Factors influencing the composition of bacterial communities found at abandoned copper-tailings dumps

Aims: To study the effect that copper residues exert on bacterial communities and the ability of bacteria to colonize different microhabitats in abandoned tailing dumps. Methods and Results: We used the terminal-restriction fragment length polymorphism technique, a culture-independent molecular approach based on PCR amplification of ribosomal genes, to compare the structure of the bacterial communities from samples taken at two nearby located abandoned tailing dumps found in the Mediterranean-climate area of central Chile. Our results show that elevated available copper content in tailings has a strong effect on the bacterial community composition, but that other factors like pH and organic matter content also play an important role in the structure of these communities. We also found that the number of abundant bacteria in these samples was significantly lower than in soils not exposed to metal pollution. Conclusions: In addition to bioavailable copper, bacterial communities found in copper-tailings dumps are also affected by several other environmental factors. Significance and Impact of the Study: This first report on environmental factors influencing microbial communities in copper-tailings dumps will help to devise appropriate restoration procedures in this type of polluted habitat.