Characterisation of bacterial communities from an active mining site and assessment of its potential metal solubilising activity

Abstract

The present work is the first report characterising bacterial communities recovered from sulphide ore from a Portuguese active mine (Neves-Corvo) and collecting samples from three independent processing stages (feed/tailings/paste), at three sampling periods over 15 months. The recovered bacterial communities demonstrated low richness and heterogeneity (intra/inter-samples). Neutrophile sulphur-oxidising chemolithoautotrophs (e.g., Thiobacillus, Halothiobacillus, Thiomicrospira) were the most abundant organisms found across all samples. The presence of these primary producers may explain the occurrence of mixotrophs and facultative chemolithoheterotrophs/chemoorganoheterotrophs (e.g., Limnobacter, Paracoccus, Marinobacter, Alishewanella, Pseudomonas) in these non-acidic (4.6 < pH> 8.7), pyrite-rich environments.The capacity of the surviving bacterial community following ore processing (tailings) to solubilise metals from mine wastes was also assessed. After 65 days at room temperature and in the presence of thiosulphate as an additional energy source, the tailings’ bacterial community solubilised pollutants detected in acid mine drainage waters, namely As (96%), Cd (58%), Cu (24%) and Zn (56%) with the concomitant decrease of pH from 7.4 to 1.8. The low solubilisation efficiencies obtained for copper, zinc, and cadmium indicate a limited technological potential of these communities. However, their ability to significantly mobilise noxious pollutants from the mine wastes to the liquid medium, particularly for As, raises environmental concern. This finding should increase awareness among stakeholders for the need to increase studies at field scale, in real scenarios.