Papers by Keyword: Sulfobacillus

Abstract: The goal of the present work was to compare the rates of pyrite oxidation by different microorganisms, representatives of the groups predominating in biohydrometallurgical processes. The experiments were conducted in flasks with 100 mL of the medium containing mineral salts, 0.02% of yeast extract, and 2 g of pyrite at 45°C on rotation shaker (200 rpm) for 30 days. Strains Acidithiobacillus caldus MBC-1, Sulfobacillus thermosulfidooxidans VKMV 1269^T, and Acidiplasma sp. MBA-1 were used in the study. Different combinations of the strains were used in the experiments (pure cultures of S. thermosulfidooxidans VKMV 1269^T, Aсidiplasma sp. MBA-1, A. caldus MBC-1, as well as mixed cultures S. thermosulfidooxidans VKMV 1269^T + A. caldus MBC-1, Aсidiplasma sp. MBA-1 + A. caldus MBC-1, S. thermosulfidooxidans VKMV 1269^T + Aсidiplasma sp. MBA-1). Iron concentrations in the medium were the highest in the variants “S. thermosulfidooxidans VKMV 1269^T + A. caldus MBC-1”, “Aсidiplasma sp. MBA-1 + A. caldus MBC-1”, and “Sb. thermosulfidooxidans VKMV 1269^T + Aсidiplasma sp. MBA-1” and achieved 3.8, 3.5, and 3.3 g/L, respectively. Iron concentration in sterile control as well as in the experiments with pure cultures of Aсidiplasma sp. MBA-1 and A. caldus MBC-1 were very low. It demonstrated that in these variants pyrite was almost not oxidized. In the experiment with the pure culture of S. thermosulfidooxidans VKMV 1269^T, the rate of oxidation was high during 10 d of the experiment but then the oxidation activity drastically decreased. The ferric iron concentration achieved a maximum of 1.8 g/L and then decreased, whereas the ferrous iron concentration began to increase. Revealed differences in pyrite oxidation rates can be explained by differences in the physiological properties between the microorganisms. Results of the present work suggest that different groups of microorganisms have different impact in pyrite biooxidation.

Abstract: Resistance of microorganisms predominating in biohydrometallurgical processes including bacteria of the genus Sulfobaсillus and archaea of the genus Acidiplasma to ferric iron ions was studied. Capabilities of the strains for growth and ferrous iron oxidation in the media containing high concentrations of ferric iron ions (of 250 to 1000 mM) were evaluated. Ferric iron ions significantly inhibited oxidative activity and growth of the studied microorganisms. It was revealed that bacteria of the genus Sulfobacillus were not able to oxidize ferrous iron actively when ferric iron concentration exceeded 500 mM, whereas archaea of the genus Acidiplasma completely oxidized ferrous iron in the medium containing 1000 mM of Fe³⁺. Growth of the microorganisms was inhibited by relatively low concentrations of ferric iron. Microorganisms did not grow in the medium containing more than 750 mM of Fe³⁺ and cells of all studied strains lysed in presence of high concentrations of ferric iron. It was shown, that archaea of the genus Acidiplasma of the family Ferroplasmaceae were more resistant to high concentrations of ferric iron than bacteria of the genus Sulfobacillus. The results obtained are important for understanding of the regularities of the formation of microbial communities performing technological processes.

Abstract: Bacteria of the genus Sulfobacillus are successfully used in biotechnologies of treatment of sulfide ore materials. However, energy processes are still poorly understood in sulfobacilli. Several enzymes encoded in the genomes of sulfobacilli are putatively involved in the initial phase of Fe²⁺ oxidation. Cytochromes c, sulfocyanins, and rusticyanin-like proteins were revealed in genomes of these bacteria. Thus, a membrane bound cytochrome c can be reduced directly by Fe²⁺, and electrons can be further transferred to sulfocyanin, rusticyanin or some other components of the transport chain. HPLC identification of prosthetic groups of cytochromes predicts the possible presence of heme c in the cells of thermotolerant sulfobacillus. Determination of metal content in the cells shows that sulfobacillus harbours higher levels of copper ions under specific conditions. This can be explained by higher expression of copper-containing proteins, including cupredoxins.

Abstract: In this study, initial attachment to and biofilm formation of Sulfobacillus thermosulfidooxidans DSM 9293^T on pyrite in the presence of Leptospirillum ferriphilum DSM 14647^T were investigated. Interactions of S. thermosulfidooxidans^T and L. ferriphilum^T were studied by means of monitoring attachment behavior and biofilm formation on pyrite. Our preliminary results showed that 1): Pre-established biofilms of L. ferriphilum^T had effects on attachment of S. thermosulfidooxidans^T to pyrite; 2): physical contact between cells of L. ferriphilum^T and S. thermosulfidooxidans^T on pyrite were visible 3): Pyrite leaching by cells of S. thermosulfidooxidans^T was inhibited by the presence of inactive cells of L. ferriphilum^T.

Abstract: The ferrous iron oxidation by mixed culture of moderately thermophilic microorganisms (Sulfobacillus thermosulfidooxidans Sh 10-1 and Acidiplasma MBA-1) was investigated in continuous experiments in three packed-bed reactors connected in series at temperature 55°C, and a pH of 1.0. Two solutions were used in the experiments. The first one contained (g L^-1) 59 Fe²⁺, the second one contained (g L^-1) 59 Fe²⁺, 16 Fe³⁺, 2 Cu²⁺, 2 Zn²⁺. The hydraulic retention time was 120 hours. Iron oxidation rates in the experiment with the first solution were 0.5, 0.35, and 0.2 g L^-1 h^-1 in first, second and third reactor, respectively. The oxidation rates in the experiment with the second solution were 0.3, 0.2, and 0.185 g L^-1 h^-1 in first, second and third reactor, respectively. Iron oxidation efficiencies in the experiments with the first and second solutions were 77% and 47%. Stable continuous iron oxidation at high temperature was successfully demonstrated, but further investigations are required for improving the rate and efficiencies of oxidation.

Abstract: Solvent extraction (SX) used for the recovery of copper is a primary low-cost hydrometallurgical process applied extensively in cases like commercial bioleaching operations. Bioleaching solutions during SX treatment are exposed to important concentrations of organic extractants, a step that has a detrimental impact on microbial activity. The following work studies and determines the effect of this exposure on the re-establishment of growth and activity of different bioleaching microorganisms after contact and phase separation. Different bioleaching iron and sulfur -oxidizing microorganisms were tested. After contact with an industrially utilized organic extractant (LIX 84IC as extractant and Oxform SX12 as solvent), cultures were grown and their substrate utilization monitored. Acidithiobacillus ferrooxidans showed only a slight increase in doubling time without significant latency period. On the contrary, for both Sulfobacillus species studied, S. thermosulfidooxidans and S. thermotolerans, were strongly impacted showing important lag phases before growth could take place. Additionally, the SX reagent showed disruption of cell walls and protein liberation during contact with all the different strains studied.

Abstract: Ferrous sulfate was added to batch cultures of Sulfobacillus (Sb.) acidophilus, Sb. thermosulfidooxidans and Sb. sibiricus during growth on tetrathionate. Soluble ferrous ion and polythionate concentrations were used as a measure of substrate utilisation. Sb. thermosulfidooxidans switched from utilising polythionates to exclusively oxidising ferrous ions, only then oxidising the remainder of the polythionates. Sb. sibiricus and Sb. acidophilus did not cease polythionate oxidation but utilised both substrates concurrently after ferrous ion addition. None of the cultures tested exhibited preferential polythionate utilisation, even though they were utilising polythionate prior to the addition of ferrous ions.

Abstract: An integrated bio-processing scheme was devised and tested in the laboratory for recovering copper, or other base metals, from pregnant leach solutions (PLS) using a two-step process involving both iron-reduction, and sulfate-reduction for H₂S generation and sulfide precipitation, as a potential alternative to conventional SX-EW. Reduction of ferric iron in the PLS was achieved using iron-reducing Acidithiobacillus spp. and Sulfobacillus thermosulfidooxidans in column reactors containing elemental sulfur as electron donor. Analysis of the column reactor effluents showed not only that most of the ferric iron was reduced to ferrous, but also that all of the copper (II) had been reduced to copper (I), i.e. cuprous copper. This copper (I) appeared to be complexed as it was not oxidized when exposed to ferric iron nor precipitated as a copper-sulfide when exposed to either sodium sulfide or H₂S. The data suggested that copper (II) was reduced and the resulting copper (I) complexed, with both reactions probably mediated by sulfur oxy-anions produced indirectly by the bacteria, in the anoxic sulfur column bioreactors. It was also noted that copper (I) produced chemically by reduction of copper (II) by hydroxylamine was more toxic to axenic cultures of Acidithiobacillus spp. and Sb. thermosulfidooxidans than was the copper (I) in the column effluent liquors.

Abstract: Ex-situ and in-situ Tapping Mode AFM were used to investigate responses of attached bacteria to stressful conditions. For ex-situ measurements, the AFM was equipped with a customised re-positioning stage and sample mount to permit re-examination of the same surface area. For in-situ measurements, the inoculated pyrite coupon was immersed in solution in a flow through cell. Initial experiments using Sulfobacillus thermosulfidooxidans indicated that increased acidity promoted EPS production but increased salinity resulted in cell detachment.

Abstract: Arsenic resistance genes were isolated from the moderately thermophilic, Gram-positive iron and sulfur-oxidizing bacterium, Sulfobacillus thermosulfidooxidans. Only arsR and arsB genes were present and attempts to identify an arsC using degenerate PCR primers or dependent arsC genes as probes in Southern hybridization experiments were unsuccessful. Although enhanced resistance to arsenite was not detected when the ars genes were cloned in Escherichia coli, the kumamolisin-As and arsRB genes were induced by arsenite. RT-PCR experiments suggested that transcription of the cloned kumamolisin-As-like and arsRB genes is linked in Escherichia coli, but not in Sb. thermosulfidooxidans. The gene order kumamolisin-As precursor, arsR and arsB was maintained among three strains of Sb. thermosulfidooxidans isolated from three continents. Southern hybridization using a Sb. thermosulfidooxidans arsB gene fragment as a probe gave a positive hybridization signal using S. acidophilus but not with S. thermotolerans genomic DNA. Comparison of partial sequence data of the arsB and 16S rRNA genes suggested that the two types of genes have undergone a similar evolutionary history and therefore that the arsB genes were present in the ancestral Sulfobacillus before its divergence into species.