Introduction and Significance

The protozoan parasite Toxoplasma gondii is a major cause of congenital birth defects, a prominent opportunistic pathogen associated with AIDS, and an important veterinary pathogen. Beyond its direct clinical importance, the experimental accessibility of this parasite also provides an outstanding model for studying related species, including Plasmodium (the causative agent of malaria), Cryptosporidium (a devastating AIDS pathogen for which no effective therapy is available), and numerous veterinary pathogens. While biologically diverse, these parasites all share many basic biological features associated with intermediary metabolism, organellar structure and function, control of cell division, motile mechanisms, and host cell invasion. Toxoplasma is a particularly attractive system for experimental study due to its ease of in vitro culture in a diverse range of cell lines, the ability to produce and isolate mutants, the potential for classical genetic analysis, the wide variety of tools available for molecular genetic manipulation of this parasite, the existence of markers suitable for visualization of numerous subcellular structures in living parasites, and the accessibility of all life cycle stages in vitro or in convenient animal models.

TIGR has been funded by the National Institute of Allergy and Infectious Diseases (NIAID) to complete a draft version of the 80 Mb genome sequence of Toxoplasma gondii. This project is being led at TIGR by Ian Paulsen, and is being undertaken in collaboration with the group of David Roos at the University of Pennsylvania. In addition to the sequencing efforts at TIGR, the Sanger Center has been funded by Beowulf Genomics to determine the complete sequence of Toxoplasma gondii chromosome 1 and to undertake BAC end sequencing; and the group of David Sibley at the University of Washington is leading a Toxoplasma gondii EST sequencing project.