Microplastics as evolving particle-chemical-microbial interfaces: plastisphere ecology, ecotoxicity, and safety-informed remediation

Microplastics (MPs) are not environmentally static particles; aging, fragmentation, contaminant acquisition, organic conditioning, and microbial colonization progressively convert them into dynamic particle-chemical-microbial interfaces. This transformation is central to their environmental fate and risk because plastisphere communities can alter particle transport, contaminant partitioning, nutrient cycling, antimicrobial-resistance dynamics, and polymer transformation. Experimental evidence shows that MP biofilms can increase conjugative transfer of antibiotic-resistance genes by approximately 7.2-19.6-fold relative to suspended bacteria, illustrating that microbial colonization can modify ecological function rather than merely change community composition. However, microbial presence, functional-gene enrichment, surface deterioration, and polymer mass loss should not be interpreted as equivalent evidence of biodegradation. Stable-isotope studies show that even biodegradable polymers may mineralize slowly and incompletely; approximately 65% mineralization of 1 3C-labeled PBS required 425 days, whereas direct mineralization of persistent polyolefins remains far more limited. Ecotoxicological effects are similarly conditional on particle size, morphology, aging, associated chemicals, exposure duration, and environmental context, and evidence for trophic transfer is stronger than that for generalized biomagnification. Interpretation is further constrained by substantial analytical heterogeneity in sampling, size cut-offs, recovery, contamination control, polymer identification, and number-vs.-mass reporting, making methodological harmonization and uncertainty assessment essential for cross-study comparison. Remediation should therefore distinguish particle capture from destruction and biodeterioration from depolymerization, microbial assimilation, mineralization, and true upcycling. Although enzymatic and microbial conversion technologies show considerable promise, most high-performance demonstrations involve defined polymers, post-consumer plastics, or prepared hydrolysates rather than heterogeneous environmental MPs. Safe application consequently requires carbon and contaminant mass balances, residue and product safety testing, microbial containment, and life-cycle verification. Climate-sensitive transport and toxicity further reinforce the dynamic nature of MP exposure, while circular-economy strategies should prioritize prevention, low-shedding design, reuse, and recovery before attempting energy-intensive reclamation of dispersed environmental particles. Overall, a microbiology-informed assessment of MPs requires progression from microbial identity to demonstrated function, from particle detection to exposure relevance, and from apparent removal or degradation to verified net risk reduction.