Bacterium Acidithiobacillus Ferrooxidans Research Articles

Application of capillary electrophoresis combined with conductometric and UV detection to monitor meteorite simulant bioleaching by Acidithiobacillus ferrooxidans.

The importance of microorganisms and biotechnology in space exploration and future planets colonization has been discussed in the literature. Meteorites are interesting samples to study microbe-mineral interaction focused on space exploration. The chemolithotropic bacterium Acidithiobacillus ferrooxidans has been used as model to understand the iron and sulfur oxidation. In this work, capillary electrophoresis with capacitively coupled contactless conductivity detection and UV detection was used to monitor bacterial growth in a meteorite simulant by measuring the conversion of Fe2+ into Fe+3 . The effect of Co2+ and Ni2+ (metals also found in meteorites) on the bacterial growth was also evaluated. The presented method allowed the analyses of all metals in a single run (less than 8 min). The background electrolyte was composted of 10 mmol/L α-hydroxyisobutyric acid/Histidine. For comparison purpose, the samples were also analyzed by UV-Vis spectrophotometry. The Fe2+ conversion into Fe3+ by A. ferrooxidans was observed up to 36 h with the growth rate constant of 0.19/h and 0.21/h in Tuovinen and Kelly (T&K) and in meteorite simulant media, respectively. The developed method presents favorable prospect to monitor the growth of other chemolithotropic microorganisms for biotechnology applications.

Bioleaching and Kinetic Investigation of WPCBs by A. Ferrooxidans, A. Thiooxidans and their Mixtures

Bioleaching was used to mobilize Cu, Zn and Ni from waste printed circuit boards (WPCBs) and eliminate hazardous metal species from these wastes. Pulp density (PD) and medium culture are two effective factors which have been optimized in this paper. The bacteria Acidithiobacillus ferrooxidans (A. ferrooxidans) and Acidithiobacillus thiooxidans (A. thiooxidans) and their mixture were grown and adapted in the presence of WPCBs and then used as bioleaching bacteria to solubilize metals from PCBs. The experimental results demonstrated that 15 g/L WPCB is the best solid concentration which can be tolerated by the bacteria. Comparing different inoculation ratios, Cu (86%), Zn (100%) and Ni (100%) were recovered after 25 days of bioleaching, which suggests that the rate of metal recovery is significantly influenced by PD. Kinetics of bioleaching reactions was investigated in this work and the shrinking core model (SCM) was used to describe the kinetics of the process of no pretreated WPCBs. A constrained multi-linear regression analysis using the least square technique was employed to determine the rate controlling mechanism in each operating condition. Based on the results, diffusion through solid product layer was the major controlling mechanism.

Bioadsorption of arsenic from aqueous solution by the extremophilic bacterium Acidithiobacillus ferrooxidans DLC-5

The bioadsorption of heavy metal ions to process industrial and solid wastes is an attractive technology from an economical and environmental point of view. This study investigated the equilibrium, thermodynamics and bioadsorption characteristics of arsenite (iAsIII) and dimethylarsinate (DMAV) by Acidithiobacillus ferrooxidans (A. ferrooxidans) DLC-5 in aqueous solution. Optimum bioadsorption conditions were determined by identifying the optimum temperature, pH, biomass dosage, initial arsenic concentration and contact time. The equilibrium data were then applied to Langmuir and Freundlich isotherm models. The results indicated that the bioadsorption processes for both iAsIII and DMAV involved pseudo-second-order kinetics. Additionally, the bioadsorption of iAsIII and DMAV by A. ferrooxidans DLC-5 was feasible, spontaneous and endothermic under the tested conditions. Fourier transform infrared spectroscopy (FT-IR) showed that –OH and –NH groups were involved in the bioadsorption process. A. ferrooxidans DLC-5 demonstrates potential for use in removing arsenic from aqueous solutions, especially those with very low arsenic concentrations.

New phosphorus biofertilizers from renewable raw materials in the aspect of cadmium and lead contents in soil and plants

Abstract Recycling phosphorus from waste for fertilization purposes appears to be an alternative for non-renewable sources and a solution for managing harmful products of civilisation. Fertilizers from secondary raw materials are considered to be safe to the environment. This study presents an assessment of the effects of five new biofertilizers made from sewage sludge ash and/or animal bones on the content of cadmium and lead in the soil, in wheat grains and straw (test plant), in the mass of the the accompanying weeds and in the post-harvest residues. Biofertilizers were produced in the form of suspension or granules and activated using Bacillus megaterium or Acidithiobacillus ferrooxidans bacteria. They were tested in four field experiments. The Cd and Pb contents of the soil and plant material were determined using the ICP-MS technique. Similar to superphosphate, new biofertilizers showed no change in the Cd and Pb contents of the soil and plants biomass when applied at amounts up to 80 kg; P2O5 ha−1. Both Cd and Pb in the soil and plants occurred naturally, and the amounts were within the acceptable standards. Biofertilizers from renewable raw materials, with low toxic element contents, are not thought to pose a hazard to the soil and plants when applied in reasonable amounts. They can be a substitute for conventional phosphorus fertilizers.

The enhanced effect of Acidithiobacillus ferrooxidans on pyrite based Cr(VI) reduction

Cr(VI) pollution attracted increasing attention in these years due to its toxic and carcinogenic effect on living body. Pyrite based remediation was an economical and efficient way in Cr(VI) reduction. However, the bulk body of pyrite cannot be effectively utilized due to the passivation effect. In this study, Fe/S oxidizing bacteria Acidithiobacillus ferrooxidans was introduced to the reduction system to relieve the inhibition effect, and resultly accelerated pyrite dissolution and increased the corresponding Cr(VI) reduction efficiency. The results showed that pyrite based Cr(VI) reduction was a proton consumption process. Pyrite dissolution in Cr(VI) reduction is inhibited due to the passivation effect when A. ferrooxidans were absent. Reduction efficiency of A. ferrooxidans system is 4.42 times higher than that of chemical system. The highest reduction efficiency was achieved under S/FeS2 ratio 1:1 condition. Cr(VI) were reduced in two ways, fast free Fe(II) reduction and the slowly pyrite surface active sites reduction. The activity of A. ferrooxidans promoted pyrite disulfide bond cleavage and Cr(III) release. In addition, it oxidized intermediate state sulfur Sn2− and S0 to sulfate, which contributed to pyrite dissolution. A. ferrooxidans adhesion and biofilm formation on pyrite surface facilitated passivation layer removal, which was the indicator of the deep interaction between bacteria and mineral. Furthermore, acidophilic bacteria mediated secondary iron mineral formation and Cr(III) coprecipitation. A. ferrooxidans play the roles as the decomposer of pyrite and template of the secondary minerals formation.

A DNA segment encoding the anticodon stem/loop of tRNA determines the specific recombination of integrative-conjugative elements in Acidithiobacillus species

ABSTRACTHorizontal gene transfer is crucial for the adaptation of microorganisms to environmental cues. The acidophilic, bioleaching bacterium Acidithiobacillus ferrooxidans encodes an integrative-conjugative genetic element (ICEAfe1) inserted in the gene encoding a tRNAAla. This genetic element is actively excised from the chromosome upon induction of DNA damage. A similar genetic element (ICEAcaTY.2) is also found in an equivalent position in the genome of Acidithiobacillus caldus. The local genomic context of both mobile genetic elements is highly syntenous and the cognate integrases are well conserved. By means of site directed mutagenesis, target site deletions and in vivo integrations assays in the heterologous model Escherichia coli, we assessed the target sequence requirements for site-specific recombination to be catalyzed by these integrases. We determined that each enzyme recognizes a specific small DNA segment encoding the anticodon stem/loop of the tRNA as target site and that specific positions in these regions are well conserved in the target attB sites of orthologous integrases. Also, we demonstrate that the local genetic context of the target sequence is not relevant for the integration to take place. These findings shed new light on the mechanism of site-specific integration of integrative-conjugative elements in members of Acidithiobacillus genus.

ПЕРЕРАБОТКА УПОРНЫХ СУЛЬФИДНЫХ КОНЦЕНТРАТОВ, СОДЕРЖАЩИХ БЛАГОРОДНЫЕ МЕТАЛЛЫ, НА ОСНОВЕ БАКТЕРИАЛЬНОГО ОКИСЛЕНИЯ

The aim of the research was to evaluate the potential possibility of bacterial oxidation of sulphide minerals of gold-containing flotation pyrite concentrate. The results of studying the concentrate material composition are presented. Laboratory studies of the bacterial oxidation of sulphides are carried out with a mixture of autotrophic bacterial populations consisting of thionic mesophilic bacteria Acidithiobacillus Ferrooxidans, Acidithiobacillus Thiooxidans and Leptospirillum Ferrooxidans. Bacterial adaptation was carried out at a pulp density of 10% solids, followed by an increase to 18%, with a constant measurement of process parameters (pH, Eh, Fe 2+ , Fe 3+ ). Three test experiments were conducted in periodic mode. The optimal parameters of bacterial oxidation were established during the studies: pH, Redox potential, concentration of Fe 2+ , Fe 3+ - ions in the liquid phase of the pulp. The results of chemical analysis of bio-oxidation products are presented. Indicators of gold recovery during cyanide leaching from bacterial oxidation cakes of BIOX-1,2 experiments were respectively 77.99% and 76.86%; in the test without microorganisms, the value was 60.47%. The results of the studies demonstrate the possibility of processing sulphide concentrates by bacterial oxidation.

Optimization of parameters affecting recovery of copper from Sarcheshmeh low-grade sulfide ore using Bioleaching

In this work, the parameters affecting the recovery of copper from the low-grade sulfide minerals of Sarcheshmeh Copper Mine were studied. A low-grade sulfide ore was used with a copper grade of 0.25%, which was about 28% of the mineral oxide, and the sulfide minerals made up the rest. Much more sulfide minerals were found to be pyrite and most of the gangue minerals were quartz, anorthite, biotite, and muscovite. In order to investigate, simultaneously, the solids (10 to 20%) and acidity (1.5 to 2.5) and shaking (110 to 150 rpm), the separation of bacteria from Sarcheshmeh Copper Mine was carried out. After adjustment of the sample, bio-leaching tests were performed in accordance with the pattern defined by the software DX7 in shaking flasks, and the Cu recovery was modeled and optimized using the response surface methodology. The influential parameters were comprehensively studied. The central composite design methodology was used as the design matrix to predict the optimal level of these parameters. Then the model equation was optimized. The results obtained showed that increasing solids (from 10 to 20%) was bad for bacteria. The highest copper recovery was equivalent to 69.91%, obtained after 21 days at 35 degrees using the Acidi Thiobacillus Ferrooxidans bacteria and a K9 medium with a pulp density of 10% and pH 1.5.

Functionality of tRNAs encoded in a mobile genetic element from an acidophilic bacterium

ABSTRACTThe genome of the acidophilic, bioleaching bacterium Acidithiobacillus ferrooxidans, strain ATCC 23270, contains 95 predicted tRNA genes. Thirty-six of these genes (all 20 species) are clustered within an actively excising integrative-conjugative element (ICEAfe1). We speculated that these tRNA genes might have a role in adapting the bacterial tRNA pool to the codon usage of ICEAfe1 genes. To answer this question, we performed theoretical calculations of the global tRNA adaptation index to the entire A. ferrooxidans genome with and without the ICEAfe1 encoded tRNA genes. Based on these calculations, we observed that tRNAs encoded in ICEAfe1 negatively contribute to adapt the tRNA pool to the codon use in A. ferrooxidans. Although some of the tRNAs encoded in ICEAfe1 are functional in aminoacylation or protein synthesis, we found that they are expressed at low levels. These findings, along with the identification of a tRNA-like RNA encoded in the same cluster, led us to speculate that tRNA genes encoded in the mobile genetic element ICEAfe1 might have acquired mutations that would result in either inactivation or the acquisition of new functions.

Examining the Effects of Typical Reagents for Sulfide Flotation on Bio-Oxidation Activity of Ferrous Iron Oxidizing Microorganisms

Mineral separation by froth flotation is widely used around the world for the beneficiation of sulfide ores. Flotation products (typically concentrate) are subjected to metallurgical processes for metal extractions. Bioleaching as a metallurgical procedure indicated many advantages over other traditional techniques (pyro- and hydro-metallurgy). However, organic flotation reagent residuals on the surface of minerals are effective on biological activities of microorganisms. In this work, to extensively study these effects, typical sulfide flotation collectors (Sodium ethyl-xanthate, Potassium isopropyl-xanthate, Potassium isobutyl-xanthate, Potassium amyl-xanthate, and Dithiophosphate (Aero)), and frothers (pine oil (PO) and methyl isobutyl Carbinol (MIBC)) were used in the presence of various bacteria (Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans) to investigate their effects on bio-oxidation. The results of this investigation can be used to better understand the mechanisms of bio-activities when reagent residues are on the surface of flotation products and they will feed to the bioleaching process.

EIS Studies of Chalcopyrite Involving Iron(II) Ions

In this work, we present an Electrochemical Impedance Spectroscopy (EIS) study using a carbon paste electrode modified with chalcopyrite (CuFeS2) containing 50 wt% of the mineral (particle size < 38 μm) and graphite (particle size < 20 μm) in naturally aerated salt acid solutions (pH 1.8) without and with the addition of 0.100 mol L-1 of ferrous ions. The aim was to evaluate the influence of the solution potential on the behavior of chalcopyrite electrode in the presence and absence of iron (II) ions. Additionally, we evaluated the influence of the bacteria Acidithiobacillus ferrooxidans in the system containing iron (II) ions without applying potential. Therefore, EIS was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The results showed that the combination of iron (II) ions with the imposition of low potential values (0.100 Fe2+ ions with +0.300 V/Ag|AgCl|KCl3mol/L) activates the chalcopyrite surface and enhances the copper recovery.

Assessment of catalytic activities of selected iron hydroxysulphates biosynthesized using Acidithiobacillus ferrooxidans for the degradation of phenol in heterogeneous Fenton-like reactions

Schwertmannite and jarosite, two secondary Fe(III)-hydroxysulfate minerals abundant in acid-mine drainage, can be biosynthesized by an Fe-oxidizing bacterium Acidithiobacillus ferrooxidans, but the differences of their catalytic activities in heterogeneous Fenton-like reactions are still unclear to date. In the present study, the catalytic activities of biosynthesized schwertmannite and jarosite were compared through investigating the heterogeneous Fenton-like degradation of a target organic pollutant phenol. Results showed that these two catalysts efficiently catalyzed heterogeneous Fenton-like degradation of phenol, and the degradation in both systems consisted of an induction period (first-stage) and a followed rapid degradation stage (second-stage). Schwertmannite exhibited a much higher catalytic capacity than jarosite, because of its shorter induction period and higher kinetic rate (k) of the second-stage, but jarosite catalytically degraded phenol in a much wider pH range (pH 3.0–7.5) over schwertmannite (pH 3.0–4.5). Based on the results of radical scavenger effect, H2O2 decomposition, Fe leaching and X-ray photoelectron spectroscopic (XPS) analysis, similar catalytic mechanisms were proposed in schwertmannite/H2O2 and jarosite/H2O2 systems, in which the induction period can be ascribed to the activation of catalysts by H2O2 and the second-stage was mainly attributed to the homogeneous Fenton reaction in bulk solution. During the catalytic degradation of phenol, catechol was firstly accumulated and was then further decomposed into smaller molecular organic acids. The repeated uses of schwertmannite and jarosite for phenol degradation manifested their stability and reusability as Fenton-like catalysts for the degradation of organic pollutants.

Quantum-chemical substantiation of the properties of the bioreagent oxidizing non-ferrous metal sulfides

The paper determines the structural formula and quantum chemical characteristics of the most energetically probable, stable conformation of the bioreagent molecule formed during the oxidation of iron (II) ions by the autotrophic mesophilic iron-oxidizing bacteria Acidithiobacillus ferrooxidans in a solution of sulfuric acid consisting of iron (III) ion and three acid residues of glucuronic acid. The bioreagent oxidant is widely used in the industry for leaching metals from non-ferrous sulfide ores and enrichment concentrates. The quantum chemical characteristics of the bioreagent molecule are analyzed in comparison with the characteristics of anhydrous iron (III) sulphate, also used in hydrometallurgy as an oxidizer. The structure and quantum-chemical characteristics are studied using the method of molecular computer simulation, the theory of boundary molecular orbitals, and the Pearson principle. It has been established that the most energetically probable, stable conformation of the bioreagent molecule contains the acid residues of glucuronic acid of a non-cyclic structure. According to the research results, the bioreagent refers to the more rigid Lewis acid – electron acceptor – than iron (III) sulphate. The bioreagent molecule is less polarized, characterized by lower absolute electronegativity and 2 times larger volume. A theoretical substantiation of the greater persistence of primary sulphides – pyrite, pentlandite, chalcopyrite, relative to the secondary minerals – pyrrhotine, chalcocite and covellite is proposed based on the calculated values of the boundary molecular orbitals, absolute stiffness and electronegativity of iron, copper and nickel sulfides. The bioreagent characteristics that determine the interaction efficiency – volume, heat of formation, steric energy and its components, total energy, etc. are many times greater than for Fe2(SO4)3. The high oxidative activity of the bioreagent relative to Fe2(SO4)3 can be justified by the higher partial charge of the iron atom, the greater length of bonds between atoms, the lower energy of the lower free molecular orbitals and the greater degree of charge transfer during the interaction of the bioreagent with the sulfide minerals.

Improving gold recovery from refractory gold ores through biooxidation using iron-sulfur-oxidizing/sulfur-oxidizing mixotrophic bacteria

The effect of biooxidation (BIOX) pre-treatment of refractory gold concentrates using mixotrophic and chemolithotrophic bacteria on the gold extraction during cyanidation of the concentrates at neutral pH was studied. A series of biooxidation and cyanidation of the biooxidized concentrates was carried out using three strains of bacteria; two mixotrophic bacteria of SKC1 and SKC2 and a chemolithotrophic bacteria Acidithiobacillus ferrooxidans (AC). Two distinct types of refractory gold concentrates with high sulfur content (i.e. S>20%) and low sulfur content (i.e. S<5%) were used. The experimental results showed that biooxidation with any of the three bacteria generally showed positive effect on the gold extraction. The highest gold extraction (91.4%) from high sulfur-concentrate was achieved by BIOX with SKC2 for 14days. It was 18% higher than the extraction level of direct cyanidation of the untreated concentrate. Biooxidation with AC, on the other hand, resulted in only slight increase of gold extraction from both concentrates due to the high solution pH of >5.0 which is not a suitable living environment for the bacteria. Cyanide consumption for cyanidation of the biooxidized concentrates with both mixotrophic bacteria was significantly increased due to reactions of sulfur and iron species that were precipitated during the biooxidation step with cyanides to form thiocyanate and ferrocyanide ions.

Editorial: Current Challenges and Future Perspectives on Emerging Bioelectrochemical Technologies.

Editorial: Current Challenges and Future Perspectives on Emerging Bioelectrochemical Technologies.

Simulating the main stages of chalcopyrite leaching and bioleaching in ferrous ions solution: An electrochemical impedance study with a modified carbon paste electrode

In this work, we present an electrochemical study using a carbon paste electrode modified with chalcopyrite (CuFeS2) in solution A of T&K medium with different ferrous ion concentrations, in the absence and presence of the bacterium Acidithiobacillus ferrooxidans. The aim was to evaluate the influence of ferrous ions and bacteria on the electrochemical behavior of chalcopyrite. Electrochemical impedance spectroscopy (EIS) was used to investigate the processes occurring at the electrode/solution interface in the different systems, considering the charge transfer reactions involving chalcopyrite and ferrous ions, the presence of a multicomponent layer, and diffusion. The main changes in the chalcopyrite response occurred before 67h or 43h of immersion, in the absence or presence of ferrous ions, respectively, indicating that the surface oxide layer present on chalcopyrite was dissolved faster in the presence of ferrous ions. The addition of bacteria decreased the charge transfer reaction resistance, especially when ferrous ions were present. In the presence of Fe2+, sulfur and jarosite were detected in the solid residues after leaching, while only jarosite was detected in the bioleaching experiment. The results suggested that ferrous ions accelerated the dissolution of chalcopyrite, and that overlayers including biofilms did not halt chalcopyrite dissolution, indicating that there was no passivation.

Not-So-Large Charge: Deep-Sea Microbes Directly Consume Electricity

The bacterium Acidithiobacillus ferrooxidans can thrive on electrons obtained directly from an electrode when its usual energy source—iron—is unavailable. This switch from using an inorganic element to consuming electricity itself as a source of electrons “demonstrates a previously unknown bioenergetic versatility,” say Ryuhei Nakamura of the RIKEN Center for Sustainable Resource Science in Saitama, Japan, and his collaborators. Thus, electrons might be a primary energy source for these bacteria while dwelling within the deep-sea hydrothermal ecosystems in which they are found, they point out. Details appeared in the September 2015 Frontiers in Microbiology (doi:10.3389/fmicb.2015.00994).

Adsorption Kinetics and Surface Characterization of Microorganisms Grown under Different Conditions

The adsorption of bacteria onto minerals is the premise for bioleaching and plays an important role in minerals oxidation. Understanding of the adsorption kinetics onto the surface will give information on the effectiveness of bioleaching. Three kinds of mixed bacteria (Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Sulfobacillus) were cultured in different substrates - copper concentrate, elemental sulfur and ferrous iron and adsorbed onto different solid surface of elemental sulfur, silica and copper concentrate. Adsorption kinetics was examined and surface properties were investigated by Zeta-potential and FT-IR spectroscopy. Bacterial adsorption equilibrium data for bacteria grown on three different substrates were well fitted to Freundlich isotherms, indicating inhomogeneous and selective adsorption. Microorganisms grown on copper concentrate and S0 showed similar adsorption kinetics whereby cell adsorptions proceeded rapidly and reached equilibrium within 30 mins of interaction. With the average KF value of 46.2, most copper concentrate-grown cells were strongly adsorbed to three solid surfaces. Microorganisms grown on copper concentrate and S0 also showed higher hydrophobicity and higher isoelectric point (IEP) (pH 3.4-3.8) as compared to the soluble Fe2+-grown cells (pH 2.1), indicating higher amount of EPS and proteins on the surfaces. The FT-IR spectra indicated the presence of COOH, NH2, OH and PO4 groups on all cell surfaces. However, more proteinaceous compounds were found on cells grown on copper concentrate and S0 substrates.

Biooxidation of Carbonaceous Refractory Gold Ores by an Iron-Sulfur-Oxidizing Mixotrophic Bacterium at Neutral pH

The ability of an iron-sulfur-oxidizing mixotrophic bacterium to treat two types of sulfide-rich carbonaceous refractory gold concentrates from Sulawesi and Sumatra in Indonesia was studied in comparison with an acidophilic chemolithotrophic bacterium Acidithiobacillus ferrooxidans. Over the course of the biooxidation experiments, the pH of the solution tended to rise (pH&gt;5) due to the high content of acid-consuming minerals such as carbonates in both concentrates. Ferric ions were frequently observed to precipitate due to high solution pH. The BIOXskc employed in this study was able to increase the gold extraction from low sulfidic carbonaceous refractory gold concentrates by ~15% higher than that by using At. ferrooxidans. It was also capable of treating carbonaceous matters which causes preg-robbing effect and retaining iron in ionic form due presumably to the production of extracellular polymeric substances (EPS) under high solution pH. Nevertheless, BIOXskc also reduced the gold extraction yield of high sulfidic gold concentrates because of passivation effect. It is suggested that the precipitation of iron and sulfur on the surface of sulfide minerals during biooxidation may prevent cyanide ion contact with gold.

Draft genome sequence of extremely acidophilic bacterium Acidithiobacillus ferrooxidans DLC-5 isolated from acid mine drainage in Northeast China

Acidithiobacillus ferrooxidans type strain DLC-5, isolated from Wudalianchi in Heihe of Heilongjiang Province, China. Here, we present the draft genome of strain DLC-5 which contains 4,232,149 bp in 2745 contigs with 57.628% GC content and includes 32,719 protein-coding genes and 64 tRNA-encoding genes. The genome sequence can be accessed at DDBJ/EMBL/GenBank under the accession no. JNNH00000000.1.