Studies in carotenogenesis. 4. Nitrogen metabolism and carotene synthesis in Phycomyces blakesleeanus

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Abstract
The" major portion of the carotene synthesized by P. blakesleeanus, using a readily assimilable source of N which does not also provide a specific carotene precursor, is produced only after the mycelial mat is fully grown, as measured by dry wt. production and/or N assimilation. Media buffered at high pH values (5.2-7.0) support normal growth of Phycomyces, although carotenogenesis is almost completely inhibited. Lipogenesis, on the other hand, is stimulated under these conditions. Well formed mats of Phycomyces dissimilating glucose can synthesize relatively more carotene in the absence of assimilable N than in its presence. Under these conditions lipid synthesis is also relatively greater on the N-free media. N uptake by Phycomyces is independent of the glucose concn. of the medium. When the glucose concn. of the medium is low, a considerable amt. of the assimilated N is lost as the mycelia age.