Microplastics (MPs), including conventional hard-to-biodegrade petroleum-based and faster biodegradable plant-based ones, impact soil structure and microbiota in turn affecting the biodiversity and functions of terrestrial ecosystems. Herein, we investigated the effects of conventional and biodegradable MPs on aggregate distribution and microbial community composition in microhabitats at the aggregate scale. Two MP types (polyethylene (PE) and polylactic acid (PLA) with increasing size (50, 150, and 300 μm)) were mixed with a silty loam soil (0-20 cm) at a ratio of 0.5 % (w/w) in a rice-wheat rotation system in a greenhouse under 25 °C for one year. The effects on aggregation, bacterial communities and their co-occurrence networks were investigated as a function of MP aggregate size. Conventional and biodegradable MPs generally had similar effects on soil aggregation and bacterial communities. They increased the proportion of microaggregates from 17 % to 32 %, while reducing the macroaggregates from 84 % to 68 %. The aggregate stability decreased from 1.4 mm to 1.0-1.1 mm independently of MP size due to the decline in the binding agents gluing soil particles (e.g., microbial byproducts and proteinaceous substances). MP type and amount strongly affected the bacterial community structure, accounting for 54 % of the variance. Due to less bioavailable organics, bacterial community composition within microaggregates was more sensitive to MPs addition compared to macroaggregates. Co-occurrence network analysis revealed that MPs exacerbated competition among bacteria and increased the complexity of bacterial networks. Such effects were stronger for PE than PLA MPs due to the higher persistence of PE in soils. Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Gemmatimonadetes were the keystone taxa in macroaggregates, while Actinobacteria and Chloroflexi were the keystone taxa in microaggregates. Proteobacteria, Actinobacteria, and Chloroflexi were the most sensitive bacteria to MPs addition. Overall, both conventional and biodegradable MPs reduced the portion of large and stable aggregates, altering bacterial community structures and keystone taxa, and consequently, the functions.

Tobacco (Nicotiana benthamiana) and Turnip mosaic virus (TuMV) were used as a model system to investigate the potential of engineered nanomaterials (ENMs) for promoting crop growth and resistance to viral infection. A 5 mL ENM suspension of 50 or 200 mg L⁻¹ consisting of either two metal-based nanoparticles (NP Fe₂O₃ or TiO₂) or two carbon-based nanomaterials (NMs) (MWCNTs or C₆₀) was foliar-sprayed onto the leaf surface of tobacco daily for 21 days. Fully developed young leaves were then inoculated with TuMV tagged with GFP and were cultivated for 5 days. Exposure to both metal- and carbon-based NMs significantly increased the shoot biomass by approximately 50%. TEM images demonstrated that exposure to NMs did not alter cellular integrity; both NP Fe₂O₃ and TiO₂ preferentially accumulated in chloroplasts. Fluorescence images of TuMV abundance on the leaf surfaces suggest that NMs significantly inhibited viral proliferation as measured by the fluorescence intensity on the newly emerged leaves. Approximately 15–60% decreases in the relative amount of TuMV coat proteins could further explain the mechanisms by which NMs suppressed viral infection. Increases in phytohormone levels of 40% also suggest that NMs play an important role in stimulating plant growth and activating defense mechanisms. These findings contribute to our understanding of the sustainable use of ENMs in agriculture.