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PubMed2006

Probiotic bacteria as potential detoxification tools: assessing their heavy metal binding isotherms.

Dietary exposure to heavy metals may have detrimental effects on human and animal health, even at low concentrations. Specific probiotic bacteria may have properties that enable them to bind toxins from food and water. We assessed the interaction of probiotic bacteria with cadmium and lead in vitro as an initial screening step to identify strains for heavy metal decontamination in food and intestinal models. Binding isotherms for cadmium and lead were characterized for Lactobacillus rhamnosus LC-705, Propionibacterium freudenreichii subsp. shermanii JS and a mix of them used by the food industry. Differences among the strains and their combinations in binding performance at a range of concentrations between 0.1 and 100 mg.L-1 were evaluated with the Langmuir model for biosorption. The effects of pH, contact time, and viability on the binding capacities were also investigated. All strains and their combinations were found to bind cadmium and lead efficiently at low concentration ranges commonly observed in foods. However, the two strains and their combinations differed significantly in their maximum binding capacities and affinities represented by the Langmuir constants Qmax and b, respectively. The binding seemed to occur instantaneously and in a pH-dependent manner, which can be perfectly described by a segmented linear-plateau model.

Algorithms↗

PubMed1997

Biomarkers for responses to heavy metals.

Biomarkers for pathophysiological responses to heavy metals are described with special reference to immunotoxic responses to them. Autoantibody induction in animals by exposure to cadmium is exemplified and discussed on its relevance to pathogenesis of cadmium-induced renal disease. The availability of autoantibodies as a mechanism-oriented biomarker is discussed further in association with cases of autoantibody induction in heavy metal workers.

Animals↗

PubMed2000

Transport of toxic heavy metals across cell membranes.

Membrane transport of nonessential toxic heavy metals (type D heavy metals) not only controls their access to intracellular target sites but also helps determine their uptake, distribution, and excretion from the body. The critical role of membranes in the toxicology of class D metals has attracted the attention of many investigators, and extensive information has been collected on the mechanism(s) of metal transfer across membranes. Characteristics of metal transport in different cells, or even on opposite sides of the same cell, or under different physiological conditions, are not identical, and no unitary hypothesis has been formulated to explain this process in all cells. However, it seems possible that the mechanisms proposed for different cells represent variations on a few common themes.

Animals↗

PubMed2003

Innovative developments in the selective removal and reuse of heavy metals from wastewaters.

Sulphide precipitation of heavy metal containing wastewaters results in low effluent concentrations. However, sulphide precipitation is not widely applied in practice because the dosing of sulphide cannot adequately be controlled. A new process was developed where the combination of a sulphide-selective electrode (pS-electrode) and pH electrode controls the sulphide addition. Precipitation experiments were performed on a laboratory-scale in batch and continuous reactor systems with synthetic wastewaters containing Cd, Cu, Ni, Pb or Zn. The response of the pS-electrode during precipitation was unique for each heavy metal and was directly related to the solubility product of the corresponding metal sulphide. The metals were removed to levels < 0.05 mg l(-1) at pH 6.0 by sulphide precipitation while maintaining a total sulphide concentration < 0.02 mg l(-1). By the control of pS at different levels and keeping the pH constant at 6.0, the metals in solutions of both Cu and Zn could be precipitated selectively from solution in a batch and continuous reactors. The use of a membrane reactor in combination with control of pH and pS offers a simple, cheap, efficient and sustainable technique with respect to obtaining very low effluent concentrations and selective removal of metals as pure metal sulphides which can be reused.

Chemical Precipitation↗

PubMed2000

Chemical and biological parameters as tools to evaluate and improve heavy metal phytoremediation.

In this review, chemical and biological parameters are discussed that strongly influence the speciation of heavy metals, their availability to biological systems and, consequently, the possibilities to use bioremediation as a cleanup tool for heavy metal polluted sites. In order to assess heavy metal availability, a need exists for rapid, cost-effective systems that reliably predict this parameter and, based on this, the feasibility of using biological remediation techniques for site management and restoration. Special attention is paid to phytoremediation as an emerging technology for stabilization and remediation of heavy metal pollution. In order to improve phytoremediation of heavy metal polluted sites, several important points relevant to the process have to be elucidated. These include the speciation and bioavailability of the heavy metals in the soil determined by many chemical and biological parameters, the role of plant-associated soil microorganisms and fungi in phytoremediation, and the plants. Several options are described how plant-associated soil microorganisms can be used to improve heavy metal phytoremediation.

Biological Availability↗

PubMedDate not supplied

[Biochemical adaptation of the barley root cells to toxic substances. II. Effect of heavy metals on phosphohydrolase activity].

We studied the effect of heavy metals such as Cu, Zn, Cd, and Pb on the activity of membrane-bound and soluble phosphohydrolases of barley root cell apoplast. The effect of heavy metals on the activity of acid phosphatase and acid nucleotidases proved to depend on the presence of calcium and magnesium ions in the incubation buffer, the condition and form of the enzymes, as well as the dose and moment of heavy metals addition. We propose changing the activity of acid phosphohydrolases in barley root cell apoplast as a possible mechanism of barley adaptation to the toxic effect of heavy metals.

Adaptation, Physiological↗

PubMed2003

Breeding performance of great tits (Parus major) along a gradient of heavy metal pollution.

The possible effects of heavy metal pollution on various breeding parameters of the great tit (Parus major) were studied at four study sites in a pollution gradient near a large nonferrous smelter in Belgium during three consecutive breeding seasons. Significantly more females interrupted their laying period near the pollution source than did females farther away. At the two most polluted sites, hatching success was significantly reduced compared to two lesser-polluted study sites. Overall breeding success was also significantly lower toward the factory complex. This lowered breeding success was caused not only by the decreased hatching success toward the pollution source but also by the significant difference in fledging success among sites. Although a clear relationship was observed between the exposure to heavy metal pollution and an impaired reproduction, not all reproductive parameters were affected. We found no significant differences in the onset of laying, clutch size, length of the incubation period, and the proportion of nests with low-quality eggs among sites. Although nest box occupancy was every year slightly lower toward the smelter compared to farther away, differences among study sites were never significant.

Animals↗

PubMed2001

Silicon and heavy metal tolerance of higher plants.

The heavy metal tolerant Cardaminopsis halleri, grown on Zn and Cu polluted soil, showed electron dense metal containing precipitates (Zn, Cu, Sn, Fe, Al) on the leaf surface, in the intercellular spaces (Zn, Cu, Sn), the cell walls and the cell wall thickenings of the xylem vessels (Zn, traces of Cu and Fe). Large amounts of Zn were measured in the vacuoles, the main storage compartment for this metal in Cardarminopsis. The cytoplasm and nuclei contained small precipitates, including mainly Zn and Si. As shown by ESI Zn was co-localized with Si in these structures. The EEL-spectra of the cytoplasmic precipitates corresponded with the spectra of Zn-silicate. Besides Zn-silicate, electron translucent structures in the cytoplasm were identified as SiO2 by their EEL spectra. It was concluded that in the cytoplasm of Cardaminopsis Zn is transiently accumulated as silicate, being slowly degraded to SiO2. Zn is translocated into the vacuole and accumulated in an unknown form. A second Si and Zn-uptake mechanism was found, excluding a membrane and cytoplasm passage. Pinocytotic vesicles, formed by the plasmamembrane and the tonoplast, enable a direct translocation of Si and Zn from extracellular compartments into the vacuole. The formation of Zn-silicate is part of the heavy metal tolerance mechanism and may be responsible for the amelioration of the Zn toxicity in Cardaminopsis.

Arabidopsis↗

PubMed2005

Enhanced phytoextraction: I. Effect of EDTA and citric acid on heavy metal mobility in a calcareous soil.

Phytoextraction, the use of plants to extract heavy metals from contaminated soils, could be an interesting alternative to conventional remediation technologies. However, calcareous soils with relatively high total metal contents are difficult to phytoremediate due to low soluble metal concentrations. Soil amendments such as ethylene diaminetetraacetate (EDTA) have been suggested to increase heavy metal bioavailability and uptake in aboveground plant parts. Strong persistence of EDTA and risks of leaching of potentially toxic metals and essential nutrients have led to research on easily biodegradable soil amendments such as citric acid. In our research, EDTA is regarded as a scientific benchmark with which degradable alternatives are compared for enhanced phytoextraction purposes. The effects of increasing doses of EDTA (0.1,1,10 mmol kg(-1) dry soil) and citric acid (0.01, 0.05, 0.25, 0.442, 0.5 mol kg(-1) dry soil) on bioavailable fractions of Cu, Zn, Cd, and Pb were assessed in one part of our study and results are presented in this article. The evolution of labile soil fractions of heavy metals over time was evaluated using water paste saturation extraction (approximately soluble fraction), extraction with 1 M NH4OAc at pH 7 (approximately exchangeable fraction), and extraction with 0.5 M NH4OAc + 05 M HOAc + 0.02 M EDTA at pH 4.65 (approximately potentially bioavailable fraction). Both citric acid and EDTA produced a rapid initial increase in labile heavy metal fractions. Metal mobilization remained constant in time for soils treated with EDTA, but a strong exponential decrease of labile metal fractions was noted for soils treated with citric acid. The half life of heavy metal mobilization by citric acid varied between 1.5 and 5.7 d. In the following article, the effect of heavy metal mobilization on uptake by Helianthus annuus will be presented.

Biodegradation, Environmental↗

PubMed1998

Molecular basis for effects of carcinogenic heavy metals on inducible gene expression.

Certain forms of the heavy metals arsenic and chromium are considered human carcinogens, although they are believed to act through very different mechanisms. Chromium(VI) is believed to act as a classic and mutagenic agent, and DNA/chromatin appears to be the principal target for its effects. In contrast, arsenic(III) is considered nongenotoxic, but is able to target specific cellular proteins, principally through sulfhydryl interactions. We had previously shown that various genotoxic chemical carcinogens, including chromium (VI), preferentially altered expression of several inducible genes but had little or no effect on constitutive gene expression. We were therefore interested in whether these carcinogenic heavy metals might target specific but distinct sites within cells, leading to alterations in gene expression that might contribute to the carcinogenic process. Arsenic(III) and chromium(VI) each significantly altered both basal and hormone-inducible expression of a model inducible gene, phosphoenolpyruvate carboxykinase (PEPCK), at nonovertly toxic doses in the chick embryo in vivo and rat hepatoma H411E cells in culture. We have recently developed two parallel cell culture approaches for examining the molecular basis for these effects. First, we are examining the effects of heavy metals on expression and activation of specific transcription factors known to be involved in regulation of susceptible inducible genes, and have recently observed significant but different effects of arsenic(III) and chromium(VI) on nuclear transcription factor binding. Second, we have developed cell lines with stably integrated PEPCK promoter-luciferase reporter gene constructs to examine effects of heavy metals on promoter function, and have also recently seen profound effects induced by both chromium(VI) and arsenic(III) in this system. These model systems should enable us to be able to identify the critical cis (DNA) and trans (protein) cellular targets of heavy metal exposure leading to alterations in expression of specific susceptible genes. It is anticipated that such information will provide valuable insight into the mechanistic basis for these effects as well as provide sensitive molecular biomarkers for evaluating human exposure.

Animals↗

PubMed2004

Immunotoxicology in wood mice along a heavy metal pollution gradient.

We carried out an immunotoxicological field study of wood mice in three populations along a heavy metal pollution gradient. Heavy metal concentrations in liver tissue indicated that exposure to silver, arsenic, cadmium, cobalt and lead decreased with increasing distance from a non-ferrous smelter. Host resistance to the endoparasite Heligmosomoides polygyrus decreased with increasing exposure, while the abundance of tick larvae and the nematode Syphacia stroma was unrelated to heavy metal exposure. Spleen mass was increased at the intermediate and the most polluted sites and was positively correlated with the number of H. polygyrus and tick larvae. Proportion of early apoptotic leukocytes increased towards the smelter and was positively related to cadmium exposure. Red and white blood cell counts and lysozyme activity showed no relationship with metal exposure. All together, our observations suggest negative effects of heavy metal exposure on the immune function of wood mice under field conditions.

Animals↗

PubMed2001

Bioleaching of heavy metals from sediment: significance of pH.

Bioleaching process, which causes acidification and solubilization of heavy metals, is one of the promising methods for removing heavy metals from contaminated sediments. The solubilization of heavy metals from contaminated sediments is governed by the sediment pH. In the present study, the significance of pH in bioleaching of heavy metals from contaminated sediment was evaluated at different solid contents of sediments in a bench-scale reactor. Results showed that a temporal change of pH in the bioleaching process was effected by the buffering capacity of the sediment particulates. The variations of pH in this bioleaching process were calculated by a modified logistic model. It was observed that solubilization of heavy metals from sediments is highly pH-dependent. In addition, a non-linear equation for metal solubilization relating pH value in the bioleaching process was established. This allows an easier and faster estimate of metal solubilization by measuring pH in the bioleaching process.

Geologic Sediments↗

PubMed2001

Characterization of a heavy metal ATPase from the apicomplexan Cryptosporidium parvum.

P1-ATPases are transporters which pump heavy metals across membranes, either to provide enzymes with essential cofactors or to remove excess, toxic metal cations from the cytosol. The first protist P1-ATPase (CpATPase2) has been isolated from the apicomplexan Cryptosporidium parvum, an opportunistic pathogen of AIDS patients. This single copy gene encodes 1260 amino acids (aa), predicting a protein of 144.7 kDa. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis confirmed CpATPase2 expression. Immunofluorescence microscopy of C. parvum sporozoites using rabbit antiserum raised against a glutathione-S-transferase (GST) fusion protein suggests that CpATPase2 is associated with the plasma- and cytoplasmic membranes. The protein shares greatest overall sequence similarity to previously characterized copper P1-ATPases. Expression and subsequent biochemical analyses of the N-terminal heavy metal binding domain (HMBD, GMxCxxC) of CpATPase2 as a maltose-binding protein (MBP) in Escherichia coli reveals that the protein specifically binds reduced copper, Cu(I), in vitro and in vivo, and that the cysteine residues of HMBD are responsible for heavy metal coordination. Overall, these data show that the apicomplexan C. parvum possesses a heavy metal P-ATPase transporter with a specificity for reduced copper. Since this discovery represents the first time a heavy metal P-ATPase has been identified and characterized from a protist, further molecular and biochemical studies are needed to understand the roles heavy metal P-ATPases play in heavy metal metabolism and potential virulence for this and other apicomplexa.

Adenosine Triphosphatases↗

PubMed2003

Critical evaluation of desorption phenomena of heavy metals from natural sediments.

In natural sediments, the majority of heavy metal ions are generally associated with the solid phase. To become bioavailable, the metal ions must desorb from the solid. Numerous studies of heavy metals in sediments have suggested that sorption and desorption exhibit hysteresis (i.e., the two processes are not reversible), while other studies have suggested that desorption hysteresis does not exist. In this study, sorption/desorption hysteresis of lead (Pb) and cadmium (Cd) was evaluated over the following range of conditions: (i) desorption induced by replacing the supernatant liquid with contaminant-free electrolyte solution; (ii) desorption induced by lowering the solution pH with mineral acid; and (iii) desorption induced by sequestration with EDTA. Given the importance of dissolved organic and inorganic ligands in regulating heavy metal behavior in nature sediments, sorption/desorption experiments were conducted on both untreated and prewashed sediments. Prewashing treatment increases the sorption potential of Cd but not Pb. Desorption hysteresis is observed in both the untreated and the prewashed sediments using the replaced supernatant method, and the desorption hysteresis appears to increase with aging time. Hysteresis is not observed when desorption is initiated by lowering the solution pH. A large fraction of the sorbed heavy metal ions can be easily desorbed by EDTA; between 0.04 and 1.2 mmol/kg Cd and Pb ions are resistant to desorption.

Adsorption↗

PubMed2006

Biosorption of chromium and nickel by heavy metal resistant fungal and bacterial isolates.

Microorganisms play a significant role in bioremediation of heavy metal contaminated soil and wastewater. In this study, heavy metal resistant fungi and bacteria were isolated from the soil samples of an electroplating industry, and the bioaccumulations of Cr(VI) and Ni(II) by these isolates were characterized to evaluate their applicability for heavy metal removal from industrial wastewaters. The optimum pH and temperature conditions for both the growth and heavy metal removal were determined for each isolate. The optimal pH for fungal isolates was lower (5-5.2) than that for bacterial isolates (7). The observed effect(s) of pH was attributable mainly to organism-specific physiology because in all the tested cases the cellular growth positively correlated with heavy metal removal. Batch and tolerance experiments provided information for solid retention time (SRT) design and the lethal tolerance limits for the isolated microorganisms. Experimental results indicated that expanded SRTs (stationary phase) can be recommended while using the fungal and bacterial Cr-resistant isolates for removing chromium. In the case of Ni-resistant bacterial isolate, a non-expanded SRT was recommended for designing continuous-flow completely stirred (CFCS) bioreactor so that a mid-log phase of cellular growth can be kept during the bioaccumulation process. The tolerance data with a high range of heavy metal concentrations revealed the Cr-resistant isolates, especially the fungal one, could tolerate chromium toxicity at up to 10,000 mg L(-1) chromium. Result indicates the applicability of the isolated Micrococcus sp. and Aspergillus sp. for the removal of chromium and nickel from industrial wastewater.

Adsorption↗

PubMedDate not supplied

Vegetation pattern and heavy metal accumulation at a mine tailing at Gyöngyösoroszi, hungary.

Vegetation at an abandoned heavy metal bearing mine tailing may have multifunctional roles such as modification of water balance, erosion control and landscape rehabilitation. Research on the vegetation of mine tailings can provide useful information on tolerance, accumulation and translocation properties of species potentially applicable at moderately contaminated sites. Analyses of the relationship between heavy metal content (Pb, Zn and Cu) and vegetation in a mine tailing were carried out. These analyses included: (1) spatial analysis of relationship among heavy metal distribution, pH and vegetation patterns, and (2) analysis of heavy metal accumulation and translocation in some plant species. Presence of vegetation was found to be significantly dependent on pH value, which confirms that phytotoxicity is a function of element concentration in solution, which is primarily controlled by pH value in mine tailings. Among the most abundant plant species, dewberry (Rubus caesius), vipersbugloss (Echium vulgare), scarlet pimpernel (Anagallis arvensis) and narrowleaf plantain (Plantago lanceolata) accumulate significant amounts of Pb, Cu and Zn, while in the case of annual bluegrass (Poa annua) only Pb can be measured in elevated contents. Considering the translocation features, scarlet pimpernel, narrowleaf plantain, and dewberry accumulate heavy metals primarily in their roots, while heavy metal concentration in vipersbugloss and annual bluegrass is higher in the shoots.

Copper↗

PubMed1985

Effect of heavy metals on fish--a review.

Heavy metals are being utilized in a variety of ways in industries, agriculture, food processing and household in many forms. Metals are unique environmental and industrial pollutants in the sense that they are neither created nor destroyed by human beings but are only transported and transformed into various products. The present communication deals with the findings of various investigators on the effect of heavy metals on fresh water fish.

Animals↗

PubMed2004

Heavy metals content of municipal wastewater and sludges in Kuwait.

Municipal wastewater may contain heavy metals, which are hazardous to the environment and humans. With stringent regulations concerning water reuse and sludge utilization in agriculture, there is a great need to determine levels of heavy metals in liquid wastes, sludges and agricultural crops. The state of Kuwait has programs to utilize waste sludge produced at wastewater treatment plants as soil conditioner and fertilizer for greenery and agricultural development projects and to reuse treated wastewater effluents in irrigation. The common metals found in Kuwait's raw wastewater and sludge are Cd, Cr, Cu, Hg, Ni, Pb, and Zn. The effects of accumulation of heavy metals in soil are long lasting and even permanent. In this study, the variations in the concentration levels of heavy metals were measured in wastewater and sludge produced at Ardiya municipal wastewater treatment plant in Kuwait. A relationship was observed between the concentrations of heavy metals in treated wastewater and sludge used for agriculture and the level of accumulated heavy metals found in residual tissues of some crops.

Agriculture↗