Soil microorganisms in the age of plastic pollution: effects of micro- and nano-plastics on soil health

Micro- and nano-plastics (MNPs) are emerging contaminants in soil ecosystems that influence microbial communities and key ecological processes through complex physicochemical and biological interactions. This review synthesizes current knowledge on MNP-microbe interactions, highlighting the central role of the eco-corona, which governs particle bioavailability and mediates interactions with microbial cells in realistic soil environments. At the nanoscale, MNPs exhibit distinct molecular mechanisms, including surface charge-driven interactions, hydrophobic insertion into lipid bilayers, and cellular internalization, leading to oxidative stress and membrane disruption. The formation of plastisphere biofilms is identified as a critical factor shaping microbial community dynamics and acting as a hotspot for antibiotic resistance gene (ARG) enrichment and horizontal gene transfer (HGT). In addition, the impacts of weathered plastics, additive leaching, and co-contaminant transport are discussed in relation to their enhanced ecological risks. The review also adopts a critical perspective on microbial degradation, distinguishing superficial surface modifications from true biodegradation involving polymer depolymerization and mineralization, and highlights the limited evidence for effective degradation of conventional plastics. Despite recent advances, significant knowledge gaps remain regarding long-term environmental behavior, standardized analytical approaches, and realistic soil conditions, underscoring the need for more integrated and mechanistic research to better understand the ecological implications of MNP contamination.