Copper toxicity to cyanobacteria and its dependence on extracellular ligand concentration and degradation (original) (raw)
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Environmental Engineering Research
The effects of copper sulphate on the cyanobacterium Nostoc ANTH were studied. The copper concentrations chosen for the study were 0.5, 1.0, and 5.0 mg/L. From the results, it was observed that removal of Cu 2+ ions by the organism was dependent on the external concentrations of Cu 2+ ions. Exposure to high concentrations of copper led to severe morphological changes in the cells, which were visible under transmission electron microscopy. Yet, complete elimination of copper from the growth medium led to poor growth, and ultimately the death, of the Nostoc ANTH cells. Cells exposed to low copper concentration (0.5 mg/L) in the medium showed comparable physiological and biochemical activities (such as growth, heterocyst frequency, nitrogenase activity, photosynthesis, and respiration) to that of the controlled cultures. However, these features were compromised as the copper concentration increased in the surrounding.
Factors regulating copper uptake in free and immobilized cyanobacterium
Folia Microbiologica, 1992
ABSI'RACT. The effect of population size, redox potential, exogenous ATP and complexing agents on Cu uptake by free and immobilized cyanobacterium Nostoc calcicola BR~. has been studied. Cu uptake was regulated by the population size. In such comparisons, the immobilized cells had a greater longevity. Low pH conditions enhanced Cu uptake. Exogenous ATP (10ttmol/L) supplied to dark-grown free and immobilized cells did not support Cu uptake to the extent of light-grown cells. Experiments involving natural as well as synthetic complexing agents clearly established the superiority of soil extract and spent medium over EDTA (10 tzmol/L) in sequestering Cu in free as well as immobilized cells. The present endeavor is an attempt to compare factors regulating copper uptake by free and immobilized cells of the diazotrophic cyanobacterium Nostoc calcicola as recent reports indicated better performance of immobilized cells over their free cell counterpart (Papageorgiou et al. 1988; Singh et al. 1989). Laboratory experiments dealing with population density vs. heavy metal uptake have revealed that dense cultures were less sensitive to cations that were otherwise highly toxic to the same organism at the reduced population size (Delcourt and Mestre 1978; Wikfors and Ukeles 1982), the possible reason being the increased intracellular distance at low cell titer (Itoh et al. 1975), contrary to reduced cell surface area in dense cultures (Kurek et al. 1982). A similar correlation was demonstrated in Chlorella (Gipps and Culler 1980), Anacystis (Singh and Yadava 1985) and Nostoc (Schecher and Driscoll 1985). The observed lowered metal uptake at alkaline pH may put the alkaliphilic cyanobacteria in the advantageous position over others but a reverse situation was encountered in some algae and even cyanobacteria (Hargreaves and Whitton 1976a, b; Yanagimoto et al. 1983; Les and Walker 1984; Schecher and Driscoll 1985; Singh and Yadava 1985). Apart from synthetic or natural eomplexing agents, several algae also produce strong Cu-complexing agents that reduce the free metal ion concentration (McKnight and Morel 1979; Vasseur et al. 1988). Hudson et al. (1979) pointed out that chelation is the single and most vital abiotic factor in decreasing Cu toxicity in aquatic ecosystems and therefore pond water, soil extract and spent medium were compared with respect to their relative metal complexing efficiency in terms of reduced Cu uptake in free and immobilized Nostoc calcicola ceils.
Cellular and molecular biology (Noisy-le-Grand, France)
In the present study, impact of low (UV—BL: 0.1 &mgr;mol m-2 s-1) and high (UV—BH: 1.0 &mgr;mol m-2 s-1) fluence rates of ultraviolet—B on growth and nitrogen metabolism in two cyanobacteria: Phormidium foveolarum and Nostoc muscorum under copper toxicity (2 and 5 &mgr;M) was investigated after 24 and 72 h of experiments. Copper and UV—BH treatment suppressed growth but more in N. muscorum which was accompanied by significant accumulation of Cu. Nitrate and nitrite uptake rates and activities of nitrogen assimilating enzymes i.e. nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS) and glutamate synthase (GOGAT) except glutamate dehydrogenase activity (GDH; aminating) were decreased following treatments of Cu and UV—BH, and under combined treatments the effect was greater. On contrary, UV—BL declined Cu toxicity significantly. The study concludes that Cu and UV—BH suppressed the activity of NR, NiR, GS and GOGAT (except GDH) hence decreased growth. However, UV—...
Journal of Plankton Research, 2009
Many studies have shown the reduction of metal toxicity in the presence of dissolved organic matter in natural waters; however, possible roles of metal-edible dissolved organic matter complexes as a vehicle of metal entrance into trophic chains have been poorly investigated. In this study copper uptake and toxicity to Ceriodaphnia cornuta Sars in the presence and absence of exudates produced by Anabaena spiroides Klebahn were investigated. Groups of 30 adult C. cornuta individuals were exposed to a range of copper concentration (10 28 -10 26 mol L 21 ) during a 24 h period. The "Trimmed Spearmen Karber" method was used to calculate EC 50 . Copper toxicity was almost 4-fold lower in the presence of 30 mg L 21 of cyanobacterial exudates; without exudates, EC 50 was 8.1 Â 10 28 mol L 21 , while with exudates it was 3.2 Â 10 27 mol L 21 . Total copper concentration in the animals was determined using differential pulse anodic stripping voltammetry and the results showed that, for both treatments, metal accumulated by the organisms was not significantly different from the negative control, except for immobile individuals. The present results suggest that the animals were able to regulate their body copper content.
Egyptian Journal of Phycology, 2004
The influence of Cu 2+ toxicity on dry mass, chl.a, carotenoids, protein content, Cu 2+ uptake, activities of some enzymes of nitrogen assimilation and alkaline phosphatase in the diazotrophic cyanobacterium Anabaena variabilis was evaluated. Lower Cu 2+ concentrations stimulated the dry weight, chl.a, and protein content, whereas, higher concentrations were inhibitory. In contrast, a prominent increase in the carotenoids content was detected in response to all Cu 2+ treatments. A. variabilis showed high uptake capacity of Cu 2+. The accumulation capacity is directly proportional to the external Cu 2+ concentrations. A stimulation in the activities of glutamine synthetase (GS), NADHglutamate synthetase (GOGAT), nitrate reductase (NR), nitrogenase and alkaline phosphatase (AP) in response to low Cu 2+ concentrations was noted. However, higher ones inhibited the enzymes activities with different degrees. The enzymes could be arranged according to their tolerance to Cu 2+ toxicity in the following order: AP > NR > GOGAT > GS > nitrogenase.
Rapid urbanization and industrialization lead to heavy metal pollution which poses a serious threat to human's health. Thus, there is a continuing need to develop a device that can be easily used to monitor and detect the presence of heavy metal pollution. Whole cells e.g. cyanobacteria have been reported as potential bio-indicators for environmental heavy metals detection. However, the intensity of the biological responses of these cells is affected by pH and the cell density. In this paper, the effect of pH and cell density to the response of cyanobacteria Anabaena cylindrica to copper (Cu) is reported. The cyanobacteria were cultured and immobilized with agarose in cuvettes before the exposure to Cu solution (1.0 mg/L). The measurement was carried out with OD= 680 nm using a spectrophotometer, which indicated the changes of chlorophyll. The most significant response of the cells was measured at pH 8 and the optimal density of the cell for the detection was 500,000 cell/mL. This study was an important stage to determine the potential of A. cylindrica to be used in heavy metal detection.
Cyanobacterial copper-binding ligands isolated from artificial seawater cultures
Marine Chemistry, 2008
This paper demonstrates a method to isolate and characterise strong biogenic copper-binding ligands from an artificial seawater matrix. Pseudo-polarography is used to detect the ligands, determine their ionic strength-corrected binding constants, and track them through each step of the extraction process. Two ligand types are found, one strong and one relatively weak, with log K′ values of 49.4 ± 1.1 and 19.8 ± 5.5 respectively, assuming that the metal is bound as copper(II). If a copper(I) complex, the log K′ of the strong copper-binding ligand would be 25. Pseudo-polarography is then used to assess different resins for ligand extraction and to determine the eluent fraction in which the strong ligand is recovered. XAD-16 is found to be a suitable resin for extracting the strong binding ligand from salt water into methanol, suggesting that the ligand is weakly hydrophobic. As ligands are identified by their complexation of copper, no assumptions are made regarding the functional groups of these natural ligands. The copperbinding ligands are successfully extracted into solvents suitable for mass spectrometric analysis using soft ionisation methods such as electrospray and MALDI.