Substrate type-driven differences in interfacial microbial community and pathogenic risk: Clay, microplastics and activated carbon

This study investigated the microbial colonization, bacterial community and potential risks in natural (montmorillonite (MMT)) and artificial substrates (activated carbon (AC), polypropylene (PP) and polystyrene (PS)) by microcosm incubations in surface water. Biofilm biomass and polysaccharide content indicate that the colonization potential of microbes on different substrates followed the order of AC > MMT > PP > PS. High-throughput sequencing results reveal that microbes selectively colonized various substrates and formed unique bacterial community. Compared to the artificial substrate, natural substrate enriched with high abundance but low diversity of microbial community. In addition, bacterial community on natural substrates exhibited stronger nitrogen cycling function than artificial substrates, whereas bacterial community on artificial substrates (especially microplastics) exhibited stronger carbon cycling functions, such as aromatic_compound_degradation and hydrocarbon_degradation. Also, Brevundimonas diminuta, Sphingomonas paucimobilis, Paracoccus sanguinis and other twenty-five species of pathogenic bacteria were identified in various substrates and their abundance was higher on MMT than on other substrates. However, many more species of pathogenic bacteria on microplastic are associated with human diseases, implying a higher environmental risk. These results indicated that microbial community composition and function on natural and artificial substrates exhibited substrate-driven differences, highlighting the lower concerns of artificial substrates than natural ones with associated biofilms in surface water.