STUDIES IN THE PHYSIOLOGY OF FUSARIA. THE RESPIRATORY AND FERMENTATIVE MECHANISMS

Abstract

1.Fusarium tricothecoides was selected for a study of the respiratory and fermentative activities of Fusaria. "Resting cell" suspensions were investigated by the Barcroft manometric technique. 2. The results of the investigation indicate clearly that the mechanism of endogenous metabolism (respiration) is distinct from the exogenous mechanism (fermentation). Anaerobically no significant CO2 production is apparent without added substrate. In the presence of glucose the anaerobic CO2 evolution is practically equal to the added CO2 evolved aerobically in the presence of added glucose. Low concentrations of iodoacetate or fluoride selectively poison the exogenous mechanism but do not affect the endogenous mechanism. Alcohol is not produced in the course of endogenous metabolism, but is produced in the presence of added glucose. 3. A study of the metabolism of the organism throughout its entire growth phase from 1 to 7 days has been made. 4. The ability of suspensions of Fusarium sp. H., obtained by growth on a variety of common substrates, to attack a large number of carbon sources with the production of exogenous CO2 was determined. It is found that organisms grown on glucose will attack only glucose, mannose, and fructose, but none of the common intermediary metabolites except pyruvic acid. Organisms grown on galactose attack galactose, as well as the other hexoses, indicating an adaptive mechanism. 5. An identical mechanism for the dissimilation of glucose, mannose, and galactose is indicated since no additive effects with these substrates were observed. Growths on non-hexose carbon sources attack glucose slightly under the experimental conditions with the evolution of CO2, but do not attack any other substrate. This would indicate a residual glucose-dissimilating mechanism in all growths investigated. 6. Striking similarities between the general metabolism of resting suspensions of Fusarium sp. H. and resting suspensions of yeast cells are apparent.