宏基因组揭示紫色土中邻苯二甲酸酯去除的微生物学机制

邻苯二甲酸酯具有内分泌干扰特性，在环境中持久存在，其去除机制备受关注.为探究邻苯二甲酸酯在紫色农田土壤中的去除机制、关键微生物及功能基因，以邻苯二甲酸二正丁酯（DBP）和邻苯二甲酸二（2-乙基己基）酯（DEHP）为目标污染物，分别设置含量为0、5、10和20 mg·kg^-1的单一污染土壤，避光培养90 d，利用宏基因组技术探究其去除的微生物生态学机制.结果表明，DBP和DEHP在土壤中的降解动态均符合一级动力学降解模型，半衰期介于17.0~38.2 d之间，5 mg·kg^-1的DBP降解速率最快，依次快于10 mg·kg^-1的DEHP、5 mg·kg^-1的DBP、5 mg·kg^-1的DEHP以及20 mg·kg^-1的DBP和DEHP.第7 d和15 d的土壤样品间细菌群落结构存在显著差异，放线菌门相对丰度随时间不断提升，且与DBP或DEHP半衰期呈反比.物种共现网络分析筛选出变形菌门的Pandoraea属为群落中的关键物种，可以用来指示DBP和DEHP污染程度.KEGG功能注释结果表明，Pandoraea在群落中负责酯键水解、苯甲酸降解、群体感应、ABC转运和双组分系统等功能，可以促进邻苯二甲酸酯上下游降解、细胞通讯和其它降解菌的生长繁殖，以此维持群落结构的稳定.由此可见，紫色土中，DBP和DEHP的去除效率取决于初始含量和自身性质，放线菌门的细菌在降解中扮演重要角色，Pandoraea在促进邻苯二甲酸酯降解和调节降解菌群结构和功能的稳定中均发挥关键作用.

Microbial Mechanisms of Removal of Phthalic Acid Esters in Purple Soils Revealed Using Metagenomic Analysis

The removal mechanisms of phthalic acid esters (PAEs) have attracted much attention because of their endocrine-disrupting properties and persistence in environmental media. In order to reveal the removal mechanism of PAEs and involved keystone taxa and functional genes, purple soils were polluted by di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP), respectively, along a gradient of 0, 5, 10, and 20 mg·kg^-1 and cultured for 90 days in the dark. The results showed that the degradation dynamics of DBP and DEHP were well-fitted by the first-order kinetic model, and the half-life of DBP and DEHP ranged from 17.0 to 38.2 days. The degradation rate of DBP (5 mg·kg^-1) was the fastest, and that of DEHP (20 mg·kg^-1) was the slowest. The soil samples of the seventh day and the fifteenth day were analyzed using metagenomic sequencing. NMDS and cluster analysis showed that there was a significant difference between the bacterial community structure of soil samples from the seventh day and the fifteenth day. The relative abundance of Actinobacteria increased from the seventh day to the fifteenth day. The smaller the half-life of DBP or DEHP, the higher the relative abundance of Actinobacteria in the different treatments. In addition, Streptomyces was the dominant genus in all polluted soils. Co-occurrence network analysis elucidated that Pandoraea was a keystone genus of the soil bacterial communities, which could be used to indicate the pollution levels of DBP and DEHP. The results of KEGG annotation demonstrated that Pandoraea was responsible for benzoate degradation, quorum sensing, ABC transporters, and the two-component system and could promote the intercellular communications and the microbial growth and proliferation and maintain the stability of the community structure. Therefore, the degradation rate of DBP and DEHP in purple soils depended on their initial content and their own properties. Actinobacteria played an important role in the PAEs degradation, and Pandoraea played a major part in promoting PAEs degradation and regulating the stability of the structure and function of degrading bacterial communities.