The relationship between heavy metals and the expression of heavy metal resistance genes (HMRGs) in the active layer (AL) and the permafrost layer (PL) are not well understood, despite being closely linked to the impact of human activity on heavy metal levels and bacterial response to heavy metal stress. Herein, we conducted a metagenomics sequencing analysis to understand how bacteria adapt to such heavy metal stress. We detected higher levels of heavy metals in the AL relative to the PL. Consistent with this, analyses of AL samples revealed the presence of more genes associated with DNA damage repair, DNA recombination, and heavy metal resistance relative to PL samples. Heavy metal-resistant bacterial phyla including Actinobacteria, Acidobacteria, Bacteroidetes, and Cyanobacteria were more abundant in the AL than the PL. At the genera level, we found that bacteria responsible for nitrification, sulfur reduction, and methane oxidation and reduction were less prevalent in the AL relative to the PL. In summary, bacteria in the AL have evolved such that they are able to resist prolonged heavy metal pollution.

尽管与人类活动对重金属水平和温度的影响密切相关，但人们对重金属与活性层（AL）和多年冻土层（PL）中重金属抗性基因（HMRGs）的表达之间的关系尚不十分了解。细菌对重金属胁迫的反应。在这里，我们进行了宏基因组测序分析，以了解细菌如何适应这种重金属胁迫。相对于PL，我们在AL中检测到更高的重金属含量。与此相一致，AL样品的分析显示，与PL样品相比，存在更多与DNA损伤修复，DNA重组和重金属抗性相关的基因。耐重金属菌门包括放线菌，酸性杆菌，拟杆菌和蓝细菌AL中的资源比PL多。在属水平上，我们发现，相对于PL，负责硝化，硫还原以及甲烷氧化和还原的细菌在AL中不那么普遍。总之，AL中的细菌已经进化，因此能够抵抗长期的重金属污染。