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.     

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.     

Inhibition of Replication of an F′lac Episome in Hfr Cells of Escherichia coli

Hfr strains of Escherichia coli K-12 were found capable of accepting a F'lac episome during mating, with a frequency approximating that of F(-) strains. However, the F'lac episome was unable to replicate in the Hfr cells, and was diluted out during the growth of the culture. The lac(+) gene of the episome can be "rescued" by recombination into the host chromosome, as shown by the appearance of variegated recombinant colonies on a lactose-fermentation indicator medium. In recA Hfr strains, however, no lac(+) offspring were obtained in crosses with F'lac donors. The induced synthesis of beta-galactosidase in F'lac(+) x Hfr zygotes was studied. Rates of enzyme synthesis were approximately constant with respect to time as expected from unilinear inheritance of the F'lac episome. However, the rate of synthesis eventually increased, presumably due to integration of the lac(+) gene in some of the zygotes. In F'lac(+) x recA Hfr zygotes the rate of beta-galactosidase synthesis remained constant with respect to time, as expected.     

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.

     

Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane

The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'_Na) and potassium (g'_K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'_Na to 82 per cent and of g'_K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'_Na to 59 per cent and of g'_K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of g_Na (as a function of conditioning membrane potential) or on such kinetic parameters as τ_h or the time course of turning on gi g_Na and g_K. It is concluded that ethanol mainly reduces g_Na and g_K in the Hodgkin-Huxley terminology.     

Phytochrom-induzierte Enzymbildung (Phenylalanindesaminase), ein schnell ablaufender Prozeß

Zusammenfassung Bei Erstbelichtung des Senfkeimlings mit Dauer-Dunkelrot tritt der P₇₃₀-abhängige Anstieg der Phenylalanindesaminase-Aktivität erst mit einer lag-Phase von 1,5 Std ein (Abb. 3, 4 unten). Bei einer Zweitbelichtung (Programm: Erstbelichtung — längere Dunkelperiode — Zweitbelichtung) fehlt die lag-Phase (Abb. 4, oben). Die Enzymaktivität steigt sofort linear an. Da der Anstieg der Enzymaktivität wahrscheinlich auf eine de novo Synthese von RNS und Enzymprotein zurückzuführen ist (Tabelle), so erscheint der Schluß berechtigt, daß P₇₃₀ sehr rasch eine differentielle Genaktivierung mit anschließender Enzymsynthese bewirken kann, falls die Gene der Aktivierung durch P₇₃₀ zugänglich sind. Die relativ lange lag-Phase nach Einsetzen der Erstbelichtung benötigt das P₇₃₀ offenbar dazu, die potentiell aktiven Gene (P₇₃₀) für das P₇₃₀ zugänglich zu machen. Das Problem der primären lag-Phase ist in einer vorangegangenen Arbeit zur P₇₃₀-abhängigen Anthocyansynthese ausführlich diskutiert worden (vgl. Lange, Bienger und Mohr, 1967).

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Phytochrome-mediated enzyme formation (Phenylalanine deaminase) as a rapid process

Summary In previous papers we have reported (Mohr and Durst, 1966a, b) that synthesis of phenylalanine deaminase (EC 4.3.1.5), an important enzyme of phenolic metabolism, can be stimulated by the physiologically active phytochrome (=P₇₃₀) in the mustard seedling. The data of the present paper suggest that induction of this enzyme is a rapid process if the gene in question is easily accessible for the activating action of P₇₃₀.The seedlings were irradiated with continuous standard far-red light. Longtime irradiation with far-red will maintain a low but virtually constant level of P₇₃₀ in the seedling over an extended period of time. At the moment when the far-red light is turned off the action of P₇₃₀ will virtually cease. — Fig. 3 and Fig. 4, lower part, show the kinetics of enzyme induction by P₇₃₀ in an etiolated seedling. The initial (or primary) lag-phase after the onset of far-red is 1.5 hours. If, however, a seedling which has been pre-irradiated with 12 hours of far-red is kept in darkness for 6 hours and is then re-irradiated with far-red no lag-phase for the action of the second irradiation can be found. Enzyme activity increases immediately after the onset of far-red. Since the action of the second irradiation as measured by increase of enzyme activity can be inhibited by relatively low doses of Puromycin and Cycloheximide (table) we conclude that the re-appearance of P₇₃₀ leads to de novo synthesis of enzyme protein. — Application of Actinomycin D (10 g/ml) only partially inhibits the action of the second irradiation as measured by increase of enzyme activity. This finding was to be expected. In preceding papers (e.g. Mohr and Bienger, 1967) it has been concluded that genes which have once been activated by P₇₃₀ remain less sensitive towards Actinomycin D even when P₇₃₀ has disappeared. Taking into account all available data the conclusion seems to be justified that the induction of enzyme synthesis by P₇₃₀ (i.e. differential gene activation followed by enzyme synthesis) is a rapid process if the genes are accessible for the action of P₇₃₀. The relatively long initial lag-phase (1.5 hours) is needed to make the potentially active genes (P₇₃₀) accessible for the action of P₇₃₀. The problem of how the initial lag-phase can be understood has been dealt with more in detail in a previous paper on phytochrome-mediated anthocyanin synthesis (Lange, Bienger and Mohr, 1967).

     

Stephanoscyphus Allman (Scyphozoa Coronatae), ein rezenter Vertreter der Conulata?

The scyphopolypStephanoscyphus Allman 1874 represents the polyp generation of the scyphomedusan order Coronatae. The benthonic polyp is known to occur with several species on the continental shelves and in greater depths of the oceans. Participating in the International Indian Ocean Expedition 1964 to 1965 on board of the German research vessel «Meteor», the author was able to collect living specimens. For the first time, it was possible to rear these polyps in laboratory cultures.Stephanoscyphus differs from all other living scyphopolyps by the possession of a firm periderm tube enclosing completely the soft body. It is this primitive feature whichStephanoscyphus has in common with the Conulata being the ancestors of the recent Scyphozoa. The characteristics found in a detailed investigation of the periderm tube ofStephanoscyphus conform well with those found in the tubes of the Conulata except for the closure of the aperture by triangular flaps which are absent inStephanoscyphus. The soft body contains primitive features as well. Hence from the existence, morphology and life history it must be concluded that the type of organization which the Conulata exhibited has survived inStephanoscyphus.