纳米银对反硝化无色杆菌的毒性作用

为研究纳米银(AgNPs)对反硝化无色杆菌(Achromobacter denitrificans)的毒性作用,选择室内培养方式,探究纳米银对Achromobacter denitrificans的生长抑制、氨化作用、同化吸收NH₄+-N、细胞膜表面结构和活性氧生成的影响。研究发现,纳米银可抑制细菌生长,抑制效果与浓度和暴露时间呈正相关。添加10 mg/LAgNPs在硝化培养基中,Achromobacter denitrificans生长抑制率12h后达38.2%,而添加1 mg/LAgNPs时生长抑制率仅为11.5%。不同AgNPs暴露浓度条件下,4~6 h后生长抑制率均趋于稳定。暴露培养后的细菌生化活性降低,AgNPs投加浓度从1 mg/L提高到10 mg/L时,NH+₄-N生成速率从2.77 mg/(L·h)降低至2.07 mg/(L·h),降低了25.3%;NH₄+-N同化速率从5.52 mg/(L·h)降低至1.71 mg/(L·h),降低了69.1%。pH是影响毒性作用的重要因素,弱酸(pH 5.0)与弱碱(pH 9.0)均不利于细菌生存。通过毒性作用机理分析可知,纳米银可导致细胞膜表面凹陷破裂,膜内物质泄漏流出,细胞内发生活性氧的累积。

TOXICITY OF SILVER NANOPARTICLES TO ACHROMOBACTER DENITRIFICANS

The indoor culture method was selected to study the toxic mechanism of AgNPs to Achromobacter denitrificans and the effects of silver nanoparticles on the growth inhibition, ammoniation, assimilation and absorption of NH₄+-N, cell membrane surface structure and the accumulation of the reactive oxygen species. The study found that AgNPs could inhibit bacterial growth, and the inhibitory effect was positively related to concentration and exposure time. In the nitrification medium supplemented with 10 mg/LAgNPs, the growth inhibition rate of Achromobacter denitrificans reached 38.2% after 12 h, while the growth inhibition rate was only 11.5% when 1 mg/LAgNPs was added. Under different AgNPs exposure concentrations, the growth inhibition rates tended to be stable after 4~6 h. The biochemical activity of bacteria after exposure to AgNPs decreased. When the dosage of AgNPs increased from 1 mg/L to 10 mg/L, the NH+₄-N generation rate decreased by 25.3%, from 2.77 mg/(L·h) to 2.07 mg/(L·h); NH₄+-N assimilation rate decreased by 69.1%, from 5.52 mg/(L·h) to 1.71 mg/(L·h). Besides, pH was an important factor affecting the toxicity. Both weak acid(pH=5.0) and weak alkaline(pH=9.0) were not conducive to bacterial survival. Through the analysis of the mechanism of toxicity, we found that AgNPs can cause the depression and rupture of the cell membrane surface, the leakage of substances in the membrane, and the accumulation of reactive oxygen species in the cells.