Years ago we made a number of interesting observations when we applied transmission electron microscopy in combination with the immuno-gold technique; we got indications for the existence of a kind of cytoskeleton, forming a lining made up of fibrils regularly arranged in web-like meshes; it is located very close to the inner face of the cytoplasmic membrane; it turned out to have a cell-shape preserving function, even after complete removal of the bacterial cell wall; electron micrographs of cells of Mycoplasma pneumoniae, a wall-less bacterium from which we hade removed the cytoplasmic membrane, indicated that the cyoplasmic membrane of this bacterium is held in place by stalks that extend from the lining outwards and end in the cytoplasmic membrane; additional fibrils were observed to extend from the lining into the inner regions of the cytoplasm; application of the immuno-gold technique, making use of antibodies directed against the bacterial elongation factor EF-Tu, revealed the presence of a substantial number of copies of this elongation factor in the fibrils; in Escherichia coli cells from which we had removed the entire cell envelope (wall and cytoplasmic membrane) we could observe, by application of conventional negative staining and transmission electron microscopy, parallel rows of particles with the size of ribosomes; the rows had distances and the direction of the fibrils mentioned above as components of the lining.
We did not continue these investigations (due to my retirement), but we feel that it could be worthwhile to perform a number of additional investigations with techniques with better preservation of the natural structural organization of the interior of the cells. For us the main aspects would be to decide whether the kind of cytoskeleton that we observed contains EF-Tu or not; if yes, we would like to see experimental data that decide whether the interaction of the functional ribosomes with the elongation factor EF-Tu takes place in such a way that the ribosomes form complexes with EF-Tu proteins integrated in the cytoskeletal fibrils. It could happen that these investigations might be important contributions to the aspect of formation of functional complexes in the bacterial cell.
We look Forward to comments and questions/answers.
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