1. Determination of the toxicity of the culture liquid of Verticilliumdahliae showed that it contains an active toxin which causes wilting of cotton plant shoots. Thus the fungus produces a toxin which it excretes into the external medium. 2. By testing a large number of strains of microorganisms from various taxonomic groups, a test microbe was found which is sensitive to the toxin of Verticillium dahliae. 3. Such a sensitive test-microbe made it possible to use chromatography with a bioassay method to select the best solvent for extraction of the toxin. 4. The toxin was obtained in concentrated form by extraction with amyl acetate. 5. A study of the physico-chemical properties of the toxin showed it to be acidic in nature, and that it has two sharp absorption maxima in the UV region at 245 and 275mμ, and is stable at high temperatures and over a wide range of pH values. 6. The toxin of Verticillium dahliae is composed of two fractions, differing in physico-chemical and biological properties. 7. The toxin of Verticillium dahliae does not appear to be highly specific, and, besides its marked inhibitory action on cotton, causes wilting of leguminous plants, during which time cereals are not sensitive to the toxin in the concentrations tested. 8. The rate of wilting under the influence of the toxin depends on the age and variety of cotton plant. Adult plants wilt more quickly than young plants. The cotton plant variety 108-F (resistant to wilting) is less sensitive to the toxin than variety 2034, which is non-resistant to wilting. The toxin causes browning of the vascular bundles and the surrounding woody parts of the stalk, and the leaves loose their turgidity. 9. The tetraene antibiotics, 18-45 and 18-80, produced by actinomycetes, have an effect on the toxin produced by Verticillium dahliae. They interact with the fungal toxin and neutralise its action. 10. Treatment of seeds with antibiotics or cultivation in soils which have been enriched with the antibiotic-producing actinomyces produces an immunity in the cotton plants which is passed on to the following generations.
Determinative studies were carried out with an obligatory anaerobic spore-forming sulfate-reducing bacterium, strain No. 64, isolated from the SKARVS NES district in the East Antarctica. This sulfate-reducing bacterium belongs to the genus Desulfotomaculum differing from all of the known species of the genus in respect to glucose fermentation, gelatin liquefaction, optimum temperature for growth, and nutritional requirements. The strain was determined to be a new species of the genus Desulfotomaculum, D. antarcticum, IIZUKA et OKAZAKI nov. sp.
Aggregation of yeast by lactobacilli was studied by a method of boundary moving electrophoresis. The isoelectric point of saké yeast and lactobacillus B-83 was at pH between 3.5 and 4, while that of wine, alcohol, brewer's, and baker's yeasts and lactobacillus B-74 was below pH 2. The aggregation was observed in the combination of the microorganisms which had different isoelectric points and in the pH range in which the signs of the cell surface charge of yeast and lactobacilli are contrary. From these results it was supposed that aggregation of yeast by lactobacilli would be due to the electrostatic force between yeast and bacterial cell surfaces.
1. One acetate kinase-negative, 53 phosphate acetyltransferase-negative, and seven isocitrate lyase-negative strains were found among 73 mutants of Brevibacterium flavum, which grew on glucose but not on acetate. The result indicates that these enzymes are essential for the utilization of acetate in B. flavum, and also that the participation of acetyl-CoA synthetase is absent in this strain. 2. The genetic defect of any one of these three enzymes had no effect on the production of L-glutamate from glucose. 3. Many mutants possessing a variety of isocitrate lyase activities were obtained by deriving revertants grown on acetate from four isocitrate lyase-negative strains. By an experiment using such revertants, it was concluded that isocitrate lyase had an important effect on the production of L-glutamate from acetate, which was shown as a positive correlation between the activity of this enzyme and L-glutamate productivity in the cells grown in an acetate medium. It was also shown that the change of this enzyme activity had no effect on the production of L-glutamate from glucose. 4. Mutants possessing a variety of phosphate acetyltransferase activities were obtained by deriving revertants grown on acetate from four strains lacking this enzyme. In this case, too, a positive correlation was observed between the activity of this enzyme and L-glutamate productivity in the cells grown in an acetate medium. 5. In connection with the present study, it was pointed out that genetic elevation of the levels of key enzymes was important for the improvement of microbial strains for industrial purposes.
Electrical conductance of phospholipid bilayer membranes formed in various electrolyte solutions was studied with special reference to the kind of related charge carriers. The conductance was extremely low (10-5-10-7mho-cm-2), depending considerably on the lipid composition but little on both the concentration and kind of the electrolytes used, and it showed a complex dependence on the pH of the media on both sides of the membrane. Because of these experimental results, it seems preferable to assume that the charge carriers through the membrane are not the ions supplied from the electrolyte added to the solution, but protons and hydroxyl ions whose mobilities depend upon the sign and magnitude of the net charge on the membrane. Potential differences caused by diffusion of protons or hydroxyl ions across the membrane were also determined to prove the above assumption.
Certain factors which affect production and accumulation of indole-3- acetic acid (IAA) and activity of enzymes associated with its synthesis from L-tryptophan were investigated in Pseudomonas savastanoi. Addition of L- tryptophan to the culture medium enhances the accumulation of IAA by the bacterium. However, both tryptophan oxidative decarboxylase and indoleacetamide hydrolase, which are involved in the conversion of L-tryptophan to IAA, are produced by the bacterium without addition of L-tryptophan to the medium. In a medium containing L-tryptophan, yields of tryptophan oxidative decarboxylase per liter of culture suspension were increased as much as 2-fold. IAA and indole-3-acetamide (IAM) strongly inhibit tryptophan oxidative decarboxylase. IAA up to 6×10-3M did not inhibit indoleacetamide hydrolase. IAA also inhibits uptake of L-tryptophan by whole cells. IAA is converted to its lysine conjugate by the bacterium. During logarithmic phase of growth in a nutrient medium, the specific activities of tryptophan oxidative decarboxylase and indoleacetamide hydrolase were 2-fold greater than that for the system converting IAA to its lysine conjugate. During the stationary growth phase, specific activity of all three enzymes decreased but that for the first two enzymes did so more rapidly than the specific activity of the lysine conjugate synthetase. Accumulation of IAA in culture filtrates is controlled to a large extent by the relative activities of the systems synthesizing and utilizing IAA.
Corynebacterium hydrocarboclastus R-7, which had been isolated as an excellent hydrocarbon utilizer, was found to produce a large amount of L-glutamic acid from various normal alkanes by the addition of penicillin. Among various factors tested, addition time of penicillin and the concentration, pH, metal ions, sulfur-containing amino acids, and (NH4)2HPO4 concentration showed marked effects on the L-glutamic acid production. Under the optimum conditions where the cultural medium contained 61.7g/liter n-hexadecane, inorganic salts, and growth factors, 20units/ml of penicillin was added after 16hr, and pH (7.30) of the medium was maintained by the continuous supply of ammonia gas with air, the highest level of L-glutamic acid production was attained after about 48-hr cultivation and it amounted to about 20g/liter of the medium. The highest yield of L-glutamic acid obtained 14hr after the penicillin addition reached about 72% (w/w) of n-hexadecane consumed.
The DNA base ratio (GC content) of 46 cultures of Hansenula and allied yeasts which represented 26 species or varieties was studied. The GC content of Hansenula DNA ranged from 28.5 to 46.3%. Intrageneric variation reached 15.6-17.8% in Hansenula sensu WICKERHAM, 14.4-15.8% in Hansenulasensu LODDER and KREGER-VAN RIJ, 13.4-14.8% in Hansenula emended by NOVÁK and ZSOLT, and 11.0-12.7% in Hansenula group (genus) of TSUCHIYA et al. The frequency curve of the DNA base ratio demonstrated the presence of two large groups in the genus Hansenula. The first group had relatively high values of GC content with maximal frequency in a range of 40-42%. The second had relatively low values of GC content with the maximal frequency in a range of 32-34%. Species arranged in each line of the phylogenetic scheme of Hansenula proposed by WICKERHAM exhibited consistent DNA base ratios individually though exceptions were found, and so did the serological groups within Hansenula group (genus) of TSUCHIYA etal. A taxonomic and phylogenetic evaluation of DNA base ratio was discussed in relation to the delimitation of the genus Hansenula by several workers and the existence of several groups having similar DNA base ratio within the genus.
Bacillus natto IAM 1212 produces α-amylase by about 5 times as much as Bacillus subtilis Marburg strain, α-amylase of which is more thermostable and moves more rapidly to anode at pH 8.3 than that of B. natto. When this high producing activity of α-amylase (Amysup character) was transferred to a Marburg strain by the DNA from B. natto, about one-tenth of the transformants with Amysup character produced recipient type, i.e. Marburg type α-amylase and the other natto type α-amylase. In other words, the former acquired only high producing activity of α-amylase. This result suggests that a gene which regulates α-amylase synthesis participates in the α-amylase-producing system of B. subtilis and this regulator gene (amyR) is closely linked to the α-amylase structure gene. Reciprocal crossing also confirmed this assumption. The amyR gene is linked to the aro116 gene which has been reported to be the linked marker of α-amylase structure gene by S. Yuki.
Catabolite repression of tryptophanase formation in E. coli K12 TAB40 was examined. Glycerol or pyruvate, if given as a sole carbon source, did not repress tryptophanase formation unlike glucose, but if they existed together, they repressed the enzyme formation like glucose. This synergistic effect was well observed in the wild strain of E. coli K12 and was pronounced also in β-galactosidase system. The combination of glycerol or pyruvate with other carbon sources directly related to glycolysis repressed the enzyme formation, while succinate or ribose did less effectively. When cells were grown on various carbon sources, glucose, glycerate, and fructose were effective in repressing the enzyme formation. It was considered that the growth rate and catabolite repression might not necessarily be directly related. Even anaerobically grown cells could show catabolite repression. Inhibition of oxidative pyruvate decarboxylation or TCA cycle provoked catabolite repression. Conclusively glycolytic steps may be associated with catabolite repression of tryptophanase synthesis.
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