Abstract Riboflavin (RF) is a widely distributed micronutrient secreted by many bacteria and can serve as a redox mediator to facilitate extracellular electron transfer. However, studies on the effect of RF on the dynamic shift of active bacterial communities and transcription of arsenate [As(V)]-respiring genes and associated bacteria in arsenic-contaminated paddy fields remain rare. In this study, anaerobic microcosms were established with arsenic-contaminated paddy soil amended with RF and lactate. Arsenic and iron transformation showed that microbial As(V) and Fe(III) reduction took place principally within the first 12 days of incubation, when both occurred simultaneously and were substantially enhanced by RF. Dynamics of the active bacterial community (16S rRNA gene based) revealed that RF mainly increased the relative abundance of Geobacter, Clostridium, and Pelobacteraceae on days 0–12 and that of Dechloromonas on days 12–40, whereas RF had no influence on bacterial diversity. A transcript clone library of arrA gene was constructed to profile the dynamic shift of As(V)-respiring bacteria stimulated by RF, which indicated that As(V)-respiring Geobacter spp. dominated in the RF and lactate microcosms during the incubation period. Quantitative reverse transcription-PCR (RT-qPCR) analyses revealed that the transcription of arrA gene and Geobacter spp. predominantly increased during the first 5 days and was substantially enhanced by RF relative to microcosms with lactate alone. Co-occurrence network analysis indicated a positive correlation between the transcript abundance of arrA gene/Geobacter spp. and dissolved As(V) in the presence of RF and lactate. Our results demonstrate that RF stimulates the activity of indigenous dominant metal-reducing bacteria; moreover, it increases transcription of the As(V)-respiring gene and bacteria to facilitate arsenic reduction and release in arsenic-contaminated paddy soil.

中文翻译：

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核黄素对砷污染稻田活性细菌群落及砷呼吸基因及细菌的影响

摘要 核黄素（RF）是一种广泛分布的微量营养素，由许多细菌分泌，可作为氧化还原介质促进细胞外电子转移。然而，关于 RF 对砷污染稻田中活性细菌群落的动态变化和砷酸盐 [As(V)] 呼吸基因和相关细菌转录的影响的研究仍然很少见。在这项研究中，用 RF 和乳酸盐改良的砷污染稻田建立了厌氧微观世界。砷和铁的转化表明微生物 As(V) 和 Fe(III) 的还原主要发生在孵化的前 12 天内，这两种情况同时发生并且通过 RF 显着增强。活跃细菌群落的动态（基于 16S rRNA 基因）表明 RF 主要增加了地杆菌的相对丰度，梭菌和 Pelobacteraceae 在第 0-12 天，脱氯单胞菌在第 12-40 天，而 RF 对细菌多样性没有影响。构建了 arrA 基因的转录克隆文库，以分析 RF 刺激的 As(V)-呼吸细菌的动态变化，这表明 As(V)-呼吸地球杆菌属。在潜伏期，在 RF 和乳酸缩影中占主导地位。定量逆转录-PCR (RT-qPCR) 分析显示 arrA 基因和地杆菌属的转录。主要在前 5 天增加，并且相对于单独使用乳酸的微观世界，RF 显着增强。共现网络分析表明 arrA 基因/地杆菌属的转录本丰度之间呈正相关。并在 RF 和乳酸盐存在下溶解 As(V)。我们的结果表明 RF 刺激了本土优势金属还原细菌的活性；此外，它增加了 As(V) 呼吸基因和细菌的转录，以促进砷污染稻田中砷的减少和释放。