Proteins of the sieve-tube exudate of Cucurbita maxima

Summary Sieve-tube exudate which appears on cut surfaces of stems of Cucurbita maxima as distinct droplets has been depicted in electron micrographs of longitudinal sections of the phloem. The exudate, which was produced from mature sieve tubes only, contained filaments of P-protein, but no mitochondria or vesicles of endoplasmic reticulum. The water-soluble part of the exudate contained at least 12 proteins, as shown by disc-electrophoresis. Enzymic activity was found for peroxidases, acid phosphatases, and aldolases. Color tests and assays for other enzymes, including ATPase, fructokinase, several dehydrogenases, and UDP-glucose: D-fructose-2-glucosyl transferase, gave negative results. With repeated cutting of a stem, the protein content of the exudate increased, while the amount of exudate decreased.Supported by Deutsche Forschungsgemeinschaft and Stiftung Volkswagenwerk. During part of this investigation the senior author held a U.S. National Science Foundation Senior Foreign Scientist Fellowship at the University of Wisconsin.     

Two Pathways of Glutamate Fermentation by Anaerobic Bacteria

Two pathways are involved in the fermentation of glutamate to acetate, butyrate, carbon dioxide, and ammonia-the methylaspartate and the hydroxyglutarate pathways which are used by Clostridium tetanomorphum and Peptococcus aerogenes, respectively. Although these pathways give rise to the same products, they are easily distinguished by different labeling patterns of the butyrate when [4-(14)C]glutamate is used as substrate. Schmidt degradation of the radioactive butyrate from C. tetanomorphum yielded equally labeled propionate and carbon dioxide, whereas nearly all the radioactivity of the butyrate from P. aerogenes was recovered in the corresponding propionate. This procedure was used as a test for the pathway of glutamate fermentation by 15 strains (9 species) of anaerobic bacteria. The labeling patterns of the butyrate indicate that glutamate is fermented via the methylaspartate pathway by C. tetani, C. cochlearium, and C. saccarobutyricum, and via the hydroxyglutarate pathway by Acidaminococcus fermentans, C. microsporum, Fusobacterium nucleatum, and F. fusiformis. Enzymes specific for each pathway were assayed in crude extracts of the above organisms. 3-Methylaspartase was found only in clostridia which use the methylaspartate pathway, including Clostridium SB4 and C. sticklandii, which probably degrade glutamate to acetate and carbon dioxide by using a second amino acid as hydrogen acceptor. High levels of 2-hydroxyglutarate dehydrogenase were found exclusively in organisms that use the hydroxyglutarate pathway. The data indicate that only two pathways are involved in the fermentation of glutamate by the bacteria analyzed. The methylaspartate pathway appears to be used only by species of Clostridium, whereas the hydroxyglutarate pathway is used by representatives of several genera.     

Mechanism of α Factor Biosynthesis in Saccharomyces cerevisiae

The biosynthesis of alpha factor, a mating-type-specific regulatory oligopeptide which is secreted by Saccharomyces cerevisiae cells of alpha mating type, was studied. In batch cultures only small amounts of the peptide were synthesized during the exponential growth phase. During the stationary phase, alpha factor was produced at a constant rate and accumulated in the culture medium. Inhibition of translation in wild-type cells by cycloheximide, or in mutant strains under conditions which blocked protein or ribonucleic acid (RNA) synthesis completely inhibited the production of alpha factor. These results indicate that the factor is produced by ribosomal translation of a specific messenger RNA and not by an extraribosomal mechanism of peptide synthesis.     

Stimulation by 6-N,2′-O-dibutyryladenosine 3′:5′-cyclic monophosphate and glucocorticoids of phosphoenolpyruvate carboxykinase in the isolated perfused rat liver (Short Communication)

Dibutyryl cyclic AMP stimulated the activity of phosphoenolpyruvate carboxykinase in perfused livers of rats, fed on a low-protein diet, linearly over a 6h period. The enzyme activity was also significantly elevated by dexamethasone, the effect being considerably lower than that of the cyclic nucleotide. Since the time-course of phosphoenolpyruvate carboxykinase activity in response to dibutyryl cyclic AMP resembled that observed after dibutyryl cyclic AMP injection into intact animals, it is suggested that induction of the enzyme in vivo is due to a direct action of the cyclic nucleotide on the liver. Combined administration of dibutyryl cyclic AMP and glucocorticoids did not lead to an additive increase of liver phosphoenolpyruvate carboxykinase activity, either in vivo or in the perfused organ.     

Interactions between Plants and Epiphytic Bacteria Regarding Their Auxin Metabolism VI. The Influence of the Epiphytic Bacteria on the Content of Extractable Auxin in the Plant

Sterile plants of maize, pea, and cucumber contain less auxin (extracted with methanol or ether) than nonsterile ones. The auxin content is restored within one day by reinfecting sterile plants (or only the shoots, with roots and culture medium remaining sterile) with epiphytic bacteria strains able to produce IAA or with soaking water of nonsterile seeds. Reinfection with bacteria, strains unable to produce IAA is ineffective. — The possibility of a bacterial auxin production during methanol extraction was excluded.     

Umwandlungen der submikroskopischen Chloroplastenstruktur parallel zur Veränderung der stoffwechselphysiologischen Leistung von Chlamydobotrys stellata

Zusammenfassung In Fortsetzung unserer Untersuchungen über den Zusammenhang von Chloroplastenstruktur und-funktion wurde die Veränderung der Chloroplastenstruktur bei der Adaptation photo-heterotroph kultivierter Organismen an photo-autotrophe Ernährungsbedingungen untersucht. Die Bildung von Partitions aus zuvor isolierten Thylakoiden erfolgt parallel zum Anstieg der photosynthetischen CO₂-Assimilation.

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Conformational changes of the submicroscopic chloroplast structure and physiological activity of Chlamydobotrys stellata

Summary Our investigation of the connection between the submicroscopic structure and the function of chloroplasts has been continued. It could be demonstrated that the formation of partitions from isolated thylakoids takes place parallel to the increase of photosynthetic activity.

     

Beziehungen zwischen submikroskopischer Chloroplastenstruktur und Art der Kohlenstoffquelle unter phototrophen Ernährungsbedingungen bei Chlamydobotrys stellata

Zusammenfassung Die Chloroplasten von photo-autotroph (Licht + CO₂) oder photo-heterotroph (Licht + Acetat) gewachsenen Chlamydobotrys stellata werden elektronenmikroskopisch untersucht. Es wird eine nahe Beziehung zwischen der Chloroplasten-Feinstruktur und der Ernährungsart gefunden. Die Thylakoide der Chloroplasten photo-heterotroph kultivierter Algen sind im allgemeinen durch Stroma voneinander getrennt und nur zu wenigen gestapelt. In photo-autotrophen Organismen kommt es durch Bildung einer charakteristischen Faltungsstruktur von Thylakoidmembranen zur Bildung von Grana (Pseudo-Grana).Die Ergebnisse werden im Hinblick auf die Photosynthese und Photoassimilation von Acetat bei Chlamydobotrys stellata diskutiert.

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Relationship between submicroscopic chloroplast structure and type of carbon nutrition of Chlamydobotrys stellata

Summary Chloroplasts from Chlamydobotrys stellata grown photo-autotrophically (light + CO₂) or photo-heterotrophically (light + acetate) have been investigated by means of electronmicroscopy. A close relationship between chloroplast fine structure and type of nutrition could be observed. Thylakoids in chloroplasts from photo-heterotrophically cultivated algae are generally separated from each other by stroma and only few thylakoid packages are present. In photo-autotrophic organisms, however, characteristic folding structure of thylakoid membranes results in the formation of grana (pseudo-grana).These results are discussed in respect to chloroplast function in photosynthesis and photoassimilation of acetate in Chlamydobotrys stellata.

     

Eine Methode zur histochemischen Bestimmung von RNS und DNS an der gleichen Zelle

Zusammenfassung Es wird eine Methode beschrieben, die die quantitative cytophotometrische Bestimmung von DNS und RNS nebeneinander am gleichen Objekt gestattet. Dazu werden die Zellen mit Gallocyaninchromalaun und anschließend mit der Feulgen-Reaktion gefärbt, wobei ein Peulgenfarbstoff verwendet wird, der im blauen Spektralbereich absorbiert. Auch unter den veränderten Färbebedingungen verlaufen beide Parbreaktionen quantitativ. Es werden für die Durchführung der Methode die geeigneten Versuchsansätze und ein Verfahren zur Auswertung der cytophotometrischen Meßergebnisse angegeben.

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Microphotometric determination of DNA and RNA within the same cell

Summary A method is described which allows the simultanous cytophotometric determination of DNA and RNA within the same cell. Cells are stained with gallocyanine chromealum and then, in an additional step, by a Feulgen procedure in which Coriphosphin 0 was used as a Schiff type reagent to accomplish absorption in the blue region of the spectrum. It could be shown that under the altered conditions both staining reactions can be used for quantitative purposes. Methods for carrying out the preparation of the material, for cytophotometric measurements and for calculating RNA and DNA values are suggested.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.

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Wir widmen diese Arbeit dem Andenken Wolfgang Zellers. Wesentliche Teile dieser Arbeit waren als Teil seiner Dissertation vorgesehen. Sein tragischer Tod hat seine Promotion verhindert.