# Alveole Symposium – 3/3 – Dr Isabelle Tardieux

Abstract: Cell migration is central to the life of not only multicellular organisms but also single-celled microorganisms including Toxoplasma gondii, the unicellular eukaryotic parasite that belongs to the phylum of Apicomplexa.  T. gondii is a highly polarized few micron-sized cell endowed with unique high-speed gliding motility mode that powers navigation through all tissues of the homeothermic hosts, but also cellular barrier crossing and entry into a hosting cell where to produce progeny. Therefore, the team investigates how forces tune the motile and invasive vital motions for T. gondii survival and expansion in the host. Through collaboration with biophysicists, we have applied time-resolved force microscopy to (i) decipher at the millisecond scale and on sub-micrometric dimensions the contact zones between the parasite and a surface, and (ii) measure the forces in these areas that would account for the typical parasite helical gliding style.  Identifying a contact area between the anterior region of the parasite and the surface at the onset of each motion sequence, we next used PRIMO to design well-demarcated micropattern areas, and established the strict necessity of a pulling force exerted by the parasite from this apical anchoring point. The traction imposes the forward curvature of the parasite which coincides with the energy charge in a spring system enabled by a spiral cytoskeleton formed of microtubules.

The Pavlou et al. has been published in the journal ‘ACS Nano’, with the movement of Toxoplasma visible in a short video produced by the journal (https://youtu.be/kG146bHn4qw).

Bio: Isabelle Tardieux is a CNRS research director who currently heads a team working on « Biomechanics of Host-Parasite Interactions” at the Institute for Advanced BioSciences (Cnrs UMR 5309 – Inserm U 1209 – Univ. Grenoble Alpes) in Grenoble (France). She obtained a PhD in Population Dynamics and Entomology before being appointed as assistant professor at the Pasteur Institute (Paris, France) working on vector-borne diseases. She has been successively trained in Cell biology and Parasitology at Yale University (Infectious Diseases Dept, USA) and at the NIH Bethesda (Parasitic Diseases Laboratory, USA) as post-doctoral fellow and visitor associate, respectively. Building on her experience in membrane and cortex dynamics and in live imaging, she has recently broadened her team framework towards biomechanics and nanobiology in collaboration with the laboratory of interdisciplinary Physics (LIPhy) at Grenoble.