Mayer F. Cytoskeletal Elements in Bacteria
Mycoplasma pneumoniae,
Thermoanaerobacterium sp., and
Escherichia coli as Revealed by Electron Microscopy.
J Mol Microbiol Biotechnol 2006;
11:228-43. [PMID:
16983198 DOI:
10.1159/000094057]
[Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Recently, electron microscopic studies on the eubacteria Mycoplasma pneumoniae, Thermoanaerobacterium sp., and Escherichia coli have revealed the existence of cytoskeletal elements so far unknown in prokaryotes. The wall-less bacterium M. pneumoniae contains, in close vicinity to the inner face of the cytoplasmic membrane, a helically organized lining composed of protein elements that form a regular network of meshes that encloses the entire cytoplasm. Numerous regularly spaced pin-like structural elements, the stalks with terminal knobs, connect the lining with the cytoplasmic membrane. In this bacterium, a specific rod-like structural element is located in the tip region. Occasionally, it is bent or twisted. It consists of two matching blade-like sub-elements. A number of parallel linkers, extending from the edges of the rod, make contact with the lining. The proximal end of the rod is attached to a wheel-like complex. Fibrils originating from the wheel cross the cytoplasm and make contact with the lining. E. coli contains a similar helically organized lining close to the inner face of the cytoplasmic membrane. Groups of ribosomes (polysomes) were seen to be attached to the helical elements of the lining. A feature that is common to both bacteria and to Thermoanaerobacterium sp. appears to be that the lining and the fibrils crossing the cytoplasm contain a high number of copies of the bacterial elongation factor Tu (EF-Tu). This indicates that this protein may play an important role as a structural element in bacterial cytoskeletons. This notion was supported by experiments in which the cytoskeleton in E. coli was destabilized by induced expression of truncated EF-Tu, with the consequence of cell lysis, and by the finding that in vitro polymerization of monomeric EF-Tu into protofilaments was hindered in a mixture of full-size EF-Tu and truncated EF-Tu consisting of domain 3 only. Current research and developmental efforts are aimed at the design of a new class of antibacterial drugs, acting by destabilization of the EF-Tu-containing bacterial cytoskeleton, and of an innovative mode of inducible lysis of recombinant bacteria by controlled destabilization of the EF-Tu-containing cytoskeleton.
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