Papers by Keyword: Acidianus

Abstract: Bioleaching and biooxidation of sulfidic ores and concentrates generate very high acidities and a great of heat, which rise the temperature in the reactors or heaps, and accumulate the sulfur on the surface of the ores. Extremely thermoacidophilic archaea, mainly from the genus of Acidianus, Sulfolobus, Metallosphaera and sulfurisphaera, have great potential to contribute to biomining processes for their inherent tolerance for low pH, high temperature, and high-soluble metal concentrations. Species of the genus Metallosphaera typically grow by aerobic respiration on CO₂ with S⁰, tetrathionate (S₄O₆²⁺), and Fe²⁺ as electron donors, particularly suitble for metal extraction under high temperature by their iron- and sulfur-oxidation ability. Several species from Metallosphaera and Acidianus genera were investigated for their ability and conditions to dissolve various ores under a range of conditions. All of them showed good performance in copper extraction from chalcopyrite, with strain M.cuprina Ar-4 displaying higher activity than others. Surface analysis of chalcopyrite leached with the strain showed the leaching products accumulated on the ores. Our study will cover new understandings on the application of these thermoacidophilic archaea in biomining.

Abstract: In this work we have studied the attachment and colonization of pyrite surfaces by the recently isolated thermophilic archaeon Candidatus Acidianus copahuensis (isolated from the geothermal Caviahue-Copahue system, Argentina). Cells pregrown with sulfur, iron (II) or pyrite were tested. In order to characterize the EPS glycoconjugates of this strain, fluorescent lectins were used. Concanavalin A (ConA) gave the best signal and was selected for further studies. Coupons and grains of pyrite were treated with DAPI (to stain attached cells) and TRITC-ConA (to stain polysaccharides from EPS). Pyrite surfaces were imaged by epifluorescence (EFM) and confocal laser microscopy (CLSM). Initial cell attachment to pyrite grains was estimated to be 26%, 35% and 43% when cells were pregrown with sulfur, iron (II) and pyrite as electron donors, respectively. It was observed that the cell adhesion correlated with an increase of EPS production; both processes were favoured when cells were pregrown with pyrite or iron (II). Also the effect of phosphate (Pi) starvation in the attachment of Acidianus was studied in similar tests using a base medium without Pi. An increase of cell attachment under Pi starvation conditions was detectable.

Abstract: The extremely thermophilic archaea have become a research hotspot in the recent years because of their extreme living conditions, physicochemical characteristics such as the oxidation of sulphur, metal sulphide ore and excellent leaching capability of metal sulphides. A novel thermoacidophilic archaea (ALE1 strain) of the genus Acidianus, Candidatus Acidianus copahuensis, was isolated from the Copahue Volcano area, in Neuquén, Argentina. This strain was able to metabolize different sulphur compounds under aerobic and anaerobic conditions. ALE1 strain was inoculated in M88, a selective medium for thermoacidophilic archaea recommended by DSMZ. Elemental sulphur (S^o) and potassium tetrathionate (T) were used alternatively as the energy source, while oxygen and iron (III) were the electron acceptors in the aerobic and anaerobic tests respectively. All systems were incubated at 70oC in shake flasks. The pH, Eh, [H⁺] and cell concentration were measured. The results from the aerobic test confirm that ALE1 strain was able to oxidize (S^o) and (T) decreasing the pH significantly, reaching the values 1 and 1.5, respectively. A light yellow precipitate was formed only in the inoculated systems in presence of (T). It was characterized by SEM and FTIR techniques showing that only sulphur atoms are bonded together in some way not confirmed yet. In the anaerobic tests, it was found that ALE1 was able to oxidize sulphur and tetrathionate ion transferring electrons to iron (III) acceptor. The Eh decreased in all inoculated systems from nearly 500mV to 300mV approximately. This work shows that ALE1 strain is helping to keep active the sulphur cycle in the Copahue volcanic environment; however the challenge is to elucidate the metabolism involved.

Abstract: This report describes the detection and identification of archaea in several sites located in the area of Copahue volcano, Neuquén province, Argentina by mean of different molecular techniques (PCR, DGGE, DNA sequencing and FISH). In order to study the archaea morphology, cultures were examined using different microscopic techniques (SEM, TEM, EFM and AFM). The corresponding archaea were identified as close relative or members of the genus Acidianus as well as other uncultured archaea clones showing a 93% of similarity to each others.

Abstract: My perceptions of the biohydrometallurgical field span four decades and stem from being a professional microbiologist conducting academic research and research for process development and applications. My experiences have given me an appreciation for knowledge gained through fundamental research and the transfer of this knowledge to development of commercial scale applications of microbial processes. The symposia series for international activities in biohydrometallurgy has been a major factor in advancing knowledge and applications for microbial bioleach systems. The first international biohydrometallurgy meeting was held in Braunschweig, Germany in 1977. This was the predecessor for the International Biohydrometallurgy Symposia. As evident from the Symposia, advances in development and applications of biohydrometallurgy technologies follow an evolutionary, rather than revolutionary progression from demonstration of knowledge at the laboratory scale to engineering commercial plants.