Archaea-driven bioremediation of polyolefins and polyesters in extreme environments

Global plastic production surpassed 436 million metric tonnes in 2023, with polyolefins, polyethylene and polypropylene, and polyesters, polyethylene terephthalate and polybutylene adipate terephthalate dominating the persistent fraction. In extreme environments, these recalcitrant polymers accumulate rapidly: hadal-trench sediments contain microplastic abundances of 71.1 items per kilogram dry weight, while bottom waters reach 2.06-13.51 particles per litre. Abiotic degradation is severely limited by hydrostatic pressure, hypersalinity, low temperature, and anaerobiosis. Although bacterial and fungal pathways have received primary attention, archaea adapted to polyextreme conditions represent an underexplored resource. Landmark discoveries include PET46, a lid-containing feruloyl esterase from uncultured Candidatus Bathyarchaeota in Guaymas Basin deep-sea sediments that hydrolyses semi-crystalline polyethylene terephthalate powder at rates comparable to established bacterial PETases while outperforming them on oligomers. Subsequent metagenomic prospecting identified GuaPA, a distinct Bathyarchaeia-derived PETase capable of film depolymerisation. Deep-sea plastispheres, hypersaline basins, and extraterrestrial analog sites further reveal archaeal colonisation and metabolic versatility. This review synthesises metagenomic, enzymatic, and community-level evidence, critically evaluates archaeal advantages relative to bacteria and fungi, addresses persistent gaps, including limited polyolefin mineralisation and cultivation bias, and outlines priorities for enzyme engineering and consortia design. The work advances sustainable bioremediation strategies aligned with climate-action goals and circular-economy frameworks in extreme and space environments.