Studies on the endogenous respiration of the psychrophilic fungus, Typhula idahoensis

Abstract

The effect of exogenous substrates on the endogenous respiration of intact mycelium of the snow mold fungus Typhula idahoensis Remsb. was studied by manometric and isotopic techniques. Endogenous respiration was stimulated by glucose at 5 °C and 20 °C and by acetate at 5 °C. Stimulation by glucose tended to be greater at 5 °C than 20 °C in unstarved and 24-h-starved medium. The extent of stimulation increased at both temperatures after longer periods of starvation.Glucose oxidation also increased after starvation, indicating that it was normally suppressed by high levels of endogenous reserves. Between 5 °C and 20 °C, exogenous respiration of glucose and acetate increased three- and four-fold respectively while endogenous respiration only doubled. Oxidative assimilation of glucose at 5 °C and 20 °C and acetate at 5 °C was extremely high; lower amounts of acetate were assimilated at 20 °C. Comparison of 14C distribution with and without the use of acid to terminate experiments indicated that considerable 14C material was released from the mycelium upon acidification.The results are discussed with relation to the possible existence of separate pools of endogenous reserves and the thermosensitivity of some aspects of endogenous metabolism.