Usnic acid and atranorin were capable of inducing a massive loss in the mitochondrial membrane potential, along with caspase-3 activation (only in HT-29 cells) and phosphatidylserine externalization in both tested cell lines. Induction of both ROS and especially RNS may be responsible, at least in part, for the cytotoxic effects of the tested compounds. Based on the detection of protein expression (PARP, p53, Bcl-2/Bcl-xL, Bax, p38, pp38) we found that usnic acid and atranorin are activators of programmed cell death in A2780 and HT-29, probably through the mitochondrial pathway.
    Toxicology in Vitro 04/2012; 26(3):462-8. DOI:10.1016/j.tiv.2012.01.017 · 3.21 Impact Factor
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    ABSTRACT: The lichen Evernia prunastri is very frequently employed in lichen biomonitoring studies and its sensitivity to air pollution has been confirmed at the community level many times. However, studies focused on the physiological responses of this lichen to pollutants are underrepresented. The degree of total as well as intracellular Cu uptake by the lichen after 4 and 24 h prolonged exposure was compared with selected physiological markers including levels of assimilation pigments, chlorophyll a fluorescence, ergosterol, soluble proteins, hydrogen peroxide, superoxide, amino acids, reducing sugars and total soluble phenols. Although the degree of total as well as intracellular Cu uptake by the lichen after 4 and 24 h prolonged exposure were comparable, metabolic responses after 4 and 24 h were very different. Carotenoids, ergosterol and soluble proteins decreased due to Cu exposure and these processes were followed with an increase of superoxide content. Excess of Cu in thalli of E. prunastri after 24 h was toxic and altered almost all tested parameters, including depletion of reducing sugars. We did not observe stimulation of free amino acid synthesis in Cu treated lichen, in fact the content of many particular amino acids decreased. Content of total soluble phenols was unaltered by Cu excess.
    Plant Growth Regulation 01/2012; 69(1). DOI:10.1007/s10725-012-9741-z · 1.63 Impact Factor
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    ABSTRACT: Effect of methyl jasmonate (MeJA) in the concentrations of 10 or 100 μM on selected physiological parameters in Scenedesmus quadricauda (Turp.) Bréb. after 24 h of exposure was studied. Results were compared with the application of general toxic metal (cadmium, Cd) to identify MeJA-specific responses. Accumulation of reactive oxygen species (ROS; hydrogen peroxide and superoxide) was the most elevated by 10 μM MeJA and 100 μM Cd, while total chls showed decrease (Cd) and increase (MeJA) in these variants. The amount of carotenoids and cell viability were affected neither by MeJA nor by Cd application. The sum of free amino acids was considerably elevated by 10 μM Cd (increase in histidine, threonine, arginine, leucine, and lysine mainly) but depleted by 100 μM MeJA (14 from 17 compounds decreased), while accumulation of soluble proteins was unaffected by Cd and enhanced by MeJA. Cadmium application reduced the amount of Ca and also Mg in the case of 100 μM Cd, while MeJA had no effect on the content of mineral nutrients. Total Cd content reached 557 and 1,334 μg · g−1 dry weight (dwt) in 10 and 100 μM Cd variant, respectively. Intracellular Cd uptake was ca. 55% from total Cd content in both Cd variants. The present findings are discussed in the context of the available literature, and possible explanations are suggested.
    Journal of Phycology 10/2011; 47(5). DOI:10.1111/j.1529-8817.2011.01027.x · 2.53 Impact Factor
  • B. Pawlik-Skowrońska, M. Bačkor
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    ABSTRACT: Many lichens can cope with heavy-metal stress, however, the mechanisms of lichen tolerance are still not fully understood. Some lichen secondary metabolites (depsides and depsidones), produced in lichens by the fungal symbiont and accumulated on the outer surface of its hyphae, are supposed to play an important role in the extracellular immoblilization of heavy metals. Lichen photobionts (algal partners in the symbiosis), although surrounded by the mycobiont hyphae, may also accumulate high amounts of trace metals. This can lead to physiological disruptions and morphological damage in algal cells and hence affect the lichen physiological status. We hypothesized that lichen species/specimens living in heavily polluted sites and showing HM tolerance possess a higher content of secondary metabolites than those living in unpolluted sites. Hence, their photobionts can be better protected from the excess of metal ions and need to produce less metal-complexing phytochelatins (PCn) to combat metal toxicity. Specimens of Hypocenomyce scalaris, Cladonia furcata and Lepraria spp. sampled from Zn/Pb-polluted and control sites were compared for the accumulation of Zn/Pb and secondary metabolites, as well as for their production of phytochelatins and glutathione in response to experimental Zn or Pb exposure. Generally, the lichen specimens sampled from the HM-polluted site contained higher amounts of Zn and Pb as well as lichen substances (different depsides and depsidones) than those from the control site. A strong positive correlation was found between the accumulation of secondary metabolites and Zn/Pb accumulation (R2 = 0.98 and 0.63, respectively). For the first time, production of phytochelatins (PC2–3) in response to Zn and Pb (50–200 μM) exposure was found in H. scalaris, L. elobata, L. incana and C. furcata. In both species of Lepraria also cysteine, a substrate for GSH and PCs synthesis was detected. The lichens from the polluted site produced under the same exposure conditions, or in response to higher metal concentrations, lower amounts of PCn than those sampled from the control site. It strongly suggests that less Zn and Pb ions reached the photobiont cells of the lichens containing higher amounts of secondary metabolites (lecanoric, fumarprotocetraric, stictic, constictic acids, antranorin). The results obtained support the putative role of some metabolites in heavy-metal tolerance of the lichens inhabiting metal-polluted habitats.
    Environmental and Experimental Botany 08/2011; 72(1):64-70. DOI:10.1016/j.envexpbot.2010.07.002 · 3.00 Impact Factor
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    ABSTRACT: In this study we assessed the degree of copper (Cu) tolerance in two common lichen species (Cladonia furcata and Cladina arbuscula subsp. mitis) that grow on both uncontaminated substrata and the surface of waste heaps from abandoned old Cu-mines. Regardless of their locality, populations of these lichens contain identical strains of photobionts (Asterochloris clade A in C. arbuscula subsp. mitis and clade D in C. furcata). Therefore, it was expected that if there were differences in Cu toxicity or tolerance between populations, that the photobiont could not be a key element of Cu tolerance in these two lichen species. In laboratory experiments samples of both lichen species (from contaminated and control sites) were incubated in Cu solutions (500 μM) for 24 h. We attempted to determine whether Cu tolerance in these lichens was constitutive, or inducible form. Based on measurements of Cu accumulation, chlorophyll a integrity, chlorophyll a fluorescence, photosynthesis, respiration, measurements of the content of thiobarbituric acid reactive substances (TBARS), the content of soluble proteins, reactive oxygen species (ROS) and the amount of extracellular secondary metabolites of both lichens we found that there were no significant differences in the response of all selected populations of both lichen species to short-term exposure to these high levels of Cu. As a result, we conclude that Cu tolerance in these two lichen species is the constitutive rather than the inducible.
    Chemosphere 06/2011; 85(1):106-13. DOI:10.1016/j.chemosphere.2011.05.035 · 3.50 Impact Factor
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    ABSTRACT: Selected physiological responses of Tillandsia albida (Bromeliaceae) and two lichens (Hypogymnia physodes and Xanthoria parietina) exposed to simulated acid rain (AR) over 3 months were studied. Pigments were depressed in all species being affected the most in Tillandsia. Amounts of hydrogen peroxide and superoxide were elevated and soluble proteins decreased only in AR-exposed Hypogymnia. Free amino acids were slightly affected among species and only glutamate sharply decreased in AR-exposed Xanthoria. Slight increase in soluble phenols but decrease in flavonoids in almost all species suggests that the latter are not essential for tolerance to AR. Almost all phenolic acids in Tillandsia leaves decreased in response to AR and activities of selected enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, ascorbate- and guaiacol-peroxidase) were enhanced by AR. In lichens, considerable increase in metabolites (physodalic acid, atranorin and parietin) in response to AR was found but amount of ergosterol was unchanged. Macronutrients (K, Ca, Mg) decreased more pronouncedly in comparison with micronutrients in all species. Xanthoria showed higher tolerance in comparison with Hypogymnia, suggesting that could be useful for long-term biomonitoring.
    Ecotoxicology 03/2011; 20(2):348-57. DOI:10.1007/s10646-010-0585-x · 2.50 Impact Factor
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    ABSTRACT: The aim of this study was to test in a short term laboratory experiment the accumulation and physiological effects of As in the epiphytic lichen Xanthoria parietina. Arsenic content in treated samples increased progressively with increasing concentration in treatment solutions. Treatment of X. parietina thalli with 0.1, 1, 10 ppm As solutions caused significant decrease of viability, measured as intensity of respiratory activity, and damages to cell membranes, assessed by increase of electric conductivity of rinsing water and lipid peroxidation products. Soluble proteins content decreased and H₂O₂ content increased already at the lowest As concentration tested (0.01 ppm). Photosynthetic efficiency, measured in terms of F(V)/F(M) ratio, decreased significantly only at the highest As concentration (10 ppm). It was concluded that As exposure causes physiological stress both on the mycobiont and the photobiont and that cell membrane damage, expressed in terms of electric conductivity of rinsing water, is the parameter most affected by As treatment.
    Chemosphere 02/2011; 82(7):963-9. DOI:10.1016/j.chemosphere.2010.10.079 · 3.50 Impact Factor
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    ABSTRACT: One of the ways for searching for potentially new anti-cancer drugs is the testing of various naturally synthesized compounds. Lichens are a source of unique chemical agents of which some have already been proved to be effective against various cancer in vitro models. Our study reports on the sensitivity of up to nine human cancer cell lines (A2780, HeLa, MCF-7, SK-BR-3, HT-29, HCT-116 p53(+/+), HCT-116 p53(-/-), HL-60 and Jurkat) to the anti-proliferative/cytotoxic effects of four typical secondary metabolites of lichens (parietin, atranorin, usnic acid and gyrophoric acid). Variations in the dynamics of tumour cell line populations were evaluated by the MTT, clonogenic and viability assays, cell proliferation and detachment, cell cycle transition and apoptotic nuclear morphology, thereby confirming their concentration- and time-dependent cytotoxicity. However, in comparison with parietin and gyrophoric acid, the suppression of viability and cell proliferation by usnic acid or atranorin was found to be more efficient at equitoxic doses and correlated more strongly with an increased number of floating cells or a higher apoptotic index. Moreover, the analysis of cell cycle distribution also revealed an accumulation of cells in S-phase. This study has confirmed a differential sensitivity of cancer cell lines to lichen secondary metabolites.
    Toxicology in Vitro 02/2011; 25(1):37-44. DOI:10.1016/j.tiv.2010.09.004 · 3.21 Impact Factor
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    ABSTRACT: This study aimed at investigating the cellular distribution of Hg in the lichens Cladonia arbuscula subsp. mitis and Peltigera rufescens treated with Hg²(+) and at testing if Hg treatment affects selected physiological parameters. In both species, increasing Hg accumulation under increasing Hg supply in the treatment solutions was found. P. rufescens showed a higher intracellular accumulation. Photosynthetic parameters were negatively affected in both species, as indicated by the decrease in photosynthetic pigments content, photosynthetic efficiency and chlorophyll integrity. Cell membranes of both species endured damage as indicated by the increase in the concentration of products of lipid peroxidation and decrease in ergosterol content. Nevertheless, differences between the two species were found, suggesting a differential sensitivity to Hg.
    Chemosphere 02/2011; 82(7):1030-7. DOI:10.1016/j.chemosphere.2010.10.062 · 3.50 Impact Factor
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    ABSTRACT: In the present work, the long-term effect (14days) of copper on the levels of intracellular and total copper accumulation, growth, assimilation pigment composition, chlorophyll a fluorescence, soluble protein content and oxidative status (production of hydrogen peroxide and superoxide) in two algal species (Scenedesmus quadricauda and Trebouxia erici) was assessed. Scenedesmus quadricauda is a free-living alga while Trebouxia erici is the photobiont of a lichen. The presence of copper negatively affected growth, assimilation pigments, chlorophyll a fluorescence, soluble protein content and oxidative status in both the algae. However, Scenedesmus was much more sensitive compared to Trebouxia. KeywordsAlgae-Copper-Growth-Lichens-Photobionts-Toxicity
    Plant Growth Regulation 01/2011; 63(1):81-88. DOI:10.1007/s10725-010-9515-4 · 1.63 Impact Factor
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    ABSTRACT: Tolerance of three Slovak populations of Silene vulgaris [from the localities "Harmanec" (total soil Cu 34.1 mg kg⁻¹), "Lubietová"; (total soil Cu 831.6 mg kg⁻¹) and "Špania dolina" (total soil Cu 1368.7 mg kg⁻¹) referred as SV1, SV2, and SV3, respectively] and Silene dioica (SD; from the locality "Špania dolina") exposed to 60 μM Cu for 7 days has been studied. Respective controls with 0.21 μM Cu were also cultured. SV3 and SD contained higher total shoot Cu than SV1. Methanol-soluble shoot Cu represented 60, 59, 59, and 55% from total shoot Cu and roots contained 16.7-, 20.4-, 9.9- and 28.9-fold more Cu than shoots in SV1, SV2, SV3, and SD, respectively. Soluble proteins were the least affected in SV3 and SD when Cu-exposed and control plants were compared. Root hydrogen peroxide and superoxide showed similar trend and were correlated with enhancement of ascorbate- and guaiacol-peroxidase activities. Malondialdehyde accumulation increased in SV1 and SV2. Phenylalanine ammonia-lyase activity and total soluble phenols were higher in SV3 Cu-exposed plants compared to SV1 and SV2. Shikimate dehydrogenase activity was enhanced in all Cu-exposed populations. Cinnamyl alcohol dehydrogenase activity and root lignin content were not affected and polyphenol oxidase activity was not detected. Within 14 detected free amino acids, majority of them decreased preferentially in the roots. Only serine increased in shoots and decreased in roots of all populations. Potassium content was not affected in SV3. Na, Ca, and Fe increased in roots of Cu-exposed plants of all populations, while Mg was the least affected and Zn increased in SV2 and SV3 shoots and roots. This study revealed the highest tolerance in population from the locality with the highest soil Cu content. Present findings as complex metabolic responses to Cu stress with special emphasis on phenolic metabolism are discussed.
    Environmental Toxicology 12/2010; 25(6):581-92. DOI:10.1002/tox.20519 · 2.56 Impact Factor
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    ABSTRACT: Lecanoric acid (1), orsellinic acid methyl ester (2), orcinol (3), and usnic acid (4) were isolated from the lichen Parmelia subrudecta, collected on Palma of the Canary Islands, Spain. Compounds 1, 2, 3, and 4 were purified by solvent extraction, silica gel column chromatography, and preparative high-performance liquid chromatography (HPLC) consecutively. The structures of the four compounds were elucidated by one- and two-dimensional nuclear magnetic resonance (NMR) experiments and mass spectrometric investigations. These compounds showed activity against important gram-positive and gram-negative pathogens like mycobacteria and multiresistant staphylococci. This activity is combined with antiproliferative activity and cytotoxicity.
    Preparative Biochemistry &amp Biotechnology 10/2010; 40(4):377-88. DOI:10.1080/10826068.2010.525432 · 0.70 Impact Factor
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    ABSTRACT: Host use by herbivores is largely determined by host properties such as nutrient content and chemical defence against foragers. The impacts of these attributes on a herbivore may largely depend on its life cycle stage. Lichen species are known to differ in nutritional quality and level of chemical defence and, consequently, vary as fodder for herbivores. The aim of this study was to explore the impact of several lichen species and the presence of their secondary metabolites on their use as hosts by a specialist lichen-feeder, Cleorodes lichenaria. This study also addressed, for the first time, how a specialist lichen-feeder deals with different lichen secondary metabolites. In the beginning of their development, larvae grew better on Xanthoria parietina than on the other host lichens, whereas older larvae grew best on Ramalina fraxinea. Lichen secondary chemicals in R. fraxinea and Parmelia sulcata hindered larval growth in the beginning but after 75 days lichen secondary chemicals had no impact on the mass of larvae. Physodic acids in Hypogymnia physodes were lethal to larvae. In general, larvae metabolized 70-95% of ingested lichen secondary chemicals and the rest of these were excreted in frass. Lichen secondary metabolites in P. sulcata restrict and in H. physodes prevent their use as a host for C. lichenaria larvae. Our main finding, the ability of larvae to metabolize several lichen secondary metabolites, indicates digestive adaptation to these chemicals. No signs of sequestration of these chemicals were found.
    Oecologia 10/2010; 164(2):423-30. DOI:10.1007/s00442-010-1682-5 · 3.25 Impact Factor
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    ABSTRACT: The photobiont is considered as the more sensitive partner of lichen symbiosis in metal pollution. For this reason the presence of a metal tolerant photobiont in lichens may be a key factor of ecological success of lichens growing on metal polluted substrata. The photobiont inventory was examined for terricolous lichen community growing in Cu mine-spoil heaps derived by historical mining. Sequences of internal transcribed spacer (ITS) were phylogenetically analyzed using maximum likelihood analyses. A total of 50 ITS algal sequences were obtained from 22 selected lichen taxa collected at three Cu mine-spoil heaps and two control localities. Algae associated with Cladonia and Stereocaulon were identified as members of several Asterochloris lineages, photobionts of cetrarioid lichens clustered with Trebouxia hypogymniae ined. We did not find close relationship between heavy metal content (in localities as well as lichen thalli) and photobiont diversity. Presence of multiple algal genotypes in single lichen thallus has been confirmed.
    Ecotoxicology and Environmental Safety 05/2010; 73(4):603-12. DOI:10.1016/j.ecoenv.2009.11.002 · 2.48 Impact Factor
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    ABSTRACT: Species of the genus Scenedesmus are frequently used in studies focused on heavy metal toxicity and phenols represent important tool for stress protection. However, deeper knowledge about accumulation of phenolic metabolites in algae still absents. We therefore studied selected metabolic responses of widely distributed green algal species Scenedesmus quadricauda to short-term (24h) effect of copper (Cu), salicylic acid (SA) and their combined application (25μM for both). Exposure to Cu led to decrease in chlorophylls while SA stimulated increase in chlorophylls. Soluble proteins and total soluble phenols were depressed by Cu treatment while SA had no effect and did not reverse influence of Cu in combined variant. Endogenous SA decreased in Cu+SA treatment and this depletion had no direct effect on the accumulation of the majority of detected phenolic acids, while individual amino acids seemed to be affected. Considerable accumulation of benzoic acids and their noticeable responses to SA may suggest involvement in protection against Cu toxicity since intracellular Cu remained unchanged by exposure to Cu+SA. These observations are discussed in the context of biosynthesis of phenols and possible signalling mechanisms are also suggested.
    Plant Science 03/2010; 178(3):307-311. DOI:10.1016/j.plantsci.2010.01.009 · 4.11 Impact Factor

Publication Stats

1k Citations
145.46 Total Impact Points


  • 2004–2015
    • Pavol Jozef Šafárik University in Košice
      • Department of Botany
      Kassa, Košický, Slovakia
  • 2002–2009
    • The University of Western Ontario
      • Department of Biology
      London, Ontario, Canada
  • 1998
    • Comenius University in Bratislava
      • Department of Plant Physiology
      Bratislava, Bratislavsky Kraj, Slovakia