Understanding the mechanism of the microbial transformation of Fe(III)-oxyhydroxysulfate minerals is of considerable interest, because this transformation plays an important role in controlling the behaviour of toxic metals from acid mine drainage (AMD). In this study, we examined a sulfate reducing enrichment culture from AMD-contaminated sediments and predicted the possible pathway of electron transfer when incubated with schwertmannite, a common Fe(III)-oxyhydroxysulfate occurring in the AMD environment. Experiments were designed to distinguish the mechanisms by which bacteria facilitate direct (i.e., bacteria allowed to adhere to the mineral) or indirect (i.e., bacteria separated from the mineral by dialysis bag) electron transfer to reduce the mineral. The effects of adding anthraquinone-2,6-disulfonate (AQDS) as an exogenous electron shuttle were also investigated. Vivianite was detected as the main product of schwertmannite transformation. Reduction of sulfate and iron were more pronounced in direct treatments, while more non-reductive dissolution were observed in indirect treatments. The addition of AQDS lead to the production of more dissolved Fe²⁺ over 20 d than in the absence of AQDS. Microbial community composition differed in direct and indirect treatments, while the addition of AQDS did not significantly affect the community structure in each treatment. After incubation for 20 d, the growth of Desulfovibrio exceeded that of the originally dominant Citrobacter in direct treatments, while an unknown genus most closely related to Citrobacter within Enterobacteriaceae was predominant in indirect treatments. This monodominant community in indirect treatments was assumed not to transfer electron directly to schwertmannite but to rely on shuttling mechanism. PICRUSt results implied that bacteria in indirect treatment have potential to produce shuttling compounds or complexing agents. The absence of dsr genes and the putative fermentative process suggested that the Enterobacteriaceae might indirectly facilitate the dissolution and transformation of schwertmannite.

深入了解Fe（III）-羟基羟基硫酸盐矿物的微生物转化机理，因为这种转化在控制酸性矿山排水（AMD）中的有毒金属的行为中起着重要作用。在这项研究中，我们检查了受AMD污染的沉积物的硫酸盐还原富集培养，并预测了当与Schwertmannite（一种在AMD环境中发生的常见Fe（III）-羟基羟基硫酸盐）孵育时电子转移的可能途径。设计实验以区分细菌促进直接（即允许细菌附着在矿物上的细菌）或间接（即通过透析袋与矿物分离的细菌）电子转移以减少矿物的机制。添加蒽醌2的效果 还研究了6-二磺酸盐（AQDS）作为外源电子穿梭体。检测到Vivianite是schwertmannite转变的主要产物。在直接处理中硫酸盐和铁的还原更明显，而在间接处理中观察到更多的非还原性溶解。AQDS的添加导致产生更多的溶解铁与没有AQDS的情况相比，在20 d内超过²⁺。在直接和间接治疗中，微生物群落组成有所不同，而添加AQDS并没有显着影响每种治疗中的群落结构。培养20 d后，生长脱硫超过了原来占主导地位的枸橼酸杆菌直接处理，而未知属最密切相关的枸橼酸杆菌内肠杆菌在间接治疗中占主导地位。间接处理中的这一单一主体群落被认为不是将电子直接转移到schwertmannite，而是依靠穿梭机制。PICRUSt结果表明，间接处理的细菌具有产生穿梭化合物或络合剂的潜力。dsr基因的缺乏和假定的发酵过程表明肠杆菌科可能间接促进schwertmannite的溶解和转化。