Integration of metagenomic analysis and metabolic modeling reveals microbial interactions in activated sludge systems in response to nanoplastics and plasticizers

Nanoplastics and plasticizers are prevalent in activated sludge and pose a potential threat to microbial communities in wastewater treatment systems. However, studies on the effects of nanoplastics and plasticizers on the interaction mechanisms and metabolic functions of microbial communities in activated sludge systems are still scarce. In this study, the responses of microbial interactions and metabolic functions to PVC nanoplastics (PVC-NPs) and bis(2-ethylhexyl) phthalate (DEHP) in activated sludge were investigated via a combination of amplicon sequencing, metagenome sequencing, and metabolic modeling. The results revealed that DEHP had a significant effect on the microbial community under short-term exposure. DEHP contamination may increase vitamin B₁₂ producers to enhance species collaboration in communities. Furthermore, community metabolic modeling revealed that DEHP-degrading bacteria could promote positive interactions among community members. The increased metabolic exchange flux of siderophores and glutathione in microbial communities under PVC-NPs and DEHP contamination implied that microbial communities may maintain iron homeostasis in response to PVC-NPs and DEHP contamination through interspecies collaboration. However, more data are needed to further validate these results. This study provides vital insights into the response mechanisms of microbial interactions to nanoplastic and plasticizer contamination in activated sludge systems.