Physiological responses of Dunaliella salina and Dunaliella tertiolecta to copper toxicity
Department of Biology, College of Sciences, Shiraz University, Shiraz 71454, Islamic Republic of Iran. Biomolecular Engineering
(Impact Factor: 3.17).
11/2005; 22(4):141-6. DOI: 10.1016/j.bioeng.2005.07.001
Species differences in heavy metal tolerance were investigated by comparing the responses of Dunaliella tertiolecta and Dunaliella salina to elevated concentrations of CuCl2. Although both species showed reduced cell number ml(-1) of algal culture, D. salina was more affected by increase in CuCl2. This reflects higher sensitivity of D. salina to CuCl2 compared to D. tertiolecta. Total chlorophyll in terms of microg ml(-1) was higher in D. tertiolecta at all tested CuCl2 levels, but in terms of microg cell(-1) no significant difference was observed between the two species. Total carotenoids in microg cell(-1) increased with increase in CuCl2 in both species and it was about five times higher in D. salina at all CuCl2 concentrations. While both species showed significant increase in lipid peroxidation at elevated CuCl2, the malondialdehyde content of D. salina cells was about three times higher at most CuCl2 concentrations. Although ascorbate peroxidase (APX) activity increased with increase in CuCl2 levels in both species, higher activity was observed in D. tertiolecta at all tested CuCl2 concentrations. Cu content of D. salina cells was higher than D. tertiolecta which may be due to larger volume of D. salina cells. In conclusion, since hydroxyl radical (HO*) produced from H2O2 by Cu2+ (Haber-Weiss cycle) is involved in lipid peroxidation, higher ascorbate peroxidase activity in D. tertiolecta may partly account for lower sensitivity of this species to CuCl2 compared to D. salina.
Available from: Maria Kostopoulou
- "Determination of lipid peroxidation in green algae D. tertiolecta Lipid peroxidation was determined by measuring the formation of thiobarbituric acid reactive substances, quantified as malondialdehyde (MDA) equivalents, according to the method described by Nikookar et al. (2005). In brief, an appropriate volume of each culture, containing 10 6 cells, was collected every day. "
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ABSTRACT: This study investigates the pro-oxidant behavior of the antiepileptic drug carbamazepine (CBZ) on the marine algal species Dunaliella tertiolecta and the immune defense-related hemocytes of mussel Mytilus galloprovincialis. A phytotoxicity test, performed in a first step, showed a significant inhibition of the growth rate and the chlorophyll alpha (Chl-α) content in algae after exposure for 24 h to different concentrations of CBZ (1-200 mg L(-1)). On the other hand, the increased levels of lipid peroxidation products, such as MDA, measured in 24 h CBZ-treated cells were attenuated with time (48-96 h), followed by a significant recovery of both the algal growth rate and the Chl-α content in all cases. The latter could be related to the concomitant enhancement of total carotenoids in CBZ-treated algae with time, which in turn could protect algal growth and survival against CBZ-induced oxidative stress. On the other hand, the increased levels of cell death, superoxide anions ((·)O2 (-)), nitric oxides (NO, in terms of nitrites, NO2 (-)) and MDA content observed in mussel hemocytes exposed to environmentally relevant (0.01-1 μg L(-1)) and/or higher (10 and 100 μg L(-1)) concentrations of the drug, clearly indicate the ability of CBZ to induce oxidative effects on cells of non-target species, such as mussels, affecting thus their overall health status. The significant relationships occurred among the tested biological parameters in both bioassays, further reinforce CBZ-mediated pro-oxidant effects on species, widely used in ecotoxicological and toxicological studies and provide a more comprehensive view on its environmental fate and ecotoxicological risk evaluation.
Available from: Manuel Antonio González-delValle
- "Iron has strong pro-oxidative properties (Guerin et al. 2003), and microalgae such as that described in this manuscript, which are naturally able to grow when exposed to high iron concentrations, could somehow overexpress antioxidative response mechanisms . That indeed was observed in other metalexposed microalgae species (Nikookar et al. 2005, Mojaat et al. 2008). In plants, it has been observed that iron-dependent oxidative damage is controlled—and even successfully reverted—by the activation of the antioxidative defenses (Martínez-Domínguez et al. 2009). "
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ABSTRACT: A heavy-metal-resistant, carotenoid-enriched novel
unicellular microalga was isolated from an acidic
river in Huelva, Spain. The isolated ribosomal 18S
subunit rDNA sequence showed homology with
known sequences from green microalgae, the closest
sequence (98% homology) belonging to the
genus Coccomyxa. The isolated microalga therefore
was an up to now uncultured microalga. The microalga
was isolated from Tinto River area (Huelva,
Spain), an acidic river that exhibits very low pH
(1.7–3.1) with high concentrations of sulfuric acid and heavy metals, including Fe, Cu, Mn, Ni, and Al. Electron micrographs show that the microalga
contains a large chloroplast with a presence of
lipid droplets, an increased number of starch
bodies as well as electron-dense deposits and plastoglobules,
the last observed only in iron-exposed
cells. Unlike other acidophile microalgae, the isolated
microalga showed high growth rates when cultivated
photoautotrophycally (up to 0.6 d-1) in a
suitable culture medium prepared at our laboratory.
The growth was shown to be iron dependent.
When the microalga is grown in fluidized bed reactors,
the high growth rates resulted in unexpectedly
high productivities for being a microalga that naturally
grows in acidic environments (0.32 g/L/d). The microalga also grows optimally on reduced carbon
sources, including glucose and urea, and at an
optimal temperature of 35�C. The alga pigment
profile is particularly rich in carotenoids, especially
lutein, suggesting that the microalga might have
potential for antioxidant production, namely, xanthophylls.
Available from: Dianne F Jolley
- "and Tetraselmis spp., are often found to be tolerant, considerable variation in toxicity among green algae occurs. D. tertiolecta was found to have higher tolerance to copper than D. salina (Nikookar et al., 2005) which may have been related to lower concentrations of copper in the cell and an increase in ascorbate peroxidase activity. Ismail et al. (2002) found that Tetraselmis sp. was three times less sensitive than T. tetrahele from the same genera, with 96-h IC50 values of 130 and 370 µg/L, respectively, showing variation in toxicity within closely related algal species. "
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ABSTRACT: Microalgae are sensitive indicators of environmental change and, as the basis of most freshwater and marine ecosystems, are widely used in the assessment of risk and development of environmental regulations for metals. However, interspecies differences in sensitivity to metals are not well understood. The relationship between metal-algal cell binding and copper sensitivity of marine microalgae was investigated using a series of 72-h growth-rate inhibition bioassays and short-term (1-h) uptake studies. A range of marine algae from different taxonomic groups were screened to determine whether copper adsorption to the cell membrane was influenced by biotic factors, such as the ultrastructure of cell walls and cell size. Minutocellus polymorphus was the most sensitive species to copper and Dunaliella tertiolecta the least sensitive, with 72-h IC50 values (concentration to inhibit growth-rate by 50%) of 0.6 and 530 microg Cu/L, respectively. Copper solution-cell partition coefficients at equilibrium (K(d)) were calculated for six species of algae on a per cell and surface area basis. The largest and smallest cells had the lowest and highest K(d) values, respectively (on a surface area basis), with a general (non-linear) trend of decreasing K(d) with increasing cell surface area (p=0.026), however, no relationship was found between K(d) and copper sensitivity, nor cell size and copper sensitivity. Interspecies differences in copper sensitivity were not related to cell size, cell wall type, taxonomic group or K(d) values. The differences in sensitivity may be due to differences in uptake rates across the plasma membrane, in internal binding mechanisms and/or detoxification mechanisms between the different microalgal species.
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