Light-dependent hydrogen evolution by Scenedesmus

Summary The effect of glucose and the uncoupler Cl-CCP upon hydrogen production was studied in adapted cells of Scenedesmus obliquus D₃. Cl-CCP at 10^-5M concentration completely inhibited the evolution of H₂ in the dark and increased the apparent rate of H₂ evolution in the light. At 10^-5M Cl-CCP, photosynthesis and photoreduction by anaerobically adapted algae were only temporarily inhibited; O₂ evolution reappeared after approximately 1 hr of illumination if CO₂ was present. Increasing the Cl-CCP concentration to 5 x 10^-5M led to a maximum rate of photohydrogen production and fully inhibited H₂ evolution, photoreduction and dark H₂ evolution. H₂ evolution was accompanied by a release of varying amounts of CO₂ in the light, as well as in the dark. Dark CO₂ production was stimulated by Cl-CCP. H₂ evolution in the light was stimulated by adding glucose to autotrophically grown cells or by growing the cells heterotrophically with glucose; starvation had an opposite effect. Adapted cells released ¹⁴CO₂ from the 3 and/or 4 position of specifically labeled glucose, indicating that degradation occurred via the Embden-Meyerhof pathway. The amount of H₂ released by autotrophically grown cells was the same either with continuous illumination or with short periods of light, followed by darkness. Scenedesmus mutant No. 11, which is unable to evolve O₂ was not inhibited in its capacity to evolve H₂ in the light. These data indicate that the evolution of H₂ in the light by adapted Scenedesmus depends upon the degradation of organic material and does not require the production of free O₂ by photosystem II.The following abbreviations are used: Cl-CCP = carbonyl cyanide m-chlorophenylhydrazone; DCMU = 3-(3,4-dichlorophenyl)-1,1-dimethylurea, DNP = 2,4-dinitrophenol.This work was supported by contract AT-(40-1)-2687 from the U.S. Atomic Energy Commission.     

Electron microscopy of crystalline micelles in cellulose elementary fibrils of Dictyostelium discoideum

Summary In negatively stained preparations the cellulose of Dictyostelium discoideum appears in the form of 35 Å wide fibrils of undetermined length. Upon mild acid hydrolysis a periodic pattern may be observed along the fibrils, in the form of fine, electron-dense bands across the full diameter of the fibril spaced apart from each other by electron-transparent segments approximately 100 Å long. We propose that the electron-transparent segments represent the crystalline micelles of the elementary cellulose fibril, whereas the electron-opaque bands represent the amorphous regions.Part of a thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree, University of Hawaii.     

Zwei neue Heterokonten (Pleurochloris polyphem undHeterococcus clavatus) aus Böden der alpinen Stufe des Mt. Kenya

Zusammenfassung Aus Bodenproben der alpinen Stufe des Mt. Kenya werden zwei neue Heterokonten beschrieben. Pleurochloris polyphem unterscheidet sich vonPleurochloris magna durch auffallend große, spindelförmige Zoosporen, deren Stigma außerhalb des Chromatophors im Zytoplasma liegt und aus einem Aggregat von Karotinoidkristallen besteht. Heterococcus Clavatus besitzt gegenüberH. vesiculosus stark verlängerte, keulenförmige Endzellen mit nur 8–10 Chromatophoren.Herrn Professor Dr.Lothar Geitler zum 70. Geburtstag gewidmet.     

Mikrospektralphotometrische Untersuchungen zum Speichermechanismus des kationischen Farbstoffes Chrysoidin durch die lebende und tote Pflanzenzelle

Wie aus Elektrophorese- und spektralphotometrischen Untersuchungen hervorgeht, liegt der kationische Farbstoff Chrysoidin G, je nach dem pH-Wert der wäßrigen Farblösungen, als I-, II-, III- und IV-wertiges Kation und elektroneutrales Farbbasenmolekül vor. Von physiologischer Bedeutung ist nur das I-wertige Kation und das Farbbasenmolekül. Die Unabhängigkeit der Absorptionsmaxima wäßriger Farbstofflösungen mit konstantem pH-Wert von der Farbstoffkonzentration deutet darauf hin, daß Chrysoidin keine Assoziate bildet. In organischen Lösungsmitteln ergibt Chrysoidin G je nach dem Grad der Polarität des Solvens und dem pH-Wert der wäßrigen Phase bei Ausschüttelungs-versuchen unterschiedliche Absorptionskurven. Natriumnucleinat bedingt eine negative Metachromasie; die jeweilige Lage des Maximums wird von der Natriumnucleinatkonzentration bestimmt. Rutin übt keinen wahrnehmbaren Einfluß auf das Absorptionsspektrum aus. Nach einer Vitalfärbung von Oberepidermiszellen der Schuppenblätter von Allium cepa mit Chrysoidin G zeigen das diffus gefärbte Plasma und die darin auftretenden gelben Kugeln übereinstimmende Absorptionsspektren mit einem breiten Bandenmaximum bei ? 420 nm. Der lebende Zellkern färbt sich nicht. Der gefärbte volle Zellsaft der Unterepidermis besitzt ein Maximum bei ? 448 nm. Aus der Lage der Absorptionsmaxima und dem Verlauf der Absorptionskurven kann geschlossen werden, daß die Färbung des lebenden Plasmas auf eine Anreicherung des einwertigen Kations und des Farbbasenmoleküls in polaren Lipoiden beruht, während es sich bei der Färbung des fixierten Zellkerns um eine Bindung des Chrysoidins an Nucleinsäuren handelt. Die Vitalfärbung des vollen Zellsaftes mit Chrysoidin G ist nicht auf den Gehalt der Vakuolen an Flavonolen zurückzuführen, sondern hängt vermutlich vom pH-Wert des Zellsaftes ab.     

Ultrastructural Changes During Germination of Dictyostelium discoideum Spores

Spores of Dictyostelium discoideum undergo significant changes in fine structure during germination. The mitochondria progressively become less dense and lose their peripherally attached ribosomes, and the tubuli become more pronounced as germination proceeds. During this period, the three-layered spore wall breaks down in two stages: first, the outer and middle layers are ruptured as a unit, and, second, the inner wall is breached. Crystals and dark (lipid) bodies disappear shortly before or during emergence of the myxamoebae. Autophagic vacuoles are found in dormant spores and throughout the entire germination process. The addition of cycloheximide to germinating spores inhibited the loss of the crystals and dark (lipid) bodies. In addition, the drug inhibited the breakdown of the inner wall layer. Cycloheximide did not prevent the formation of the water expulsion vesicle or the apparent function of the autophagic vacuoles.     

Mutant of Escherichia coli with Anomalous Cell Division and Ability to Decrease Episomally and Chromosomally Mediated Resistance to Ampicillin and Several Other Antibiotics

In a mutation experiment with a rough, ampicillin-resistant strain, we isolated two smooth mutants which were both sensitive to ampicillin and carried defects in the cell envelope. One of the strains (with the envA gene) is hindered in its completion of septa and forms chains of cells. The envA gene has been mapped to a position between leu and proB, at 2 to 4 min. The envA gene decreased the resistance mediated by both episomal and chromosomal genes for resistance to several antibiotics. During growth the envA mutant was characterized by abnormal ratios between viable count or cell count and optical density. The ratio between viable count and optical density was affected during shift-up and shift-down experiments. When compared to the parent strain, the envA mutant was found to be more resistant to ultraviolet irradiation on plates. Prestarvation for tryptophan had a protective effect against irradiation both on the parent strain and the envA mutant.     

Glutamatdehydrogenase im photosynthetischen Bakterium Rhodospirillum rubrum

Zusammenfassung Glutamatdehydrogenase wurde aus Rhodospirillum rubrum durch Fällung mit Ammoniumsulfat und Chromatographie an DEAE-Cellulose 35 fach angereichert. Das Enzym ist spezifisch auf NAD als Wasserstoffdonator/acceptor und -Ketoglutarat bzw. Glutamat. Hg-Ionen blockieren die Reaktion in beiden Richtungen; Nitrit- und Nitrationen hemmen in höheren Konzentrationen. Die Abbaurate wird durch die Anwesenheit von ATP verringert. Die Stickstoffquelle des Nährmediums wirkt sich nur wenig auf die Ausbildung des Enzyms in den Zellen aus, dagegen wird durch Produkthemmung im natürlichen Milieu bei Wachstum auf Malat und NH₄ ⁺ der Glutamatabbau praktisch unterdrückt.

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Glutamate dehydrogenase from the photosynthetic bacterium Rhodospirillum rubrum

Summary Glutamate dehydrogenase from Rhodospirillum rubrum was purified 35 fold by ammonium sulfate precipitation and chromatography on DEAE-cellulose. The enzyme is specific for NAD as hydrogen donor/acceptor and -ketoglutarate and glutamate for the synthesis, respectively the degradation of the amino acid. Hg²⁺ ions completely inhibit both synthesis and degradation; a weaker inhibition can be shown by addition of various inorganic nitrogen compounds. The rate of the glutamate degradation is reduced by ATP. The nitrogen source of the culture medium is without effect on the formation of the glutamate dehydrogenase, however, under growth conditions in a malate-NH₄ ⁺-solution the glutamate degradation is almost completely suppressed by product inhibition.