Purification and electron microscopy of the microtubles of Azotobacter vinelandii strain-o

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It has been possible to isolate microtubules from Azotobacter vinelandii strain-o by using osmotic lysis and differential centrifugation followed by isopycnic ultracentrifugation. The microtubules found in this organism were characterized by electron microscopic analyses in penicillin G treated whole cells, thin sections of untreated cells and in an enriched, purified preparation. The microtubule, as an ultrastructure, was shown to differ from the rhapidosome by morphological analyses. Unlike rhapidosomes, microtubules do not appear to be a product of defective phage synthesis, nor can their formation be induced by mitomycin C treatment or ultraviolet irradiation. Microtubules are distinct morphological entities from the bacterial flagella. A complete morphological characterization of the A. vinelandii microtubule was made regarding dimensions, rigidity and internal structure. There was no direct attempt made to determine the function of these microtubular ultrastructures within A,, vinelandii.