Evaluating the Metal Tolerance Capacity of Microbial Communities Isolated from Alberta Oil Sands Process Water

Anthropogenic activities have resulted in the intensified use of water resources. For example, open pit bitumen extraction by Canada’s oil sands operations uses an estimated volume of three barrels of water for every barrel of oil produced. The waste tailings–oil sands process water (OSPW)–are stored in holding ponds, and present an environmental concern as they are comprised of residual hydrocarbons and metals. Following the hypothesis that endogenous OSPW microbial communities have an enhanced tolerance to heavy metals, we tested the capacity of planktonic and biofilm populations from OSPW to withstand metal ion challenges, using Cupriavidus metallidurans, a known metal-resistant organism, for comparison. The toxicity of the metals toward biofilm and planktonic bacterial populations was determined by measuring the minimum biofilm inhibitory concentrations (MBICs) and planktonic minimum inhibitory concentrations (MICs) using the MBEC ™ assay. We observed that the OSPW community and C. metallidurans had similar tolerances to 22 different metals. While thiophillic elements (Te, Ag, Cd, Ni) were found to be most toxic, the OSPW consortia demonstrated higher tolerance to metals reported in tailings ponds (Al, Fe, Mo, Pb). Metal toxicity correlated with a number of physicochemical characteristics of the metals. Parameters reflecting metal-ligand affinities showed fewer and weaker correlations for the community compared to C. metallidurans, suggesting that the OSPW consortia may have developed tolerance mechanisms toward metals present in their environment.

人类活动导致水资源开发利用强度持续加剧。例如加拿大油砂矿区的露天沥青开采作业，每产出1桶原油，预计需消耗3桶水资源。其产生的尾矿——油砂工艺废水（oil sands process water, OSPW）——被储存于尾矿池中，由于该废水含有残留烃类与金属离子，因此引发了环境安全隐患。基于“内源性油砂工艺废水微生物群落对重金属具有更强耐受性”这一假说，本研究以已知金属抗性模式菌金属嗜氢杆菌（Cupriavidus metallidurans）作为对照，测试了油砂工艺废水中浮游菌群与生物膜菌群抵御金属离子胁迫的能力。本研究采用MBEC™测定法，通过检测最小生物膜抑菌浓度（minimum biofilm inhibitory concentrations, MBICs）与浮游菌最小抑菌浓度（planktonic minimum inhibitory concentrations, MICs），评估了金属对生物膜菌群及浮游菌群的毒性强弱。研究结果显示，油砂工艺废水群落与金属嗜氢杆菌对22种不同金属的耐受性水平相近。尽管亲硫元素（碲Te、银Ag、镉Cd、镍Ni）被证实毒性最强，但油砂工艺废水菌群对尾矿池中常见的金属（铝Al、铁Fe、钼Mo、铅Pb）表现出更高的耐受性。金属毒性与该金属的多项理化性质存在相关性。相较于金属嗜氢杆菌，油砂工艺废水菌群与反映金属-配体亲和力的参数之间的相关性更弱且更少，这表明该群落可能已演化出针对环境中常见金属的耐受性机制。