A metagenomic analysis of tailings microbial communities from both cold and hot environments

Abstract

Mining practices produce a substantial waste product in the form of tailings, a problematic liability particularly in materials where iron and sulfur become oxidized leading to acid mine drainage (AMD). Native microbial consortia in tailings sites accelerate this oxidation by a factor of 106. The oxidative capabilities of these consortia can be harnessed to bioleach low-grade, refractory metals from the waste materials while also allowing for the potential stabilization of nuisance elements. This project explores the contributions of native microbes isolated from sulfide tailings from two different climates: colder climate tailings around Sudbury, Ontario and warmer climate arsenopyrite refractory gold tailings from Ecuador (ECT). The cold community project encountered technical challenges as is summarized here as an appendix. This thesis focuses primarily on the ECT community. The ECT tailings were enriched in medium ahead of bioleaching trials and a metagenomic analysis was performed to identify key organisms responsible for driving bioleaching. The main contributors to the ECT system at the order level were Acidithiobacillales, Bacillales, Burkholderiales, Clostridiales, and Thermoplasmatales. The dominant organisms representing these orders were found to have complementary genetic systems that drive iron and sulfur oxidation. Understanding these key players will help optimize the conditions that the ECT culture will be applied in using stirred-tank bioreactors and will provide the baseline metagenomic information to help monitor the health of these organisms throughout bioleaching campaigns.