A comparison of the thermodynamics of metal adsorption onto two common bacteria

Daughney, Christopher J.; Fein, Jeremy B.; Yee, Nathan

doi:10.1016/s0009-2541(97)00124-1

Cited by 143 publications

(81 citation statements)

References 23 publications

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“…The use of microbes for the bioremediation of trace metals has shown potential for enabling a site to meet regulatory specifications. Experiments have demonstrated the ability of bacteria to immobilize and concentrate metal ions (6,14,28,37,46).Mechanisms by which cells accumulate, sequester, and detoxify metals have been investigated. One indirect approach has been the determination of uptake and retention as a function of pH or competition with some other cation (14,16,20,35).…”

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confidence: 99%

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confidence: 99%

“…One indirect approach has been the determination of uptake and retention as a function of pH or competition with some other cation (14,16,20,35). Another has been to chemically modify plant or cell matter (for example, by esterification) to render specific classes of prospective ligands unavailable and to evaluate the impact on metal binding capacity (7,21).…”

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confidence: 99%

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Determination of Cu Environments in the CyanobacteriumAnabaena flos-aquaeby X-Ray Absorption Spectroscopy

Kretschmer

Meitzner

Gardea‐Torresdey³

et al. 2004

Appl Environ Microbiol

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Whole cells and peptidoglycan isolated from cell walls of the cyanobacterium Anabaena flos-aquae were lyophilized and used at pH 2 and pH 5 in Cu(II) binding studies. X-ray absorption spectra measured at the Cu K-edge were used to determine the oxidation states and chemical environments of Cu species in the whole-cell and peptidoglycan samples. In the whole-cell samples, most of the Cu retained at both pH values was coordinated by phosphate ligands. The whole-cell fractions contained significant concentrations of Cu(I) as well as Cu(II). An X-ray absorption near-edge spectrum analysis suggested that Cu(I) was coordinated by amine and thiol ligands. An analysis of the peptidoglycan fractions found that more Cu was adsorbed by the peptidoglycan fraction prepared at pH 5, due to increased chelation by amine and carboxyl ligands. The peptidoglycan fractions, also referred to as the cell wall fractions, contained little or no Cu(I). The Cu loading level was 30 times higher in the cell wall sample prepared at pH 5 than in the sample prepared at pH 2. Amine and bidentate carboxyl ligands had similar relative levels of importance in cell wall peptidoglycan samples prepared at both pH values, but phosphate coordination was insignificant.Heavy metals damage the environment since they are nonbiodegradable and have toxic effects on plants, animals, and humans. Precipitation, coagulation, membrane-based processes, and ion exchange are some of the current approaches to the remediation of contaminated sites, but these methods are expensive and lose effectiveness as metal concentrations fall (54). The use of microbes for the bioremediation of trace metals has shown potential for enabling a site to meet regulatory specifications. Experiments have demonstrated the ability of bacteria to immobilize and concentrate metal ions (6,14,28,37,46).Mechanisms by which cells accumulate, sequester, and detoxify metals have been investigated. One indirect approach has been the determination of uptake and retention as a function of pH or competition with some other cation (14,16,20,35). Another has been to chemically modify plant or cell matter (for example, by esterification) to render specific classes of prospective ligands unavailable and to evaluate the impact on metal binding capacity (7,21). In a study of binding sites in cell walls of gram-positive bacteria, teichoic acid, presenting phosphate sites, was extracted with aqueous alkali in order to quantify its contribution to metal binding (7).The chemical studies described are informative but involve many assumptions due to the complexity of biological systems. Also, because of that complexity, few analytical probes can illuminate the chemistry of metals associated with cells. X-ray absorption spectroscopy (XAS) is element specific, returning information for a single atomic number in an arbitrarily complicated mixture (52). XAS is nondestructive, and no sample reduction or digestion is required which would alter the chemistry of the element of interest. XAS can be used to determine the ...

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Determination of Cu Environments in the CyanobacteriumAnabaena flos-aquaeby X-Ray Absorption Spectroscopy

Kretschmer

Meitzner

Gardea‐Torresdey³

et al. 2004

Appl Environ Microbiol

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“…These surface functional groups deprotonate with increasing pH and thus impart to the microorganism a net negative surface charge (1,5,11). Recently, the proton binding and charge properties of bacterial surfaces have been investigated in detail by using acid-base titrations to determine the types and abundances of these ligands (5,6,11,26,41). A prime reason for such investigations is to determine the capacity of bacteria to sorb cations from the aqueous environment.…”

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Characterization and Implications of the Cell Surface Reactivity of Calothrix sp. Strain KC97

Phoenix

Martinez

Konhauser

et al. 2002

Appl Environ Microbiol

124

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The cell surface reactivity of the cyanobacterium Calothrix sp. strain KC97, an isolate from the Krisuvik hot spring, Iceland, was investigated in terms of its proton binding behavior and charge characteristics by using acid-base titrations, electrophoretic mobility analysis, and transmission electron microscopy. Analysis of titration data with the linear programming optimization method showed that intact filaments were dominated by surface proton binding sites inferred to be carboxyl groups (acid dissociation constants [pK a ] between 5.0 and 6.2) and amine groups (mean pK a of 8.9). Sheath material isolated by using lysozyme and sodium dodecyl sulfate generated pK a spectra similarly dominated by carboxyls (pK a of 4.6 to 6.1) and amines (pK a of 8.1 to 9.2). In both intact filaments and isolated sheath material, the lower ligand concentrations at mid-pK a values were ascribed to phosphoryl groups. Whole filaments and isolated sheath material displayed total reactive-site densities of 80.3 ؋ 10 ؊5 and 12.3 ؋ 10 ؊5 mol/g (dry mass) of cyanobacteria, respectively, implying that much of the surface reactivity of this microorganism is located on the cell wall and not the sheath. This is corroborated by electrophoretic mobility measurements that showed that the sheath has a net neutral charge at mid-pHs. In contrast, unsheathed cells exhibited a stronger negative-charge characteristic. Additionally, transmission electron microscopy analysis of ultrathin sections stained with heavy metals further demonstrated that most of the reactive binding sites are located upon the cell wall. Thus, the cell surface reactivity of Calothrix sp. strain KC97 can be described as a dual layer composed of a highly reactive cell wall enclosed within a poorly reactive sheath.

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“…The outer cellular membranes of microbes have net negative charges and would tend to bind heavy metal cations. These cell walls have various surface functional groups such as carboxyl, phosphate and hydroxyl groups (Daughney et al 1998, Fein et al 1997. These are efficient metal building agents and are of importance in metal removal from solution (Hersman 1997).…”

Section: Microbial Sorptionmentioning

confidence: 99%

In-Drift Microbial Communities

Jolley¹

2000

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A comparison of the thermodynamics of metal adsorption onto two common bacteria

Cited by 143 publications

References 23 publications

Determination of Cu Environments in the CyanobacteriumAnabaena flos-aquaeby X-Ray Absorption Spectroscopy

Determination of Cu Environments in the CyanobacteriumAnabaena flos-aquaeby X-Ray Absorption Spectroscopy

Characterization and Implications of the Cell Surface Reactivity of Calothrix sp. Strain KC97

In-Drift Microbial Communities

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