ALBERT

Beschreibung: A program of geophysical research was carried out as a preliminary stage of study of the Santorini volcanic group. This area is of remarkable geothermal and volcanological interest, and the definition of a volcanological structural model is the starting point for an understanding of the local geodynamic processes. Gravity, magnetic and geoelectrical data proved that: (i) the core of the volcanic edifice consists of a sedimentary-metamorphic basement; (ii) the basement is tectonically disturbed and a linear tectonic system produces a graben-type structure in the middle part of the area.

Beschreibung: Die Probleme, die bei Speciesuntersuchungen von Spurenelementen mit Hilfe der Differentialpuls Anodic Stripping Voltammetrie auftreten, werden zu-sammenfassend dargestellt. Neben den bei der eigentlichen Bestimmung auftretenden Problemen, werden auch solche erwähnt, die mit der Probennahme sowie der Lagerung und Vorbehandlung der Proben in Zusammenhang stehen.

Beschreibung: Sponges are diploblastic acoelomate Metazoa. They are sedentary, filter-feeding animals which utilize a layer of flagellated cells to pump a unidirectional water current through themselves. They are found in freshwater, but more abundantly in marine habitats. Sponges have been persistent throughout geological time from the Precambrian to the Recent, with special success during the Paleozoic. They are apparently the most primitive multicellular animals on a phylogenetic scale ranked by morphological complexity, although the levels of physiological and biochemical complexity found in sponges easily measure up to the degree of sophistication found in so-called higher animals. The Porifera (sponges) and Coelenterata are related as two phyla representing distinct stocks, but stemming from a presumed common although presently unknown origin (Hyman, 1940).

Beschreibung: Mesozoic deep water sedimentary rocks uplifted and exposed in basement complexes on the islands of Fuerteventura (Canary Islands) and Maio (Cape Verdes) help document the early Atlantic ocean and the volcanic history of these islands. On Fuerteventura ca. 1.5 km of terrigenous quartzose clastics, black shales, and subordinate redeposited limestones of early Cretaceous age are overlain first by Albian-Cenomanian marls and clastics, showing extensive soft sediment slumping, then after a hiatus by Senonian nannofossil chalks with chert nodules. After a further break alkalic submarine volcanic rocks, largely hyaloclastics, were erupted, then overlain by redeposited bioclastic limestones and volcaniclastics of Oligocene age. A dyke complex was intruded, then the basement complex was uplifted, peneplaned, and overlain by Neogene plateau lavas. On Maio the basement complex comprises mafic pillow lavas of midocean ridge character overlain by up to 4 00 m of deep water sedimentary rocks. Upper Jurassic to lower Cretaceous radiolarianrich pelagic limestones are succeeded by middle and upper Cretaceous sequences of mudstones, redeposited limestones, chalks, tuffs, and volcaniclastics which document the onset of volcanism. During a sedimentary hiatus plutonic rocks were intruded, uplifted, then eroded to produce conglomerates of late Miocene age. These are overlain by several series of gently dipping subaerial alkaline basalt flows. Comparisons with D.S.D.P. sites, oil wells and on land geology confirm that the lower Cretaceous Fuerteventura quartzose clastics formed part of a deep water fan complex located close to the Atlantic continent-ocean boundary. Comparable flysch is known in the Moroccan basin, in the Betic-Maghrebide system and the feeding Tan-Tan-Cape Bojador delta system. The inferred disconformity between Cenomanian and Senonian is part of a widespread depositional hiatus associated with slumping on the adjacent west African continental margin. On Maio pelagic limestones comparable with the Tethyan Maiolica facies were deposited on a subsiding? middle/late Jurassic ocean ridge before uplift related to onset of volcanism probably in the late Cretaceous.

Beschreibung: M. Dunbar (1957) called attention to the existence of a small circular polynya about 50 m in diameter in Cambridge Fiord in northern Baffin Island for which there was no obvious explanation. Other small polynyas are known in arctic fjords which are usually the result of turbulent mixing in areas of strong currents (Sadler 1974), but Cambridge Fiord is 100 km long, its tidal range is small, and the polynya is situated within 300 m of the delta face at the head of the fjord so that strong turbulence is very unlikely. The annual reappearance of the polynya in late winter is confirmed by a series of aerial survey photographs taken by the Royal Canadian Air Force between 1952 and 1957 and also by reports from Inuit hunters from Pond Inlet. It is first seen within about two weeks of 15 March appearing in exactly the same position each year as a circle with a diameter of about 40 m. Over a period of about a week, a lead extends from the polynya to the shore and open water is visible in the tide crack for several hundred metres either side of the shore end of the lead. The lead, unlike the polynya, changes its position from year to year, but once formed it remains fixed until general break-up (Figure 1).

Beschreibung: Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.

Beschreibung: The ability to use adenosine 5′-phosphosulfate (APS) or 3′-phosphoadenosine 5′-phosphosulfate (PAPS) as the substrate for the initial reductive step in sulfate assimilation has been tested in most of the known Rhodospirillaceae species and in some chemotrophic bacteria. Improved and optimized methods for the synthesis and purification of the sulfonucleotides APS and PAPS are described. The production of acid volatile radioactivity from 35S-APS and 35S-PAPS was measured under various conditions in the presence and absence of non-labeled sulfate. Specific differences in the ability to reduce APS or PAPS were observed among the Rhodospirillaceae species and also the chemotrophic bacteria. APS was found to be the substrate of the thiolsulfotransferase in Rps. acidophila, Rps. globiformis, Rm. vannielii, Rc. purpureus, R. tenue, Rps. gelatinosa, in Alcaligenes eutrophus and Pseudomonas aeruginosa. PAPS was the substrate in Rps. capsulata, Rps. sphaeroides, Rps. sulfidophila, Rps. palustris, Rps. viridis, R. rubrum, R. fulvum, in Paracoccus denitrificans and in several Enterobacteriaceae. The presence of different enzymatic systems for sulfate reduction in the Rhodospirillaceae family is compared with their taxonomical grouping and their possible phylogenetic relatedness.

Beschreibung: The mechanism of sulfate assimilation was investigated in Rhodopseudomonas sulfidophila, a bacterium able to grow either photoautotrophically, with sulfide as electron donor, or photoheterotrophically with sulfate as sole sulfur source. ATP sulfurylase, adenosine-5′-phosphosulfate kinase, 3′-phosphoadenosine-5′-phosphosulfate sulfotransferase, thiosulfonate reductase and cysteine synthase were present. Reduced sulfur compounds, especially sulfide and sulfite repressed all steps of sulfate activation and reduction including sulfate uptake. Adenosine-5′-phosphosulfate kinase activity in contrast to the other activities was high in the presence of cysteine or reduced glutathione in the growth medium. Sulfur was incorporated into the cellular sulfolipid from sulfate and also from reduced sulfur compounds like cysteine and thiosulfate. The activity of 3′-phosphoadenosine-5′-phosphosulfate sulfotransferase was rapidly lost during gel filtration or dialysis. From comparison with other sulfotransferases and from the specific cofactor requirement for the enzyme of R. sulfidophila it is concluded that two different low molecular weight cofactors are required in this system. A reaction sequence is proposed involving thioredoxin as the reductant of another dialysable low molecular weight cofactor, that binds to the protein.

Beschreibung: A new purple nonsulfur bacterium was isolated from enrichment cultures of a sulfide-containing marine lagoon. The bacterium is similar to Rhodopseudomonas capsulata and is described as a new species of the genus Rhodopseudomonas: Rhodopseudomonas adriatica. Cells are non-motile, 0.5–0.8 μm by 1.3–1.8 μm, and multiply by binary fission. Intracytoplasmic membranes are of the vesicular type. The photosynthetic pigments are bacteriochlorophyll a and carotenoids of the spheroidene group. Growth is possible anaerobically in the light and at low pO2 in the dark. Biotin and thiamine are required as growth factors. A wide variety of organic compounds, as well as sulfide and thiosulfate, are used as photosynthetic electron donors. Sulfide is oxidized to elemental sulfur, which is subsequently converted to sulfate, whereas thiosulfate oxidation occurs without measurable intermediate. Rhodopseudomonas adriatica is unable to assimilate sulfate, growth is only possible in the presence of a reduced sulfur compound.