A method to measure the cytoplasmic pH of single, living Plasmodium falciparum parasites

Here we describe a novel methodology for the investigation of the intracellular pH of P. falciparum. This method is based on a fluorescent dye with pH-dependent spectral properties, which can be monitored using a digital imaging system. This non-invasive method allows the cytoplasmic pH of single, living P. falciparum parasites to be measured while still within the host erythrocyte. It was found that schizonts from the P. falciparum clone D10 have a cytoplasmic pH of 7.18 to 7.23, differing slightly on the buffering system used. The pH of uninfected erythrocytes is 7.10 +/- 0.05. This method offers an opportunity to study the parasite's physiology and define transport mechanisms essential for parasite growth.