The toxicity effects of nano/microplastics on an antibiotic producing strain - Streptomyces coelicolor M145.

The toxic effects of nano/microplastics on microorganisms are still unclear. In this study, Streptomyces coelicolor (S. coelicolor) M145 was selected to study the toxicity and mechanism of nano/microplastics (20 nm, 100 nm, 1 μm and 1 mm) at concentration of 0.1, 1 and 10 mg/L on microorganisms. Results showed that the cytotoxicity, reactive oxygen species (ROS) level, permeability, and antibiotic production of M145 cells changed significantly after the addition of nano/microplastics, and the trends were size and concentration dependent. After M145 was exposed to 10 mg/L of 20 nm nanoplastics, its fatality rate was 64.8%, which was the highest among the particle size of 20 nm to 1 mm at a concentration of 0.1-10 mg/L. And the ROS level and cell permeability also reached their highest values, which was about 2.7 folds and 2.2 folds of control, respectively. After this treatment, the maximum yields of actinorhodin and undecylprodigiosin were 6.7 and 5.3 mg/L, respectively. Transcriptome analysis indicated that nanoplastics could inhibit the transport capacity, primary metabolism, and oxidative phosphorylation of M145, and that the inhibition extend was negatively related to the particle size. Moreover, the toxicity of microplastics to M145 was significantly less than that of nanoplastics. This study provides a new perspective for understanding the toxicity of nano/microplastics on microorganisms in nature.