Prokaryotic cytoskeletons: in situ and ex situ structures and cellular locations
Cytoskeletons have long been perceived to be present only in eukaryotes. However, this notion changed drastically in the 1990s, with observations of cytoskeleton-like structures in several prokaryotes. Homologs of the main components of eukaryotic cytoskeletons, such as microtubules, microfilaments, and intermediate filaments, have been identified in bacteria and archaea. Tubulin homologs include filamenting temperature-sensitive mutant Z (FtsZ), bacterial tubulin A/B (BtubA/B), and tubulin/FtsZ-like protein (TubZ), whereas actin homologs comprise murein region B (MreB) and crenactin. Unlike other proteins, crescentin (CreS) is a homolog of intermediate filaments. Recent findings elucidated their localization, structural organization, and helical properties in prokaryotes, thus revising traditional models. FtsZ is involved in cell division, forming a bundle of overlapping filaments that cover the entire division plane. Cryogenic transmission electron microscopy identified tubular structures of BtubA/B that were not previously identified using conventional ultrathin plastic sections. TubZ generates two joint filaments to form a quadruplex structure. After a long debate, MreB, a cell shape determinant, was shown to form filament stretches that move circumferentially around rod-shaped bacteria. Initially characterized as single-stranded, crenactin was eventually identified as right-handed double-stranded helical filaments. CreS, another cell shape determinant, forms filament bundles located inside the inner membrane of the concave side of cells. These observations suggest that the use of in situ or ex situ microscopy in combination with structural analysis techniques will enable the elucidation and further understanding of the current models of prokaryotic cytoskeletons.
KeywordsCytoskeleton Prokaryotes Microscopy
Conflict of interest
The author declares that there is no conflict of interest.
- Bagchi S, Tomenius H, Belova LM, Ausmees N (2008) Intermediate filament-like proteins in bacteria and a cytoskeletal function in Streptomyces. Mol Micobiol 70:1037–1050Google Scholar
- Haydon DJ, Stokes NR, Ure R, Galbraith G, Bennett JM, Brown DR, Baker PJ, Barynin VV, Rice DW, Sedelnikova SE, Heal JR, Sheridan JM, Aiwale ST, Chauhan PK, Srivastava A, Taneja A, Collins I, Errington J, Czaplewski LG (2008) An inhibitor of FtsZ with potent and selective anti-staphylococcal activity. Science 321:1673–1675CrossRefGoogle Scholar
- Merino F, Raunser S (2016) The mother of all actins. eLife 5:e23354Google Scholar
- Stokes NR, Baker N, Bennett JM, Berry J, Collins I, Czaplewski LG, Logan A, Macdonald R, MacLeod L, Peasley H, Mitchell JP, Nayal N, Yadav A, Srivastava A, Haydon DJ (2013) An improved small-molecule inhibitor of FtsZ with superior in vitro potency, drug-like properties, and in vivo efficacy. Antimicrob Agents Chemother 57:317–325CrossRefGoogle Scholar
- Wintrebert P (1913) La rotation immédiate de l’oeuf pondu et la rotation d’activation chez Discoglossus pictus. Otth C R Soc Biol 106:439–442Google Scholar