Soil microorganisms play an important role in the detrimental impact of biodegradable microplastics on plants

Abstract

Biodegradable plastics were developed to mitigate environmental pollution caused by conventional plastics. Research indicates that biodegradable microplastics still have effects on plants and microorganisms as their non-biodegradable counterparts, yet the effects on vegetable crops are not well-documented. Additionally, the function of soil microorganisms affected by biodegradable microplastics on the fate of microplastics remains unverified. In this study, Brassica chinensis was cultivated in soil previously incubated for one year with low-density polyethylene (LDPE-MPs) and poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) at 0.05 % and 2 % concentrations. High concentrations of PBAT-MPs significantly reduced the biomass to 5.83 % of the control. The abundance of Methyloversatilis, IS-44, and UTCFX1 in the rhizosphere bacterial community increased significantly in the presence of PBAT-MPs. Moreover, these microplastics significantly enhanced soil enzyme activity. Incubation tests were performed with three PBAT plastic sheets to assess the function of the altered bacterial community in the soil of control (Control-soil) and soil treated with high concentrations of PBAT-MPs (PBAT-MPs-soil). Scanning Electron Microscopy and Atomic Transfer Microscopy (SEM/ATM) results confirmed enhanced PBAT degradation in the PBAT-MPs-soil. PICRUST2 analysis revealed that pathways related to substance degradation were upregulated in the PBAT-MPs-soil. Furthermore, a higher percentage of strains with PBAT-MPs-degrading ability was found in PBAT-MPs-soil. Our results confirm that PBAT-MPs significantly inhibit the growth of vegetable crops and that soil bacterial communities affected by PBAT-MPs are instrumental in degrading them.