Kirst, Gunter-Otto
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Kirst, Gunter-Otto
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Kirst, Gunter-Otto
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Kirst, Gunter Otto
Kirst, Gunther-Otto
Kirst, Gunther Otto
Kirst, Gunter-O.
Kirst, Gunter O.
Kirst, Gunther-O.
Kirst, Gunther O.
Kirst, G.-O.
Kirst, G. O.
Kirst, G.
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Item-typ:Veröffentlichung, Wechselwirkungen zwischen der antarktischen Eisdiatomee Amphiprora kufferathii MANGUIN und epiphytischen Bakterien unter besonderer Berücksichtigung des Oxidationsschutzes(2004-06-04); ; ; 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.Dissertation358 244 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Zur Definition biozönotisch relevanter Fließgewässertypen anhand des aktuellen Vorkommens benthischer Algen (excl. Charales und Diatomeen) in Fließgewässern Deutschlands(2006-12-19); ; ; The present occurrence of benthic algae (excl. Charales and diatoms) was investigated at 187 sampling sites at streams and rivers all over Germany. In total, more than 170 taxa from 11 algal classes were found. Multivariate statistical analyses showed that species composition at the sampling sites differed mostly with respect to water hardness and acid neutralizing capacity, but also with respect to anthropogenic degradation (higher levels of nutrients or pollution). Five types of running waters could be defined which show a characteristic species composition under reference conditions. Out of these, the siliceous waters in the Central Highlands are the most species-rich. Further research should focus on calcareous waters in the Northern Plains as here a great part of variation in species composition is not well understood yet. Parts of this work were conducted within the PHYLIB project which led to an assessment routine as needed for the application of the Water Framework Directive.Dissertation387 288 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Streßphysiologie bei antarktischen Diatomeen:Ökophysiologische Untersuchungen zur Bedeutung von Prolin bei der Anpassung an hohe Salinitäten und tiefe Temperaturen.(2002-10-28); ; ; Four of totally nine examined antarctic ice diatoms have been exposed to a long-term experiment to give the proof that not only the sell size but also physiological properties are responsible for the vertical distribution of the ice diatoms in the ice column. Therefore Chaetoceros sp., Corethron pennatum, Amphiprora kufferathii and Nitzschia lecointei are compared with respect to some of their physiological characteristics in relation to their natural distribution: Chaetoceros sp. mainly occurs in the upper part and A. kufferathii at the bottom of the ice column; N. lecointei is spread within the ice but preferably more in the lower parts, whereas C. pennatum is mainly distributed in the open water. In the upper part of the ice life conditions are variable with low temperatures and high salinities. In comparison the conditions at the bottom of the ice column are stable. According to their occurrence in the ice column the ability of the four species to acclimatise varies: Chaetoceros sp. has to cope with highly variable conditions unlike A. kufferathii and C. pennatum. Physiological properties obtained with the mentioned experiment indicate that Chaetoceros sp. and N. lecointei best tolerate extreme life conditions compared to the other two species because they endure a greater range of temperature and salinity, e.g. up to 151 PSU (N. lecointei) and more than 196 PSU (Chaetoceros sp.). Additionally the accumulation pattern of the main osmolyte proline proves the species specific ability to acclimatise to cold temperatures and high salinities. But there are differences in the way of acclimatisation between N. lecointei and Chaetoceros sp.: the former accumulates proline and other organic osmolytes only to an amount of 40 mM at maximum whereas the latter is able to synthesise proline up to 4.5 M. The concentrations are reflected by different properties of the Pyrroline-5-carboxylate Reductase which is one of the proline synthesising enzymes.Dissertation310 267 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Investigations into the role of bacteria/dinoflagellate interactions in Paralytic Shellfish Poisoning(2003-07-09); ; ; The interactions of purportedly toxic bacteria with dinoflagellates in the occurrence of Paralytic Shellfish Poisoning (PSP) were investigated. Dinoflagellates of the genus Alexandrium were examined to determine their bacterial population by the use of fluorescently labelled probes. Extracellular associated bacteria were shown to be associated with A. andersonii, A. tamarense and A. lusitanicum. Intracellulae bacteria were found in A. tamarense. Cyanoditolyltetrazolium chloride was used to detect endocytic metabolically active bacteria in these dinoflagellates. Intracellular bacteria were detected in A. tamarense and A. lusitanicum. In field studies, the occurrence of putatively toxic bacteria together with Alexandrium spp. and PSP in mussels was investigated. Lugol's fixed field samples from the Orkney Islands were screened for these bacteria in two sequential years. For the first time, fluorescently labelled probes were successfully applied to Lugol's fixed environmental samples. The bacteria were detected in high numbers in the samples, when both Alexandrium spp. were present and absent in the water column and when mussels contained PSP. The effect of purportedly toxic bacteria on mussel toxicity was examined with feeding experiments. The bacteria were detected in situ in tissue sections of the mussels gut. Mussel flesh did not show toxification after feeding upon the putatively toxic bacteria, although the blue mussels have filtered the bacteria in high numbers. The physical interactions between bacteria and dinoflagellates were investigated by conducting reassociation experiments with purportedly toxic bacteria which were originally isolated from the Alexandrium tamarense clone used in this experiments, or isolated from another related A. tamarense clone, respectively. No intracellular reassociated PTB-bacteria were detected in the dinoflagellates. However, a preferred extracellular attachment of the PTB-1 bacteria to the A. tamarense strain was observed.Dissertation222 186 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Biology of toxic algae: A study of species of the genus Chrysochromulina (Prymnesiophyceae) and Alexandrium (Dinophyceae)(2002-05-17); ; ; The role of toxins in algal/protozoan interactions, Alexandrium strains were tested against the dinoflagellates Oblea rotunda&Oxyrrhis marina. Some non-toxic Alexandrium strains caused motility loss&grazer cell lysis indicating that PSP toxins weren t involved. Two clones of the haptophyte, Chrysochromulina polylepis, differing in their toxicity, were used in grazing experiments with O. marina. When O. marina was fed the toxic clone, O. marina food vacuoles contained fewer particles&cells grew slower than those fed the non-toxic clone. Allelochemicals from Alexandrium spp.&C. polylepis may support bloom formation by detrimental effects on grazers. Toxicity analysis of C. polylepis synchronized cultures was conducted using an hemolytic assay. Its toxicity was induced by light&increased during early G1 phase. Spirolide production was studied in A. ostenfeldii batch cultures. Total spirolide concentration per unit culture volume was related to cell concentration. An increase in spirolide cell quota occurred at the beginning of the dark phase. Phylogenetic analysis of the A. tamarense species complex with LSU rDNA sequences found a new non-toxic clade from the Mediterranean. Fossil records of the Peridiniales (~190 Ma), Gonyaulacaceae (~180 Ma)&Ceratiaceae (145 Ma) calibrated a molecular clock. Average age of Alexandrium is 77 Ma (Late Cretaceous&Early Paleogene) with earliest possible age at Mid Cretaceous (119 Ma). A. tamarense species complex likely diverged at Early Neogene (23 Ma)&late Paleogene (45 Ma). Hypotheses were proposed to explain the historical biogeography of the species. Amplified Fragment Length Polymorphism (AFLP) was established for species genetic diversity studies and used to investigate the genetic diversity within a distinct geographic region or a bloom. SSU&LSU rRNA sequences of Alexandrium ssp. were used to develop probes for the species complex, geographic clades&for A. ostenfeldii to identify them in field samples by FISH.Dissertation461 212 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Die SekundärmetaboliteDMSP und Toxinein Dinophyceae der Gattungen Prorocentrum Ehrenberg und Alexandrium Halim(2006-09-21); ; ; A common feature among Dinophyceae is the presence of intracellular secondary metabolites. The exact function and relevance of most of these secondary compounds for its host and the interplay between different secondary metabolites is not well understood. A better characterized secondary metabolite is the tertiary sulfonium compound dimethylsulfoniopropionate (DMSP) which - as compatible solute - is for example involved in the process of osmoregulation. In some species of dinoflagellates toxins are another large class of secondary metabolites that are structurally far more complex than DMSP.The main interest of this work was focused on the existence of competition among secondary metabolites like DMSP and toxins in the metabolism of dinoflagellates. In Alexandrium minutum the synthesis of DMSP and paralytic shellfish poisoning (PSP)- toxins are induced by light and were highest in the phase of exponential growth. For that a competition for energy to reduce sulfate (for DMSP-synthesis) and nitrate (for PSP-toxinsynthesis) might occur. The investigation of different stress situations on A. minutum and A. lusitanicum shows that nitrate limitation was of no effect on the cellular accumulation of DMSP and PSP-toxins. On the other side the intracellular DMSP concentration shows a positive correlation with changing salinities, because of its function as compatible solute in osmoregulation. The contrary negative correlation between salinity and the content of PSP-toxins may be explained by the competition with DMSP which is primarily synthesized under hyperosmotic situations.Dissertation244 435 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Salt stress tolerance in the psychrophilic diatom Fragilariopsis cylindrus(2006-06-12); ; ; This thesis was conducted to find mechanisms responsible for the adaptation success of Fragilariopsis cylindrus to the extreme polar environment, especially sea ice, manifested in the genetic repertoire. The generated molecular information was afterwards utilized in expression studies focused on the regulation of the proline metabolism during acclimatisation to elevated external salt concentrations. An expressed sequence tag (EST) approach was used to establish two complementaryDNA (cDNA) datasets, based on cultures subjected to temperature and salt stress conditions, the major abiotic constraints in sea ice. The genetic information (ca. 2600 tentative unique sequences) gathered with these two cDNA libraries covered about 20 % of all genes present in F. cylindrus, taken the genome of the centric diatom Thalassiosira pseudonana as a reference. A comparison of the salt stress cDNA library to the genomes of the mesophilic species T. pseudonana and Phaeodactylum tricornutum revealed about one third of the sequences to be unique to F. cylindrus, indicating substantial genomic variation between the mesophilic and psychrophilic lifestyle. This indicates the potential of yet unknown adaptation mechanisms. A putative function could be assigned to 44 % of the sequences and a large number of genes involved in transport processes, oxidative stress defence, osmolyte synthesis and protein turnover as well as chaperones could be identified, stressing the importance of these mechanisms in salt stress acclimatisation. Furthermore, four different full length sequences encoding a new class of ice-binding proteins yet unknown in animals and plants were found and further studies proved its occurrence in a number of polar diatom species, but not in mesophilic ones. These proteins are most probably exuded into the extracellular space and hence might be of fundamental importance in enabling survival in the brine channel system. The finding of all relevant proteins involved in the ana- and catabolic pathways of proline metabolism enabled a detailed expression study of these genes in a physiological salt shock (elevation from 34 to 70 PSU) experiment. Expression levels of Delta1-pyrroline-5-carboxylate synthase (P5CS), the rate limiting enzyme in synthesis from glutamate, strongly decreased, whereas copy numbers of ornithine delta-aminotransferase (delta-OAT) increased, indicating a shift from the glutamate to the ornithine route under elevated external salinities. This contrasts with findings in higher plants, where the opposite regulation of P5CS and delta-OAT was observed. A shortage in reduction equivalents caused by a severe inhibition of linear electron transport revealed by the measurement of the photosynthetic quantum yield might force F. cylindrus to use energy saving pathways of proline synthesis. Interestingly, a further temperature decrease in addition to the elevated salt concentration exhibited no more negative effects in a number of physiological parameters, thus leading to the conclusion that salt is the dominating abiotic stressor in sea ice.Dissertation522 179 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Morphometric and molecular investigations of species limits in Cyclotella meneghiniana (Bacillariophyceae) and closely related species(2005-05-09); ; ; Comparative molecular genetic and morphometric methods were used to clarify long-standing taxonomic uncertainties in one of the most common freshwater diatom species, Cyclotella meneghiniana Kützing. First a single C. meneghiniana population was sampled by isolating clonal cultures. Frustule ultrastructure of the cultures and of field samples was analysed using two different morphometric methodologies. These analyses contributed significantly to clarifying a problem concerning the delimitation of C. meneghiniana from a closely related species, C. scaldensis Muylaert&Sabbe. Next, patterns of ribosomal DNA sequence variation among fifteen cultures displaying the characteristic C. meneghiniana morphology were explored. The patterns observed indicated the presence of genetic structuring in the population sampled, suggesting that C. meneghiniana was either a complex of multiple, cryptic species, or that of strictly clonally or autogamously reproducing lineages. The following step was surveying sequence variation in the D1/D2 regions of the nuclear ribosomal DNA and in a region of the plastid encoded psaA gene in a collection of strains including C. meneghiniana strains with diverse geographic origins and cultures of some closely related species. Strict covariation was observed in the two genomic regions sequenced, further reinforcing the conclusion that C. meneghiniana is a structured species. The hypothesis that this genetic structuring was caused by the complete lack of allogamous sexual reproduction in this morphospecies was tested by quantifying phylogenetic incompatibility present in AFLP (amplified fragment length polymorphism) genotypes of strains from two populations. The results indicated no significant deviation from panmictic expectations, suggesting that Cyclotella meneghiniana is a complex of several, reproductively isolated species, rather than that of strictly autogamous lineages.Dissertation246 179 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Taxonomic Revision of Diatoms belonging to the family Naviculaceae based on morphological and molecular data.(2006-09-11); ; ; Based on morphology, the taxonomy of the family Naviculaceae (sensu Krammer&Lange-Bertalot, 1986) has been highly changed (e.g., Round et al., 1990), but little work has been carried out with molecular data for this large and ecologically important group of diatoms. My thesis was aimed at the investigation of evolutionary relationships within the naviculoid pennates using molecular and morphological data. Phylogenies based on sequences of the nuclear-encoded SSU rRNA gene, the LSU rRNA gene, the chloroplast rbcL gene and a combined dataset were compared. This study confirms the assumption that the genus Navicula sensu lato is a very heterogenous group and my results support the monophyly of Navicula sensu stricto. Several 'Navicula' species, which do not belong to the section Lineolatae could be recombined. The monophyly of several genera could be supported. But the actual differentiation of the genera Caloneis and Pinnularia is rejected. The separation of the subgenus Halamphora from the genus Amphora is supported by molecular and morphological data. This study also resolve several relationships between different genera.Dissertation229 116 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Möglichkeiten der Wertschöpfung durch ungenutzte Rohstoff-Potenziale der Seafood Industrie : Ein Upgrading-Konzept zur Gewinnung von Phycocyanin aus Cyanobakterien und Astaxanthin-reicher Protein-Öl-Konzentrate aus Crustaceen durch molekularbiologische und biotechnologische Methoden(2006-04-24); ; ; The question of how knowledge of certain organisms can be used to upgrade whole product lines lies at the centre of current research. For the purpose of clarification, this process, in-cluding control and assessment of the interactions between process design and properties, was divided into four steps through observation, analysis, and evaluation completed at pre-determined intervals:1.Substance characterisation2.Narrowing of goals3.Product and process conceptualisation4.Application and optimisationPotential sources of the blue pigment phycocyanine were studied within the framework of "substance characterisation". If enough can be extracted at an acceptable price, phycocya-nine can be widely used in organic foods and cosmetics. Phycocyanine can be extracted through the use of Cyanobacteria, whose substitute Spirulina sp. yields more than 3.000 tons of biomass annually and is sold in many health food markets mainly in the U.S., Canada, Japan, and Europe. Products based on Spirulina were analysed based on their concentration of phycocyanine and were compared with Spirulina strains from independent reference stocks. To "narrow the goals", Spirulina products that hadn't been characterised/identified were appropriately classified, and the fermentation behaviour of comparable strains, based on an increased yield of phycocyanine, were studied. This process determined that different cul-tures from the same collection of strains had a higher production potential as those that had been used for biomass production. This could also be further increased by targeted fermenta-tion optimisation. This observation leads to the conclusion that previous production strains were chosen specifically based on their biomass productivity. However, there are more ap-propriate strains from which to extract phycocyanine. So that production isn't bound to cer-tain strains that are easily available, which makes a business vulnerable to competition, a genetic marker was developed with the goal of a "unique selling proposition." This marker allows unknown isolates to be tested for their phycocyanine production potential. Appropri-ate samples could be subjected to fermentation screening and used for production.The phase "product- and process conceptualisation" was further illustrated through a study of the processing of the arctic prawn Pandalus borealis. 10.000 tons of these prawns are fished annually from the seas surrounding the EU. A by-product of this processing is a wastewater which, besides proteins and fats, contains carotinoides, in particular astaxanthin. Astaxanthin has commercial value in the production of aquaculture products, such as farmed salmon or crustaceans, to create the red flesh colouring expected by the consumer. Astaxan-thin is produced by several microorganisms in nature, however it is artificially created through chemical syntheses to standardise aquaculture feed. By implementing flotation methods used by the wastewater treatment industry, the released matter from the processing of the prawns could be separated and dried to a residual moisture of 10%, making it capable of being stored. A vacuum paddle wheel dryer proved particularly useful for the steps of "application and optimisation". The product derived from this process contained 336 mg/kg DW of astaxanthin, which is four times more astaxanthin as is currently used in feed for aquacultures. This product, as well as astaxanthin components, could be combined with fishmeal and plant proteins for fish or crustacean farming, which would be especially rele-vant in farms who are restricted from using synthetic ingredients in their feed.In conclusion, the sensible combination of nature and engineering creates potential upgrad-ing concepts to create valuable products from what would otherwise be waste material. This creates new possibilities even for small businesses, and besides lowering the environmental impact of wastewater, it also raises the (cost effectiveness, efficiency, profitability) of a whole manufacturing process.Dissertation336 485