Factors Affecting Endogenous Respiration in a Freshwater Fungus

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 oxygen consumption is reduced, but exogenous glucose increases oxygen 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 oxygen 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 have been unsuccessful.

Key Words:

• endogenous respiration
• aquatic fungi
• 2,4-dinitrophenol
• metabolic compartmentation
• Phlyctochytrium punctatum