Adaptation of protein expression by Escherichia coli in the gastrointestinal tract of gnotobiotic mice

The gastrointestinal tract of mammals is inhabited by several hundred bacterial species. While the effects of the gut microbiota upon the host have been widely studied, the microbial response to host factors has only recently attracted attention. In order to investigate the influence of the host on the physiology of gastrointestinal bacteria, a simplified model of host–bacteria interaction was created by associating germfree mice with commensal Escherichia coli . Here we demonstrate the feasibility of analysing the bacterial response to the conditions in the digestive system by a proteomics-based approach. Two-dimensional gel electrophoresis (2D-GE) followed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was used to identify bacterial proteins from caecal and faecal samples. In a set of 60 arbitrarily chosen spots of stably and differentially expressed proteins, 50 different bacterial proteins were identified. Their ascribed functions suggest that the host-associated bacteria adapt their metabolism to the conditions in the intestine by utilizing arginine, asparagine and aspartate as well as glucose/galactose, ribose, maltose, glucuronate, galacturonate and gluconate as substrates. Thirteen proteins not previously detected on 2D-gels and 10 proteins with unknown or poorly characterized physiological function were identified, while the existence of three proteins had so far only been inferred from predictions or by homology.     

A second site occupied by Octopus tetricus at high densities,with notes on their ecology and behavior

We report wild octopuses (Octopus tetricus) living at high density at a rock outcrop, the second such site known. O. tetricus are often observed as solitary individuals, with the species known to exist at similar densities and exhibiting complex social behaviors at only one site other than that described here. The present site was occupied by 10–15 octopuses on eight different days. We recorded frequent interactions, signaling, mating, mate defense, eviction of octopuses from dens, and attempts to exclude individuals from the site. These observations demonstrate that high-density occupation and complex social behaviors are not unique to the earlier described site, which had been affected to some extent by remains of human activity. Behavior at this second site confirms that complex social interactions also occur in association with natural substrate, and suggest that social interactions are more wide spread among octopuses than previously recognized.     

Polyamines regulate their synthesis by inducing expression and blocking degradation of ODC antizyme

Polyamines are essential organic cations with multiple cellular functions. Their synthesis is controlled by a feedback regulation whose main target is ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis. In mammals, ODC has been shown to be inhibited and targeted for ubiquitin-independent degradation by ODC antizyme (AZ). The synthesis of mammalian AZ was reported to involve a polyamine-induced ribosomal frameshifting mechanism. High levels of polyamine therefore inhibit new synthesis of polyamines by inducing ODC degradation. We identified a previously unrecognized sequence in the genome of Saccharomyces cerevisiae encoding an orthologue of mammalian AZ. We show that synthesis of yeast AZ (Oaz1) involves polyamine-regulated frameshifting as well. Degradation of yeast ODC by the proteasome depends on Oaz1. Using this novel model system for polyamine regulation, we discovered another level of its control. Oaz1 itself is subject to ubiquitin-mediated proteolysis by the proteasome. Degradation of Oaz1, however, is inhibited by polyamines. We propose a model, in which polyamines inhibit their ODC-mediated biosynthesis by two mechanisms, the control of Oaz1 synthesis and inhibition of its degradation.     

The UBAP1 subunit of ESCRT-I interacts with ubiquitin via a SOUBA domain

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Highlights? ESCRT-I subunit UBAP1 is essential for degradation of antiviral protein tetherin ? UBAP1 has a domain consisting of a solenoid of overlapping UBAs (SOUBA) ? Each of the three UBAs in the SOUBA binds monoubiquitin     

Hisactophilin, a histidine-rich actin-binding protein from Dictyostelium discoideum

The purification, cloning, and complete cDNA-derived sequence of a 17-kDa protein of Dictyostelium discoideum are described. This protein binds to F-actin in a pH-dependent and saturable manner. It induces actin polymerization in the absence of Mg2+ or K+, and is enriched in the submembranous region of the amoeboid cells as indicated by immunofluorescence labeling of cryosections. The mRNA as well as the protein are present throughout growth and all stages of development. The protein is detected in both soluble and particulate fractions of the cells. From a plasma membrane-enriched fraction, minor amounts of the protein are stepwise solubilized with 1.5 M KCl, 0.1 M NaOH, and Triton X-100, but most of the protein is only solubilized with 1% sodium dodecyl sulfate. As judged by the apparent molecular mass in sodium dodecyl sulfate-polyacrylamide gels, immunological cross-reactivity, and two-dimensional electrophoresis, the 17-kDa proteins from the soluble and particulate fraction resemble each other. The cDNA sequence does not reveal any signal peptide, trans-membrane region, or N-glycosylation site. Southern blots hybridized with a cDNA probe that spans the entire coding region show that the 17-kDa protein is encoded by a single gene. The most characteristic feature of the protein is its high content of 31 histidine residues out of 118 amino acids. We designate this protein as hisactophilin and suggest that this histidine-rich protein responds in its actin-binding activity to changes in cellular pH upon chemotactic signal reception.     

Genetic and anti-tubulin effects induced by pyridine derivatives

A series of pyridine derivatives, 2-methyl-, 2-chloro-, 2-acetyl-, 3-acetyl-, 4-acetyl, 2-phenyl-, 2,4-dimethyl-, 2,6-dimethyl- and 2-methyl-5-ethyl-pyridine, were shown to induce mitotic aneuploidy in strain D61.M of Saccharomyces cerevisiae. Induction of mitotic recombination was also observed with 3- and 4-acetylpyridine and 2-phenylpyridine in strain D61.M. 4-Acetylpyridine and 2-phenylpyridine were found to induce mitotic gene conversion and 2-phenyl-pyridine also induced reverse mutation in strain D7 of Saccharomyces cerevisiae. These two agents also inhibited the GTP-mediated assembly of porcine brain tubulin in vitro.     

Untersuchungen über einen weißbunten Klon von Armoracia lapathifolia Gilib

V. Zusammenfassung 1. Die Scheckung der weißbunten Armoracia ist im jahreszeitlichen Ablauf verschieden. Im Frühjahr sind die Sprosse fast reinweiß und werden zum Herbst hin mehr und mehr grün.2. In der Ontogenese der einzelnen Pflanzen konnten endgültige Entmischungen nicht festgestellt werden. Weder reingrüne noch reinweiße Sprosse, die stabil geblieben wären, wurden beobachtet. Neben marmorierten traten in den verschiedensten Stadien der Individualentwicklung auch einzelne sektorialpanaschierte Blätter auf. Jedoch waren Sprosse mit durchgehenden Sektoren oder meriklinalchimärischer Streifung (unter entsprechender Färbung der einzelnen Blätter) nicht zu finden.3. Im anatomischen Bau lassen die Blätter keinen periklinalchimärischen Status erkennen. Die Verteilung des weißen und grünen Gewebes weist keine bestimmte Gesetzmäßigkeit auf.4. Die zahlreich provozierten Sproßregenerate aus isolierten Wurzeln und Blättern weißbunter Pflanzen ergaben auf die Dauer immer wieder nur gescheckte Pflanzen. Eine selektive Verklonung nach grün oder weiß war nicht möglich.5. Da von anatomisch-histogenetischer Seite her der chimärische Aufbau des weißbunten Meerrettichs nicht gesichert werden kann, liegt die Annahme einer genbedingten Weißbuntheit nahe. Eine Virose scheint nach den bisherigen Erfahrungen nicht vorzuliegen.

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Research on a white-variegated clone of Armoracia lapathifolia Gilib

Summary 1. Albo-variegation of Armoracia varies with season. In spring shoots are almost pure white, becoming increasingly green towards autumn.2. In the ontogeny of individual plants permanent demixing could not be found. Neither pure green nor pure white shoots, which would have remained stable, could be observed. In the various stages of ontogeny there were mosaic-like variegated as well as sectorially variegated leaves. However, shoots with white sectors running from the leaves into the stalks or mericlinal chimerically striped shoots (with corresponding colouring of the leaves) were not found.3. In anatomical structure the leaves did not show any periclinal chimerical status. The distribution of white and green tissue does not follow definite laws.4. The numerous shoot regenerates from isolated roots and leaves of albo-variegated plants continuously produced only variegated plants. Selective cloning towards green or white was not possible.5. Since, from an anatomic histogenetic view, the chimerical structure of albo-variegated horse-radish could not be confirmed, gene-conditioned albo-variegation is to be supposed. According to experiences so far virosis does not seem to exist.

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Teil einer Dissertation der Math.-Nat. Fakultät der Päd. Hochschule Potsdam (1964, gekürzt).