Accumulation of gold in the sheath of<i>Plectonema terebrans</i>(filamentous marine cyanobacteria)

Dyer, Betsey Dexter; Krumbein, Wolfgang E.; Mossman, David J.

doi:10.1080/01490459409377975

Cited by 15 publications

(5 citation statements)

References 18 publications

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“…Precipitation can also be due to the production of reactive components which either bind metals or catalyse precipitation (Macaskie et al ., 1994; Mossman et al ., 1999; Wang et al ., 2001). Among the wide array of metal cations implicated in biomineralization, the binding and precipitation of gold is interesting because its mineralization requires reduction to its metallic form (Beveridge and Murray, 1976; Beveridge, 1989 ; Dyer et al ., 1994). Colloidal gold is formed and these colloids eventually coalesce into larger crystals over time (Southam and Beveridge, 1994; Southam et al ., 2000).…”

Section: Introductionmentioning

confidence: 99%

Pseudomonas aeruginosa biofilms react with and precipitate toxic soluble gold

Karthikeyan

Beveridge

2002

Environmental Microbiology

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The interaction between biofilms of Pseudomonas aeruginosa PAO1 and 0.01-5 mM gold chloride was investigated using flow-cells. Scanning confocal laser microscopy (SCLM) of these biofilms revealed the formation of two distinct structural features: (i) confluent areas of uniform thickness and (ii) cell clusters which often emerged as 30-40 micro m, tall narrow pillars (or pedestals) of cells and exopolymeric substance (EPS). When 5-day-old, quasi-steady state biofilms (as indicated by the stability of film thickness and overall structure) were exposed to relatively high AuCl3 (i.e. 0.5-5 mM) for 30 min at 20 degrees C, reduction of the auric ion resulted in the formation of both extracellular and intracellular metallic gold colloids, as revealed by transmission electron microscopy (TEM). Most mineralization occurred on cell surfaces with lesser amounts within cells and little throughout the EPS. Little to no mineralization of gold was seen at 0.01-0.1 mM concentrations. As initial AuCl3 concentrations approached 0.5 mM or greater, more gold particles were seen and cell viability, as determined by a BacLight live/dead viability probe, approached zero. At an intermediate concentration of 0.1 mM, the live:dead ratio increased to 4:1. However, when planktonic cells were exposed to this same 0.1 mM concentration, it resulted in a 4-log reduction in viable counts as determined by plating. The higher resistance of biofilm cells to 0.1 mM gold can be attributed to its binding to the EPS and cell surfaces of the biofilm which ensured a (presumably) low effective cytoplasmic concentration of gold (i.e. no gold crystals were seen in cells by TEM). In addition, SCLM revealed the formation of larger extracellular gold crystals at the substratum (coverslip) level of the biofilms, with a higher proportion of crystals detected beneath pillars (cell cluster structures), suggesting the possibility of unique cell types, more reduced microenvironments at the base of each cluster, or a combination of both. These results suggest that the biomineralization of gold is impacted by biofilm structure.

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Section: Introductionmentioning

confidence: 99%

Pseudomonas aeruginosa biofilms react with and precipitate toxic soluble gold

Karthikeyan

Beveridge

2002

Environmental Microbiology

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“…A number of aerobic microorganisms adsorb Au(III) on the cell surface, with the subsequent reduction of the adsorbed Au(III) to Au(0), through poorly understood mechanisms (3,23,25). However, the anaerobic Fe(III)-reducing microorganisms that reduced Au(III) did not appear to have a significant capacity for adsorption of Au(III) prior to reduction, because there was no loss of Au(III) from solution in the absence of hydrogen or when cells were incubated at temperatures that inhibited metabolism.…”

mentioning

confidence: 99%

Reductive Precipitation of Gold by Dissimilatory Fe(III)-Reducing Bacteria and Archaea

Kashefi

Tor

Nevin

et al. 2001

Appl Environ Microbiol

192

118

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Studies with a diversity of hyperthermophilic and mesophilic dissimilatory Fe(III)-reducing Bacteria andArchaea demonstrated that some of these organisms are capable of precipitating gold by reducing Au(III) to Au(0) with hydrogen as the electron donor. These studies suggest that models for the formation of gold deposits in both hydrothermal and cooler environments should consider the possibility that dissimilatory metalreducing microorganisms can reductively precipitate gold from solution.A wide diversity of both Bacteria and Archaea have the ability to transfer electrons to Fe(III) (11,12,14). Many of these Fe(III)-reducing microorganisms are also capable of transferring electrons to other metals and metalloids. Microbial reduction of Fe(III) and other metals can influence the fate of metals in aquatic sediments, submerged soils, and the subsurface (10,11,13). One of the more geologically significant impacts of microbial metal reduction is the formation of minerals that can be important geological signatures of the activity of metal-reducing microorganisms and, in some instances, that may represent economically important ore deposits. For example, the formation of magnetite during Fe(III) oxide reduction (21) has been considered to be an indication of the activity of Fe(III)-reducing microorganisms in aquatic sediments (4), in the deep, hot biosphere (5), and on Mars (22). The massive magnetite accumulations formed in the Precambrian period, presumably as the result of microbial activity (1,8,27), represent an important source of iron ore. It has also been suggested that microbial reduction of U(VI) to U(IV), which precipitates uranium from solution (19), might account for the formation of some uranium ores (6, 17).Like uranium, gold is soluble in the oxidized form, Au(III), but the reduced form of gold, Au(0), is insoluble (23). The finding that addition of Au(III) to cell suspensions of Geobacter metallireducens oxidized c-type cytochromes, which are thought to be involved in electron transport to metals (15), suggested that this dissimilatory metal reducer might be able to transfer electrons to Au(III) (9). Furthermore, the c 3 -cytochrome of Desulfovibrio vulgaris, known to be involved in the reduction of U(VI) (20) and Cr(VI) (18), can also transfer electrons to Au(III) (9). However, the possibility that whole cells of either G. metallireducens, D. vulgaris, or other dissimilatory Fe(III)-reducing microorganisms reduced Au(III) was not further evaluated.In order to determine the potential for dissimilatory Fe(III)-reducing microorganisms to precipitate gold from solution, the following organisms were cultured (800 ml) in 1-liter bottles, using strict anaerobic techniques as previously described (16 (ATCC 35115), "Desulfitobacterium metallireducens" (laboratory culture collection), and the acetate-oxidizing hyperthermophile strain 234 (laboratory culture collection). Cell suspensions were prepared as previously described (26). Briefly, cells were harvested anaerobically by centrifugation, resuspended in 8...

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“…Notwithstanding the accumulating evidence for involvement of organic matter in the transport and deposition of Pt at very low temperatures (e.g., Chyi 1982, Wood 1990, Chernyshov & Korobkina 1995, Plyusnina et al 2000 and biogeochemical cycling of gold (Dyer et al 1994, Southam 1998, the available evidence favoring an authigenic origin for the Bom Sucesso PtPd nuggets is not overwhelming. Cassedanne & Alves (1992) reported that Pt-Pd nuggets in sediments from the Bom Sucesso stream are too delicate to withstand significant alluvial transport, and supported the diagenetic hypothesis of Hussak (1906).…”

Section: Platinum -Palladium -Potarite Assemblagesmentioning

confidence: 91%

Botryoidal Platinum, Palladium and Potarite From the Bom Sucesso Stream, Minas Gerais, Brazil: Compositional Zoning and Origin

Fleet¹,

Almeida²,

Angeli³

2002

The Canadian Mineralogist

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Platinum-Pd nuggets from the Bom Sucesso stream alluvium, Minas Gerais, Brazil, have been investigated by electron-probe microanalysis. The nuggets attain 1 mm in maximum dimension and have a botryoidal habit, with pronounced compositional core-to-margin zoning of internal structures. Although there is a wide variation in internal morphology and individual zones vary markedly in thickness (<1-100 m), a typical composite arborescent nugget comprises a broad irregular core region of massive auriferous Pd-Hg alloy (potarite; ␦-PdHg) or cavity space + relict potarite enclosed by a narrow zone of platiniferous palladium or alloy of near Pt 50 Pd 50 composition, and is progressively oscillatory zoned by palladian platinum, with growth eventually enveloping the whole botryoidal "colony", to a narrow rim of palladian platinum or pure platinum. Other nuggets comprise an arborescent to dendritic core of auriferous potarite, a broad internal zone of either pure platinum or palladian platinum, and a narrow rim of platinum. The mineral palladium contains up to about 65 at.% Pd; this is the first detailed modern confirmation of palladium in its type locality. Auriferous potarite ranges in composition from ~Pd 3 Hg 2 to near Pd(Hg,Au). The origin of these nuggets remains unclear, but their mineralogy is broadly equivalent to that of palladian gold, potarite and platinum in alluvial sediments and overburden from Devon, England, which are considered to be detrital, and their platinum-group-element geochemistry is consistent with precipitation from hydrothermal fluids. We suggest that the Bom Sucesso nuggets resulted from high-level episodic hydrothermal alteration of mafic and ultramafic rocks within the drainage basin, with the remobilized Pt and Pd precipitated in open spaces in the enclosing metaquartzites. SOMMAIRENous avons caractérisé des pépites alluvionnaires de platine et de palladium provenant du ruisseau Bom Sucesso, dans l'état de Minas Gerais, au Brésil, par analyses à la microsonde électronique. Ces pépites atteignent 1 mm et possèdent un aspect botryoïdal, avec une zonation compositionnelle prononcée des structures internes allant du coeur vers la bordure. Quoiqu'il y a une variation importante de la morphologie interne et que les zones individuelles varient de façon importante en épaisseur (<1-100 m), une pépite arborescente composite typique contient un noyau large et irrégulier fait d'un alliage Pd-Hg aurifère massif (potarite; ␦-PdHg) ou d'un espace vide avec des reliques de potarite, qu'entoure une zone étroite de palladium platinifère ou d'un alliage ayant une composition proche de Pt 50 Pd 50 . Cette zone centrale est enveloppée progressivement par des zones oscillatoires de platine palladifère, avec une croissance éventuelle enveloppant toute la "colonie", menant à un liséré externe de platine pur ou légèrement palladifère. Dans d'autres cas, les pépites contiennent un noyau de potarite aurifère arborescent ou dendritique, une zone interne relativement large composé de platine pur ou légèrement palladifère,...

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Accumulation of gold in the sheath ofPlectonema terebrans(filamentous marine cyanobacteria)

Cited by 15 publications

References 18 publications

Pseudomonas aeruginosa biofilms react with and precipitate toxic soluble gold

Pseudomonas aeruginosa biofilms react with and precipitate toxic soluble gold

Reductive Precipitation of Gold by Dissimilatory Fe(III)-Reducing Bacteria and Archaea

Botryoidal Platinum, Palladium and Potarite From the Bom Sucesso Stream, Minas Gerais, Brazil: Compositional Zoning and Origin

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