Martin Mandl

Migration of arsenic(III) during bacterial oxidation of arsenopyrite in chalcopyrite concentrate by Thiobacillus ferrooxidans

During bacterial oxidation of the arsenopyrite that contaminated a chalcopyrite concentrate, the bioextraction of arsenic from the concentrate was examined. A long-term constant As(III) concentration, representing a large portion of the total arsenic, occurred in the leaching medium. As(III) was not further oxidized, either under bioextraction conditions or by Fe(III) in the presence of the mesophilic bacterium Thiobacillus ferooxidans. These results are discussed in relation to the influence of leaching microorganisms on the form of arsenic in the solution. Dissolved As(III) could be reversed into a solid phase by adsorption of As(III) by forming an iron precipitate.

Kinetics of arsenic(III) oxidation by iron(III) catalysed by pyrite in the presence ofThiobacillus ferrooxidans

SummaryA simple kinetic model of As(III) oxidation by Fe(III) in the presence of pyrite andThiobacillus ferroxidans is described based on the stoichiometry of the reaction and bioproduction of Fe(III). The environmental consequences of this reaction were considered.

Kinetic constant variability in bacterial oxidation of elemental sulfur

ABSTRACT Wide ranges of growth yields on sulfur (from 2.4 × 1010 to 8.1 × 1011 cells g−1) and maximum sulfur oxidation rates (from 0.068 to 1.30 mmol liter−1 h−1) of an Acidithiobacillus ferrooxidans strain (CCM 4253) were observed in 73 batch cultures. No significant correlation between the constants was observed. Changes of the Michaelis constant for sulfur (from 0.46 to 15.5 mM) in resting cells were also noted.

Determination of rhodanese enzyme activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of rhodanese activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of SCN- was monitored by sequential capillary zone electrophoretic runs. The determinations were performed in a 75-micron fused-silica capillary using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, a separation voltage of 18 kV (negative polarity), a capillary temperature of 25 degrees C and direct detection at 200 nm. Short-end injection or long-end injection procedures were used for sample application. The method is rapid, able to be automated and requires only small amounts of sample and substrates, which is especially important in the case of highly toxic cyanide. The developed capillary electrophoretic method also has great potential for thiocyanate determinations in other applications.

Metabolic activity of Thiobacillus ferrooxidans on reduced sulfur compounds detected by capillary isotachophoresis

Abstract The sulfur-oxidizing activity of Thiobacillus ferrooxidans was investigated using capillary isotachophoresis. The oxidation of pyrite and sulfur was detected through sulfate formation while oxidation of thiosulfate was detected by thiosulfate consumption. Electrolyte systems and the conditions for the isotachophoretic determination of sulfate (leading electrolyte: HCl, 1 mmol l −1 ; CaCl 2 , 2 mmol l −1 and β -alanine, pH 4.0; terminating electrolyte: citric acid, 1 mmol l −1 ) and thiosulfate (leading electrolyte: HCl, 1 mmol l −1 ; CaCl 2 , 4 mmol l −1 and β -alanine; terminating electrolyte: hexanoic acid, 5 mmol l −1 ) are described. Oxidation of pyrite and sulfur occurred without sulfur intermediate formation; however, during thiosulfate oxidation, sulfur intermediates were detected.

Cellular ATP Changes in Acidithiobacillus ferrooxidans Cultures Oxidizing Ferrous Iron and Elemental Sulfur

Cellular ATP content of Acidithiobacillus ferrooxidans cultures was determined with a bioluminescence assay in relation to batch growth and oxidation of ferrous iron and elemental sulfur. Inhibitory effects of inorganic substrates and products on luciferase were eliminated. Extracellular ATP levels were negligible. The ATP content of sulfur-grown cells decreased anomalously due to a culture pH increase at the stationary phase. Although the rates of growth and sulfur oxidation reached the original levels, the ATP content of the culture remained constant because of gradual decrease in the cellular ATP. The maximum ATP levels in A. ferrooxidans grown with Fe2+ and S0 were 1.16 and 0.33 amol per cell, respectively. The results defined conditions under which biomass growth could be monitored by the ATP assay to study biogeochemical activities of acidophilic iron- and sulfur-oxidizing bacteria.

Membrane biosensor for the determination of iron(II,III) based on immobilized cells of Thiobacillus ferrooxidans

The bacterial electrode for amperometric determination of iron ions is based on a Clark-type oxygen electrode, on the measuring part of which a paste containing a mixture of jarosite precipitate and iron-oxidizing bacteria is mounted with the aid of a cellophane membrane. In acidic media a biochemical oxidation of Fe2+ connected with oxygen consumption takes place in the biocatalytic layer. Fe3+ is determined after its reduction to Fe2+. The determination limit is 60 μmol/L, the stability of the electrode is two months at room temperature.

Ferrous iron oxidation by sulfur-oxidizing Acidithiobacillus ferrooxidans and analysis of the process at the levels of transcription and protein synthesis

In contrast to iron-oxidizing Acidithiobacillus ferrooxidans,A. ferrooxidans from a stationary phase elemental sulfur-oxidizing culture exhibited a lag phase in pyrite oxidation, which is similar to its behaviour during ferrous iron oxidation. The ability of elemental sulfur-oxidizing A. ferrooxidans to immediately oxidize ferrous iron or pyrite without a lag phase was only observed in bacteria obtained from growing cultures with elemental sulfur. However, these cultures that shifted to ferrous iron oxidation showed a low rate of ferrous iron oxidation while no growth was observed. Two-dimensional gel electrophoresis was used for a quantitative proteomic analysis of the adaptation process when bacteria were switched from elemental sulfur to ferrous iron. A comparison of total cell lysates revealed 39 proteins whose increase or decrease in abundance was related to this phenotypic switching. However, only a few proteins were closely related to iron and sulfur metabolism. Reverse-transcription quantitative PCR was used to further characterize the bacterial adaptation process. The expression profiles of selected genes primarily involved in the ferrous iron oxidation indicated that phenotypic switching is a complex process that includes the activation of genes encoding a membrane protein, maturation proteins, electron transport proteins and their regulators.

Phytotoxicity of iron in relation to its solubility conditions and the effect of ionic strength

The effect of iron on root elongation and seed germination of Lactuca sativa was investigated within the limits of the plants sensitivity to an acidic environment and iron solubility under experimental conditions. Because ionic strength was found to have phytotoxic effects, the same pH and ionic strength conditions were kept constant over the entire iron concentration range, so as to evaluate solely the effect of iron. 0.14 mM Fe3+ was found to be the lowest effective concentration inhibiting root elongation. The low solubility of iron at a pH of 3 (the lowest value which could be applied for root elongation) excluded the testing of higher iron concentrations. Due to the lower sensitivity of seed germination to acidity, a pH of 2.6 could be applied in this case. The lowest effective iron concentration (the lowest applied concentration causing a significant decrease in germination as compared to the control, P < 0.05), EC50 (the concentration at which germination was 50% of that of the control specimens) and the completely effective iron concentration (the concentration that completely inhibited seed germination) were 0.6, 0.92 and 2.0 mM, respectively.

An ultraviolet spectrophotometric method for the determination of oxidation of iron sulphide minerals by bacteria

A method based on absorption of Fe(III) at 300 nm was developed and then applied to bacterial leaching of iron-containing metal sulphides.