Grant: Operating Grant

Microsporidia and Apicomplexa are obligate intracellular parasites that include numerous medical and commercially important pathogens. Both lineages also have surprising evolutionary origins that have forced us to re-interpret basic characteristics such as genomes, metabolism, and infection apparatus. Microsporidia were formerly considered to be primitive, but we now know they are in fact closely related to fungi and that their simplicity is the really result of severe reduction. In the case of apicomplexans, despite being intracellular parasites they were found to contain a plastid, the organelle responsible for photosynthesis in plants and algae. we have learned a great deal about these parasites from comparative genomics, but population- and environmental-genomic data remains limited for both groups, restricting our fundamental knowledge in several ways. Here, we propose to fill these gaps, and address specific key questions. For microsporidia, we will focus on population genomics and potential environmental reservoirs of the human parasite Encephalitozoon, which includes species with the most reduced nuclear genomes known. Sequencing whole genomes from genetically distinct strains will reveal how their extremely reduced genomes change over time, and whether cultivation affects model strains at the genomic level, while environmental surveys will reveal whether parasites can jump between vertebrate and invertebrate hosts. For apicomplexans, we will test the hypothesis that they emerged through a symbiotic interaction with animals based on photosynthesis by genome -wide characterization of several newly-discovered free-living and photosynthetic relatives, to determine what roles the loss of photosynthesis and the infection apparatus played in their adaptation to parasitism. Overall, this work will use high-throughput genomic methods to address fundamental questions about two important groups of parasites at levels previously restricted by the absence of data.