Société Française de Biochimie et Biologie Moléculaire


Faculty Of Biology, Molecular Biology of Archaea,Freiburg

« Cell division in the archaeon Haloferax volcanii relies on two FtsZ proteins with distinct functions in division ring assembly and constriction. »
Nature Microbiology volume 6, pages594–605 (2021)

Yan Liao*, Solenne Ithurbide*, Christian Evenhuis, Jan Löwe & Iain G. Duggin 


Dr Solenne Ithurbide, 33 years old is a Postdoctoral Research Associate at the University of Freiburg, Germany. In 2015, she obtained her PhD at the University Paris-Saclay, France in the laboratory of Prof. Susanne Sommer where she studied the DNA recombination mechanisms in Deinococcus radiodurans, one of the most radio-resistant organisms known to date. Since then, she pursued her interest in extremophile organism’s molecular biology and expanded her research about archaea cell biology. In 2016, for her first postdoctoral position, she joined the laboratory of A/Prof Iain Duggin at the University of Technology Sydney, Australia. She studied the cell division mechanisms in the halophilic archaeon Haloferax volcanii. In the presented study, recently published in Nature Microbiology, Solenne and colleagues revealed the differing roles of the 2 FtsZ homologues during archaeal cell division. FtsZ1 has a major role in the scaffolding of the division ring and probably the entire divisome whereas FtsZ2 is mainly involved in the constriction and the final stages of cell division. This study revealed the fundamental differences between bacterial and archaeal FtsZ-based cell division mechanisms rising interesting questions regarding the evolution of cell division mechanisms in general. Solenne is currently continuing her research on archaeal cell division in the laboratory of Prof Sonja-V. Albers at the University of Freiburg, Germany. 


Molecular Biology of Archaea 
Institute of Biology II,
Faculty of Biology, University of Freiburg, 
Schänzlestr. 1, 79104 Freiburg, Germany
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Summury of the article

In bacteria, the tubulin homologue FtsZ assembles a cytokinetic ring, termed the Z ring, and plays a key role in the machinery that constricts to divide the cells. Many archaea encode two FtsZ proteins from distinct families, FtsZ1 and FtsZ2, with previously unclear functions. Here, we show that Haloferax volcanii cannot divide properly without either or both FtsZ proteins, but DNA replication continues and cells proliferate in alternative ways, such as blebbing and fragmentation, via remarkable envelope plasticity. FtsZ1 and FtsZ2 colocalize to form the dynamic division ring. However, FtsZ1 can assemble rings independent of FtsZ2, and stabilizes FtsZ2 in the ring, whereas FtsZ2 functions primarily in the constriction mechanism. FtsZ1 also influenced cell shape, suggesting it forms a hub-like platform at midcell for the assembly of shape-related systems too. Both FtsZ1 and FtsZ2 are widespread in archaea with a single S-layer envelope, but archaea with a pseudomurein wall and division septum only have FtsZ1. FtsZ1 is therefore likely to provide a fundamental recruitment role in diverse archaea, and FtsZ2 is required for constriction of a flexible S-layer envelope, where an internal constriction force might dominate the division mechanism, in contrast with the single-FtsZ bacteria and archaea that divide primarily by wall ingrowth.