Advanced Materials Research Vols. 71-73

Abstract: The adhesion of microorganisms to minerals is one of the least understood aspects of bioleaching processes. Mineral and microorganism type are determinant factors affecting the capacity of a microbial community to form biofilms in these processes. In this paper the adhesion capacity of different microorganisms to different copper sulfide minerals generally present in bioleaching processes was studied. The minerals, chalcosite, chalcopyrite and pyrite were used and the composition of the microbial population which adhered to the mineral surfaces was determined using the Catalyzed Reporter Deposition Fluorescent In Situ Hybridization (CARD-FISH) technique. This technique involves the fluorescent marking of the cells using specific DNA probes and their observation with a confocal microscope. Three probes were used against the microorganisms: Acidithiobacillus ferooxidans, Acidithiobacillus thiooxidans and Leptospirillum. Polished fragments of the three minerals were placed in a tube with a culture medium which was inoculated with cells from a mixed culture capable of growing at 25°C. The adhered microorganisms were counted with CARD-FISH and compared with the total count which was carried out with DAPI staining. The results show that microorganisms adhered indistinctly to pyrite and chalcopyrite but not chalcosite. It was also observed that in pyrite 60% of the adhered microorganisms were Acidithiobacillus thiooxidans, 35% Acidithiobacillus ferrooxidans, and 1 % Leptospirillum. The remaining 4% were unidentified microorganisms.

Abstract: This work presents an overview of the physicochemical and biological studies carried out along Rio Agrio and in different hot springs belonging to the geothermal Copahue volcano system, in Neuquén Argentina. This is an extreme environment characterized by wide ranges of temperature, pH (<1 to 8) and heavy metals concentration. In these extreme conditions chemolitho-autotrophic bacteria, archaea, heterotrophic bacteria, yeasts and filamentous fungi were detected. Members of Leptospirillum ferrooxidans, Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Acidianus spp., among others, were successfully cultivated and physiological properties of different isolates were determined. Additionally, bioleaching and biooxidation of regional ores were carried out using mixed native cultures.

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: The largest lignite mining area in Europe is located 150 km southeast of Berlin. Acidic lakes exist in this area, known to be caused by marcasite oxidation. Thirty-two samples from the open-pit brown coal-mine Jaenschwalde were analyzed for microorganisms. Cell numbers determined after separation from sand particles revealed concentrations of 102 to 107 microorganisms per g sample. In samples exposed to the air within an hour, up to 4x107 cells were counted. Measurement of metabolic activity by microcalorimetry showed for such samples up to 50 µW per g sand, whereas in heap samples (with low moisture) low or even no activity was measurable. DNA extraction was successful for 28 samples. In 26 samples microbial 16S rRNA genes were amplified by PCR. Acidithiobacillus ferrooxidans and At. thiooxidans specific amplificates were detected by nested PCR in 23 and 10 cases, respectively. A specific signal indicating Leptospirillum ferrooxidans was obtained with nine samples. Random samples were sequenced and showed 96 to 99 % identity with published data of all three species. Surprisingly, in four samples archaeal 16S rRNA genes were amplified by PCR. Sequencing of two samples showed 99 % identity with unidentified or uncultured archaea found in NCBI-databases. Molecular biology results for At. ferrooxidans as well as for At. thiooxidans were supported by successful isolations of pure cultures in 23 cases. Cultivation of the archaea failed so far. These data indicate that iron- and sulfur-oxidizing microorganisms occur at these sites in large numbers. If in addition the evidence for archaea can become verified, a screening for hot spots as the sites of their occurrence would become interesting.

Abstract: Microbial diversity studies of lignite mines of Rajpardi, Amod, Tadkeshwar and Panandhro, Gujarat, India, were carried out by substrate utilization-based, community-structure analysis. In Biologâ EcoPlates out of 31 different substrates, 1 to 28 substrates were metabolized. On the basis of these, similarity index and diversity indices were studied. From an extreme mine site Gram-positive, Gram-negative, fungi and yeasts were isolated and identified. One of the yeasts isolated is for the first time reported from a lignite mine ecosystem Apart from this auto- and heterotrophic iron oxidizers; sulphur oxidizers and sulphate reducers were also isolated. So, lignite mine ecosystems, inspite of the extreme environment showed rich microbial diversity.

Abstract: The biogeochemical activity of microorganisms from sulphide biogeocoenosis in the zones of sulphide copper ores deposits in East Serbia has been studied by us since 1975. All deposits of copper mineralization were dominantly sulphides and arsenic sulphides with the constant presence of pyrite. The obtained results proved that the biochemical and chemical activity of thionic bacteria have an influence on the global pollution of waters. All the waters were characterized by a low pH value and by high Eh values, mineralization (over 7 gL-1) and in total iron (even more than 4 gL-1) dominantly as Fe3+ ions. These waters were characterized by toxic concentrations of copper ions, within the limits from about 2 to almost 200 mgL-1 and arsenic, up to more than 4 mgL-1. These waters partly arrive in an aquifer and the major part flows into surface water¬ courses gravitating towards the Danube River, which empties into the Black Sea. In a hypothetical case, if maximum concentrations of copper and arsenic and maximum capacity of the springs are considered, under the assumption that the pollutants do not precipitate on the way to the main recipient, the striking information is obtained that the Danube River receives about 31 t of copper and more than 0.6 t of arsenic per annum from one place alone, which undoubtedly points to the contribution of thionic bacteria as "biological agents" to global pollution of surface and ground waters.

Abstract: Rio Tinto, a natural extreme acidic environment with a rather constant acidic pH and a high concentration of heavy metals, is the product of the metabolic activity of chemolithotrophic microorganisms thriving in the rich complex sulfides of the Iberian Pyritic Belt. Up to now the microbial characterization has been made mainly in the water column and biofilm samples. Since all ferric reducing activities will not benefit the bioleaching operations, we consider it critical to ascertain the ecology and metabolic properties of the microorganisms inhabiting the anoxic part of the sediments, to facilitate the design and control the operation of heap bioleaching processes, maximizing their efficiency. The implication of these microorganisms in biohydrometallurgical operations is discussed.

Abstract: A 1.2 km long effluent from La Zarza-Perrunal mine (Iberian Pyritic Belt, IPB) was characterized and compared with Río Tinto. In La Zarza effluent microbial oxidation of ferrous iron is responsible for the drastic increase in ferric iron, from a ratio of Fe(III)/Fetotal of 0.11 at the origin, up to 0.99 downstream. Prokaryotic and eukaryotic diversity throughout the effluent were determined. Bacteria related to the sulfur cycle as well as iron-reducing bacteria were mainly detected near the anoxic origin. Iron-oxidizing microorganisms increased along the course of the effluent following an increase in the oxygen content in the water column. Eukaryotic diversity varied drastically along the effluent. Rio Tinto (92 km length) is a natural extreme acidic environment with a rather constant acidic pH (mean pH value 2.3) and a high concentration of heavy metals. The Tinto ecosystem is under the control of iron [1]. The geomicrobiological comparisons of both habitats were performed to unravel some basic questions of biohydrometallurgical interest.

Abstract: The aim of this work was to determine the microbial diversity of the acid mine drainage (AMD) material collected at an abandoned pyrite mine in Ouro Preto, Brazil. AMD samples were compared to a nickel sulfide column bioleaching pregnant solution which was used as reference. Fluorescent in situ hybridization analyses (FISH) and Denaturing Gradient Gel Electrophoresis (DGGE) were used. FISH analysis was carried out using specific 16S rRNA probes. The extracted DNA was amplified using universal primers for bacterial 16S rRNA genes and analyzed by DGGE. Acidithiobacillus. ferrooxidans was not detected in AMD samples. However, the presence of Acidithiobacillus thiooxidans was confirmed. In other hand, in the bioleaching tanks samples studied, both bacteria species were detected. The non-identified DNA bands were cloned and sequenced for complete characterization.