Temperature and nutrients as drivers of microbially mediated arsenic oxidation and removal from Acid Mine Drainage

Microbial oxidation of iron (Fe) and arsenic (As) followed by their co-precipitation lead to the natural attenuation of these elements in As-rich Acid Mine Drainage (AMD). The parameters driving the activity and diversity of bacterial communities responsible for this mitigation remain poorly understood. We conducted batch experiments to investigate the effect of temperature (20 vs 35°C) and nutrient supply on the rate of Fe and As oxidation and precipitation, the bacterial diversity (high-throughput sequencing of 16S rRNA gene) and the As oxidation potential (quantification of aioA gene) in AMD from the Carnoulès mine (France). In batch incubated at 20°C, the dominance of iron-oxidizing bacteria related to Gallionella spp. was associated with almost complete iron oxidation (98%). However, negligible As oxidation led to the formation of As(III)-rich precipitates. Incubation at 35°C and nutrient supply both stimulated As oxidation (71-75%), linked to a higher abundance of aioA gene and the dominance of As-oxidizing bacteria related to Thiomonas spp. As a consequence, As(V)-rich precipitates (70-98% of total As) were produced. Our results highlight strong links between indigenous bacterial community composition and iron and arsenic removal efficiency within AMD, and provide news insights for the future development of a biological treatment of As-rich AMD

铁（Fe）与砷（As）的微生物氧化及其后续共沉淀作用，可促使富砷酸性矿山排水（Acid Mine Drainage, AMD）中的上述元素发生自然衰减。目前，介导该污染修复过程的细菌群落的活性与多样性的驱动参数仍未被充分阐明。本研究以法国卡尔努莱斯（Carnoulès）矿场的AMD为实验材料，开展批量培养实验，系统探究温度（20℃与35℃）与营养供给对铁、砷氧化及沉淀速率的调控作用，同时解析细菌群落多样性（基于16S核糖体RNA基因的高通量测序）与砷氧化潜力（aioA基因定量分析）。在20℃培养的批量体系中，与嘉利翁氏菌属（Gallionella spp.）亲缘关系相近的铁氧化细菌占据群落优势，铁几乎被完全氧化（转化率达98%）。然而此时砷氧化作用极弱，最终形成富三价砷（As(III)）的沉淀物。当培养温度提升至35℃且补充营养时，砷氧化活性显著增强（转化率达71%~75%），这与aioA基因丰度的显著提升以及硫单胞菌属（Thiomonas spp.）相关砷氧化细菌的群落优势密切相关。在此条件下，最终生成富五价砷（As(V)）的沉淀物（占总砷的70%~98%）。本研究结果揭示了AMD中土著细菌群落组成与铁、砷去除效率之间的紧密关联，可为未来富砷AMD生物修复技术的开发提供全新的研究视角。