Cyanobacterial metallothioneins: Biochemistry and molecular genetics

Turner, Jennifer S.; Robinson, Nigel J.

doi:10.1007/bf01569893

Cited by 103 publications

(41 citation statements)

References 63 publications

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“…The common research organism Synechococcus leopoldiensis is the only cyanobacterium in which metallothionein has been shown to occur (40,46). Growth of S. leopoldiensis was less sensitive to Hg than that of Limnothrix planctonica, showing virtually no effect at 120 ppb ( Fig.…”

Section: Resultsmentioning

confidence: 98%

Biotransformation of Hg(II) by Cyanobacteria

Lefebvre

Kelly

Budd

2007

Appl Environ Microbiol

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The biotransformation of Hg(II) by cyanobacteria was investigated under aerobic and pH-controlled culture conditions. Mercury was supplied as HgCl 2 in amounts emulating those found under heavily impacted environmental conditions where bioremediation would be appropriate. The analytical procedures used to measure mercury within the culture solution, including that in the cyanobacterial cells, used reduction under both acid and alkaline conditions in the presence of SnCl 2 . Acid reduction detected free Hg(II) ions and its complexes, whereas alkaline reduction revealed that meta-cinnabar (␤-HgS) constituted the major biotransformed and cellularly associated mercury pool. This was true for all investigated species of cyanobacteria: Limnothrix planctonica (Lemm.), Synechococcus leopoldiensis (Racib.) Komarek, and Phormidium limnetica (Lemm.). From the outset of mercury exposure, there was rapid synthesis of ␤-HgS and Hg(0); however, the production rate for the latter decreased quickly. Inhibitory studies using dimethylfumarate and iodoacetamide to modify intra-and extracellular thiols, respectively, revealed that the former thiol pool was required for the conversion of Hg(II) into ␤-HgS. In addition, increasing the temperature enhanced the amount of ␤-HgS produced, with a concomitant decrease in Hg(0) volatilization. These findings suggest that in the environment, cyanobacteria at the air-water interface could act to convert substantial amounts of Hg(II) into ␤-HgS. Furthermore, the efficiency of conversion into ␤-HgS by cyanobacteria may lead to the development of applications in the bioremediation of mercury.Mercury in the form of divalent ions constitutes the bulk of that in soils, where it is bound to organic compounds, to clay, and as sulfides (31). Although industrialization in the beginning of the last century is the cause of most of the mercury contamination found in the environment today, rainfall continues to carry mercury [Hg(II)] into aquatic and terrestrial systems worldwide (16,44). Despite a comprehensive knowledge of the mercury cycle and the aquatic chemistry of its constituents (12, 43, 52), several microbial taxa have not been characterized with respect to their roles in the biotransformation of this heavy metal.Several mercury biotransformation mechanisms have been described previously (4,12,39,41), and of these, prokaryotic methylation and reduction to Hg(0) may play only limited roles in the biotransformation of Hg(II) in aquatic environments (15,19). Furthermore, the reduction reaction simply refracts meteorologically precipitated Hg(II) back into the atmosphere. As such, it follows that other processes must make significant contributions to the biogeochemical cycle of Hg even though relative quantitative data are scarce (31). Insight into this area requires an understanding of the major biotransformation processes leading to mercury retention in ecosystems.The lack of quantitative, mechanistic data behind cellular accumulation versus that for volatilization of Hg is evident even in the eukar...

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Section: Resultsmentioning

confidence: 98%

Biotransformation of Hg(II) by Cyanobacteria

Lefebvre

Kelly

Budd

2007

Appl Environ Microbiol

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“…Their metal binding properties are mediated via the abundant cysteine residues and their characteristic Journal of Hazardous Substance Research, Volume 1 2-3 organization into -Cys-Cys-, -Cys-X-Cys-, or -Cys-X-X-Cys-sequences (x corresponds to any other amino acid in the protein sequence). Synthesis of metallothioneins has been shown to be prompted by elevated concentrations of some metals (Turner and Robinson, 1995).…”

Section: Introductionmentioning

confidence: 99%

Ability of Immobilized Cyanobacteria to Remove Metal Ions From Solution and Demonstration of the Presence of Metallothionein Genes in Various Strains

Torresdey¹,

Arenas²,

N.M.C.³

et al. 1998

Journal of Hazardous Substance Research

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Synechococcus sp. PCC 7942 has the ability to grow in mass quantity under ideal conditions; such an ability provides usable biomass at a minimal effort. Using lyophilized biomass grown under normal conditions, Synechococcus was tested for its potential to bind metal ions from solution. Batch experiments have determined the optimum binding pH, time dependency, and metal binding capacities for copper(II), lead(II), nickel(II), cadmium(II), chromium(III), and chromium(VI), along with desorption of the metal bound. The biomass studied showed an affinity for five of the metal ions, with an optimum binding at pH 5. Time dependency studies showed that this cyanobacterium had rapid binding, while capacity experiments showed this cyanobacterial strain to bind 11. 2M HCl resulted in nearly 100% recovery for both copper(II) and lead(II) from the column, 79% recovery of cadmium(II), while recovery for nickel(II) was 42%. Experiments were conducted to determine if many cycles of metal bindingstripping by the immobilized biomass were possible. Further, attempts were made to demonstrate the presence of metallothioneins in various strains of cyanobacteria which may serve as defense mechanisms against metal ion toxicity. Such proteins may be used to develop engineered strains of cyanobacteria with increased metal ion binding ability. Synechococcus can eventually be used as a source for a novel approach in using biosystems to remediate contaminants from solution and making those contaminants available to industry through an environmentally friendly biofiltration system.

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“…The low-MW region probably includes iron-binding peptides of MW of 500-1500 Da called siderophores, which are secreted by cyanobacteria under conditions of iron stress and enable the transport of ferric ions into cells (Albrecht-Gary and Crumbliss 1998). In addition, low-MW compounds might be cyanobacteri- Effect of cyanobacterial peptides and proteins on coagulation of kaolinite 87 al metallothioneins, cysteine-rich peptides/proteins that bind, sequester and buffer the excess intracellular metal cations through the thiol group of its cysteine residues (Turner and Robinson 1995). The isolated iron-binding protein of MW 52 kDa probably is the cyanobacterial metalloenzyme bidirectional hydrogenase, which has an affinity for iron and is present in M. aeruginosa (Tamagnini et al 2007).…”

Section: Coagulation Of Com Peptides and Proteinsmentioning

confidence: 99%

Effect of cyanobacterial peptides and proteins on coagulation of kaolinite

Novotná

Barešová

Čermáková

et al. 2016

European Journal of Environmental Sciences

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Coagulation of peptides and proteins produced by the cyanobacterium Microcystis aeruginosa and their influence on the coagulation of hydrophobic kaolinite particles were investigated. For this purpose, the dose of ferric sulphate used as the coagulant was optimized and jar tests with kaolinite, peptides/proteins and both kaolinite and peptides/proteins were carried out under different pH conditions. At pH 4-5.5, the peptides/proteins were efficiently coagulated and peptides/proteins were also found to contribute to the coagulation of kaolinite particles at this pH. Charge neutralization and adsorption were found to be the dominant coagulation mechanisms. The coagulation efficiency and the character of the prevailing coagulation mechanism were strongly dependent on the charge characteristics of the peptides/proteins, kaolinite and hydrolysis products of iron, thus on the pH value. At a pH of about 6, the coagulation process deteriorated due to the formation of soluble Fe-peptide/protein complexes.

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Cyanobacterial metallothioneins: Biochemistry and molecular genetics

Cited by 103 publications

References 63 publications

Biotransformation of Hg(II) by Cyanobacteria

Biotransformation of Hg(II) by Cyanobacteria

Ability of Immobilized Cyanobacteria to Remove Metal Ions From Solution and Demonstration of the Presence of Metallothionein Genes in Various Strains

Effect of cyanobacterial peptides and proteins on coagulation of kaolinite

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