Kinetic studies on elemental sulfur oxidation by Acidithiobacillus ferrooxidans: sulfur limitation and activity of free and adsorbed bacteria

The kinetics of sulfur oxidation by Acidithiobacillus ferrooxidans in shaking flasks and a 10-L reactor was studied. The observed linearity of growth and sulfur oxidation was explained by sulfur limitation. Total cell yield was not significantly different for exponential growth as compared to growth during the sulfur-limiting phase. Kinetic studies of sulfur oxidation by growing and nongrowing bacteria indicated that both free and adsorbed bacteria oxidize sulfur. Changes in the number of free bacteria rather than cells adsorbed on sulfur were better predictors of the kinetics of sulfur oxidation, indicating that the free bacteria were performing sulfur oxidation. The active growth phase always followed adsorption of bacteria on sulfur; however, the special metabolic role of adsorbed bacteria was unclear. Their activity in sulfur solubilization was considered.     

Kinetics of sulfur oxidation by thiobacillus ferrooxidans

Abstract

Thiobacillus ferrooxidans ATCC 23270 was grown with elemental sulfur as the energy source. Substrate oxidation was measured using a Clark‐type oxygen electrode. Whole cells demonstrated a broad pH optimum for sulfur oxidation between pH 2.0 and 8.0. The V _max and K_sfor sulfur oxidation varied depending on pH. Sulfite was oxidized at 227 nmol O₂/min/mg protein. Thiosulfate oxidation was slow, and tetrathionate oxidation was not detected. At a concentration of 2 mM, sodium azide completely inhibited sulfur, sulfite, and thiosulfate oxidation. Inhibition by N‐ethylmaleimide, antimycin A, and 2‐heptyl‐4‐hydroxyquinoline N‐oxide varied with substrate.     

Anaerobic growth on elemental sulfur using dissimilar iron reduction by autotrophic Thiobacillus ferrooxidans

Abstract Anaerobic growth on elemental sulfur using dissimilar iron reduction by Thiobacillus ferrooxidans has been demonstrated. The ferric ion reducing activity (FIR) of the anaerobic cells was double that of the aerobic cells. Significant differences in inhibition of FIR by respiratory inhibitors were observed between aerobic and anaerobic cells. A higher amount of cytochrome was detected in anaerobic cells compared to aerobic cells. Absorption minima developed with the addition of ferric sulfate in the dithionite reduced cell suspension demonstrated that the ferric ion could accept electrons from the cytochrome system of this bacterium. The possibility of two different electron transport chains in ferric ion reduction is discussed.     

氧化亚铁硫杆菌氧化亚硫酸盐的动力学研究

实验用Ms培养基,利用去除铁离子的氧化亚铁硫杆菌(Thiobacillus ferrooxidans)进行了细菌亚硫酸盐的生长代谢研究。实验结果表明氧化亚铁硫杆菌对亚硫酸根具有一定的氧化能力。用Origin 7.0对实验数据进行拟合处理,表明了氧化亚铁硫杆菌催化氧化亚硫酸盐的动力学方程符合Hill方程。氧化亚铁硫杆菌催化氧化亚硫酸盐是一个底物抑制的细胞反应,其KS值随pH值和底物浓度的改变而变化。pH值对反应有很大的影响,pH值越接近中性KS就越小,反应速率就越大。     

Bioleaching of zinc sulfide concentrate by Thiobacillus ferrooxidans

The kinetics of the bioleaching of ZnS concentrate by Thiobacillus ferrooxidans was studied in a well-mixed batch reactor. Experimental studies were made at 30 degrees C and pH 2.2 on adsorption of the bacteria to the mineral, ferric iron leaching, and bacterial leaching. The adsorption rate of the bacteria was fairly rapid in comparison with the bioleaching rate, indicating that the bacterial adsorption is at equilibrium during the leaching process. The adsorption equilibrium data were correlated by the Langmuir isotherm, which is a useful means for predicting the number of bacteria adsorbed on the mineral surface. The rate of chemical leaching varied with the concentration of ferric iron, and the first-order reaction rate constant was determined. Bioleaching in an iron-containing medium was found to take place by both direct bacterial attack on the sulfide mineral and indirect attack via ferric iron. In this case, the ferric iron was formed from the reaction product (ferrous iron) through the biological oxidation reaction. To develop rate expressions for the kinetics of bacterial growth and zinc leaching, the two bacterial actions were considered. The key parameters appearing in the rate equations, the growth yield and specific growth rate of adsorbed bacteria, were evaluated by curve fitting using the experimental data. This kinetic model allowed us to predict the liquid-phase concentrations of the leached zinc and free cells during the batch bioleaching process.     

Occurrences at mineral-bacteria interface during oxidation of arsenopyrite by Thiobacillus ferrooxidans

The combination of an improved bacterial desorption method, scanning electron microscopy (SEM), diffuse reflectance and transmission infrared Fourier transform spectroscopy, and a desorption-leaching device like high-pressure liquid chromatography (HPLC) was used to analyze bacterial populations (adhering and free bacteria) and surface-oxidized phases (ferric arsenates and elemental sulfur) during the arsenopyrite biooxidation by Thiobacillus ferrooxidans. The bacterial distribution, the physicochemical composition of the leachate, the evolution of corrosion patterns, and the nature and amount of the surface-oxidized chemical species characterized different behavior for each step of arsenopyrite bioleaching. The first step is characterized by a slow but strong adhesion of bacteria to mineral surfaces, the appearance of a surface phase of elemental sulfur, the weak solubilization of Fe(II), As(III), and As(V), and the presence of the first corrosion patterns, which follow the fragility zones and the crystallographic orientation of mineral grains. After this short step, growth of the unattached bacteria begins, while ferrous ions in solution are oxidized by them. Ferric ions produced by the bacteria can oxidize the sulfide directly and are regenerated by Fe(II) bacterial oxidation. At this time, a bioleaching cycle takes place and a coarse surface phase of ferric arsenate (FeAsO(4) . xH(2)O where x approximately 2) and deep ovoid pores appear. At the end of the bioleaching cycle, the high concentration of Fe(III) and As(V) in solution promotes the precipitation of a second phase of amorphous ferric arsenate (FeAsO(4) . xH(2)O where x approximately 4) in the leachate. Then the biooxidation process ceases: The bacteria adhering to the mineral sufaces are coated by the ferric arsenates and the concentration of Fe(III) on the leachate is found to have decreased greatly. Both oxidation mechanisms (direct and indirect oxidation) have been stopped. (c) 1995 John Wiley & Sons, Inc.     

Use of Thiobacillus ferrooxidans for iron oxidation and precipitation

Fe(II) oxidation reaction was carried out using an acidophilic microorganism, Thiobacillus ferrooxidans. Four different parameters such as pH, Fe(II), Fe(III) and biomass concentration were studied. The oxida-tion reaction follows a pseudo first order rate equation. Apparent reaction rate constants were calculated. Unified rate equation was developed using the four parameters. Along with oxidation, a part of the iron also was precipitated. The extent of Fe(III) precipitation in each case was calculated. © Rapid Science 1998     

Modelling of sulfur oxidation from elemental sulfur

An elemental S oxidation model has been developed which combines a maximum S release rate with modifiers for temperature and soil moisture conditions. This model has been combined with a pasture growth and CNSP nutrient cycling model to match S oxidation rate to pasture S demand. In two Southern Australian enviroments, 100m elemental S was superior to 200m particles whilst in Northern Australia the 200m particles were superior. These models can be used to match S release to plant demand.     

Anaerobic oxidation of thiosulfate and elemental sulfur in Thiobacillus denitrificans

Thiobacillus denitrificans strain RT could be grown anaerobically in batch culture on thiosulfate but not on other reduced sulfur compounds like sulfide, elemental sulfur, thiocyanate, polythionates or sulfite. During growth on thiosulfate the assimilated cell sulfur was derived totally from the outer or sulfane sulfur. Thiosulfate oxidation started with a rhodanese type cleavage between sulfane and sulfone sulfur leading to elemental sulfur and sulfite. As long as thiosulfate was present elemental sulfur was transiently accumulated within the cells in a form that could be shown to be more reactive than elemental sulfur present in a hydrophilic sulfur sol, however, less reactive than sulfane sulfur of polythionates or organic and inorganic polysulfides. When thiosulfate had been completely consumed, intracellular elemental sulfur was rapidly oxidized to sulfate with a specific rate of 45 natom S°/min·mg protein. Extracellularly offered elemental sulfur was not oxidized under anaerobic conditions.     

Kinetics of uranous iron and ferrous iron oxidation by thiobacillus ferrooxidans

Archives of Microbiology -     

The production and utilization of intermediary elemental sulfur during the oxidation of reduced sulfur compounds by Thiobacillus ferrooxidans

The intermediary production of elemental sulfur during the microbial oxidation of reduced sulfur compounds has frequently been reported. Thiobacillus ferrooxidans, an acidophilic chemolithoautotroph, was found to produce an insoluble sulfur compound, primarily elemental sulfur, during the oxidation of thiosulfate, trithionate, tetrathionate and sulfide. This was confirmed by light and electron microscopy. Sulfur was produced from sulfide by an oxidative step, while the production from tetrathionate was initiated by a hydrolytic step, probably followed by a series of chemical reactions. The oxidation of intermediary sulfur was severely inhibited by sulfhydryl-binding reagents such as N-ethylmaleimide, by the addition of uncouplers or after freezing and thawing of the cells, which probably damaged the cell membrane. The mechanisms behind these inhibitions have not yet been clarified. Finally, it was observed that elemental sulfur oxidation by whole cells depended on the medium composition. The absence of sulfate or selenate reduced the sulfur oxidation rate.Non-standard abbreviations NEM N-ethylmaleimide - CCCP carbonyl cyanide m-chlorophenyl hydrazone     

嗜酸氧化亚铁硫杆菌ISC铁硫簇系统的合成

【目的】铁硫簇是最古老的一种氧化还原中心,它普遍存在于所有生命体内,在光合作用、呼吸作用和固氮作用这三个地球生命最基本的代谢途径中扮演着重要的角色。【方法】以嗜酸氧化亚铁硫杆菌(A.ferrooxidans ATCC 23270)基因组为模板,克隆表达其ISC铁硫簇组装的3个核心蛋白,IscS(半胱氨酸脱硫酶蛋白)、IscU(支架蛋白)和IscA(铁供体蛋白)。【结果】研究发现IscS能催化半胱氨酸脱硫,为铁硫簇的组装提供硫,支架蛋白IscU不具备结合铁的能力,IscA具有较强的铁结合能力。【结论】铁硫簇体外组装证明Fe-IscA在体外能将结合的铁传递给IscS,并在IscU上进行铁硫簇的组装。     

Chemolithoautotrophic growth on elemental sulfur (S°) and respiratory oxidation of S° by Thiobacillus versutus and another sulfur-oxidizing bacterium

Abstract Thiobacillus versutus was shown to grow chemolithoautotrophically under microaerophilic conditions, with crystalline elemental sulfur (S°) and thiosulfate as sole electron source. The exponential growth rate on S° ( μ = 0.106 h⁻¹) measured in batch culture was similar to the reported maximum growth rate on thiosulfate in chemostat cultures. The rates of thiosulfate, S° and sulfite oxidation were measured respirometrically using an oxygen electrode. During growth under air on thiosulfate, as well as under low oxygen pressure on S° and thiosulfate, a relatively strong sulfuroxidizing activity (SOA) was measured. The induction of the SOA on cells growing with thiosulfate and the similar growth rates on S° and thiosulfate strongly suggest that S° could be an important intermediate during thiosulfate utilization.     

Purification and characterization of two new c-type cytochromes involved in Fe2+ oxidation from Thiobacillus ferrooxidans

Abstract Two new c -type cytochromes have been purified from cell membranes of the acidophilic Thiobacillus ferrooxidans . In contrast to a soluble cytochrome c with molecular mass of 14 kDa reported earlier, a membrane-bound cytochrome c with a mass of 21 kDa was solubilized with octylthioglucoside and purified to homogeneity. In addition, a high molecular mass c -type cytochrome (68 kDa) was also solubilized and purified using Triton X-100 as a detergent. Both acid-stable species are partially released during osmotic shock and chloroform treatment of the bacteria; they are integral components in the respiratory chain donating electrons to the terminal cytochrome oxidase.     

Identification of two outer membrane proteins involved in the oxidation of sulphur compounds in Thiobacillus ferrooxidans

Abstract: Shift of three Thiobacillus ferrooxidans strains from Fe(II) to S⁰ or thiosulphate liquid medium caused distinctive changes in the outer membrane protein profile. In addition to a new 55-kDa protein which was synthesized only in the presence of sulphur compounds, a higher expression of a 47-kDa protein was observed. This latter protein appeared to be constitutively synthesized, since it was detectable in small amounts even in tile presence of ferrous iron as sole energy source, but its expression was greatly enhanced when elemental sulphur or thiosulphate were present in the growth medium.     

Mechanism of microbial flotation using Thiobacillus ferrooxidans for pyrite suppression

Microbial desulfurization might be developed as a new process for the removal of pyrite sulfur from coal sluries such as coal-water mixture (CWM). An application of iron-oxidizing bacterium Thiobacillus ferrooxidans to flotation would shorten the periods of the microbial removal of pyrite from some weeks by leaching methods to a few minutes. The floatability of pyrite in flotation was mainly reduced by T. ferrooxidans itself rather than by other microbial substances in bacterial culture as additive of flotation liquor. Floatability was suppressed within a few seconds by bacterial contact. The suppression was proportional to increasing the number of cells observed between bacterial adhesion and the suppression of floatability. If 25% of the total pyrite surface area covered with the bacteria, pyrite floatability would be completely depressed. Bacteria that lost their iron-oxidizing activities by sodium cyanide treatment were also able to adhere to pyrite and reduced pyrite floatability as much as normal bacteria did. Thiobacillus ferrooxidans ATCC 23270, T-1, 9, and 11, which had different iron-oxidizing abilities, suppressed floatability to similar-levels. The oxidizing ability of bacteria did not influence the suppressing effect. These results showed the mechanism of the suppression of pyrite floatability by bacteria. Quick bacterial adhesion to pyrite induced floatability suppression by changing the surface property from hydrophobic. The quick adhesion of the bacterium was the novel function which worked to change the surface property of pyrite to remove it from coal. (c) 1993 John Wiley & Sons, Inc.     

Resistance to heavy metals in different strains of Thiobacillus ferrooxidans

Ten different isolates of Thiobacillus ferrooxidans were studied with regard to their degree of resistance to the metals copper, nickel, uranium, and thorium. Inhibitory concentrations for a particular metal were those which showed a statistically-significant decrease in the amount of ferrous iron oxidized by the bacterium compared to an untreated control. The different isolates had different susceptibilities to the metals tested, and none of the metals had a stimulatory effect. Uranium and thorium were 20 to 40 times more toxic to ferrous iron oxidation than either copper or nickel.     

The reductive reactions of Thiobacillus ferrooxidans on sulphur and selenium

Abstract An investigation into the sulphur oxidation of iron grown Thiobacillus ferrooxidans is reported. A new mechanism for sulphur catabolism in this obligate acidophile, involving the initial reduction of the substrate, is proposed. Evidence to support substrate reduction comes from the evolution of H₂S in both aerobic and anaerobic conditions (O₂ and Fe³⁺ acting as terminal electron acceptors, respectively) and a accurate trapping method of detection is described. Levels of sulphur reduction are such that a role in the full catabolism of sulphur can be envisaged. In addition, red selenium reduction was investigated and the bioenergetic implications for both substrates are discussed.