Electron microscopy of Gallionella ferruginea.

For over 80 years prior to the work of Cholodny (1924, 1926) the twisted ribbons of ferric hydroxide found in iron-bearing waters were described as living organisms of the genera Gallionella and Spirophyllum. These early observations have been conveniently summarized and evaluated by Pringsheim (1949), so that at the present time Spirophyllum may be considered synonymous with Gallionella. It remained for Cholodny (1924) to reveal that these twisted ribbons of ferric hydroxide were actually fragments of inert stalks which had been secreted by bean-shaped apical cells. By allowing the organism to grow on cover-slips which had been immersed in appropriate natural waters it was possible to observe for the first time the intact cell and stalk. His excellent photographs have established the general morphology of Gallionella ferruginea. At the present time four species of Gallionella described from natural sources are recognized, but as suggested by Pringsheim (1949) perhaps these descriptions represent but a single species. Van Beneden (1951) has questioned Cholodny's interpretation of stalk secretion and has suggested that the twisted stalk represents a collapsed sheath from which a chain of cells has escaped. More recently, Berger and Bringmann (1953) have presented electron micrographs of stalk fragments from natural deposits of iron bacteria which suggest a finer netlike or fiber structure within the stalk, but much of the detail is obscured possibly because of inorganic chemical precipitation in the natural habitat. The present report is an extension of the morphological observations on Gallionella ferruginea and represents, in contrast to previous observations, the results of a study of seriallycultivated laboratory strains of the organism. The details of the cultivation method will be presented in a future communication. A brief report of this method and some of the morpho-