Carbon-Driven Metabolic Activation (CDMA): A conceptual framework linking biodegradable plastic degradation to...

Biodegradable plastics are increasingly promoted as environmentally sustainable alternatives to conventional plastics, yet their unintended microbiological consequences remain insufficiently explored. Here, we propose the Carbon-Driven Metabolic Activation (CDMA) framework as a conceptual hypothesis (not an established mechanism) to explain how polymer degradation may influence resistome dynamics through localized release of bioavailable carbon. During biodegradation, enzymatic depolymerization generates dissolved organic carbon that may transiently alleviate microbial carbon limitation, stimulating metabolic activity, biofilm formation, and horizontal gene transfer (HGT) under favourable environmental conditions. We distinguish CDMA from existing microbial ecological concepts by emphasizing polymer-specific degradation kinetics and temporally dynamic carbon release unique to biodegradable polymers. We critically synthesize recent experimental evidence (2022-2026), including both supporting and contradictory findings, demonstrating that the ecological consequences of biodegradable plastics vary substantially among polymer types and environmental compartments. Notably, the extremely slow hydrolysis of polylactic acid (PLA) outside industrial composting (half-life >5 years in marine environments) suggests that CDMA is unlikely to operate in many natural settings. We further introduce the Degradation-Risk Temporal Mismatch concept, whereby biodegradable plastics may generate transient ARG enrichment during active degradation, whereas conventional plastics act as persistent long-term reservoirs. We emphasize that CDMA is a testable conceptual framework requiring rigorous empirical validation before informing environmental risk assessment or regulatory decision-making. This perspective aims to stimulate mechanistic research on biodegradable plastic-resistome interactions within a One Health framework.