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A type of temperature gradient plate (called the thermograde) is described. It has been used in this institute for three years, chiefly in experiments with fungi, and proved handy and reliable. In the present study the usefulness of this instrument for the detection of temperature-dependent nutritional requirements is shown with Aspergillus niger as the test organism. With glucose as carbon source the maximum growth temperature for Aspergillus niger proved to he slightly below 44°, with rhamnose between 41.8° and 42.8°C. By adding malt extract or a vitamin mixture to the medium growth with rhamnose became possible even above 42.8°C up to 43.2°C. Biotin proved to be the most active component of the vitamin mixture. The temperature limits for growth could he raised by increasing the density of the cell suspension used for inoculation. [ABSTRACT FROM AUTHOR]

Evidence obtained by paper chromatography indicates that corn root curvatures caused by culture filtrates of Aspergillus niger are caused by the same compound which causes curvatures and malformations on the stems and petioles of bean plants. The R(f) values obtained for this compound were substantially different from those of indoleacetic acid.

1. The molecular weight of 3-carboxy-cis-cis-muconate cyclase obtained from Aspergillus niger has been determined under dissociating conditions. Equilibrium sedimentation studies in the presence of 5 M guanidine hydrochloride (0.1% v/v with respect to 2-mercaptoethanol) and dodecylsulphate-calibrated polyacrylamide gel electrophoresis suggested a minimum covalent molecular weight of approximately 24000 for the reduced enzyme. 2. Sedimentation equilibrium studies in the presence of a denaturant but in the absence of a reducing agent gave a value of 47000 for the molecular weight. 3. The amino acid and carbohydrate composition of the enzyme was determined and the presence of one thiol per subunit was shown to be available for titration with 5,5'-dithio-bis(2-nitrobenzoic acid). 4. The enzyme was digested with trypsin, and peptide-mapping experiments confirmed the hypothesis that 3-carboxy-cis-cis-muconate cyclase consists of eight subunits of approximately 24000 molecular weight and identical chemical composition. [ABSTRACT FROM AUTHOR]

The action pattern and kinetics of an Aspergillus niger extracellular endopolygalacturonase were studied with oligogalacturonic acids (digalacturonic acid through hexagalacturonic acid) and their derivatives in which the terminal aldehyde group was reduced. The rate of hydrolysis catalyzed by the enzyme decreases with the shortening of oligogalacturonide chain length; digalacturonic acid is not hydrolyzed. With tetragalacturonic acid one productive complex is formed resulting in (1 + 3) cleavage. Two and three modes of cleavage occur with pentagalacturonic acid and hexagalacturonic acid, respectively. The enzyme is competitively inhibited by trigalacturonic acid whereas digalacturonic acid does not affect the activity. Reduced pentagalacturonic acid forms one productive complex. Reducing trigalacturonic acid and nonreducing digalacturonic acid are the products of the reaction. Lower reduced oligogalacturonic acids are nut degraded by the enzyme. The action pattern and k2 values obtained with the oligouronides suggest that the binding site of the endopolygalacturonase contains four subsites and that the catalytic groups of the enzyme are located in the proximity of the first bond, counting from the reducing end, of the substrate segment bound in the complex. [ABSTRACT FROM AUTHOR]

A glycoprotein-mannosyltransferase, utilising an endogenous acceptor found in Aspergillus niger is herein characterized. Data presented indicate that among the subcellular fractions, only microsomes are active in the mannose transfer reactions. The enzyme catalising the transfer requires Mn++ or Mg++ (1-2 mM) and has an optimum pH of 6.8 and an optimum temperature of 22°. It exibits a Km of 0.2 µM for GDP-mannose. The transfer is inhibited by ATP, CTP and also by GTP or its structural analogue β-γ-mthylene-guanosine triphosphate, but AMP or GDP have only a slight inhibitory action. Triton X-100 causes a 2- to 3-fold enhancement of incorporation of mannose when a suitable detergent:protein ratio is applied. The efficiency of this enzyme-acceptor system is discussed. [ABSTRACT FROM AUTHOR]

Ergosterol was found to be the main sterol in the mycelia of Ophiobolus graminis, Neurospora crassa, and Aspergillus niger. A correlation was found between the amount of sterols in the rnycelia of different fungi and the inhibitory effect of aescin. Aescin treatment caused a reduction of the amount of extractable sterols in the mycelia. The sterols seemed to be located mainly in the plasma membranes, and only trace amounts were found in the mitochondrial membranes. The relative amount of sterols in the plasma membrane was found to be higher in O. graminis than in N. crassa and A. niger. Ca2+ interfered with the interaction, of sterols and aescin. In 2+ was due to the reduced binding of the inhibitor to the siterols in the plasma membrane. [ABSTRACT FROM AUTHOR]

Strains of Claviceps purpurea (Fr.) Tul., producing peptide or clavine type alkaloids have been tested on media containing various amounts of oxine. Very low concentrations of this substance brought about a sclerotia-like mode of growth and inhibition of the germination of conidiospores. At oxine concentrations higher than those necessary for this effect, a stimulatory action on growth and especially alkaloid production by the peptide strains occurred, preceded by a prolonged phase of very slow growth. The stimulatory action of oxine was bimodal and greatest at a concentration just below that inhibiting growth. In the cultures of the clavine strain no stimulatory effect on alkaloid production was obtained by oxine. However, during the long phase of very slow growth, caused by higher amounts of oxine, the major quantity of the clavine alkaloids was formed. During the following phase of rapid growth, alkaloid production per unit weight of mycelium was much less. Possible interpretations of these differences between the strains are discussed. Attempts have been made to determine the absorbed amounts of oxine by the mycelium at different concentrations in the medium. Oxine does not serve as precursor for the alkaloids. Of the other 10 quinoline derivatives tested only 2-phenyl-quinoline showed a tendency of being stimulating for growth and alkaloid production. The others had no effect. Salicylic acid and salicylaldehyde stimulated growth and alkaloid production but did not change the morphological appearance of the culture. Of three homologues of dithiocarbamates tested, dimethyldithiocarbamate showed an effect similar to that of oxine. This investigation was supported by grants from the Swedish Natural Science Research Council. The author is greatly indebted to Professor Nils Fries for valuable discussion and criticism and to Mrs Margareta Danielsson for skilful technical assistance. [ABSTRACT FROM AUTHOR]

Oxine has no effect on growth and alkaloid production if it is added after 3-5 days' incubation. Agar media containing 4.1 x 10-5 Mil oxine and 2.5 x 10-6 Mu copper induced a sclerolia-like mode of growth, which was reversed by cobalt or iron in amounts of 1-10 and 1000 times that of copper. respectively. These proportions of cobalt or iron to copper also reversed the inhibition of growth caused by ten-fold increase of the copper concentration. Zinc had a slight stimulatory effect on selerotization. whereas increased amounts of manganese and nickel had no effect. The inhibition of growth caused by ten-fold increase of the oxine concentration was reversed by iron and to some extent by cobalt. Corresponding results were obtained in liquid media. The alkaloid production was inhibited by concentrations of metals too high to permit optimal growth. In zinc- and/or iron-deficient media containing oxine. alkaloid production was reduced. and the effect of oxine was limited to the inhibition of spore germination. Flistidine. EDTA and Na-1)131)T, but not tryptophan reversed the action of oxine. With ascorbate in the oxine-medium there was no selerotization but stimulation of growth. and the alkaloid production was not reduced. There was an interaction between copper and cysteine in oxine media, resulting in a partial reversal of the effect of oxine at small copper •oncentrations. and an intensified effect at supra-optimum copper concentrations. [ABSTRACT FROM AUTHOR]