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.
Keywords: bacterial community; keystone taxa; metagenome; network analysis; phthalic acid esters(PAEs).