Donald Bren School of Environmental Science and Management, 2308 Bren Hall, University of California at Santa Barbara, Santa Barbara, CA 93106-5131, USA.
Appl Environ Microbiol. 2010 Nov;76(21):7292-8. doi: 10.1128/AEM.00324-10. Epub 2010 Sep 17.
Engineered nanoparticles are increasingly incorporated into consumer products and are emerging as potential environmental contaminants. Upon environmental release, nanoparticles could inhibit bacterial processes, as evidenced by laboratory studies. Less is known regarding bacterial alteration of nanoparticles, including whether bacteria affect physical agglomeration states controlling nanoparticle settling and bioavailability. Here, the effects of an environmental strain of Pseudomonas aeruginosa on TiO₂ nanoparticle agglomerates formed in aqueous media are described. Environmental scanning electron microscopy and cryogenic scanning electron microscopy visually demonstrated bacterial dispersion of large agglomerates formed in cell culture medium and in marsh water. For experiments in cell culture medium, quantitative image analysis verified that the degrees of conversion of large agglomerates into small nanoparticle-cell combinations were similar for 12-h-growth and short-term cell contact experiments. Dispersion in cell growth medium was further characterized by size fractionation: for agglomerated TiO₂ suspensions in the absence of cells, 81% by mass was retained on a 5-μm-pore-size filter, compared to only 24% retained for biotic treatments. Filtrate cell and agglomerate sizes were characterized by dynamic light scattering, revealing that the average bacterial cell size increased from 1.4 μm to 1.9 μm because of nano-TiO₂ biosorption. High-magnification scanning electron micrographs showed that P. aeruginosa dispersed TiO₂ agglomerates by preferential biosorption of nanoparticles onto cell surfaces. These results suggest a novel role for bacteria in the environmental transport of engineered nanoparticles, i.e., growth-independent, bacterially mediated size and mass alterations of TiO₂ nanoparticle agglomerates.
工程纳米粒子越来越多地被纳入消费产品，并成为潜在的环境污染物。在环境释放后，纳米粒子可能会抑制细菌的过程，这一点在实验室研究中得到了证明。然而，关于细菌对纳米粒子的改变，包括细菌是否会影响控制纳米粒子沉降和生物有效性的物理团聚状态，人们知之甚少。在这里，描述了环境型铜绿假单胞菌对在水介质中形成的 TiO₂纳米粒子团聚体的影响。环境扫描电子显微镜和低温扫描电子显微镜直观地显示了在细胞培养液和沼泽水中形成的大团聚体的细菌分散。对于细胞培养液中的实验，定量图像分析证实，在 12 小时生长和短期细胞接触实验中，大团聚体转化为小纳米粒子-细胞组合的程度相似。在细胞生长培养基中的分散进一步通过粒径分离来表征：对于无细胞的团聚 TiO₂悬浮液，在 5μm 孔径的过滤器上保留了 81%的质量，而对于生物处理，仅保留了 24%。通过动态光散射对滤出物的细胞和团聚体尺寸进行了表征，结果表明，由于纳米 TiO₂的生物吸附，铜绿假单胞菌的平均细胞尺寸从 1.4μm 增加到 1.9μm。高倍扫描电子显微镜照片显示，铜绿假单胞菌通过优先将纳米粒子吸附到细胞表面来分散 TiO₂团聚体。这些结果表明，细菌在工程纳米粒子的环境传输中具有新的作用，即与生长无关的、细菌介导的 TiO₂纳米粒子团聚体的大小和质量变化。
