Inhibition of the development of Schizophyllum commune germlings by the ammonium ion

Ammonium ions at a concentration of 1 mM completely inhibitthe growth and further development of 12–15 hr germlingsof Schizophyllum commune. The NH₄⁺, inhibition of germling growthis reversed by acetate and pyruvate, but it is reversed moreeffectively by TCA intermediates. Glucose, is not effectivein reversing the ammonium inhibition. From these data it isapparent that functional TCA enzymes are present in the germlingstage and that the mechanisms for incorporating acetate andpyruvate into the TCA cycle are also operative. There may be,however, an impaired glycolytic pathway, and, as a consequence,no intermediates are supplied to the TCA cycle, making the germlingssensitive to a disruption in the TCA cycle. The possible modeof action of ammonium ions is the activation of NADP-glutamatedehydrogenase, the subsequent enhancement of glutamic acid biosynthesis,and the final depletion of TCA intermediates. ¹This investigation was supported in part by Research GrantAI-06570 from the National Institute of Allergy and InfectiousDiseases of the U.S. Public Health Service (Received January 26, 1970; )