Microbial colonization of microplastics in wastewater accelerates the aging process associated with oxidative stress and the insulin/IGF1 signaling pathway*

Although polystyrene (PS)-induced toxicity in organisms has been documented, adverse effects on lifespan and molecular mechanisms underlying microbial colonization of PS remain elusive. Herein, physicochemical properties of biofilm-developed PS (B-PS) incubated in wastewater were altered compared with virgin PS (V-PS). Bacterial community adherence to the B-PS surface were also impacted. Acute exposure to V-PS (100 & mu;g/L) and B-PS (10 & mu;g/L) significantly altered the mean lifespan and lipofuscin accumulation of Caenorhabditis elegans, suggesting that B-PS exposure at environmentally relevant concentrations could more severely accelerate the aging process than V-PS. Generation of ROS, gst-4::GFP expression, and oxidative stress-related gene expression were significantly altered following B-PS exposure. Moreover, B-PS exposure increased the nucleus-cytoplasm translocation of DAF-16 and altered the expression of genes encoding the insulin/IGF1 signaling (IIS) pathway. Compared with wild-type nematodes, the daf-16 mutation markedly enhanced lipofuscin accumulation and reduced mean lifespan, whereas daf-2, age-1, pdk-1, and akt-1 mutants could recover lipofuscin accumulation and mean lifespan. Accordingly, B-PS exposure accelerated the aging process associated with oxidative stress and the IIS pathway, and the DAF-2-AGE-1-PDK-1-AKT-1-DAF-16 signaling cascade may play a critical role in regulating the lifespan of C. elegans. This study provides new insights into the potential risks associated with microbial colonization of microplastics.

Automated summary

This study found that the physicochemical properties of biofilm-developed PS (B-PS) incubated in wastewater were altered compared with virgin PS (V-PS), and bacterial adherence to the B-PS surface was impacted. Exposure to B-PS at environmentally relevant concentrations accelerated the aging process more severely than exposure to V-PS, affecting the lifespan and lipofuscin accumulation of Caenorhabditis elegans. The study provides new insights into the potential risks associated with microbial colonization of microplastics.