Role of organic acid metabolism in the biosynthesis of peptide ergot alkaloids.

Regulatory mechanism of primary metabolism responsible for the biosynthesis of peptide ergot alkaloids was proposed on the basis of experimental results from the production phase of Claviceps purpurea (FR.) Tul. in parasitic and saprophytic cultures. The production-phase metabolism is characterized by uncoupling of glycolysis from the citric acid cycle and by a break in this cycle at the level of the 2-exoglutarate dehydrogenase complex. This regulation is due to the inhibition by citrate and malate, i.e. the final products continuously taken up from the external medium. The rate of the intact reaction steps of the citric acid cycle is therefore not limited by the actual acetyl-CoA or oxaloacetate pool. The regulation also leads to an excessive synthesis of acetyl-CoA, 2-oxoglutarate and oxaloacetate, which represent the key metabolites of primary metabolism, and to their utilization in the biosynthesis of peptide alkaloids.

Fine structure of imbibed sclerotial cells of Claviceps purpurea (Fr.) Tul revealed by freeze-etching.

The fine structure of the cortex of the natural sclerotium of Claviceps purpurea was studied. The cell wall of sclerotial cells is thickened due to overproduction of the fibrillar component of the wall. The intracellular spaces of the cortex tissue form a continuous system which is apparently instrumental in mediating communication between the growing sclerotium and the external milieu. The cytoplasmic membrane of imbibed sclerotial cells carriers abundant signs of secretory activity. Secretion vesicles, the content of which is discharged into external space, apparently contain exo 1,3-glucanase. Cytoplasmic vesicles migrating toward the plugged pores of the thickened septa apparently involve hydrolase secretion too. Spherosomes with lipid content are a predominant component of the cytoplasm of sclerotial cells. The activity of the membrane systems of imbibed cells indicates that the mobilization of lipids sets in only after activation of the hydrolases. Findings of phagocytosis of lipid granules by vacuoles are relatively frequent so that lipolysis might proceed in the vacuoles. Alkaloids could not be detected with the aid of freeze-etching.

A simple device for stationary cultivation of microorganisms.

A new device is designed that is suitable for both laboratory- and industrial-scale cultivation of microorganisms, particularly filamentous fungi, on the surface of liquid media. The device reliably ensures the sterility of cultivation, regardless of its duration. Its installation costs are relatively low and maximum production is reached per unit of installation space. In comparison with submerged cultures in fermentors, the proposed mode does not use a high consumption of energy for stirring and aeration (consequently, the duration of cultivation is not an economically relevant factor) and does not require maintenance of complicated equipment. Due to the building and construction of the technological equipment, the production plant is capable of very fast expansion and, when the need arises of very fast and economical liquidation.

Ergot alkaloids. VI. Nitrogen metabolism during the development of sclerotium of Claviceps purpurea.

The developmental transition of ergot from the sphacelial to the sclerotial phase is accompanied by marked changes in morphology, growth and metabolism. The production of alkaloids is paralleled by a concomitant protein synthesis, a decline in the contents of both total N and P, and an attendant rise in the value of the N/P ratio. The total level of free amino acids drops with proceeding development of the sclerotium. The most conspicuous drop, observed at the beginning of the production phase, is due to a sharp decrease in the level of free lysine. This drop attests to profound changes in the metabolism of the parasite in the period of transition from nonproducing sphacelium to producing sclerotium. The gradually decreasing level of free proline reflects the accumulation of the alkaloids. In a parasitic culture, proline is probably supplied in sufficient amounts by the host plant and the main difference between the metabolism of fungal sphacelium and sclerotium is a different utilisation of acetyl-CoA.