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Microplastic and lead shift microbiomes enriching viral auxiliary metabolic genes for potential polylactic acid degradation.
Summary
Researchers exposed buckwheat and its rhizosphere microbiome to polylactic acid microplastics, lead, and their combination, finding that co-contamination suppressed bacterial carbon and phosphorus metabolism while enriching viral auxiliary metabolic genes—including a newly identified carbohydrate esterase confirmed to hydrolyze PLA ester bonds—suggesting viruses may play an underappreciated role in biodegradable microplastic degradation in soil.
Biodegradable microplastics and heavy metals increasingly co-occur in soils through plastic mulching, organic amendments, and legacy metal contamination. Yet, their combined effects on soil-plant-microbiota interactions remain unclear, particularly for the virus. Here we evaluated the impacts of bio-MPs, polylactic acid (PLA), lead (Pb), and their combination on buckwheat and rhizosphere bacterial-viral communities. Co-contamination reduced soil pH and nutrient availability, increased Pb accumulation in plant tissues and suppressed buckwheat growth. Metagenomic analyses revealed that both bacterial and viral communities were altered under Pb-containing treatments. Bacterial genes associated with carbon and phosphorus metabolism were suppressed, while viral auxiliary metabolic genes (AMGs) related to carbon utilization were enriched, especially carbohydrate esterases that hydrolyze PLA ester bonds. A putative AMG-associated carbohydrate esterase gene (P9222_28545) was identified and the esterase activity confirmed via heterologous expression in E. coli. These findings highlight a potential role of viruses in mediating microplastic degradation in soils.