Early stage of biofilm assembly on microplastics is structured by substrate size and bacterial motility.

The taxonomic structure of biofilms on 0.3-mm microplastics differed significantly from that on 3-mm microplastics or glass particles. Compared with the 3-mm microplastics, biofilms on 0.3-mm microplastics were enriched for genes involved in flagellar-based motility and chemotaxis, pointing to a more 'mobile' community. The association between motility and bacterial colonization of 0.3-mm microplastics was observed through laboratory experiments using isolated strains.