Rapid Evolution of Plastic-degrading Enzymes Prevalent in the Global Ocean

Abstract

Estimates of marine plastic stocks, a major threat to marine life, are far lower than expected from exponentially-increasing litter inputs, suggesting important loss factors. These may involve microbial degradation, as the plastic-degrading polyethylene terephthalate enzyme (PETase) has been reported in marine microbial communities. An assessment of 416 metagenomes of planktonic communities across the global ocean identifies 68 oceanic PETase variants (oPETase) that evolved from ancestral enzymes degrading polycyclic aromatic hydrocarbons. Nearly 20 oPETases have predicted efficiencies comparable to those of laboratory-optimized PETases, suggesting strong selective pressures directing the evolution of these enzymes. We found oPETases in 90.1% of samples across all oceans and depths, particularly abundant at 1,000 m depth, with a strong dominance of Pseudomonadales containing putative highly-efficient oPETase variants in the dark ocean. Enzymatic degradation may be removing plastic from the marine environment while providing a carbon source for bathypelagic microbial communities.