Fischer, Ulrich
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Fischer, Ulrich
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Fischer, Ulrich
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Item type:Publication, Untersuchungen zur Charakterisierung von marinen Cyanobakterien der Gattung Anabaena und ihrer Licht- und UV-absorbierenden Substanzen(2003-07-18); ; ; Ten marine Anabaena strains from the Baltic Sea have been characterised and classified using morphological, chemotaxonomic, and molecular methods. A main objective of this work was the detection and analysis of light- and UV-absorbing compounds as well as extracellular coloured substances released into the liquid culture medium. One extracellular coloured substance of a particular isolate was analysed in detail using Photometry, Chromatography, SDS-Page, and Mass Spectrometry.doctoral thesis246 301 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Nachweis zum Vorkommen von Bakterien und deren physiologischer Aktivitäten auf marinen Partikeln in der Wassersäule(2004-05-14); ; ; Ten heterotrophic bacterial strains, isolated from particles of the upper water column of the Equatorial Atlantic, taken during a cruise on the R/V METEOR (1997), were investigated concerning their physiological and phylogenetic properties using classical microbiological and modern molecular-biological methods. All isolates are gram-negative rods able to use polymers such as cellulose, chitin or starch as sole carbon source. The phylogeny of the isolates was investigated by fluorescence in situ hybridization (FISH) and 16S rDNA-sequencing. The ten isolated strains belong to the :i:Cytophaga/Flavobacteria:/i:, gamma-Proteobacteria, and alpha-Proteobacteria. In order to study succession during growth with naturally in marine habitats occurring polymers, fluorescence in situ hybridization (FISH) was used as a new instrument to detect cells from different phylogenetic clusters in course of a growth experiment. Mixed cultures consisting of three strains which belong to different phylogenetic groups in equal amounts were incubated with cellulose, chitin, and starch. It could be demonstrated that isolate 4301-10/2, a member of the gamma-Proteobacteria, dominates the mixed cultures with cellulose, chitin, or starch already after 10 days with 55, 60, and 95%, respectively, of cells hybridized with DAPI.doctoral thesis242 416 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Physiologische, chemotaxonomische und molekularbiologische Eigenschaften mariner Partikel-assoziierter Bakterien aus dem Atlantik(2004-07-15); ; ; The morphological, physiological, chemotaxonomical, and molecular properties of heterotrophic particle associate bacteria from the South Atlantic (Antarctica) were examined to get more information about the ability of these bacteria to metabolize organic compounds. BIOLOG GN- and API 50 CH-system as well as tests with sole carbon sources in ASNIII-medium showed that these isolates differed strongly in their ability to use high and low molecular weight organic compounds as carbon sources.The 16S rDNA sequences assigned the bacteria into the following genera: Loktanella, Sulfitobacter, Paracoccus, Pseudoalteromonas, Psychrobacter, and Polaribacter. A new species was described and the name Psychrobacter nivimaris sp. nov. was proposed.Additionally, morphological and molecular properties of particle associated bacteria from samples of different water depths of the equatorial Atlantic are investigated, to examine if there is a change of diversity with increasing water depth. Some isolates formed yellowish pigmented colonies. The pigments of selected isolates were characterized with photometric, chromatographic and mass spectrometric methods. One isolate formed Zeaxanthin. The pigments of two other isolates, forming greenish yellow colonies, could probably be Bacteriorubixanthin. These two showed a great similarity in their 16S rDNA to species of the genus Erythrobacter.doctoral thesis555 128 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Untersuchungen zur Bioverfügbarkeit von Elementarschwefel und biogenem Schwefel und zur biotechnologischen Sulfidentfernung durch Grüne- und Purpurschwefelbakterien(2006-12-21); ; ; The following model organisms were used to study bioavailability of both elemental sulfur (SÃ °) and biologically produced sulfur (biogenic SÃ °) by anoxygenic phototrophic bacteria: Prosthecochloris vibrioformis (green sulfur bacterium), Allochromatium vinosum and A. vinosum mutant strain 21D. During photolithoautotrophic growth of P. vibrioformis with SÃ ° it could be observed that cells attached to the SÃ °-particles 24 h after the addition of the latter. The SÃ ° became hydrophilic, which was not attributed to abiotic reactions. If cells of P. vibrioformis were separated from SÃ ° by a dialysis membrane (exclusion size: 12-14 kDa), growth was not observed. If SÃ ° was added directly to the medium, growth of P. vibrioformis was dependent on the SÃ ° concentration in the medium. The protein pattern of extracellular enzymes from growth of P. vibrioformis with SÃ ° and sulfide was compared by SDS PAGE but no differences were observed. Furthermore, the protein pattern of whole cell proteins (WCP) from growth of P. vibrioformis with SÃ °, biogenic SÃ ° and sulfide, respectively, was compared. Two bands (ca. 38 kDa and ca. 40 kDa) were detected, which were only expressed during growth on SÃ ° and biogenic SÃ °, respectively.A. vinosum mutant strain 21D was used as a biocatalyst to remove sulfide from synthetic wastewater in a 5 L photobioreactor. The process type was semicontinuous with three fed-batch periods. Running time of the experiment was 1464 h. Due to a genetic modification in A. vinosum strain 21D, the formation of sulfate, which was unwanted in this process, and the attachment of biogenic SÃ ° on the glass wall, were circumvented.The average sulfide removal rate was 49.3 Ã µM/h and the maximal sulfide removal 98.7 %. An average sulfide removal of 91.7 % and an overall biogenic SÃ ° recycling of 60.4 % was achieved. By means of these results, it was shown that the use of A. vinosum 21D for sulfide elimination and recycling of biogenic SÃ ° is a competitive alternative to the currently dominating physicochemical methods.doctoral thesis341 98 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Strategien zur Detektion und Identifizierung von Naturstoffen bei Cyanobakterien am Beispiel von Geitlerinema Stamm Flo1 und Fischerella ambigua(2011-12-02); ; ; Marine cyanobacteria are known as producer of a large number of bioactive substances. Geitlerinema strain Flo1 and the strain Fischerella ambigua showed production of an antibacterial substance and a brownish colored substance, respectively. These substances can be synthesized either ribosomally or on large enzyme complexes called "Non-ribosomal Peptide Synthetases" (NRPS) and "Polyketide Synthases" (PKS). Different strategies were used to prove the way of synthesis and to identify the substances. Finally knock-out mutagenesis caused by homologous recombination and HPLC-MS analyses were successfully used to identify five possible molecules that were produced by NRPS. The inhibitory effect of culture supernatant derived from strain Flo1 is caused by an L-amino acid oxidase (L-AAO). In-gel detection of the flavoenzyme using non-denaturing SDS-PAGE linked with antibacterial assays reveals that strain Flo1 produces an L-lysine oxidase with an approximate molecular weight of 55 kDa. The brownish substance secreted by Fischerella ambigua showed characteristics typical for hydrolysable tannins (polyphenols).doctoral thesis272 165 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Mobilization of sulfur by green sulfur bacteria : physiological and molecular studies on Chlorobaculum parvum DSM 263(2011-07-07); ; ; Green sulfur bacteria are photolithotrophs that use inorganic sulfur compounds as electron donors for photosynthesis. Elemental, solid sulfur is one of the electron donors used. Sulfur is produced by green sulfur bacteria during the oxidation of sulfide to sulfate, and during the oxidation of thiosulfate to sulfur and sulfate. Green sulfur bacteria have been known for long, and the genomes of 12 strains have been sequenced. Yet, it is not clear how green sulfur bacteria can access elemental sulfur, which is practically insoluble at the temperatures at which most of them grow. The present work has been done using pure cultures of the mesophilic strain Chlorobaculum parvum DSM 263. By studying the dynamics of inorganic sulfur compounds in growing cultures of Cla. parvum DSM 263, it was shown that the sulfur produced during thiosulfate oxidative disproportionation can be either oxidized immediately to sulfate, or released outside the cells. Extracellular sulfur oxidation needs a dedicated system, which is not synthesised in the presence of thiosulfate. Experiments conducted at low light intensities revealed that thiosulfate is not consumed exclusively via the Sox multienzymatic system, known thus far as the only thiosulfate oxidizing system present in green sulfur bacteria. It is not clear yet if this additional pathway for thiosulfate consumption allows strain DSM 263 to obtain electrons for thiosulfate, or if it is used by bacteria to consume the reducing power that cells might have in excess. Physiological studies conducted on Cla. parvum DSM 263 fed with sulfur furnished evidence that the oxidation of elemental sulfur to sulfate is accompanied by the formation of yet unidentified sulfur compound(s). Similarly to what commented for thiosulfate consumption, these compounds could be intermediates in the oxidation of sulfur to sulfate, or could be side products of sulfur consumption. Essential elements for the utilisation of elemental sulfur were shown to be present in the membranes of Cla. parvum DSM 263. Differential membrane proteomic studies were thus performed on cells of Cla. parvum DSM 263 grown on sulfur or on sulfide. Seven proteins were found to be overexpressed in sulfuric conditions, revealing that bacteria do possess different proteomic equipment for oxidizing the insoluble sulfur rather than the soluble sulfide. Identification of these overexpressed proteins and of their interaction partners will probably help revealing the cellular apparatus of extracellular solid sulfur mobilization.doctoral thesis274 114 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Molecular Biological and Physiological Investigations of Heterotrophic Bacteria Associated with Marine Filamentous Cyanobacteria(2009-12-16); ; ; The composition of the heterotrophic community within the cultures of the cyanobacteria Oscillatoria brevis and Nodularia harveyana was investigated. 51 heterotrophic strains were isolated, of which 4 were chosen for further investigations: a red, a pink, and a colourless one, grouping with Porphyrobacter, Roseobacter, and Rhodobacter respectively, and a yellow one grouping with Muricauda. For further investigations specific FISH probes were designed for Muricauda and for the Erythrobacteraceae. Axenic cultures of Nodularia and Oscillatoria were prepared, which then were mixed with single pure cultures of the four heterotrophs. A detrimental effect was determined only for Oscillatoria. It could be shown that in all cases new heterotrophic communities developed in the cultures. The occurrence of the heterotrophs was studied with ten further cyanobacterial cultures. Furthermore, the heterotrophs were characterised concerning their morphological, biochemical, and physiological properties.doctoral thesis273 116 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Characterisation of inhibitory substances produced by two Pseudoalteromonas species and the cyanobacterial strain Flo1(2011-07-14); ; ; In the present study the inhibitory substances of P. aurantia NCIMB 2052T and P. citrea NCIMB 1889T were investigated with respect to their substantial and functional nature, their inhibitory potential, their stability against various treatments as well as the growth phases and incubation conditions when the substances are produced. In addition, an inhibitory substance produced by strain Flo1 was examined regarding its structure, function, and inhibitory potential. Furthermore, its taxonomic position amongst closely related cyanobacteria was investigated by re-constructing phylogenetic trees, showing that strain Flo1 is most closely related to the genus Geitlerinema. The results clearly indicate that the inhibitory substances produced by both Pseudoalteromonas species as well as by Geitlerinema strain Flo1 are L-amino acid oxidases (L-AAOs) with broad respectively very specific substrate spectra. Furthermore, it could be shown that the Pseudoalteromonas L-AAOs are active against methicillin-resistant Staphylococcus aureus (MRSA).doctoral thesis325 200 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, A multi-gene approach in the systematics of the phototrophic purple sulfur bacteria genera Marichromatium and Allochromatium with description of the new species Allochromatium humboldtianum and the new biotype Marichromatium gracile biotype thermosulfidiphilum.(2009-07-23); ; ; In the present thesis two genera of the photosynthetic Purple Sulfur Bacteria (PSB) of the family Chromatiaceae are revised by molecular techniques which include extensive DNA-DNA hybridization (DDH) studies and a multi-gene analysis. Traditionally, species of PSB have been described based on some easily recognizable phenotypic properties and separated in two families the Chromatiaceae and Ectothiorhosdopiraceae. Within the Chromatiaceae the genus Chromatium was also separated in several genera being the most important the genera Marichromatium and Allochromatium. Type species within each genus does not exhibit remarkable phenotypic properties and phylogenetically they are difficult to resolve using a high conserved loci such as the 16S rRNA. In the present study the analysis of the concatenated protein-coding gene sequences for the genera Marichromatium (4331 bp) and Allochromatium (4427 bp) allowed the separation of all examined strains within each genus in several independent clusters of phylotypes that in many cases reflect previous species circumscription based on phenotypic analysis. Thus, MLSA approach could be used as a valuable tool for separating closely related strains.doctoral thesis358 191