Terrestrial and Aquatic Plastisphere: Formation, Characteristics, and Influencing Factors

The increasing number of plastic particles in the environment gives rise to a unique ecological niche called the plastisphere, which is characterized by a dynamic assemblage of microorganisms comprising autotrophs, heterotrophs, predators, and pathogens. This paper reviews the formation, characteristics, and factors influencing the terrestrial and aquatic plastisphere. The terrestrial and aquatic plastisphere forms when hitchhiking microorganisms, often bacteria, in the environment adhere to the surfaces of plastic particles and alter the surface properties of the particles for subsequent colonization of increasingly tightly clinging microorganisms. The terrestrial plastisphere is not as mobile as the aquatic plastisphere and is defined by the characteristics of the soil anchoring it. The microorganisms on the plastisphere are often defined by the dominant microorganisms in the surroundings, particularly those of the phyla Proteobacteria, Actinobacteria, Bacteroidota, Firmicutes, Chloroflexi, Acidobacteria, Cyanobacteria, Ascomycota, Basidiomycota, Chytridiomycota, Ciliophora, Ochrophyta, and Chlorophyta. However, the compositions and dominant microbial species on different plastic surfaces vary widely as they change with time, plastic properties, and biotic and abiotic environmental factors. Temporal changes in the plastisphere are due to succession. Plastic properties, particularly the type, surface properties, size, color, degree of aging, and chemical leaching, also affect the composition of the plastisphere. Biotic environmental factors comprising the dominant ambient microorganisms and interspecies interactions, together with the abiotic ones, including pH, temperature, nutrient availability, soil properties, salinity, and light, significantly shape the plastisphere. This review provides insight into the biodiversity of the plastisphere, and its roles in spreading pathogens and degrading plastics.