The Plastisphere "Microbiome"

Alongside other ocean stressors, plastic marine debris (PMD) is now considered a major source of marine pollution and potential source of invasive alien species, two important ocean health index criteria. While macroplastics are recognized as a visible problem in coastal environments, the less conspicuous microplastics (< 5 mm) numerically dominate pristine open ocean gyres where their impact is much less understood. Central to biological interactions with plastic is the almost instant colonization upon entry into the sea by a thin film of microorganisms, the Plastisphere microbiome. While the phylogenetic diversity of the Plastisphere is now recognized to be highly variable and diverse in nature, less is known about its metabolic potential. Using shotgun metagenomics techniques, we characterized the metabolic potential of Plastisphere microbiomes from ocean gyre-collected microplastics and contrasted it with those of known biotic substrates such as macroalgae. Our data reveal that microbial eukaryotic assemblages dominate some Plastisphere communities, and bacteria dominate others, while archaea appear to be consistently rare inhabitants. We have successfully recovered dozens of draft bacterial genomes and several partial eukaryotic genomes from our libraries. Our data allow us to conduct comparative genomics on commonly occurring Plastisphere residents, further gaining insights into their physiology, ecology, pathogenicity, and substrate transformation potential.