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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED APPROACH TO THE DETECTION AND CONTROL OF FOODBORNE PARASITES AND THE IMPACT ON FOOD SAFETY

Location: Animal Parasitic Diseases

Title: Mechanics of the Toxoplasma gondii oocyst wall

Authors
item Dumètre, Aurelien -
item Dubey, Jitender
item Ferguson, David -
item Bongrand, Pierre -
item Azas, Nadine -
item Puech, Pierre-Henri -

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2013
Publication Date: July 1, 2013
Citation: Dumètre, A., Dubey, J.P., Ferguson, D., Bongrand, P., Azas, N., Puech, P. 2013. Mechanics of the Toxoplasma gondii oocyst wall. Proceedings of the National Academy of Sciences. 110:11535-11540.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating under-cooked meat from infected animals and food and water contaminated with oocysts. The oocyst is a bilayered structure. In the present study, authors ivestigated the physical and chemical resistance of the two layers of the oocysts using atomic force microscopy and by electron microscopy. The results indicated that both layers contribute to resistance, and the parasites remain protected even after removal of outer layer. The results will be of interest to biologists and parasitologists.

Technical Abstract: The ability of microorganisms to survive under extreme conditions is closely related to the physicochemical properties of their wall. In the ubiquitous protozoan parasite Toxoplasma gondii, the oocyst stage possesses a bilayered wall that protects the dormant but potentially infective parasites from harsh environmental conditions until their ingestion by the host. None of the common disinfectants are effective in killing the parasite, since the oocyst wall acts as a primary barrier to physical and chemical attacks. Here, we address the structure and chemistry of the wall of the T. gondii oocyst by combining wall surface treatments, fuorescence imaging, electron microscopy and measurements of its mechanical characteristics by using Atomic Force Microscopy (AFM). Elasticity and indentation measurements indicated that the oocyst wall resembles hard plastic materials, based on the Young moduli, E, evaluated by AFM. Our study demonstrates that the inner layer is as robust as the bilayered wall itself. Besides wall mechanics, our results suggest important differences regarding the non specific adhesive properties of each layer. All together, these findings suggest a key biological role for the oocyst wall mechanics in maintaining the integrity of the T. gondii oocysts in the environment or after exposure to disinfectants, and therefore their potential infectivity to humans and animal.

Last Modified: 7/28/2014