Studies in our laboratory employ modern techniques in cell biology and molecular genetics to investigate host-pathogen interactions.  At present, we focus primarily on the protozoan parasite Toxoplasma gondii, a single-celled organism that replicates within specialized vacuoles inside the cells of infected animals.  Various genetic and cell-biological techniques can be applied to Toxoplasma rendering it accessible to scientific analysis.  The available genetic tools for T. gondii enable us to examine fascinating phenomena such as the relationship between the parasite and the parasitized host cell, or the regulation of parasite differentiation throughout its complex life cycle.

Toxoplasma gondii also serves as a model for thousands of related parasites of the phylum Apicomplexa, including the human pathogens of the genusPlasmodium (the causative agents of malaria).  Many questions that have been difficult to address in Plasmodium are more tractable in Toxoplasma - including the analysis of drug-resistance mechanisms and the identification and characterization of subcellular organelles.

Head of Lab  

Dr. David S. Roos Professor of Biology & Microbiology, Director of Penn Genomics Institute

Project: Parasite Cell Biology

Molecular dissection of T. gondii protein targeting, regulation of cell cycle, purification and characterization of organelles and analysis of cytoskeletal components.

Project: Parasite Differentiation & In vivo Biology

Characterization of tachyzoite/bradyzoite differentiation, identifcation of stage specific genes, isolation of differentiation mutants, and study host immune response to parasite in vivo

Project: Parasite Metabolism and Drug Targets

Identification of drug targets and mechanisms of action, molecular basis of drug resistance, and discovery of novel drug targets within apicomplexan parasites, e.g. fatty acid synthesis, heme synthesis and purine salvage.

Project: Computational Biology & Evolution
 

Mining the Toxoplasma and Plasmodium databases to identify metabolic functions of the apicoplast, to identify events of lateral genetic transfer between the genomes participating in the multiple endo-symbioses, genome evolution and comparative genomics on apicomplexan parasites.

You can also view pages of the comparison of the apicoplast genomes of T. gondii and P. falciparum at the following sites (courtesy of Dr. Jessica C. Kissinger and Dr. D. S. Roos): Dot Plot of coding sequences within the plastid genome of T. gondii compared to P. falciparum View the Toxoplasma gondii 35 kb plastid DNA annotation View the Toxoplasma go ndii 35 kb plastid DNA annotation (site 2) Comparison of the the plastid genomes of T. gondii and P. falciparum (view 1) Comparison of the the plastid genomes of T. gondii and P. falciparum (view 2) Comparison of the the plastid genomes of T. gondii and P. falciparum (view 3) toxogenbank.html

Project: PlasmoDB

The Plasmodium Genome Resource. Database of nucleic-acid and protein sequences of various Plasmodium parasites that is also available as a CD version: Plasmodium Geneplot.

Project: ToxoDB

The Toxoplasma Genome Resource. The Toxoplasma genome project is initiated. Current sequencing efforts at TIGR and the Sanger Centre will quickly produce nucleic-acid sequence data. These data and derived ORF/peptide sequences of Toxoplasma gondii will always be made available as soon as possible on this web-site.