Letter | Published:

Myxobacteria Mistaken for Nitrifying Bacteria

Naturevolume 168page561 (1951) | Download Citation



IN connexion with the communication under this title by Miss Joyce B. Grace, published in Nature of July 21, p. 117, a careful re-reading of Winogradsky's papers on the subject1 leads me to believe that he has described two quite different species under the name of Nitrosocystis. In the first place, there is the organism isolated by Romell2 from forest soil by Winogradsky's later technique of placing grains of soil on the surface of silica gel plates. Imsenecki repeated this work, and obtained Nitrosomonas, and a non-nitrifying myxobacterium, Sorangium symbioticum3. In the second place, there is the zooglœa-forming species, isolated by Winogradsky from Zurich soil by the enrichment culture technique, originally described in 1892 as a Nitrosomonas, and reclassified by Winogradsky in 1933 as a Nitrosocystis. This species forms the ‘hard colonies’ mentioned by Kingma Boltjes4, whose work Miss Grace dismisses with the statement that there was “no evidence that the cultures were pure”; the cultures in question, however, were single-cell isolations. As regards hard colonies, I have seen them formed by my own pure cultures of an ammonia-oxidizing bacterium, which I have every reason to believe is a Nitrosomonas5. I think that the formation of hard or soft colonies depends on the density of the silica gel in the plate, and also on whether the colony is buried or superficial; Kingma Boltjes observed both types on his plates made from pure cultures of Nitrosomonas.

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  1. 1

    Winogradsky, S., “Microbiologie du Sol” (Paris, 1949).

  2. 2

    Romell, L-G., Medd. Skogsförsöksanst, Stockholm, 24, 57 (1927).

  3. 3

    Imsenecki, A., Nature, 157, 877 (1946).

  4. 4

    Kingma Boltjes, T. Y., Arch. Mikrobiol., 6, 79 (1935).

  5. 5

    Meiklejohn, J., J. Gen. Microbiol., 4, 185 (1950).

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  1. Rothamsted Experimental Station, Harpenden, Herts



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