Function and diversity of sulfate- and iron-reducing bacteria in mine tailings submitted to various physico-chemical conditions

微生物铁还原和硫酸盐还原被提出作为一种生物修复技术，以减轻采矿影响环境（如湖泊）和尾矿中的酸性矿山水（AMD）。这两种微生物过程都能产生碱度，降低尾矿中现有的酸度，硫酸盐还原促进有毒重金属以金属硫化物的形式沉淀，从而降低AMD和重金属负荷对邻近水生和陆地生态系统的影响。D. Fortin实验室正在进行的研究表明，铁还原细菌（FeRB）和硫酸盐还原细菌（SRB）广泛存在于Cu-Zn和Au尾矿中，但它们在尾矿库中的活性取决于各种生物地球化学因素，包括有机底物的有效性、电子受体、pH、氧化还原和温度。例如，Cu-Zn尾矿中硫酸盐还原活性在春季（融雪后）大大降低，此时尾矿酸性较强，有机碳含量较低。另一方面，由于缺乏与SRB种群的竞争，FeRB种群倾向于在春季增加。这些结果表明，在设计适宜的温带地区尾矿生物修复技术之前，必须首先了解在各种物理化学条件下发生的尾矿中FeRB和SRB的微生物多样性和功能。生物修复技术必须是全年有效的，而不是依赖于物理化学因素。本研究拟采用微观方法评价不同物理化学条件下贱金属矿尾矿中SRB和FeRB的多样性和功能。

Microbial  iron- and sulfate- reduction  have been proposed as a bioremediation technologies to attenuate acid mine drainage (AMD) in mining impacted environments (such as lakes) and mine tailings. Both microbial processes generate alkalinity which can reduce the existing acidity in the tailings and  sulfate reduction promotes the precipitation of toxic heavy metals as metal sulfides, therefore lowering the impact of AMD and heavy metal loading to adjacent aquatic and terrestrial ecosystems. Ongoing research in D. Fortin's laboratory has shown that iron-reducing bacteria (FeRB) and sulfate-reducing bacteria (SRB) are widespread in Cu-Zn and Au tailings, but their activity in tailings impoundments  is dependent on various biogeochemical factors, including availability or organic substrates, electron acceptors, pH, redox and temperature. For instance, sulfate reduction activity is greatly reduced in the spring in Cu-Zn tailings (after snowmelt), when the tailings are more acidic and low in organic carbon. On the other hand, FeRB populations tend to increase in the spring, likely as the result of the lack of competition with SRB populations. Such results indicate that microbial diversity and function of FeRB and SRB in mine tailings occurring under a wide range of physico-chemical conditions must first be understood before designing  appropriate bioremediation technologies for mine tailings residues residing in temperate climate regions. Bioremediation technologies must be effective all year around and not be dependent on  physico-chemical factors. The proposed research plans to use a microcosm approach to assess SRB and FeRB diversity and function in base-metal mine tailings submitted to various physico-chemical conditions.