University of Pittsburgh Department of Biological Sciences Presents:
Friday Noon Seminar Series 2017-2018
Graduate Student: Sarah Sokol
"Utilizing interspecies comparisons between Toxoplasma gondii and Hammondia hammondi to elucidate mechanisms driving life stage development and life cycle"
Toxoplasma gondii is the most common human parasitic infection. Although generally asymptomatic, T. gondii can cause severe disease in utero and in immunocompromised individuals. T. gondii follows a facultative homoxenous/heteroxenous life cycle, allowing it to infect new and diverse intermediate hosts with orally infectious agents derived from both sexual (oocysts) and asexual reproduction (tissue cysts). This phenomenon is unique to T. gondii among other Apicomplexans, including its closest relative Hammondia hammondi. Despite its extensive genomic similarity with T. gondii, H. hammondi is naturally avirulent and possesses dramatic phenotypic differences with regards to life cycle, infectivity, and host range. These differences suggest that despite possessing a similar genetic tool kit, H. hammondi and T. gondii differentially utilize their genetic components to progress through their distinct life stages. To understand the mechanisms that drive life stage progression in both species, I have characterized the temporal dynamics H. hammondi’s in vitro growth and spontaneous stage conversion. I have found this process measured by tissue cyst formation, occurs with 100% efficiency in H. hammondi in comparison to occurring in less than 20% of vacuoles in T. gondii infections. I have also found that conditions known to induce stage conversion in T. gondii do not induce tissue cyst formation in H. hammondi. This result suggests that these two species utilize different mechanisms for stage progression and provides a novel comparative system that will allow for the identification of genetic components uniquely driving stage progression in T. gondii.
Friday, December 1, 2017
A219B Langley Hall
12:00 PM Seminar