Factors Affecting Endogenous Respiration in a Freshwater Fungus

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Abstract
Studies of factors affecting the utilization of endogenous reserves and of several exogenous substrates were performed using the freshwater chytridiomycete Phlyctochytrium punctatum. In starved cells, overall O2 consumption is reduced, but exogenous glucose increases O2 consumption. This increase results solely from respiration of exogenous glucose, in addition to the endogenous glucose used. Electron transport reagents such as 2,4-dinitrophenol increase O2 consumption by stimulating endogenous respiration but not exogenous glucose utilization. The C6:C1 ratio of expired 14CO2 = 1, suggesting that the major route of glucose catabolism in P. punctatum is via the Embden-Meyerhof glycolytic pathway. Efforts to purify and isolate active mitochondria from these and related organisms were unsuccessful.