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Deinococcus radiodurans cell morphology and nucleoid organisation & dynamics

Vendredi 8 février 14:00 - Duree : 2 heures
Lieu : Salle des séminaires de l’IBS - 71, avenue des Martyrs - Grenoble

Orateur : Soutenance de Thèse de Kevin FLOC'H (IBS/Dynamique et Cinétique des processus moléculaires)

During this PhD work, we have studied on D. radiodurans, a coccus, known for its intriguing outstanding resistance to different stress factors. Studies on D. radiodurans have been mainly focusing on its tremendous radioresistance. 52 years after its discovery, its nucleoid organization/segregation as well as its cell morphology during its cell cycle still remain elusive. Most of our knowledge on the bacteria shape during division and on the nucleoid organization/segregation arises from the study of a small number of “model bacteria”, that are mainly rod-shaped or ovoid. In contrast, little is known on the nucleoid organization/segregation of cocci. Moreover, the small relative size of bacteria and of their nucleoids (<1μm3) has limited their studies by conventional microscopy.

One of the aims of this PhD project is to contribute to a better understanding of the cell morphology and the nucleoid organization/segregation in cocci. For that matter, we explored the 4D organization and the dynamics of D. radiodurans nucleoids, as a function of the cell cycle progression and growth phase. Several strategies were undertaken : (i) timelapse 3D stacks by spinning confocal microscopy (ii) dynamics studies with FRAP analysis and SptPALM acquisitions, and (iii) cartographies of nucleoid associated proteins using super-resolution microscopy (PALM). We were thus able to show that the multiple copies of the 4 replicons that possess D. radiodurans are grouped into a single nucleoid, which adopts distinct shapes throughout the cell cycle : a toroid shape in new-born cell, a square shape or a crescent shape in the next phases of the cycle, a rod shape at the beginning of septation, a branched shape during later stage of septation and a double ring shape at the end of cytokinesis. These observations will be the basis of future works on the dynamics of DNA repair machineries and also bring new perspective on DNA organization and segregation in cocci.

Contact : ibs.seminaires@ibs.fr

Discipline évènement : (Biologie / Chimie)
Entité organisatrice : (IBS)
Nature évènement : (Soutenance de thèse)
Site de l'évènement : Polygone scientifique

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