Heavy metal (HM) contamination caused by mining and smelting activities can be harmful to soil microbiota, which are highly sensitive to HM stress. Here, we explore the effects of HM contamination on the taxonomic composition, predicted function, and co-occurrence patterns of soil bacterial communities in two agricultural fields with contrasting levels of soil HMs (i.e., contaminated and uncontaminated natural areas). Our results indicate that HM contamination does not significantly influence soil bacterial α diversity but changes the bacterial community composition by enriching the phyla Gemmatimonadetes, Planctomycetes, and Parcubacteria and reducing the relative abundance of Actinobacteria. Our results further demonstrate that HM contamination can strengthen the complexity and modularity of the bacterial co-occurrence network but weaken positive interactions between keystone taxa, leading to the gradual disappearance of some taxa that originally played an important role in healthy soil, thereby possibly reducing the resistance of bacterial communities to HM toxicity. The predicted functions of bacterial communities are related to membrane transport, amino acid metabolism, energy metabolism, and carbohydrate metabolism. Among these, functions related to HM detoxification and antioxidation are enriched in uncontaminated soils, while HM contamination enriches functions related to metal resistance. This study demonstrated that microorganisms adapt to the stress of HM pollution by adjusting their composition and enhancing their network complexity and potential ecological functions.

中文翻译：

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重金属污染影响农业土壤细菌群落的结构和共生模式

采矿和冶炼活动引起的重金属（HM）污染可能对土壤微生物群有害，而土壤微生物群对重金属胁迫高度敏感。在这里，我们探讨了 HM 污染对两个农田土壤细菌群落的分类组成、预测功能和共现模式的影响，以及土壤 HM 水平对比（即受污染和未受污染的自然区域）。我们的结果表明，HM污染不会显着影响土壤细菌α多样性，但会通过丰富Gemmatimonadetes、Planctomycetes和Parcubacteria门以及降低Actinobacteria的相对丰度来改变细菌群落组成。我们的结果进一步表明，HM污染可以增强细菌共生网络的复杂性和模块化，但削弱关键类群之间的正相互作用，导致一些原本在健康土壤中发挥重要作用的类群逐渐消失，从而可能减少细菌群落对 HM 毒性的抵抗力。细菌群落的预测功能与膜运输、氨基酸代谢、能量代谢和碳水化合物代谢有关。其中，未污染土壤中富集了重金属解毒和抗氧化相关功能，而重金属污染则丰富了抗金属相关功能。本研究表明，微生物通过调整其组成、增强其网络复杂性和潜在生态功能来适应重金属污染的胁迫。