Dynamic Alterations of Extracellular Polymeric Substances and Their Associations with Microbial Communities in the Soil Plastisphere

Extracellular polymeric substances (EPS) facilitate microbiome adhesion on microplastic surfaces and ensure matrix cohesion, playing a crucial role in establishing the structure and function of the plastisphere. Nevertheless, the dynamic alterations in the composition and features of plastisphere EPS and their relationships with biotic and abiotic factors remain poorly understood, especially in soil ecosystems. The study investigated the variations in the EPS secretion behavior of the plastisphere using three types of microplastics across three representative soils with three incubation durations. Results showed that plastisphere EPS had a more complex composition and lower aromaticity, apparent molecular weight, and polarity than natural soil dissolved organic matter did. Continuous changes in EPS composition and features were detected during incubation. The bacterial plastisphere community played a central role in regulating EPS secretion, and other factors (such as soil properties, incubation time and microplastic types) influenced EPS secretion via the bacterial composition of the plastisphere. A decrease in the number of microbial OTUs was significantly correlated with EPS components that governed the dynamics of the EPS composition and features of the plastisphere during incubation, a pattern that was particularly evident for bacteriomes. This study advances our insight into microbiome-EPS interactions within the soil plastisphere and deepens our understanding of its formation mechanisms.