From Microbes to Molecules: Biodegradable Microplastics Reshape Soil Carbon Metabolism and Composition of Dissolved Organic Matter

Microplastics (MPs) are ubiquitous in the environment, yet how conventional MPs (CMPs) and biodegradable MPs (BMPs) alter microbial carbon (C) metabolism and dissolved organic matter (DOM) remains unclear. Using metagenomic sequencing and Fourier transform ion cyclotron resonance mass spectrometry, we found that BMPs altered microbial C cycling profiles more profoundly than CMPs. This was driven by a significant enrichment of functional genes involved in aerobic respiration, C fixation, intracellular C decomposition, and fermentation. In addition, BMPs exerted stronger influences on prokaryotic and viral community structures than CMPs. Notably, BMPs specifically enriched unique microbial taxa and virus-host linkages carrying diverse C-cycling genes, coregulating key metabolic pathways, and promoting a "viral shuttle" mechanism that accelerated DOM turnover. These effects were mediated through enhanced accumulation of labile and recalcitrant C components in relation to fertilization regimes. These findings revealed mechanisms by which BMPs reshape soil carbon dynamics through microbial-viral interactions.