D. radiodurans septation viewed by 3D fluorescence imaging and cryo-electron tomography on cryo-FIB-milled lamellae
Unlike most bacteria, Deinococcus radiodurans divides using a “sliding doors” mechanism. Instead of the cell wall closing like an iris from all around the cell periphery, two new cell walls with flat leading edges grow inward from opposite sides of the cell, meeting and fusing at mid-cell. To elucidate the molecular mechanisms underlying this unusual division process, we teamed up with the MICA and PG groups at IBS and combined cutting-edge imaging approaches. Live fluorescence microscopy performed on the M4D imaging platform allowed us to watch cells divide in real time, while cryo-electron tomography performed on thin, frozen lamellae of the bacteria, revealed various cell division intermediates and the cell wall’s fine architecture at each step of the process. This powerful combination uncovered the complex layered structure of the bacterium’s envelope and showed how the “sliding doors” septa grow, straighten, and fuse.
One striking discovery was the presence of thin membrane protrusions at the tips of the growing septa. Another was the presence of a double-arched structure at the tip of growing septa bearing a thick, rigid peptidoglycan layer, corresponding to FtsZ and FtsA, two key players of bacterial cell division. These findings suggest that the FtsA/FtsZ pair plays an important role in the rigidification of the septa by regulating the location of the peptidoglycan synthesis machinery with which it interacts.
Publications
Gaifas L, Kleman JP, Lacroix F, Schexnaydre E, Trouvé J, Morlot C, Sandblad L, Gutsche I & Timmins J. Combining live cell fluorescence imaging with in situ cryo-electron tomography sheds light on the septation process in Deinococcus radiodurans. Proc. Nat. Acad. Sciences (2025) DOI : 10.1073/pnas.2425047122