Currently, microplastic pollution is more serious and complicates the toxic effects of other co-existing pollutants in the environment. However, the effect and mechanism of biodegradable plastics on the growth and metabolism of probiotic remain unclear. This work selected Bacillus amyloliquefaciens as model bacterium for a three-day exposure experiment to probe the issues. The results showed that 100 mg/L polylactic acid microplastics (PLA MPs) (3-4 mm, flake shape) caused oxidative damage to cell membranes, disrupted cell wall composition and inhibited cell growth by 21.2%-27.5%. The toxicity was not simply additive or synergistic effects when PLA MPs (100 mg/L) and copper ions (10 mg/L) coexisted. PLA MPs did not significantly increase the toxicity of copper to bacteria, instead triggered some mechanisms to resist the toxicity of copper. The bacteria formed spores to resist PLA MPs, while the copper ions toxicity was weaken by chelation and efflux. It is worth noting that copper ions instead increased the expression of genes related fengycin and iturin then improving the bacteriostatic activity of the probiotic. This paper deeply analyzes the toxicity mechanism of combined pollution on Bacillus amyloliquefacien, and also provides new perspective for helping to inhibit pathogenic bacteria under biodegradable microplastics and metal stress.

目前，微塑料污染更为严重，并使环境中其他共存污染物的毒性作用复杂化。然而，可生物降解塑料对益生菌生长和代谢的影响和机制尚不清楚。这项工作选择解淀粉芽孢杆菌作为模型细菌，进行为期三天的暴露实验来探讨这些问题。结果表明，100  mg/L 聚乳酸微塑料 (PLA MPs)（3-4  mm，片状）对细胞膜造成氧化损伤，破坏细胞壁组成并抑制细胞生长 21.2%-27.5%。当 PLA MPs (100  mg/L) 和铜离子 (10 毫克/升）共存。PLA MPs并没有显着增加铜对细菌的毒性，反而触发了一些抵抗铜毒性的机制。细菌形成孢子来抵抗PLA MPs，而铜离子的毒性通过螯合和外排减弱。值得注意的是，铜离子反而增加了fengycin和iturin相关基因的表达，从而提高了益生菌的抑菌活性。本文深入分析了复合污染对解淀粉芽孢杆菌的毒性机制，也为帮助抑制可生物降解微塑料和金属胁迫下的病原菌提供了新的视角。