Electrophoretic mobility of Cryptosporidium oocysts and Giardia cysts

Electrophoretic mobilities were measured and zeta potentials calculated for oocysts of Cryptosporidium and for cysts of both Giardia lamblia and G. muris, Measurements were made in both distilled water and in an unfiltered low-turbidity river water, and included measurements for both fresh and preserved organisms. Electrophoretic mobilities of oocysts and cysts were between -2.72 and -3.12 mu m/s/V/cm corresponding to zeta potentials of -35 and -40 mV at neutral pH and decreased to less than -0.78 mu m/s/V/cm (-10 mV) as pH was decreased to about 3.5. The electrophoretic mobilities and corresponding zeta potentials of oocysts and cysts were substantially modified in the presence of fulvic acid and of natural organics in unfiltered water. Common methods of oocyst and cyst preservation also altered electrophoretic mobilities and corresponding zeta potentials indicating that caution should be taken when conducting laboratory and pilot studies using preserved organisms.