Silver toxicity to ferrous iron and pyrite oxidation and its alleviation by yeast extract in cultures ofThiobacillus ferrooxidans

Tuovinen, Olli H.; Puhakka, Jaakko A.; Hiltunen, Paula; Dolan, Katherine M.

doi:10.1007/bf01166209

Cited by 18 publications

(4 citation statements)

References 11 publications

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“…As found in the present study, copper (I) is much more toxic to these bacteria ( Table 2 ), with MICs being generally an order of magnitude or more lower that those reported for copper (II). Copper occurs immediately above silver in the Periodic Table of elements, and it is interesting to note that monovalent silver (Ag + ) is highly toxic to acidophilic bacteria, inhibiting growth when present in micro-molar concentrations ( Tuovinen et al, 1985 ). Copper (I) is, however, both relatively insoluble and highly unstable in most aqueous solutions, where it disproportionates to copper (II) and elemental copper (2 Cu + → Cu 2+ + Cu 0 ).…”

Section: Discussionmentioning

confidence: 99%

Indirect Redox Transformations of Iron, Copper, and Chromium Catalyzed by Extremely Acidophilic Bacteria

2017

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Experiments were carried out to examine redox transformations of copper and chromium by acidophilic bacteria (Acidithiobacillus, Leptospirillum, and Acidiphilium), and also of iron (III) reduction by Acidithiobacillus spp. under aerobic conditions. Reduction of iron (III) was found with all five species of Acidithiobacillus tested, grown aerobically on elemental sulfur. Cultures maintained at pH 1.0 for protracted periods displayed increasing propensity for aerobic iron (III) reduction, which was observed with cell-free culture liquors as well as those containing bacteria. At. caldus grown on hydrogen also reduced iron (III) under aerobic conditions, confirming that the unknown metabolite(s) responsible for iron (III) reduction were not (exclusively) sulfur intermediates. Reduction of copper (II) by aerobic cultures of sulfur-grown Acidithiobacillus spp. showed similar trends to iron (III) reduction in being more pronounced as culture pH declined, and occurring in both the presence and absence of cells. Cultures of Acidithiobacillus grown anaerobically on hydrogen only reduced copper (II) when iron (III) (which was also reduced) was also included; identical results were found with Acidiphilium cryptum grown micro-aerobically on glucose. Harvested biomass of hydrogen-grown At. ferridurans oxidized iron (II) but not copper (I), and copper (I) was only oxidized by growing cultures of Acidithiobacillus spp. when iron (II) was also included. The data confirmed that oxidation and reduction of copper were both mediated by acidophilic bacteria indirectly, via iron (II) and iron (III). No oxidation of chromium (III) by acidophilic bacteria was observed even when, in the case of Leptospirillum spp., the redox potential of oxidized cultures exceeded +900 mV. Cultures of At. ferridurans and A. cryptum reduced chromium (VI), though only when iron (III) was also present, confirming an indirect mechanism and contradicting an earlier report of direct chromium reduction by A. cryptum. Measurements of redox potentials of iron, copper and chromium couples in acidic, sulfate-containing liquors showed that these differed from situations where metals are not complexed by inorganic ligands, and supported the current observations of indirect copper oxido-reduction and chromium reduction mediated by acidophilic bacteria. The implications of these results for both industrial applications of acidophiles and for exobiology are discussed.

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Section: Discussionmentioning

confidence: 99%

Indirect Redox Transformations of Iron, Copper, and Chromium Catalyzed by Extremely Acidophilic Bacteria

2017

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“…The toxicity of the metal ion will be greatly reduced under these conditions as it will be strongly complexed. This explains why Tetrahymena pyrifbrmis can tolerate a 1 00-fold higher concentration of Cu(I1) in a rich organic medium than in a defined one (Nilsson, 1981), why addition of yeast extract to cultures of Aerobacter aerogenes (Klebsiella pneumoniae) protects the bacteria from the usual toxic effects of Cu(I1) (MacLeod et al, 1967), and why yeast extract can alleviate the toxic effects of Ag(1) on the oxidation of Fe( 11) by Thiobacillus jerrooxidans (Tuovinen et al, 1985). Bird et al (1985) have also drawn attention to the effect of growth medium on the chemical speciation of Cu(II), and the implication for toxicity studies.…”

Section: Complexa T Ionmentioning

confidence: 99%

Metal speciation and microbial growth--the hard (and soft) facts

Hughes

Poole

1991

Journal of General Microbiology

311

197

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“…This decrease in copper bioleaching indicated that the 1000 mg l À1 silver concentration exceeded the level needed for the catalytic effect. The toxic threshold level of silver in culture solution of iron-oxidizing acidithiobacilli in the absence of sulfide minerals is in the order of <1 mg Ag l À1 (Tuovinen et al, 1985). This level of sensitivity to silver is not applicable to chalcopyrite bioleaching systems because the silver catalyst circulates between the solid and solution phases (reactions 2e5), minimizing silver bioavailability and alleviating the toxicity.…”

Section: Mesophilic Testsmentioning

confidence: 98%

Silver-catalyzed bioleaching of copper, molybdenum and rhenium from a chalcopyrite–molybdenite concentrate

Abdollahi

Noaparast

Shafaei

et al. 2015

International Biodeterioration & Biodegradation

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Silver toxicity to ferrous iron and pyrite oxidation and its alleviation by yeast extract in cultures ofThiobacillus ferrooxidans

Cited by 18 publications

References 11 publications

Indirect Redox Transformations of Iron, Copper, and Chromium Catalyzed by Extremely Acidophilic Bacteria

Indirect Redox Transformations of Iron, Copper, and Chromium Catalyzed by Extremely Acidophilic Bacteria

Metal speciation and microbial growth--the hard (and soft) facts

Silver-catalyzed bioleaching of copper, molybdenum and rhenium from a chalcopyrite–molybdenite concentrate

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