ena-STUDY-Patricya-29-08-2014-12:27:44:735-22
Acidophilic Sulphur-reducing Bacteria
Microbial life in extreme conditions has attracted considerable attention due to the peculiar physiology and ecology of extremophiles, as well as their biotechnological importance, such as in bioremediation processes from mining and metallurgical activities with acidic streams rich in dissolved heavy metals. Sulphidogenesis is one of the biological approaches more widely applied to recover metals. The hydrogen sulphide released from sulphur compounds reduction can bind to the dissolved metals and form insoluble metal sulphides. Sulphate is the most used compound for the treatment of mining and metallurgical streams via sulphidogenesis. Elemental sulphur, however, can lead to process costs reduction, since sulphur reduction needs 4 times less e-donor in comparison with sulphate, and lower pH in the process can be achieved with sulphur reducers than with sulphate reducers. Tinto River is an extreme environment broadly studied due to the high acidity and large amounts of dissolved heavy metals. Microorganisms involved in iron, sulphur and carbon cycles have already been identified in this environment. This research aimed to enrich acidophilic sulphur reducing microorganisms from Tinto River sediments, varying the pH from 2 to 5 at 30 and 55ºC, and to isolate novel species well adapted to the lowest pH possible. Steady enrichments of microorganisms able to reduce elemental sulphur were obtained at pH?5, 55ºC, with methanol, and at pH?4 and 3, 30ºC, with acetate, glycerol and hydrogen as electron donors, and sequences showed that the majority of the cultured microorganisms were related to sulphur-reducing bacteria belonging to Firmicutes (Desulfotomaculum spp., co-enriched at pH 5 and 55ºC) and Proteobacteria (Desulfurella spp., co-enriched at pH 3 and 4, with hydrogen and acetate as electron donors respectively, at 30ºC.). Although, this strain showed 97% 16S rRNA gene sequence similarity with all the described members of Desulfurella, it was found in mesophilic and acidophilic conditions, while the species described so far grow in thermophilic and neutrophilic environments. By repeated serial dilutions, antibiotics application against possible contaminants and anaerobic tubes culturing, the isolates were obtained for further characterization and biotechnological application.
Microbial life in extreme conditions has attracted considerable attention due to the peculiar physiology and ecology of extremophiles, as well as their biotechnological importance, such as in bioremediation processes from mining and metallurgical activities with acidic streams rich in dissolved heavy metals. Sulphidogenesis is one of the biological approaches more widely applied to recover metals. The hydrogen sulphide released from sulphur compounds reduction can bind to the dissolved metals and form insoluble metal sulphides. Sulphate is the most used compound for the treatment of mining and metallurgical streams via sulphidogenesis. Elemental sulphur, however, can lead to process costs reduction, since sulphur reduction needs 4 times less e-donor in comparison with sulphate, and lower pH in the process can be achieved with sulphur reducers than with sulphate reducers. Tinto River is an extreme environment broadly studied due to the high acidity and large amounts of dissolved heavy metals. Microorganisms involved in iron, sulphur and carbon cycles have already been identified in this environment. This research aimed to enrich acidophilic sulphur reducing microorganisms from Tinto River sediments, varying the pH from 2 to 5 at 30 and 55ºC, and to isolate novel species well adapted to the lowest pH possible. Steady enrichments of microorganisms able to reduce elemental sulphur were obtained at pH?5, 55ºC, with methanol, and at pH?4 and 3, 30ºC, with acetate, glycerol and hydrogen as electron donors, and sequences showed that the majority of the cultured microorganisms were related to sulphur-reducing bacteria belonging to Firmicutes (Desulfotomaculum spp., co-enriched at pH 5 and 55ºC) and Proteobacteria (Desulfurella spp., co-enriched at pH 3 and 4, with hydrogen and acetate as electron donors respectively, at 30ºC.). Although, this strain showed 97% 16S rRNA gene sequence similarity with all the described members of Desulfurella, it was found in mesophilic and acidophilic conditions, while the species described so far grow in thermophilic and neutrophilic environments. By repeated serial dilutions, antibiotics application against possible contaminants and anaerobic tubes culturing, the isolates were obtained for further characterization and biotechnological application.