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Nucleoid organization and dynamics in Deinococcus radiodurans
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International audience. Most of our knowledge of the spatial organization and dynamics of bacterial chromosomes originates from studies of rod-or crescent-shaped bacteria. We have used Deinococcus radiodurans, a spherical bacterium, well-known for its exceptional radioresistance, to study the structure and dynamics of its nucleoid. By combining different fluorescence microscopy approaches, we have determined that D. radiodurans increases in size throughout its cell cycle and that its nucleoid is highly compact at all times, but also surprisingly dynamic, adopting six distinct configurations, including the previously described toroid, as it progresses through its cell cycle. This remarkable plasticity is notably permitted by the loose binding of the highly abundant histone-like HU protein to the genomic DNA, as revealed by single-molecule and ensemble measurements of HU dynamics. More recently, we have probed the changes in nucleoid morphology in response to the energetic and harmful UV-C rays. We have shown that exposure of D. radiodurans to high doses of such UV-light induces a rapid reorganization of its chromosomes into a highly compact structure that may contribute to genome protection and/or facilitate its repair and reassembly.[1] Floc’h K, Lacroix F, Servant P, Wong YS, Kleman JP, Bourgeois D and Timmins J. Cell morphology and nucleoid dynamics in dividing D. radiodurans. Nat Commun. (2019) 10 (1). p.3815. DOI: 10.1038/s41467-019-11725-5
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