Studies in the biochemistry of micro-organisms

Abstract

IT has already been reported in Parts XIX and XXIX of this series that when Penicillium griseo-fulvum Dierckx is grown on liquid media containing glucose as sole source of carbon, and sodium nitrate as sole source of nitrogen, the following products are to be found in the metabolism solution when most of the glucose has been utilised: 6-methylsalicylic acid [Anslow and Raistrick, 1931]; gentisic acid, fumaric acid and mannitol [Raistrick and Simonart, 1933]. The factors governing the formation of these products are temperature of incubation and ratio of glucose to sodium nitrate. The presence of the two phenolic acids mentioned above causes the metabolism solutions to give respectively a purple or blue coloration with ferric chloride. Further experiments have now shown that when the nitrogen source is changed from NO3to NH4+ the course of the metabolism of the glucose is entirely changed. The coloration given with ferric chloride is now no longer purple or blue but green, and in place of the above two colourless phenolic acids there is formed a much more complex yellow phenolic acid, of empirical formula C04H1208, which gives a deep green colour with aqueous ferric chloride, and for which we propose the name fulvic acid. The yield of fulvic acid from this organism is however small and its isolation in a pure state from the metabolism solution is very difficult. The reaction given by fulvic acid with ferric chloride and also certain of its other properties are very similar to those of the complex mould product citromycetin, C14H1007, produced by species of Citromyces