Composition Characteristics and Construction Mechanism of Microbial Community on Microplastic Surface in Typical Redox Environments

Microplastics are widely distributed in the biogeochemical cycle driven by microbes. Their surface is enriched with unique microbial communities, called plastispheres. Various redox environments that exist widely in the natural environment can affect the microbial composition in the plastisphere and the fate of the microplastics. To explore the microbial community composition and construction mechanism on the surface of microplastics in typical redox environments, three microplastics, PHA (polyhydroxyalkanoates), PLA (polylactic acid), and PVC (polyvinyl chloride), were placed in five specific redox environments:aerobic, nitrate reduction, iron oxide reduction, sulfate reduction, and methane production. The culture experiment simulated the microcosm, which was inoculum by sludge. The results showed that microplastic factors affected 18.94% and 46.67% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Redox factors affected 31.04% and 90.00% of the microbial communities on the plastisphere in taxonomy and phylogeny, respectively. Compared with that in sludge, the microbial community richness and diversity were reduced on the three microplastics. The most apparent reduction was found on the plastisphere of more degradable PHA. At the same time, microbial communities on the refractory PLA and PVC surfaces remained similar. Anaerocolumna (26.44%) was the dominant genus on the surface of PHA microplastics, whereas microbes related to the redox reaction were less enriched. Clostridium_sensu_stricto_7 (15.49% and 11.87%) was the dominant strain on PLA and PVC microplastics, and the microbes related to the redox reaction were significantly enriched. Thus, characteristic microbes involved in the redox reaction will be enriched in the surface of refractory microplastics, and microplastics may affect the rate of biogeochemical cycling.