Butkus Michael A, Bays J Timothy, Labare Michael P
Environmental Engineering Program, Department of Geography and Environmental Engineering. United States Military Academy, West Point, NY 10996, USA.
Appl Environ Microbiol. 2003 Jul;69(7):3819-25. doi: 10.1128/AEM.69.7.3819-3825.2003.
Microelectrophoresis is a common technique for probing the surface chemistry of the Cryptosporidium parvum oocyst. Results of previous studies of the electrophoretic mobility of C. parvum oocysts in which microelectrophoresis was used are incongruent. In this work we demonstrated that capillary electrophoresis may also be used to probe the surface characteristics of C. parvum oocysts, and we related the surface chemistry of C. parvum oocysts to their stability in water. Capillary electrophoresis results indicated that oocysts which were washed in a phosphate buffer solution had neutrally charged surfaces. Inactivation of oocysts with formalin did not influence their electrophoretic mobility, while oocyst populations that were washed in distilled water consisted of cells with both neutral and negative surface charges. These results indicate that washing oocysts in low-ionic-strength distilled water can impart a negative charge to a fraction of the oocysts in the sample. Rapid coagulation experiments indicated that oocysts did not aggregate in a 0.5 M NaCl solution; oocyst stability in the salt solution may have been the result of Lewis acid-base forces, steric stabilization, or some other factor. The presence of sucrose and Percoll could not be readily identified on the surface of C. parvum oocysts by attenuated total reflectance-Fourier transform infrared spectroscopy, suggesting that these purification reagents may not be responsible for the stability of the uncharged oocysts. These findings imply that precipitate enmeshment may be the optimal mechanism of coagulation for removal of oocysts in water treatment systems. The results of this work may help elucidate the causes of variation in oocyst surface characteristics, may ultimately lead to improved removal efficiencies in full-scale water treatment systems, and may improve fate and transport predictions for oocysts in natural systems.
微电泳是一种用于探究微小隐孢子虫卵囊表面化学性质的常用技术。此前使用微电泳对微小隐孢子虫卵囊电泳迁移率进行研究的结果并不一致。在本研究中，我们证明了毛细管电泳也可用于探究微小隐孢子虫卵囊的表面特性，并将微小隐孢子虫卵囊的表面化学性质与其在水中的稳定性联系起来。毛细管电泳结果表明，在磷酸盐缓冲溶液中洗涤过的卵囊表面带中性电荷。用福尔马林灭活卵囊不会影响其电泳迁移率，而在蒸馏水中洗涤的卵囊群体则由表面带中性电荷和负电荷的细胞组成。这些结果表明，在低离子强度的蒸馏水中洗涤卵囊会使样品中的一部分卵囊带上负电荷。快速凝聚实验表明，卵囊在0.5 M NaCl溶液中不会聚集；卵囊在盐溶液中的稳定性可能是路易斯酸碱力、空间稳定作用或其他因素导致的。通过衰减全反射傅里叶变换红外光谱法无法轻易确定微小隐孢子虫卵囊表面是否存在蔗糖和聚蔗糖，这表明这些纯化试剂可能与不带电荷的卵囊的稳定性无关。这些发现意味着沉淀截留可能是水处理系统中去除卵囊的最佳凝聚机制。本研究结果可能有助于阐明卵囊表面特性变化的原因，最终可能提高全尺寸水处理系统的去除效率，并改善自然系统中卵囊的归宿和迁移预测。
