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 the 'plastisphere') whose functional potential remains unexplored. We evaluated 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 taxonomic units across both oceans. We found fewer coding genes, smaller genome sizes and lower GC-content in plankton in comparison to the plastisphere, despite residing in the same environment, reflecting a greater nutrient demand in the plastisphere. A functional gene analysis confirmed that the plastisphere consists of microorganisms with a higher potential to control their nutrient supply, metabolize a wider range of carbon sources, attenuate free radicals 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 new functional units within oligotrophic oceans, with the potential to impact biogeochemical cycles.