Fungi-Driven Shifts in Soil DOM Molecular Composition under Biobased Biodegradable Microplastic Exposure.

Area of Science:

• Environmental Microbiology
• Soil Science
• Biogeochemistry

Background:

• Biobased biodegradable microplastics (Bio-MPs) impact soil dissolved organic matter (DOM) quantity and molecular composition, influencing soil organic matter (SOM) stability.
• The microbial mechanisms, especially the role of fungi, in Bio-MP-induced DOM turnover are not well understood.

Purpose of the Study:

• To investigate the microbial mechanisms driving DOM turnover under Bio-MP exposure, focusing on the role of fungi.
• To characterize the changes in DOM molecular composition and microbial communities in response to different Bio-MPs.

Main Methods:

• Soil incubation experiment with polylactic acid (PLA-MPs) and polyhydroxyalkanoate (PHA-MPs) for 30 days.
• Analysis of DOM molecular dynamics using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).
• Characterization of microbial communities via 16S rRNA and ITS amplicon sequencing.

Main Results:

• PHA-MPs, unlike PLA-MPs, rapidly increased DOM content and CO2 emissions.
• PHA-MPs shifted DOM composition from recalcitrant (lignins, tannins) to labile compounds (lipids, proteins/amino sugars).
• Fungal depolymerization of PHA-MPs and SOM initiated a cascade, leading to labile DOM formation and bacterial assimilation, with enrichment of fungi like *Neocosmospora*.

Conclusions:

• Fungi play a pivotal role in mediating Bio-MP-induced DOM turnover.
• Fungal activity drives the transformation of soil DOM composition under PHA-MP exposure.
• The study highlights a fungal-initiated metabolic cascade influencing soil DOM dynamics and SOM stability.