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

Area of Science:

• Microbiology
• Mycology
• Biochemistry

Background:

• Fusarium species are significant plant pathogens and spoilage organisms.
• Understanding their metabolic pathways is crucial for controlling their growth and impact.
• Previous research has not fully elucidated the distinct mechanisms of respiration and fermentation in Fusaria.

Purpose of the Study:

• To investigate the respiratory and fermentative activities of Fusarium tricothecoides.
• To differentiate between endogenous (respiration) and exogenous (fermentation) metabolic mechanisms.
• To examine the metabolic adaptability of Fusarium species to various carbon sources.

Main Methods:

• Utilized the Barcroft manometric technique to study "resting cell" suspensions.
• Investigated CO(2) production under aerobic and anaerobic conditions with and without substrates.
• Assessed the effects of iodoacetate and fluoride on metabolic pathways.
• Analyzed metabolism across the organism's growth phase (1-7 days).

Main Results:

• Endogenous respiration and exogenous fermentation pathways were found to be distinct.
• Significant CO(2) production occurred anaerobically only with added glucose, mirroring aerobic conditions.
• Iodoacetate and fluoride selectively inhibited exogenous metabolism without affecting endogenous respiration.
• Organisms grown on glucose primarily metabolized glucose, mannose, and fructose, showing adaptive hexose utilization.
• A residual glucose-dissimilating mechanism was observed in all tested Fusarium growths.

Conclusions:

• Fusarium species exhibit separate mechanisms for respiration and fermentation.
• Metabolic pathways are adaptive, particularly in response to different carbon sources like hexoses.
• The metabolism of Fusarium sp. H. shares notable similarities with that of yeast cells.