Predicting the plastic biodegradation potential within microbial lineages and across global ecosystems.

Plastic waste pollution is a global issue that threatens biodiversity and human health. Current plastic waste management practices are not sufficient to keep up with increasing plastic production rates. Microorganisms have the capacity to degrade different types of bio-based and synthetic plastics through enzymatic reactions, offering an alternative solution to traditional plastic recycling techniques. A limited number of plastic-degrading enzymes have been identified, sequenced and characterized; however, studies exploring the distribution of homologues of these enzymes across habitats and microbial taxa have remained scarce. Here, we applied analytical techniques to search for genes encoding potential plastic-degrading enzymes in environmental metagenome datasets and genomes of the Genome Taxonomy Database (GTDB) to explore the geographic and taxonomic distribution patterns of plastic-degrading microorganisms. Hidden Markov Models (HMMs) were constructed from amino acid sequences of known, experimentally verified and putative plastic-degrading enzymes. The HMMs were applied to landfill, soil, river, lake and ocean metagenomes and all archaeal and bacterial genomes in the GTDB. An abundance of hits was discovered across aquatic and terrestrial metagenomes with the majority occurring in polluted rivers, polar oceans and deep ocean samples. GTDB hits were mainly consistent with known plastic-degrading microbial lineages, while also revealing potential plastic-degrading archaeal taxa. The results of this study may be able to assist in the discovery of novel plastic-degrading enzymes for application in plastic waste biodegradation solutions.