The resting cells of Bacterium succinicum grown aerobically in bouillon citrate medium hardly fermented citrate under anaerobic conditions. But when a small amount of glucose was added to these cells along with citric acid under anaerobic conditions, a remarkable increase in the rate of citrate breakdown was observed. This was confirmed to be typical enzymatic adaptation. The occurrence of the splitting reaction in the adapted cells was demonstrated with the inhibition experiments by dipyridyl and with the isotopic experiments. Soluble enzyme preparations were obtained from the adapted cells which dissimilated citrate under anaerobic conditions. One molecule of pyruvate and one molecule of carbon dioxide were formed per molecule of citrate decomposed by the extracts when further oxidation of pyruvate was blocked. Therefore, the presence of the splitting enzyme of citrate in the extracts was confirmed. The enzyme, however, was different either from the condensing enzyme or the citridesmolase in its adaptive nature and as to the requirements of cofactors.
The experimental data presented above show clearly that the unicellular algae such as Chlorella, Scenedesmus and Chlamydomonas, are excellent feed for daphnids. Although less effective than these algae, filamentous blue-green algae Tolypothrix and Nostoc, also serve as nutrient for daphnids. For the past several years we have been conducting experiments of seeding Tolypothrix and other nitrogen-fixing blue green algae on the paddy-field in order to test the possibility of increasing rice crop by virtue of their nitrogen-fixing capacity(9). One of the serious problems arising in these field-experiments was that, occasionally, the seeded algae dissappeared 1955 Micro-algae as a Source of Nutrients for Daphnids 141 completely from the field within 1 or 2 weeks In such cases we found, almost without exception, that the field water became abundant first with unicellular algae such as Chlorella and Scenedesnzus, and then with water- fleas which eventually ate up the seeded blue-green algae. We learn from the above experiments that in order to assure the growth of nitrogen-fixing blue-green algae in the paddy-field, some measure must be taken to prevent the growth of water-fleas or to suppress the growth of unicellular green algae which remarkably favors the increase of the population of daphnids.
1. The unknown substance reported in the previous paper was identified as glucosone. The formation of glucosone from fructose by Gluconoacetobacterroseus is a similar reaction with the formation of reductone (enol form of glycerosone) from dihydroxyacetone by the same bacterium. A presumable pathway of ketose oxidation would be shown as follows: 2. The fructose dehydrogenase of G. roseus was investigated by Thunberg method. The activity of this dehydrogenase was the same order as that of gluconic acid dehydrogenase and was inhibited by the addition of 1:5.000mol. of 2, 4-dinitrophenol, when other dehydrogenases such as glucose, gluconic acid, and mannitol dehydrogenase were not affected. The fructose dehydrogenase of this bacterium seemed to be of the same type as the dihydroxyacetone dehydrogenase of Acetobacter suboxydans. 3. The author isolated a new substance from the fermented broth of fructose. The chemical structure of this compound is now under further investigation. This compound developes purple color with ferric chloride solution and gives different m.p. and Rf value from those of kojic acid, comenic acid, and rubiginol. 4. Although the biological induction of kojic acid from glucosone is not yet attained, the author assumes that glucosone would be the most possible intermediate of kojic acid formation, because Bond, Knight and Walker proved in 1937 the existance of the same substance in the brothh fermented by Aspergillus cryzae.
1. Eleven strains of typical Aspergillus species were irradiated with ultraviolet rays. The authors obtained the Albino type mutants from 8 of them, i.e. A. nidulans, A. oryzae, A. tamarii, and A. wentii. 2. From A. candidus no color mutants were obtained. The green or bluish species never produce black mutants and from the black species no green or bluish mutant. 3. Color mutants of conidial heads obtained from each strain were classified into 8 types: i.e. Black, Brown, Cinnamon, Buff, Albino, Yellow, Yellowish Green, and Green. 4. The mutants obtained were classified also from the characteristics other than the color of conidial heads, that is from the size of conidial heads, the pigment on the reverse of colonies, and the appearance of mycelia. 5. The sclerotia producing mutant has been prevalently obtained from A. tamarii and A. ochraceus. 6. The correlations were discussed between the classification of Aspergillus species and the tendencies of colorations of their color mutants.
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