Isolation of acidophilic bacteria from Agrio River, Neuquen-Argentina: the effects of temperature, pH and the presence of heavy metals

摘要

The Agrio River, situated in the geothermal area of the Copahue volcano in Neuquen, Patagonia Argentina, is characterized by low pH values. Sulfide ore deposits are present in this area, and reddish-brown ferric iron and sulfur precipitates have been observed on the banks of most of the streams and rivulets of the system. These characteristics suggest that this area may be an important source of acidophilic bioleaching bacteria. It has been shown that native microorganisms tend to adapt to the local ores and in many cases they may improve metal recovery by bioleaching. The aim of this study was to isolate and characterize local acidophilic bacteria. Three acidophilic, chemolithotrophic and ferrous oxidizing bacteria were isolated from different places of Agrio River using 9 K enrichment medium and then purified on solid ferrous iron-agarose medium. Ferrous iron oxidation by these isolates, and by a strain obtained from a culture collection, was compared at different temperatures (20, 25, 30, 35 and 40℃) and pH values (1.6,1.8 and 2.3). Isolated bacteria proved to be less susceptible to low temperatures or high acidity. These strains showed adequate growth in iron-free 9K medium using sulfur as a sole energy source. Iron (Ⅱ) oxidation inhibition in the presence of different heavy metals (Ag~+, Cd~(2+), Cu~(2+), Zn~(2+)) and anions (NO_3~- Cl-) was also investigated.