()0 PHYSIOLOGY OF THE FUNGI 



thenate-dependent strains of yeast to the synthesis of pantothenate has 

 been studied in some detail (Lindegren and Rant, 1947; Lindegren, 1949). 

 Changes to pantothenate independence occurred by an adaptation, which 

 was transmitted vegetatively, and by a gene mutation. The adaptation 

 occurred only in the media of low pantothenate content, while the muta- 

 tions were apparently not affected by the concentration of pantothenate. 

 Leonian and Lilly (1943) studied the induced ability of eight strains of 

 Saccharoniyces cerevisiae to synthesize various vitamins for which they 

 were normally deficient. This was accomplished by long "training" in 

 media "free" from various vitamins. The ability of various yeast strains 

 to synthesize a given vitamin varied. These yeasts which had been 

 trained "reverted" to their deficient status when cultured for 6 months on 

 media containing vitamins and yeast extract. 



ENERGY AND ENERGY UTILIZATION BY FUNGI 



Fungi need energy, as well as certain elements and chemical compounds, 

 for life, growth, and reproduction. Since the life processes of the fungi 

 are controlled by interlocking systems of enzymes, the utilization of 

 energy is also an enzymatic process. The chemical reactions which 

 accompany or underlie life processes may be divided into those which 

 yield energy (exergonic) and those which require energy (endergonic) 

 (Coryell, 1940). The oxidation reactions whereby such substrate mole- 

 cules as glucose are converted into carbon dioxide and alcohol or carbon 

 dioxide and water yield energy, while the reactions involved in the syn- 

 thesis of protoplasm and reserve materials require energy. Let us con- 

 sider an analogy first. When water falls from a higher to a lower level, 

 there is a decrease in energy content, and this decrease in energy content is 

 the same whether the water has passed through a turbine or not. The 

 water that passes over a spillway does no useful work, while the water that 

 turns a turbine makes part of the energy available (as mechanical or 

 electrical power) for doing useful work. The energy given up by the 

 falling water is the same in both cases, but only where the proper mecha- 

 nism is available is any useful work obtained. 



A similar situation occurs when a fungus oxidizes glucose to water and 

 carbon dioxide. If energy-requiring synthetic reactions are coupled with 

 the degradation reactions, a portion of the available energy becomes useful 

 to the fungus. The remainder of the energy liberated appears as heat, 

 which is unavailable to the fungus for lack of suitable mechanisms to 

 utilize it. 



Winzler and Baumberger (1938) have investigated the liberation of 

 energy by yeast cells during metabolism. Washed yeast cells were sus- 

 pended in a phosphate buffer containing glucose but no nitrogen. The 

 reaction vessel was placed in an adiabatic calorimeter, and the heat 



