Unveiling the mechanism of the effect of polyethylene microplastics on phenanthrene degradation in agricultural soils through DNA-based stable isotope probing.

Polyethylene microplastics (MPs) derived from plastic mulch films are ubiquitous in agricultural soils. However, the mechanism underlying the effect of MPs on the degradation of polyaromatic hydrocarbons remains unclear. In this study, we investigated the influence of MPs amendment on the profiles of active microbes involved in phenanthrene (PHE) degradation in agricultural soils using DNA-based stable isotope probing (SIP) combined with high-throughput sequencing. Results showed that biodegradation dominated the removal of PHE, and MPs promoted the PHE degradation rate from 79.0 % to 92.3 % in agricultural soils. The addition of MPs could stimulate and prolong the activities of original active microbes responsible for PHE degradation including the genera Flavisolibacter and Nocardioides. Furthermore, the presence of MPs could also recruit novel active microbes, including Gaiella, Methylopila, JGI_0001001-H03, and unclassified Intrasporangiaceae, to participate in PHE degradation. Notably, Flavobacterium, Methylopila, Lysobacter, and unclassified Blastocatellaceae were directly linked with PHE degradation for the first time by SIP. This study provides novel insights into the mechanism underlying the effect of MPs on PHE degradation and enhances our comprehensive understanding of the co-contamination of MPs and PHE in agricultural soils.