Carbohydrate Metabolism and Oxalic Acid Synthesis by Botrytis cinerea.

Abstract

Various sugars and sugar derivatives were used as respiratory substrates to detn. the ability of starved pellets of mycelium to oxidize these compounds. Botrytis cinerea was capable of using glucose, fructose, gluconic acid, phosphogluconic acid, xylose, arabanose, ribose-5-phosphate, and 3-phosphoglyceraldehyde as respiratory substrates. Triose-phosphate dehydrogenase was present and oxygen uptake was severely inhibited by fluoride and azide. Neither CO2 nor lactic acid was produced anaerobically. Evidence for the operation of a Krebs cycle is presented and is based on the oxidation of several Krebs cycle acids by the organism, the chromatographic identification of Krebs cycle acids in the culture medium and the reversible inhibition of respiration with malonic acid. A six-week time course study revealed that oxalic acid is synthesized, most of which is formed during the first week of growth. Oxalic acid production does not parallel growth but occurs when the organism is in a phase of high oxidation, and is independent of the pH of the medium. The main pathway of oxalic acid synthesis is via direct oxidation of malic acid, although some oxalic acid is formed by the hydrolytic dismutation of oxaloacetic and oxalosuccinic acids. Oxalic acid was not utilized as a carbon source for growth or as a respiratory substrate by this microorganism.