The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, P. R. China.
Environ Sci Technol. 2010 Apr 1;44(7):2393-9. doi: 10.1021/es9027937.
The significance of extracellular polymeric substances (EPS) on cell transport and retained bacteria profiles in packed porous media (quartz sand) was examined by direct comparison of the overall deposition kinetics and retained profiles of untreated bacteria (with EPS) versus those of treated cells (without EPS) from the same cell type. Four representative cell types, Pseudomonas sp. QG6 (gram-negative, motile), mutant Escherichia coli BL21 (gram-negative, nonmotile), Bacillus subtilis (gram-positive, motile), and Rhodococcus sp. QL2 (gram-positive, nonmotile), were employed to systematically determine the influence of EPS on cell transport and deposition behavior. Packed column experiments were conducted for the untreated and treated cells in both NaCl (four ionic strength ranging from 2.5 mM to 20 mM) and CaCl(2) (5 mM) solutions at pH 6.0. The breakthrough plateaus of untreated bacteria were lower than those of treated bacteria for all four cell types under all examined conditions (in both NaCl and CaCl(2) solutions), indicating that the presence of EPS on cell surfaces enhanced cell deposition in porous media regardless of cell type and motility. Retained profiles of both untreated and treated cells for all four cell types deviated from classic filtration theory (log-linear decreases). However, the degree of deviation was greater for all four untreated cells, indicating that the presence of EPS on cell surfaces increased the deviation of retained profiles from classic filtration theory. Elution experiments demonstrated that neither untreated nor treated cells preferentially deposited in secondary energy minima. Furthermore, the release of previously deposited cells in the secondary energy minima did not change the shape of retained cell profiles, indicating that deposition in secondary energy minima did not produce the observed deviations of retained profiles from classic filtration theory.
通过直接比较未经处理细菌（带 EPS）和经处理细胞（不带 EPS）的整体沉积动力学和保留分布，可以研究细胞外聚合物 (EPS) 对多孔介质（石英砂）中细胞传输和保留细菌分布的影响。采用 4 种代表性细胞类型，即假单胞菌 QG6（革兰氏阴性，运动型）、突变大肠杆菌 BL21（革兰氏阴性，非运动型）、枯草芽孢杆菌（革兰氏阳性，运动型）和红球菌 QL2（革兰氏阳性，非运动型），系统地确定了 EPS 对细胞传输和沉积行为的影响。在 pH 值为 6.0 的 NaCl（离子强度范围为 2.5 mM 至 20 mM）和 CaCl2（5 mM）溶液中，对未经处理和经处理的细胞进行了填装柱实验。在所有研究条件下（NaCl 和 CaCl2 溶液中），未经处理细菌的穿透平台均低于经处理细菌，表明无论细胞类型和运动性如何，细胞表面 EPS 的存在均增强了多孔介质中的细胞沉积。所有 4 种细胞类型的未经处理和经处理细胞的保留分布均偏离了经典过滤理论（对数线性减少）。然而，未经处理的所有 4 种细胞的偏离程度更大，表明细胞表面 EPS 的存在增加了保留分布对经典过滤理论的偏离。洗脱实验表明，未经处理和经处理的细胞都不会优先沉积在二次能量最小处。此外，先前沉积在二级能量最小处的细胞的释放并没有改变保留细胞分布的形状，这表明在二级能量最小处的沉积并没有产生观察到的保留分布对经典过滤理论的偏离。
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