Fig. 2.

TK-expressing P. falciparum can incorporate BrdU, which is a sensitive indicator of DNA replication. a ELISA on wild-type (WT) and +TK parasites (2 × 10⁵ parasites/well) after exposure to 1 mM BrdU for 4 h at the trophozoite stage. Error bars show standard deviation of triplicate readings; star indicates the only significantly differing dataset (One-way ANOVA, p < 0.0001). b Immunofluorescence assay on (WT) and +TK parasites exposed to 100 mM BrdU for 12 h at trophozoite stage. c SYBR Green I staining of +TK parasites after exposure to no BrdU (−) or to 100 mM BrdU (+) for 1, 2 or 4 h. Parasites were released from erythrocytes and suspended in PBS [as for the ELISA assay shown in (a)], then plated with MSF lysis buffer at 1 × 10⁶ parasites/well. The increase in DNA content over 3 h is not detectable by this MSF-type assay. Error bars show standard deviation of triplicate readings. rfu, relative fluorescence units. d ELISA on the same +TK parasites as in (c), plated at 1x10⁶ parasites/well after exposure to no BrdU (−) or to 100 mM BrdU (+) for 1, 2 or 4 h. Background signal, obtained from the same parasites incubated without BrdU, has been subtracted from all readings, and error bars show standard deviation of triplicate readings. Figure c confirms that approximately the same numbers of parasites were plated in all cases