Specificity and dynamics of early microbial colonization on common plastic polymers in a marine environment

Millions of tons of plastic litter end up in the oceans every year where it is gradually broken down into small particles. This plastic debris serves as substrates for the colonization of a variety of prokaryote and eukaryote organisms. Several studies have used a DNA metabarcoding approach to characterize the taxonomic composition of the plastic microbiome. However, very little is known about microorganisms with a specific preference for different plastic polymers over non-plastic natural/artificial substrates. We designed a controllable experiment set up in a marine aquarium in which we monitored early microbial colonization on four abundant plastic polymers (Polyethylene- PE, Polypropylene - PP, Polyethylene terephthalate- PET, and Polystyrene- PS) as well as on wood and glass. The plastic microbiome taxonomic composition was analyzed 2, 7, 14, 30- and 90-days post-incubation initiation. We used the full 16S rRNA gene as a barcode for bacteria, which was amplified and sequenced with the Nanopore MinION system. Our results demonstrated the specificity of certain bacterial genera such as Alcanivorax to specific plastic polymers at the early biofilm stage, particularly polyolefin polymers, PE, and PP. The relative abundances of a variety of different Alcanivorax species followed a similar pattern of expression between PE and PP over the time of the experiment. This research may shed light on the formation and structure of the plastic microbiome in its early development stages and may help in the identification of plastic biodegrading species.