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Candida albicans sur puce microfluidique : réponse des hyphes aux contraintes physiques et cycle cellulaire

Abstract : The opportunistic pathogen Candida albicans is one of the most important fungi from a clinical point of view, responsible for mucosal diseases in healthy individuals up to severe infections in immunocompromised patients. A striking property of C. albicans is its ability to grow under distinct morphological forms, from the spherical budding yeast form to long filaments called hyphae.The mechanisms of fungal invasion are still poorly understood, but they involve both penetration of hyphae through the epithelial barriers and dissemination of yeasts in the bloodstream. Therefore, the mechanical properties of the fungus appear crucial to its virulence, as well as its ability to sense its environment and respond to various constraints.We developed a microfluidic device for the measurement of bending rigidity of hyphae.Yeasts are placed in front of microchannels and grow as hyphae.%Yeasts are first seeded and placed in front of microchannels where they are allowed to grow as hyphae, tThen a flow is applied to bend the filaments and the bending rigidity and Young’s modulus are computed from their deflection.We have found that the modulus of the hyphal cell wall ranges around ten of micronewtons.By using microfluidic devices, we can implement guidance of hyphae into microchannels of various sizes in order to probe their behavior under confinement. Surprisingly, a 2D confinement can trigger a switch from a normal straight growth to a sinusoidal growth. Studies of the characteristics of these specific trajectories and of different experimental conditions triggering them have been carried out. Helices in 3D have also been observed either in agar gel or immediately upon release of the 2D confinement. Several leads to explain this behavior are explored such as the position at the tip of the Spitzenkörper, a polarity complex in hyphae.Finally, the cell cycle progression in hyphae is quite interesting and very well regulated, but nevertheless poorly studied compared to the one in budding or fission yeasts.The use of microchannels and of various stainings (nucleus, septum, microtubules) allow a precise monitoring of the different events of the cycle, leading to a better understanding of the regulation and dynamics of cell cycle in hyphae.
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Submitted on : Monday, May 17, 2021 - 11:52:19 AM
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  • HAL Id : tel-03227426, version 1

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Elodie Couttenier. Candida albicans sur puce microfluidique : réponse des hyphes aux contraintes physiques et cycle cellulaire. Médecine humaine et pathologie. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLS032⟩. ⟨tel-03227426⟩

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