METHODOLOGY

Transfection with thymidine kinase permits bromodeoxyuridine labelling of DNA replication in the human malaria parasite Plasmodium falciparum Catherine J. Merrick* Background: Plasmodium falciparum, the causative agent of severe human malaria, is an early-diverging protozoan whose lifecycle has many unusual features, including its modes of replication. Research on the Plasmodium cell cycle, which occurs primarily via schizogony instead of canonical binary fission, has been hampered by a lack of tools and markers that can be transferred from cell cycle studies in model organisms. A common tool used to study DNA repli-cation and the cell cycle in human cells is the labelling of newly-replicated DNA with the modified nucleotide bromo-deoxyuridine (BrdU), followed by immunofluorescent detection. Plasmodium parasites, however, do not incorporate BrdU because they rely only on de novo synthesis of pyrimidines and do not salvage thymidine analogues like BrdU for conversion into nucleotides. Methods: Analysis of biochemical pathways in Plasmodium indicated that the absence of the enzyme thymidin