Advanced Materials Research Vol. 825

Abstract: Microbial consortia taken from an extreme environment were grown at different temperature and enrichment media. The consortia response to environmental changes was evaluated in order to investigate their metabolic flexibility. The molecular technique, DGGE (denaturing gel gradient electrophoresis) was carried out to evaluate the biodiversity. The results show that each consortium was able to grow according to the available resources, demonstrating their flexibility. A selective development was detected when growing conditions were similar to those found in the natural environment even though some species were able to grown even in conditions far away from those present in the sampling sites.

Abstract: In this work we have examined the bacterial diversity from the hot spring sediment Agua del Limón (AL1) present at the geothermal Caviahue-Copahue system using a combination of molecular and cultivation techniques, with particular emphasis on indigenous anaerobic prokaryotes. Microorganisms involved in the iron (Acidithiobacillus ferrooxidans and Leptospirillum spp.) and sulphur (Acidithiobacillus spp., Thermotogales-like bacteria, Thiomonas sp., and Desulfurella sp.) cycles were identified in the clone library. Although no obvious sulfate-reducing bacteria were detected by culture-independent techniques, several isolates related to the mesophilic, spore-forming sulfate-reducer "Desulfobacillus acidavidus" strain CL4 were isolated at 30°C and 40°C. The 16S rRNA gene of another isolate showed 94% similarity to Desulfotomaculum thermobenzoicum. Sulfate-reducing enrichment cultures of the Copahue samples were also dominated by "Dsb. acidavidus" CL4.

Abstract: Copahue is a geothermal field located in the Northwest corner of Neuquén province in Argentina. It is dominated by the still active Copahue volcano. In the area there are many acidic pools, hot springs and solfataras with different temperature and pH conditions that influence their microbial diversity. On the surrounding rocks and the borders of the pools, where water movements and thermal activity are less intense, many biofilms can be found. They have different aspects and structure, and they present less extreme temperature and pH conditions than the ponds and hot springs. Biofilms are a different ecological niche and they have different microbial community structure. In this study carried out by molecular ecology techniques, mainly 16S and 18S rRNA sequencing, we report a strong presence of cyanobacterias, cloroflexi and eukaryotes, not detected in previous biodiversity studies done on water samples. Almost no acidophilic bacteria were found, with the exception of members of genus Thiomonas, also found in the acidic pools. Archaea were detected only in one of the biofilms and the structure of that community seems to be similar to those found in water samples, with many uncultured species mainly related to order Sulfolobales. The aim of this study is to assess microbial community diversity in the biofilms present in this acidic geothermal area, with particular emphasis on detection of cyanobacterias and eukaryotes with potential biotechnological applications like production of alternative energy sources, synthesis and accumulation of biomolecules with antiviral or antibiotic activities or potential ability to bioremediate contaminated areas.

Abstract: The geomicrobiological characterization of Río Tinto, an extreme acidic environment, has proven the importance of the iron cycle, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals) but also in maintaining the high level of microbial diversity detected in the water column and the sediments. The extreme conditions detected in the Tinto basin are not the product of industrial contamination but the consequence of the presence of an underground bioreactor that obtains its energy from the massive sulfide minerals of the Iberian Pyrite Belt (IPB). To test this hypothesis, a drilling project (IPBSL) to intersect ground waters interacting with the mineral ore is under way, to provide evidence of subsurface microbial activities. A dedicated geophysical characterization of the area selected two drilling sites due to the possible existence of water with high ionic content. Two wells have been drilled in Peña de Hierro, BH11 and BH10, with depths of 340 and 630 meters respectively, with recovery of cores and generation of samples in anaerobic and sterile conditions. The geological analysis of the retrieved cores showed an important alteration of mineral structures associated with the presence of water, with production of expected products from the bacterial oxidation of pyrite. Ion chromatography of water soluble compounds from uncontaminated samples showed the existence of putative electron donors, electron acceptors, as well as variable concentration of metabolic organic acids, which suggest the presence of an active subsurface ecosystem associated to the high sulfidic mineral content of the IPB. Enrichment cultures from selected samples showed evidences of an active iron and sulfur cycle, together with unexpected methanogenic, methanotrophic and acetogenic activities. The geological, geomicrobiological and molecular biology analyses which are under way, should allow the characterization of this ecosystem of biohydrometallurgical interest

Abstract: The microbiology and geochemistry of two pit lakes at former metal mines (Cueva de la Mora and Guadiana) located in the Iberian Pyrite Belt in Spain were investigated. Both lakes are meromictic, with more acidic and oxidized mixolimnion zones overlying anoxic monimolimnion zones, and transitional chemoclines with characteristic sharp pH and redox potential gradients. Stratification in the pit lakes was reflected in the size and diversity of the microbial communities in the different zones, with the chemocline of Cueva de la Mora pit lake and the hypolimnion (the lower layer of the mixolimnion) in the Guadiana pit lake containing the most complex and abundant microbial communities. Acidophiles that oxidize and reduce both iron and sulfur co-exist within the chemocline/hypolimnion zones, implying that biogeochemical cycling of these two elements is most intense within these layers of the pit lakes. Novel species of bacteria were detected using molecular techniques and, in some cases, isolated and partially characterized. The latter included a novel acidophilic iron-reducing gammaproteobacterium (Acidibacter ferrireducens)

Abstract: Abstract. In mining areas in which sulfur-containing ores are exposed, the oxidation of sulfides leads to the formation of acidic mine drainage (AMD) waters. Both traditional and molecular microbial studies have shown that chemolithotrophic sulfur- and iron-oxidizing bacteria are responsible for this activity. The Iberian Pyrite Belt (IPB), located in southwestern Spain represents one of the world’s largest accumulations of mine wastes and AMD waters. Mineralogical and textural characteristics of the IPB ores favor the oxidation and dissolution of pyrite and the subsequent formation of AMD waters. Acidic pit lakes in the IPB are a hotspot for this activity. These pit lakes are former open pit mines where ores have been exposed leading the formation of AMD waters. At present, there are more than 25 of these pit lakes between the provinces of Huelva and Seville (SW Spain). This work reports the physical properties, hydrogeochemical characteristics, and microbial diversity of two pit lakes located in the IPB Nuestra Señora del Carmen (NSC), and Concepción (CN). Both pit lakes are acid (pH 2-4) and showed chemical and thermal stratification with well defined chemoclines. One particular characteristic of NSC is that it has developed a chemocline very close to the surface (2 m depth). Microbial community composition of the water column was analyzed by 16S and 18S rRNA gene cloning and sequencing. The microorganisms detected in NSC are characteristic of acid mine drainage (AMD), including iron oxidizing bacteria (Leptospirillum) and facultative iron reducing bacteria and archaea (Acidithiobacillus ferrooxidans, Actinobacteria, Acidimicrobiales, Ferroplasma) detected in the bottom layer. Diversity in CN was higher than in NSC. Microorganisms known from AMD systems (Acidiphilium, Acidobacteria and Ferrovum) and microorganisms never reported from AMD systems were both identified.

Abstract: Acidic saline lake systems are an uncommon type of natural extreme environment described in Northern Chile and in Australia. These environments are considered a terrestrial analogue to certain ancient Martian terrains and a source of new material for biotechnological applications as bioleaching at high ionic strength conditions and biological systems for precipitating metal sulfides. The aim of this study is to describe the occurrence of redox couples that support prokaryotic life in the system and to obtain representative cultures of predominant microorganisms/metabolisms. Mapping of the area of interest and geochemical analysis of sediments, bedrock and water samples were performed. The original microbial community and enriched cultures were studied by direct count and culturing dependent and independent techniques. In the distal part of the alluvial fans some ponds are found with acidic brines (up to pH 1) of the Cl-SO4-Na (-Mg) type that are surrounded by yellow efflorescences. Other ponds towards the basin center progressively increase in concentration due to capillary evaporation. Brines are rich in aluminium and boron with lower concentration of manganese, lithium, iron and arsenic. An advanced hydrothermal argillic alteration affecting the country rocks, native sulfur associated to active solfataras, alunite and jarosite occurrences in sediments and chloride and sulfate efflorescent salts were evidenced. The microbial community in brines and sediments (10⁵ and 10⁶ cells/mL, respectively) was dominated by Firmicutes, Proteobacteria and Actinobacteria, and by Proteobacteria and Cyanobacteria, respectively. Sulphur and iron oxidation activity were detected depending on the salinity of the samples. Culture enrichments that respire and reduce As (V) and sulfate have been only obtained from sites with the highest pH (4-5). Microbial assemblages in those heterotrophic cultures were closely related to the Gamma and Betaproteobacteria, meanwhile, Rhodanobacter and Shewanella were the only microorganisms detected in the autotrophic cultures supplemented by Na₂S and by H₂. Relevant information to describe the occurring surface biogeochemical processes in that acidic saline system has been obtained. In addition, the occurrence of new prokaryotic genera capable of arsenic redox transformation has been evidenced in acidic systems.

Abstract: Lateritic deposits contain oxide ores and usually consist of three layers, namely the limonitic, the saprolite and the garnieritic layer. Limonite, which comprises the top lateritic layer, is a homogeneous ore consisting mainly of goethite with which nickel is associated. Microbe-mineral interactions are of interest for biogeochemical cycles. Microorganisms which are able to mediate redox transformation of Fe-oxide containing minerals are of particular interest when effective bioremediation strategies for insoluble hydroxide and oxide minerals are designed. Quantitive real-time polymerase chain reaction (qPCR) is a culture independent method which is used for the quantification of environmental microorganisms. The aim of this work was to enumerate the microorganisms in different lateritic deposits at Moa mine (Holguin, Cuba) by qPCR and also to obtain Fe (III)-reducing enrichment cultures. A higher microbial abundance was detected in the sampling sites 5124 and 5125 and a lower one in the site 5121. Both, Archaea and Bacteria occurred in all samples except for site 5121 where Bacteria were not detected by qPCR. The Geobacteraceae which comprise Fe-(III)-reducing bacteria were detected at all five lateritic ore sites. The results indicate that these bacteria play a role fundamental in the formation of sediments with a number of oxidized or partially oxidized iron compounds such as magnetite, hematite, goethite and various Fe (III)-oxyhydroxides.

Abstract: The Salar de Gorbea, located at the hyperarid Atacama region of the north of Chile, is an unusual extreme environment. Its unique characteristics of high acidity and salt concentration as well as the presence of sulfide and hydrothermal alterations, makes it an unprecedented source of novel microbial communities with potential biotechnological prospects. Several lakes covering a wide range of chloride concentrations were sampled, characterized and enriched under acidic and high salt conditions. Site samples were characterized by the presence of novel Proteobacteria and Actinobacteria strains with closest relatives of the genera Leifsonia, Francisella, Novosphingobium, Mycobacterium, Dunaliela and Rickettsia. Several enrichments on diverse conditions and substrates (pyrite, elemental sulfur, ferrous iron and different organic compounds) were tested although few enrichments provided considerable and reproducible growth. Successful enrichments showed the presence and growth of novel strains of the genera Acidisoma and Alkalibacter, genera that have been identified as part of communities that prosper in acid mine drainage systems. The later enrichments were grown under mixotrophic conditions and gradually exposed to increasing concentrations of chloride.