New insights into effect of PBAT microplastics on latosol microbial metabolic functions

This study systematically investigated the underexplored effects of poly(butylene adipate-co-terephthalate) (PBAT) microplastics on latosol microbial metabolic fnctions by integrating a Biolog Eco microplate with two-dimensional correlation spectroscopy (2D-COS) analysis. Our results revealed that the main phyla Chloroflexi and Actinobacteria presented a non-monotonic pattern with the PBAT dosage and functioned as keystone taxa in shaping the metabolic functions and pathways of the latosol microbial community. PBAT microplastics elevated the activity of soil C-cycling enzymes while suppressing most N-cycling enzymes activities (except for urease). In the early degradation stage, microbial carbon substrate utilization (AWCD) exhibited a positive dose-response to PBAT concentration, accompanied by an increase in the consumption of nitrogen-containing carbon sources. 2D-COS analysis indicated a preferential microbial utilization of labile carbon sources under PBAT treatment, in contrast to the dominant consumption of recalcitrant carbon sources in control treatment. However, in the later degradation stage, the AWCD values in the PBAT treatments decreased and were even lower than those in the control treatment. Compared to those in the PBAT treatment, the microorganisms in the control treatment used significantly more carbon sources containing N. The key factors affecting microbial metabolic activity and diversity included latosol properties (such as C/N, MBC, and MBN) and enzyme activities (such as ROL, PO, AMO, and UR). Our findings provided mechanistic insights for more accurately predicting alterations in soil carbon cycling and storage under the increasingly prevalent use of biodegradable films in the future.