Ecological Roles and Shared Microbes Differentiate the Plastisphere from Natural Particle-Associated Microbiomes in Urban Rivers

The “plastisphere,” comprising microbes
associated
with microplastics (MPs), may have substantial ecological impacts
on riverine ecosystems. However, little is known about how the microbiomes
associated with anthropogenic MPs compare with those associated with
natural particles (NPs) in urban rivers with varying MP pollution
levels. We therefore conducted a comparative analysis of the metagenomes
associated with MPs and NPs (100–5000 μm) and river water
(RW) across 10 urban river systems. Although we found similarities
in taxonomic and functional compositions between the microbiomes associated
with MPs and NPs, the plastisphere exhibited distinct associations
with specialized taxa and life-history strategies. These unique traits
enhanced the potential of the plastisphere for complex carbohydrate
and plastic degradation, nitrate and nitric oxide reduction, and antibiotic
resistance and virulence compared with the NP or RW microbiomes. Furthermore,
MPs supported the sharing of unique microbes with the surrounding
RW; these shared microbes possessed enhanced horizontal gene transfer
capabilities and potentially could disperse traits of the plastisphere
into the broader RW microbiomes. This study highlights the distinct
ecological roles and shared microbes of the plastisphere, indicating
that MP pollution may substantially and uniquely impact the function
and health of riverine ecosystems.