Conventional and biodegradable microplastics elicit contrasting taxon-level responses in rhizosphere microbiomes of maize and strawberry

Microplastics (MP) are relevant contaminants in agroecosystems, influencing soil nutrient dynamics and soil-plant-microbial interactions. As agriculture shifts from conventional to biodegradable plastics, their impacts on different crop rhizosphere microbiomes considering both total (DNA-derived) and transcriptionally active (rRNA-derived) communities have not been clearly elaborated. We hypothesized that microbiome impacts would be distinct across different plants and polymer types. Maize and strawberry plants were cultivated with 1% MP by soil weight, including two conventional polymers (low-density polyethylene-LDPE and polyethylene terephthalate-PET) and one biodegradable polymer (poly(butylene adipate-co-terephthalate)-PBAT). Strawberry plants increased biomass across all MP treatments, accompanied by greater soil nitrate depletion. MP-induced impacts on soil prokaryotic communities were mostly additive to plant effects, as determined by 16S rRNA amplicon sequence profiling. PBAT stimulated Cupriavidus spp. and members of Saccharimonadales, suggesting a selection of potential polymer-degraders and microbial interactions, independent of plant species and root proximity. In contrast, conventional MPs induced a less selective response with compositional shifts across a greater number of taxa. MP-induced changes were more apparent in rRNA- than DNA-derived profiles, suggesting a profound response of putative active taxa. Together, we demonstrate that plant species and MP type jointly modulate rhizosphere microbial community response to MP pollution, with direct implications for soil biogeochemistry, rhizosphere functioning, and crop performance.