Effects of Biodegradable Microplastics on Soil and Lettuce Health: Rhizosphere Microbiome and Metabolome Responses

Biodegradable microplastics (BMPs) have been widely detected in soils due to their widespread production and utilization. However, their impacts on rhizosphere microbial consortia and plant metabolic adaptation mechanisms have been insufficiently characterized. Here, two typical BMPs, polybutylene adipate-<i>co</i>-terephthalate and polyhydroxybutyrate, were selected to assess the effects of individual and combined exposure on the rhizosphere and metabolomes of lettuce at different concentration levels (0.1 and 2%). Results revealed that both 2% BMPs inhibited lettuce growth. Similarly, 2 wt % BMPs also altered community structures. Several biomarkers, including <i>Bacillus</i> and <i>Streptomyces</i>, were identified for BMP exposure. The metabolomic analysis revealed that 2% BMPs significantly altered the root and leaf metabolomes of lettuce. Pathways and metabolites related to plant defense toward environmental stresses, like aucubin, bisnorbiotin, l-rhamnose, and niazimin, were also enriched after BMPs treatment. This study highlights the impact of BMPs on soil and plant health, improving our comprehension of their combined ecological impact on the soil environment.