Aug 2026· Molecular Microbiology· 0 citations· 40 references
Medicine
TL;DR
The results suggest that roles of CetZ1 in cell shape or potentially the organisation and structure of the cell poles influence the polar assembly of the motility machinery.
Abstract
The archaeal tubulin-like cytoskeletal protein CetZ1 is required for rod-cell morphogenesis during the development of motility in Haloferax volcanii. This is expected to improve swimming speed and directionality. Here, we found that deletion of cetZ1 or expression of a GTPase-defective mutant caused the expected defects in cell shape, and also resulted in a substantial defect in the assembly of the motility machinery, including the archaellum base marker protein ArlD1, the chemotaxis sensory array adapter CheW1, and signal transducer CheY. Interestingly, moderate overexpression of cetZ1 (by 2-3 fold) reduced motility and the assembly and polar placement of the motility machinery without detectably affecting the rod shape of motile cells. We also investigated deletion of the conserved paralog cetZ2, which caused no detected defects in swimming or rod shape. However, overexpression of cetZ2 caused mild hyper-motility, whereas the cetZ2 GTPase-defective mutant reduced motility; these effects were dependent on the presence of cetZ1, suggesting that the altered cetZ2 might interfere with CetZ1's role in motility. Finally, we saw that a functional CetZ1-mTurquoise2 fusion strongly localized at the poles of mature motile cells, where it partially co-localized with the motility machinery markers. Overall, our results suggest that roles of CetZ1 in cell shape or potentially the organisation and structure of the cell poles influence the polar assembly of the motility machinery.
Salmonella can assemble functional flagella, even when the acetylglucosaminidase activity of FlgJ is genetically inactivated, showing that early steps in flagellar assembly are more diverse than previously thought and that differences in cell wall structure between gram-positive and -negative bacteria likely determine whether a cell wall hydrolyzing activity is required for flagellum assembly.
Yann H. U. Chevance, M. Kinoshita, F. Chevance et al.· Journal of Bacteriology· 0 citations
The cytoskeleton, comprising intracellular filamentous structures composed of polymerized proteins, is crucial for the survival of both eukaryotes and prokaryotes. Although bacterial cytoskeletal proteins have diverged, they generally do not drive cellular motility. Spiroplasma, a genus of wall-less helical bacteria, swims by propagating a helicity-switching point (kink) along its cell axis. Unlike typical walled bacteria, whose motility depends on widespread motility machineries such as flagella and pili, Spiroplasma swimming is powered by the coordinated dynamics of five isoforms of bacterial actin MreB (SMreB1–5), which are grouped into three phylogenetic classes: SMreB1 and 4, SMreB2 and 5, and SMreB3. Despite the efforts to understand Spiroplasma swimming, its molecular mechanism remains unclear. In this review, we summarize how in vitro analyses of SMreBs have provided mechanistic insights into Spiroplasma swimming. While all SMreBs conserve the canonical actin fold, each SMreB class exhibits unique characteristics in its polymerized structures, ATPase activities, polymerization dynamics, and membrane binding. Studies of an essential SMreB subset for Spiroplasma swimming, i.e. SMreB1 and SMreB5, have revealed that SMreB1 binds to polymerized SMreB5 and disassembles it depending on the nucleotide state. These results challenge the previous model in which Spiroplasma swimming is driven by the coordinated extension and contraction of two distinct SMreB filaments. Finally, we discuss potential molecular mechanisms underlying Spiroplasma swimming and highlight key questions that must be answered to validate these models.
It is shown that deletion of mreB is viable in P. aeruginosa, but results in spherical cells that lose all forms of motility despite retaining flagella, and a previously overlooked polar effect of the in-frame mreB deletion on the downstream mreCD genes is uncovered.
M. Tunç, Mattéo Gérard, A. Barbotin et al.· bioRxiv· 0 citations
This work uncovered an unprecedented role of V-ATPase in shaping the macropinocytic cup in the pathogenic amoeba Entamoeba histolytica and highlights the novel role of V-ATPase in directly driving actin polymerization, in conjunction with phosphatidic acid, to shape the macropinocytic cup.
The possibility that microtubule architecture and dynamics evolved in Asgard archaea prior to eukaryogenesis is raised, as well as the broad occurrence of tubulins in Asgard archaea.
Jan Löwe, Andriko von Kügelgen, V. J. Planelles-Herrero et al.· Science Advances· 0 citations
Key mechanistic steps coordinating ATP-driven MreB polymerization and turnover are established and provide a basis for a complete MreB assembly–disassembly cycle and for further elucidating how MreB dynamics contribute to cell-wall organization.
Alba de San Eustaquio-Campillo, C. Cornilleau, Sana Afensiss et al.· bioRxiv· 0 citations
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