A short-oligonucleotide microarray that allows improved detection of gastrointestinal tract microbial communities

Background  

The human gastrointestinal (GI) tract contains a diverse collection of bacteria, most of which are unculturable by conventional microbiological methods. Increasingly molecular profiling techniques are being employed to examine this complex microbial community. The purpose of this study was to develop a microarray technique based on 16S ribosomal gene sequences for rapidly monitoring the microbial population of the GI tract.     

Zur Digestion bei Pseudomicrothorax dubius Mermod Nahrungsvakuolen-Vesikulation (Ciliophora) im Anschluß an die Phagocytose

Zusammenfassung Der Schlinger Pseudomicrothorax dubius ingestiert innerhalb von 1–2 min ein großes Volumen fädiger Blaualgen. Die Nahrung ist unmittelbar nach dieser rapiden Phagocytose in einer einzigen, sehr großen Vakuole eingeschlossen, die fast den ganzen Ciliaten ausfüllt. Im Verlaufe der folgenden Stunde vesikuliert diese große Nahrungsvakuole über Zwischenstufen zu einer Vielzahl von Vakuolen mit 1–2 m Durchmesser. Gleichzeitig erfolgt eine Kondensierung des Vakuoleninhaltes. Erst zu diesem Zeitpunkt setzt die Verdauung der Nahrung ein, wie an Hand von zahlreichen Dictyosomen belegt wird, die nun in unmittelbarer Nähe der Nahrungsvakuolen nachzuweisen sind. Durch die Vesikulation der großen Nahrungsvakuole in kleinere Einheiten sowie durch die Kondensierung der Nahrung wird bewirkt, daß die über Lysosomen in die Nahrungsvakuolen abgegebenen Verdauungsenzyme optimal eingesetzt werden. Nach Beendigung der Verdauung liegen viele leere Vakuolen vor, die durch eine stark gefaltete Kontur gekennzeichnet sind. Diese Vakuolen gehen allem Anschein nach wieder in den Membranhaushalt der Zelle ein.

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On the digestion in Pseudomicrothorax dubius Mermod (Ciliophora) vesiculation of the food vacuole following phagocytosis

Summary The gulper Pseudomicrothorax dubius ingests a large volume of filamentous blue-green algae within 1–2 min. Immediately after this rapid phagocytosis, the food is enclosed in a single, extremely large food vacuole, which fills up the ciliate almost entirely. During the following hour this giant food vacuole vesiculates. Finally numerous small vacuoles are present, 1–2 m in diam. Simultaneously the content of the vacuoles is noticeably condensed. At this time the digestion of the food starts as is indicated by numerous dictyosomes, which now surround the periphery of the food vacuoles. Due to both, the prior vesiculation of the food vacuole and the condensation of the food, the digestive enzymes can act very effectively. After 6–8 hours, when the digestion of the food is finished, numerous empty vacuoles are found. Each is characterized by a highly irregular, convoluted outline. Apparently these vacuoles are eventually recycled to the membrane pool of the cell.

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Für umsichtige und sorgfältige technische Assistenz danke ich Frl. A. Rüskens. Die Deutsche Forschungsgemeinschaft unterstützte diese Untersuchung durch die Sachbeihilfe Ha 818/7     

Protective effect of bixin on carbon tetrachloride-induced hepatotoxicity in rats

Background

The liver is an important organ for its ability to transform xenobiotics, making the liver tissue a prime target for toxic substances. The carotenoid bixin present in annatto is an antioxidant that can protect cells and tissues against the deleterious effects of free radicals. In this study, we evaluated the protective effect of bixin on liver damage induced by carbon tetrachloride (CCl₄) in rats.

Results

The animals were divided into four groups with six rats in each group. CCl₄ (0.125 mL kg^-1 body wt.) was injected intraperitoneally, and bixin (5.0 mg kg^-1 body wt.) was given by gavage 7 days before the CCl₄ injection. Bixin prevented the liver damage caused by CCl₄, as noted by the significant decrease in serum aminotransferases release. Bixin protected the liver against the oxidizing effects of CCl₄ by preventing a decrease in glutathione reductase activity and the levels of reduced glutathione and NADPH. The peroxidation of membrane lipids and histopathological damage of the liver was significantly prevented by bixin treatment.

Conclusion

Therefore, we can conclude that the protective effect of bixin against hepatotoxicity induced by CCl₄ is related to the antioxidant activity of the compound.     

Background and peak evaluation of one parameter flow karyotypes on a PC/AT computer

Flow cytometry has become a fast, quantitative method for the classification of metaphase chromosomes in suspension (flow karyotyping) stained with fluorescent dyes. Such a flow karyotype (frequency distribution of the fluorescence signals) consists of several peaks. The peak pattern characterizes the analyzed chromosome complement. In many cases flow karyotypes contain a continuum of an unspecific background deriving from chromosome fragments or chromosome aggregates. For the quantitative evaluation of a flow karyotype this background has to be subtracted by a suitable background function. In this approach the application of chi 2-functions is described. The feasibility of this method to flow karyotypes has been concluded from a computer simulation of chromosome breaking under different conditions. In spite of the rather rough assumptions of the model compared to the complex reasons that influence chromosome breaking, the chi 2-function fits the background better than the exponential function in current use. The approximation of a Gaussian distribution function by the chi 2-function also makes it possible to use the same subtraction procedure for chromosome aggregates. The procedure was tested for isolated chromosomes of Chinese hamster cell lines under different states of breaking. For further evaluation of one parameter flow karyotypes a setup of computer routines has been developed for PC/AT and compatible computer systems. Different peak values of these flow karyotypes can be determined (e.g. peak mean, standard deviation, absolute and relative peak area etc.). The applied method is to fit Gaussian curves to each peak of an experimentally measured histogram by using an interactive program. Fluctuations depending on 'noise' may be suppressed by a 'k-nearest-neighbours' smoothing procedure.     

Kinetic analysis and modeling of the liquid-liquid conversion of emulsified di-rhamnolipids by Naringinase from Penicillium decumbens

The enzymatic conversion of an aggregate-forming substrate was kinetically analyzed and a model was applied for the prediction of reaction-time courses. An L-rhamnose molecule from a di-rhamnolipid is cleaved by Naringinase from Penicillium decumbens leading to a mono-rhamnolipid. Optimal reaction rates were found when both, substrate and product build large co-aggregates in a slightly acidic aqueous phase. On the other hand, reaction rates were independent of initial di-rhamnolipid concentration and this was interpreted by assuming that the reaction occurs in the aqueous phase according to Michaelis-Menten kinetics in combination with competitive L-rhamnose inhibition. Rhamnolipids were therefore assumed to be highly concentrated in aggregates, a second liquid phase, whereas diffusive rhamnolipid transport from and to the aqueous phase occurs due to the enzymatic reaction. Furthermore, ideal surfactant mixing between di- and mono-rhamnolipid was assumed for interpretation of the negative effect of the last on the reaction rate. A model was created that describes the system accordingly. The comparison of the experimental data, were in excellent agreement with the predicted values. The findings of this study may beneficially be adapted for any bioconversion involving aggregate-forming substrate and/or product being catalyzed by hydrophilic enzymes.     

Isolation of cyanophycin from tobacco and potato plants with constitutive plastidic cphATe gene expression

A chimeric cyanophycin synthetase gene composed of the cphATe coding region from the cyanobacterium Thermosynechococcus elongatus BP-1, the constitutive 35S promoter and the plastid targeting sequence of the integral photosystem II protein PsbY was transferred to the tobacco variety Petit Havanna SRI and the commercial potato starch production variety Albatros. The resulting constitutive expression of cyanophycin synthetase leads to polymer contents in potato leaf chloroplasts of up to 35 mg/g dry weight and in tuber amyloplasts of up to 9 mg/g dry weight. Both transgenic tobacco and potato were used for the development of isolation methods applicable for large-scale extraction of the polymer. Two different procedures were developed which yielded polymer samples of 80 and 90% purity, respectively.     

An aminoacyl-tRNA synthetase:elongation factor complex for substrate channeling in archaeal translation

Translation requires the specific attachment of amino acids to tRNAs by aminoacyl-tRNA synthetases (aaRSs) and the subsequent delivery of aminoacyl-tRNAs to the ribosome by elongation factor 1 alpha (EF-1α). Interactions between EF-1α and various aaRSs have been described in eukaryotes, but the role of these complexes remains unclear. To investigate possible interactions between EF-1α and other cellular components, a yeast two-hybrid screen was performed for the archaeon Methanothermobacter thermautotrophicus. EF-1α was found to form a stable complex with leucyl-tRNA synthetase (LeuRS; K_D = 0.7 μM). Complex formation had little effect on EF-1α activity, but increased the k_cat for Leu-tRNA^Leu synthesis ~8-fold. In addition, EF-1α co-purified with the archaeal multi-synthetase complex (MSC) comprised of LeuRS, LysRS and ProRS, suggesting the existence of a larger aaRS:EF-1α complex in archaea. These interactions between EF-1α and the archaeal MSC contribute to translational fidelity both by enhancing the aminoacylation efficiencies of the three aaRSs in the complex and by coupling two stages of translation: aminoacylation of cognate tRNAs and their subsequent channeling to the ribosome.     

Novel insights into biosynthesis and uptake of rhamnolipids and their precursors

Applied Microbiology and Biotechnology - The human pathogenic bacterium Pseudomonas aeruginosa produces rhamnolipids, glycolipids with functions for bacterial motility, biofilm formation, and...     

Membrane behavior of exocytic vesicles: II in fate of the trichocyst membranes in paramecium after induced trichocyst discharge

A specific exocytic process, the discharge of spindle trichocysts of paramecium caudatum was examined by means of the electron microscope. This exocytosis is induced by an electric shock simultaneously in nearly all of the trichocysts (ca. 6,000-8,0000 of a single cell. Single paramecia were subjected to the shock and then fixed at defined times after the shock so that the temporal sequence of the pattern of changes of the trichocyst membranes after exocytosis could be studied. The trichocyst vacuoles fuse with the plasma membrane only for that length of time required for expulsion to take place. After exocytosis, the membrane of the vacuole does not become incorporated into the plasma membrane; rather, the collapsed vacuole is pinched off and breaks up within the cytoplasm. The membrane vesiculates into small units which can no longer be distinguished from vesicles of the same dimensions that exist normally within the cell's cytoplasm. the entire process is completed within 5-10 min. These results differ from the incorporation of mucocyst membranes into the plasma membrane as proposed for tetrahymena.