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Isolation of Arsenic Resistant and Arsenopyrite Oxidizing Acidithiobacillus Species from pH Neutral Colombian Mine Effluents

posted on 2020-05-20, 14:54 authored by Carlos Eduardo Barragán, Marco Antonio Márquez, Mark Dopson, Dolly Montoya Castaño

Inactive mines provide a great source of bacterial diversity for studying acidophilic communities and their biotechnological applications, but prospecting of these anthropogenic environments in Colombia has been limited. Conventional microbiological methods were used to isolate acidophilic bacterial strains from effluents emanating from the Colombian gold mine ‘El Zancudo’ (Titiribí, Antioquia). Despite the drainage waters having circumneutral pH, all of the isolated strains were phylogenetically related to the extreme acidophile Acidithiobacillus genus. However, based upon 16S rRNA gene sequences the mesophilic sulfur-oxidizing indigenous strains could not be assigned to a species. Pure cultures were selected by screening in medium with soluble inorganic arsenic (III) and their mineral-oxidative activity was evaluated at 30 °C in Erlenmeyer flasks with arsenopyrite ore under rotary shaking conditions. The indigenous strains were able to catalyze arsenopyrite oxidation in a mixed culture with a pulp density of 10%, maintaining their growth in the presence of >80mM leached arsenic. This research provides information regarding the isolation of arsenic resistant bacterial communities from neutral effluents from El Zancudo mine and the possibility of the isolated strains to be useful in the biooxidation pretreatment of refractory gold-bearing arsenopyrite ores and concentrates.


This research was supported by Dirección de Investigación, Universidad Nacional de Colombia through the program for strengthening research, creation and innovation 2016–2018 [QUIPU: 201010013078] and by Colombian Ministry of Science, Technology and Innovation (COLCIENCIAS), program 647 for the formation of high-level human resource.