An Explanation of the Action of the So-called Accessory Substances in the Association of Azotobacter and Cellulose Decomposing Organisms

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Abstract
In media cotaining an NH4 salt and cellulose, Azotobacter chroococcum increased the rapidity of change toward an acid reaction in the decomposition of cellulose by Spiro-chaeta cytophaga, a strain of sterile mycelium, and the "Y" organism of Dubos. The same effect on the rapidity of change toward a basic reaction was evinced in a medium containing KN03, A. chroococcum had little or no effect on the change of reaction produced by Tri-choderma koningi. The increased change in reaction was very probably due to the utilization by A. chroococcum of the by-products formed in cellulose decomposition. A. chroococcum was thus able to develop by using the inorganic N, leaving the medium more acid in presence of (NH4)2SO4, and more basic when the nitrate was used. Cellulose cultures containing T. koningi, which is known to form few or no intermediate products in cellulose decomposition, was therefore unaffected by the presence of A. chroococcum, A. chroococcum had no noticeable effect on the amount of cellulose decomposed by T. koningi or S. cytophaga. It is not necessary to postulate the existence of a growth-promoting factor secreted by A. chroococcum to explain the change in pw in cellulose-decomposing cultures containing this organism. Sanborn''s data may be explained in a similar way.

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