Wechselwirkungen zwischen der antarktischen Eisdiatomee Amphiprora kufferathii MANGUIN und epiphytischen Bakterien unter besonderer Berücksichtigung des Oxidationsschutzes

The Antarctic ice diatom Amphiprora kufferathii is covered by epibacteria in its natural environment. This community is maintained under culture conditions. In my work the physiological interactions between the diatom and the bacteria were investigated with special regard to their antioxidative defense systems. The experiments were carried out with bacterized and axenic cultures of the diatom.The bacteria were identified by isolation and cloning of total 16S rRNS of the bacterized diatom culture. Phylogenetic analysis showed that A. kufferathii is covered by alphaproteobacteria of the genera Octadecabacter and Sulfitobacter as well as by members of the bacteriodetes phylum of the genera Cellulophaga and Psychroflexus. Most of the free living bacteria were classified as gammaproteobacteria of the genera Colwellia. Quantitative fluorescence in situ hybridization showed a 70% coverage of the diatom by Octadecabacter. Bacteriodetes and gammaproteobacteria showed a maximal abundance of 10% to 13%. The epibacteria stimulate the growth of A. kufferathii. Experiments under nutrient limitation showed that this effect can be explained by the remobilization of nitrogen and silicate by the bacteria. The epibacteria have also effects on A. kufferathii under osmotic and temperature stress. Physiologic investigations demonstrate that the epibacteria are participated in the antioxidative defense of A. kufferathii by scavenging hydrogen peroxide produced by the diatom.I investigated the most common antioxidative enzmes of the diatom and the isolated bacteria. In A. kufferathii two superoxide dismutases and two glutathione reductases were found, whereas catalase was not detected.Several isoenzymes of superoxide dismutse have been identified in Cellulophaga and Sulfitobacter but not in Colwellia. Catalase and Glutathione reductase were detected in all isolated bacteria

On the dynamics of the adenylate energy system: homeorhesis vs homeostasis.

Biochemical energy is the fundamental element that maintains both the adequate turnover of the biomolecular structures and the functional metabolic viability of unicellular organisms. The levels of ATP, ADP and AMP reflect roughly the energetic status of the cell, and a precise ratio relating them was proposed by Atkinson as the adenylate energy charge (AEC). Under growth-phase conditions, cells maintain the AEC within narrow physiological values, despite extremely large fluctuations in the adenine nucleotides concentration. Intensive experimental studies have shown that these AEC values are preserved in a wide variety of organisms, both eukaryotes and prokaryotes. Here, to understand some of the functional elements involved in the cellular energy status, we present a computational model conformed by some key essential parts of the adenylate energy system. Specifically, we have considered (I) the main synthesis process of ATP from ADP, (II) the main catalyzed phosphotransfer reaction for interconversion of ATP, ADP and AMP, (III) the enzymatic hydrolysis of ATP yielding ADP, and (IV) the enzymatic hydrolysis of ATP providing AMP. This leads to a dynamic metabolic model (with the form of a delayed differential system) in which the enzymatic rate equations and all the physiological kinetic parameters have been explicitly considered and experimentally tested in vitro. Our central hypothesis is that cells are characterized by changing energy dynamics (homeorhesis). The results show that the AEC presents stable transitions between steady states and periodic oscillations and, in agreement with experimental data these oscillations range within the narrow AEC window. Furthermore, the model shows sustained oscillations in the Gibbs free energy and in the total nucleotide pool. The present study provides a step forward towards the understanding of the fundamental principles and quantitative laws governing the adenylate energy system, which is a fundamental element for unveiling the dynamics of cellular life

Liefergebiets - Charakterisierung proterozoischer Goldseifen in Ghana anhand von Fluideinschluß - Untersuchungen.

The gold-bearing Tarkwaian conglomerates of the so-called Banket Series in the Ashanti Belt are oligomictic and consist of vein-quartz pebbles within a quartzitic matrix. The matrix consists, besides fine grained quartz, of secondary carbonates, chlorite, muscovite, tourmaline, epidote, actinolite, rutile, altered plagioclase, detrital zircon and opaque minerals. The opaque phases are mostly hematite and magnetite, which occur in about the same proportions. Free particles of gold and pyrite are rare.Fluid inclusion investigations revealed that the quartz-pebbles of the conglomerates contain predominantly CO2-rich fluids, some of which have unusually high densities (up to 1.13 g/cm3). These inclusions were probably trapped in the provenance area of the quartz pebbles. The matrix of the conglomerates is dominanted by H20-CO2-rich inclusions.The Banket Series conglomerates are underlain by the Kawere Series. The conglomerates of this series are polymictic and frequently matrix supported. Furthermore, the quartzitic matrix of the conglomerates contain small amounts of muscovite, plagioclase and epidote. These conglomerates carry no economic gold-contents, which are normally below 50 ppb. Quartzpebbles ofthese conglomerates possess H20- and H20-CO2-rich inclusions.6

Interactions between the Antarctic ice-diatom Amphiprora kufferathii MANGUIN and epiphytic bacteria with special regard to their antioxidative defence systems

The Antarctic ice diatom Amphiprora kufferathii is covered by epibacteria in its natural environment. This community is maintained under culture conditions. In my work the physiological interactions between the diatom and the bacteria were investigated with special regard to their antioxidative defense systems. The experiments were carried out with bacterized and axenic cultures of the diatom.The bacteria were identified by isolation and cloning of total 16S rRNS of the bacterized diatom culture. Phylogenetic analysis showed that A. kufferathii is covered by alphaproteobacteria of the genera Octadecabacter and Sulfitobacter as well as by members of the bacteriodetes phylum of the genera Cellulophaga and Psychroflexus. Most of the free living bacteria were classified as gammaproteobacteria of the genera Colwellia. Quantitative fluorescence in situ hybridization showed a 70% coverage of the diatom by Octadecabacter. Bacteriodetes and gammaproteobacteria showed a maximal abundance of 10% to 13%. The epibacteria stimulate the growth of A. kufferathii. Experiments under nutrient limitation showed that this effect can be explained by the remobilization of nitrogen and silicate by the bacteria. The epibacteria have also effects on A. kufferathii under osmotic and temperature stress. Physiologic investigations demonstrate that the epibacteria are participated in the antioxidative defense of A. kufferathii by scavenging hydrogen peroxide produced by the diatom.I investigated the most common antioxidative enzmes of the diatom and the isolated bacteria. In A. kufferathii two superoxide dismutases and two glutathione reductases were found, whereas catalase was not detected.Several isoenzymes of superoxide dismutse have been identified in Cellulophaga and Sulfitobacter but not in Colwellia. Catalase and Glutathione reductase were detected in all isolated bacteria

Adenylate concentration and energy charge in different thallus regions and after UV radiation in brown, red and green algae

A method was developed to extract adenine nucleotides AMP, ADP, and ATP from marine macroalgal tissue to gain information on the cellular energy charge. Quantification was carried out by high performance liquid chromatography (HPLC). Three species from the rocky shore of the island of Helgoland (German Bight) were examined: Laminaria saccharina (Phaeophyta), Chondrus crispus (Rhodophyta), and Ulva lactuca (Chlorophyta). In L. saccharina and C. crispus, the adenylate energy charge (AEC) was determined in different thallus regions. AEC varied in relation to tissue age and function. Higher AEC values typically occurred in thallus regions with meristematic activity. Furthermore, L. saccharina and U. lactuca were exposed to UV-A and elevated UV-B radiation. The AEC was calculated and the maximal quantum yield of photosystem II (Fv/Fm) was determined as indicators for UV stress. In both species, the AEC remained at high values (0.72 ± 0.04), while Fv/Fm dropped rapidly. The results show that the photosynthesis of the phaeophyte is more resistant to UV radiation than the chlorophyte