Nanchang Key Laboratory of Microbial Resources Exploitation & Utilization from Poyang Lake Wetland, College of Life Sciences, Jiangxi Normal University, Nanchang, 330022, China.
State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, 430062, China.
Appl Biochem Biotechnol. 2024 Aug;196(8):4862-4873. doi: 10.1007/s12010-023-04787-1. Epub 2023 Nov 18.
Polyferric sulfate (PFS), an economical coagulant widely used for removing heavy metal contaminants from water, is susceptible to reduction and transformation by iron-reducing bacteria prevalent in sediments. However, the effect of heavy metal ions adsorbed in PFS flocs on this biological process remains unclear. According to our results, compared with other heavy metal cations (e.g., Cu, Cd, Zn, Ni, Pb, and Co), Cu had a stronger inhibitory effect on PFS floc reduction by Shewanella putrefaciens CN32, a typical dissimilatory iron-reducing bacterium. The presence of Cu remarkably influenced the global transcription of CN32, resulting in 782 upregulated genes and 713 downregulated genes that are mainly annotated in energy production, amino acid metabolism, protein biosynthesis, and oxidation‒reduction processes. The anaerobic TCA cycle for energy (electron) production was significantly activated in the presence of Cu, while the transcription of many genes related to the extracellular electron transfer pathway was downregulated, which is responsible for the decreased Fe reduction. Moreover, the pathways of assimilatory sulfate reduction and subsequent cysteine biosynthesis were significantly enriched, which is hypothesized to result in the consumption of abundant energy produced from the enhanced anaerobic TCA cycle, revealing a strategy to address the oxidative stress caused by Cu. This work elucidates the unusual suppressive effects of Cu on the microbial reduction of PFS flocs, which reveals the high resistance of PFS flocs to microbial destruction when used to treat Cu pollution in water, thus demonstrating their tremendous practical prospects.
聚合硫酸铁（PFS）是一种经济实用的混凝剂，广泛用于去除水中的重金属污染物。但它易被沉积物中普遍存在的铁还原菌还原和转化。然而，PFS 絮体中吸附的重金属离子对这一生物过程的影响尚不清楚。根据我们的研究结果，与其他重金属阳离子（如 Cu、Cd、Zn、Ni、Pb 和 Co）相比，Cu 对 Shewanella putrefaciens CN32（一种典型的异化铁还原菌）还原 PFS 絮体的抑制作用更强。Cu 的存在显著影响了 CN32 的全局转录，导致 782 个上调基因和 713 个下调基因，这些基因主要注释在能量产生、氨基酸代谢、蛋白质生物合成和氧化还原过程中。在 Cu 存在的情况下，用于能量（电子）产生的厌氧三羧酸循环明显被激活，而许多与细胞外电子传递途径相关的基因转录被下调，这导致 Fe 还原减少。此外，同化硫酸盐还原和随后的半胱氨酸生物合成途径明显富集，这被假设是为了消耗从增强的厌氧三羧酸循环中产生的丰富能量，揭示了一种应对 Cu 引起的氧化应激的策略。这项工作阐明了 Cu 对 PFS 絮体微生物还原的异常抑制作用，揭示了当用于处理水中的 Cu 污染时，PFS 絮体对微生物破坏具有很高的抵抗力，从而展示了其巨大的实际前景。
