Microbial Fe(III) reduction significantly influences the fate of various elements and contaminants. Previous research has employed different Fe(III)-OM complexes and ferrihydrite to study Fe(III)-reduction-related biogeochemistry processes. However, the effects of adding specific Fe(III)-OM complexes and ferrihydrite on the Fe(III)-reducing bacterial community, Fe(III)-reducing kinetics, and Fe(III)-related functional genes remain largely unexplored. This study applied microcosm experiments and metagenomic analysis of lake sediments with and without amendments of ferrihydrite, Fe(III)-citrate, or Fe(III)-EDTA. Results showed that sediments amended with Fe(III)-citrate and Fe(III)-EDTA exhibited faster Fe(III) reduction rates and more significant changes in bacterial community structures compared to those amended with ferrihydrite. Geobacter and Clostridium were enriched in the sediments amended with Fe(III)-EDTA and Fe(III)-citrate, respectively. Despite a slower reduction rate and lack of enrichment of specific Fe(III)-reducing bacteria, ferrihydrite still led to an increase in the copy numbers of genes related to Fe(III) reduction and iron assimilation in the metagenomes, suggesting an increase in these capacities. These results suggest that introducing various Fe(III)-OM complexes and ferrihydrite into the environment would result in differences in not only Fe(III) reduction rates and Fe(III)-reducing bacterial communities but also in iron-related functional genes. Meanwhile, variations in Fe(III) reduction rates and Fe(III)-reducing bacterial communities do not necessarily correlate with changes in the abundances of functional genes relevant to Fe(III) reduction and iron assimilation in the metagenomes. These results provide a better understanding of the adaptive mechanisms of Fe(III)-reducing bacteria in different environmental systems.

微生物 Fe（III） 还原显著影响各种元素和污染物的命运。以前的研究采用了不同的 Fe（III）-OM 配合物和水铁矿来研究 Fe（III） 还原相关的生物地球化学过程。然而，添加特定的 Fe（III）-OM 复合物和水铁矿对 Fe（III） 还原细菌群落、Fe（III） 还原动力学和 Fe（III） 相关功能基因的影响在很大程度上仍未得到探索。本研究对含和不含水铁矿、Fe（III）-柠檬酸盐或 Fe（III）-EDTA 改性的湖泊沉积物进行了微观实验和宏基因组分析。结果表明，与水铁酸盐改性的沉积物相比，用 Fe（III）-柠檬酸盐和 Fe（III）-EDTA 改性的沉积物表现出更快的 Fe（III） 还原速率和更显着的细菌群落结构变化。Geobacter 和 Clostridium 分别在用 Fe（III）-EDTA 和 Fe（III）-citrate 改性的沉积物中富集。尽管还原速率较慢且缺乏特异性 Fe（III） 还原细菌的富集，但水铁矿仍然导致宏基因组中与 Fe（III） 还原和铁同化相关的基因拷贝数增加，表明这些能力增加。这些结果表明，将各种 Fe（III）-OM 复合物和水铁矿引入环境中不仅会导致 Fe（III） 还原速率和 Fe（III） 还原细菌群落的差异，还会导致铁相关功能基因的差异。同时，Fe（III） 还原率和 Fe（III） 还原细菌群落的变化不一定与宏基因组中与 Fe（III） 还原和铁同化相关的功能基因丰度的变化相关。 这些结果为不同环境系统中 Fe（III） 还原细菌的适应机制提供了更好的理解。