Microplastics (diameters <5mm) are a global concern in aquatic ecology and are readily colonized by bacteria in the environment. The term”plastisphere” has been used to describe bacterial communities residing on microplastics. The composition of the communities inside the plastisphere have been affected by the physicochemical properties of different microplastic types. Plastics have variations in physicochemical properties based on their intended applications. For example, polyethylene (PE) has a net negative charge while polypropylene (PP) has a net neutral charge at the pH of seawater. In this study, we investigated bacterial community composition by placing 4 different microplastic disks (diameters <5mm) in a stream for 4 weeks. Disks were placed in bags constructed mesh fabric with 1000 µm diameter. Sampling was done at various intervals to determine early and late colonizers within bacterial communities on microplastics in freshwater. Subsequently, disks will be used for DNA extraction and plastisphere community composition from the V6 hypervariable region of 16S rDNA using 16S MiSeq 250 sequencing. Sampled disks will also be analyzed for differences in surface roughness, buoyancy, and weight after bacterial colonization. Moreover, fluorescent and SEM microscopy was also performed to determine bacterial abundance.
Results/Conclusions
Fluorescent and SEM microscopy revealed that bacterial abundance differed among bacterial species and plastic types after 4 weeks. As the study progressed, microplastic disks broke down and had increased surface roughness. Our results indicate that bacterial colonization of microplastics is affected by the physicochemical properties of the substrates and physiological properties of colonizing bacteria. They also suggest that early colonization and biofilm formation on microplastics prime the substrates for further bacterial colonization in the environment.