Micro-nanoplastics induce the physiological toxicity and metabolic disorder of Bacillus cereus DFH-1

Micro-nanoplastics (MNPs) as emerging contaminant significantly affect the structure and function of microbial communities in diverse aquatic ecosystems, yet studies regarding their physiological and metabolic effects on microbes at single-strain level remain relatively limited, representing a critical knowledge gap in assessing their ecological risks. In this case, MNPs with varying types (polyethylene terephthalate, PET; polyvinyl chloride, PVC) and particle-sizes (5.0 μm, 150.0 nm) were subject in our study to evaluate their physiological toxicity and metabolic effects on Bacillus cereus DFH-1. Compared to the MNP-free counterpart, 150.0 nm PET-NP inhibited bacterial growth in early stage, while 5.0 μm PET-MP, 5.0 μm PVC-MP, and 150.0 nm PVC-NP had little effect. Superoxide dismutase activity significantly decreased in all MNP-treated groups (p < 0.05), while catalase activity showed slight and non-significant decrease (p > 0.05). Scanning electron microscopy demonstrated that exposure to 150.0 nm PET-NP induced the morphological alteration of bacterial cells, such as deformation and particle adhesion. Furthermore, metabolomic profiling identified 890 differential accumulated metabolites (DAMs) in PET-NP group compared to the control, including 449 up-regulated and 441 down-regulated. Among these DAMs, most related to basic metabolism (e.g., alanine, aspartate, glutamate, and phenylalanine metabolism, tricarboxylic acid cycle) were significantly down-regulated, while tryptophan metabolism-related DAMs were predominantly up-regulated. Collectively, the findings reveal the physiological dysregulation and metabolic disruption of B. cereus DFH-1 when exposed to 150.0 nm PET-NP, providing important scientific guidance for assessing the potential ecological risk of MNPs.