Metagenomic analyses of the plastisphere reveals a common functional potential across oceans

Trillions of plastic particles have accumulated in the oceans, covered by microbial biofilms (termed 'plastisphere') whose functional potential remains underexplored. We evaluated as one of the first of its kind genome-resolved bacterial metagenomes of the plastisphere from the North Atlantic and North Pacific garbage patches and compared their structure and functional potential to ambient plankton. Our data revealed a characteristic genetic potential of the plastisphere with functionally equivalent traits across both oceans. We found more coding genes, bigger genomes and higher GC-content in the plastisphere in comparison to the surrounding plankton community, despite residing in the same environment, reflecting an increased metabolic capacity in the plastisphere. An analysis of 340 functional genes confirmed that the plastisphere consists of microorganisms with a higher potential for nutrient metabolism, metabolize a wider range of carbon sources, attenuate radicals, fix their own nitrogen and use alternative energy sources like anoxygenic photosynthesis. Our results suggest that the overriding factor for the high functional similarity of the plastisphere in both oceans is the habitat for biofilm formation with the potential to support mutualism and nutrient sharing making genomic streamlining as found in plankton, unnecessary. Consequently, increasing plastic pollution promotes the expansion of a new functional unit at the surface of the oligotrophic oceans with various roles in biogeochemical cycles.