title: Cytoskeletal elements in bacteria Mycoplasma pneumoniae, Thermoanaerobacterium sp., and Escherichia coli as revealed by electron microscopy.
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.
authors.affiliation: Institut fur Mikrobiologie und Genetik, Georg-August-Universitat Gottingen, Gottingen, Germany. fmayer12@gmx.de
authors.forename: Frank
authors.initials: F
authors.lastname: Mayer
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D004926:Escherichia coli / Q000378:metabolism / Q000648:ultrastructure*; D046529:Microscopy, Electron, Transmission; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000378:metabolism; D009177:Mycoplasma pneumoniae / Q000378:metabolism / Q000648:ultrastructure*; D010444:Peptide Elongation Factor Tu / Q000378:metabolism; D010457:Peptidoglycan / Q000378:metabolism; D011485:Protein Binding; D046950:Thermoanaerobacterium / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D020409:Molecular Motor Proteins; D010457:Peptidoglycan; D010444:Peptide Elongation Factor Tu