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  • 1
    Call number: AWI Bio-01-0058 ; AWI Bio-01-0212
    In: Bibliotheca diatomologica, Band 45
    Description / Table of Contents: The freshwater diatom flora from arctic and subarctic regions of North America remains poorly known. The aim of this investigation is to improve our knowledge of diatoms in lakes from eastern subarctic Canada, and to provide a stronger foundation for the use of diatoms in limnological and palaeolimnological studies. To this end, we analysed the modern diatom assemblages in surficial sediments from 123 lakes in northern Québec and Labrador. The two study transects in Jamésie-Hudsonie (data set including 59 lakes and 38 environmental variables) and in Québec-Labrador (data set consisting of 64 lakes and 29 environmental variables) extend over a vast area from the boreal forest in the south to the arctic tundra conditions in the north. Of a total of 516 diatom taxa in the Jamésie-Hudsonie data set, 218 species were used for the development of a transfer function for the reconstruction of dissolved organic carbon (DOC). In the Québec-Labrador data set, two inference models were developed for the reconstruction of water colour and alkalinity based on 128 of 303 diatom taxa. The majority of taxa belonging to this surprisingly species-rich boreal-subarctic diatom flora are illustrated in photographic plates, accompanied by a short description of the distribution of each taxon.
    Type of Medium: Monograph available for loan
    Pages: VI, 200 Seiten , Illustrationen
    ISBN: 3443570364
    Series Statement: Bibliotheca diatomologica 45
    Language: English
    Note: Contents: 1. Introduction. - Overview. - 1.1 The use of diatoms in paleolimnology. - 1.2 Studies of freshwater diatoms in northern Québec and Labrador. - 1.3 Purpose of this project. - 2. Diatoms as indicators of dissolved organic carbon (DOC), alkalinity, and water colour. - Overview. - 2.1 Study area. - 2.2 Methods. - 2.2.1 Sampling and measurement procedures. - 2.2.2 Numerical analysis. - 2.3 Ordination results. - 2.3.1 PCA. - 2.3.2 CCA. - 2.4 Inference models. - 2.4.1 WA-PLS. - 2.4.2 Potential indicator taxa. - 2.5 Implications for paleoecological studies. - 3. Diatom taxa. - Overview. - Diatom flora. - References. - Plates. - Appendix I Raw environmental data for the 59 study sites of Jamésie-Hudsonie. - Appendix II Raw environmental data for the 64 study sites of Québec-Labrador. - Appendix III Taxonomic index of the 218 most abundant diatom species used for CCA plotting in Jamésie-Hudsonie. - Appendix IV Taxonomic index of the 128 most abundant diatom species used for CCA plotting in Québec-Labrador. - Species index
    Location: AWI Reading room
    Location: AWI Reading room
    Branch Library: AWI Library
    Branch Library: AWI Library
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Helicobacter pylori genome contains a gene (hp1338 or nikR) that encodes a nickel-dependent regulator that is homologous to the Escherichia coli nickel-responsive regulator, NikR. The H. pylori nikR product acts as a pleiotropic metal-dependent regulator. We constructed a non-polar isogenic mutant deleted for the nikR gene. NikR was essential for the survival of H. pylori in the presence of high nickel and cobalt ion concentrations in vitro. We screened a DNA macroarray for genes that were differentially expressed in parental and nikR-deficient H. pylori strains grown in the presence of excess nickel. We found that H. pylori NikR mediates the expression of nickel-activated and -repressed genes. In the presence of excess nickel, NikR activated the transcription of ureA-ureB (hp72–73), nixA (hp1077 ), copA2 (hp1072), hpn (hp1427 ) and hpn-like (hp1432) genes and repressed the expression of genes encoding proteins involved in ferric iron uptake and storage [pfr (hp0653), fur (hp1027 ), frpB4 (hp1512), exbB/exbD (hp1339–1340), ceuE (hp1561)], motility [cheV (hp616), flaA (hp0601), flaB (hp0115 )], stress responses [hrcA-grpE-dnaK (hp111–110–109)] and encoding outer-membrane proteins [omp11(hp0472), omp31 (hp1469), omp32 (hp1501)]. Slot blot DNA/RNA hybridization experiments using RNA from three independent bacterial cultures confirmed the transcriptome data for 10 selected genes. The results of gel shift experiments using purified native NikR, β-galactosidase assays with the region between nikR and the exbB/exbD divergent operon, and the study of exbB gene expression using a gentamicin/apramycin reporter gene in H. pylori indicated that NikR is an autorepressor that binds to this intergenic region and also controls the expression of the exbB/exbD/tonB operon, which provides energy for ferric iron uptake. Thus, as previously suggested for Fur in H. pylori, NikR appears to be a global regulator of the metabolism of some divalent cations within a highly complex regulated network.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 34 (1986), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The fdhF gene of Escherichia coli, coding for at least one component of benzyl viologen-linked formate dehydrogenase (FDH-BV) activity, was isolated on a ColE1-fdhF hybrid plasmid from the Clarke and Carbon colony bank.Endonuclease restriction maps of this plasmid and its pBR322-subcloned derivative, pLW06, were constructed. Various hybrid plasmids were further obtained by deletion of endonuclease-cleaved fragments from pLW06 DNA. Their complementation pattern was analyzed after introduction into different fdhF mutant strains. The fdhF gene was shown to be located on a 5.5 kb BamHI-PvuII-DNA fragment, which restored FDH-BV activity to the wild-type level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 221 (2003), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Degradation of type I collagen by Porphyromonas gingivalis was monitored by fluorogenic, sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE), and growth assays. All three assays showed that inactivation of both the rgpA and rgpB genes was necessary to completely eliminate the capacity of P. gingivalis to cleave type I collagen. Leupeptin, an Arg-gingipain-specific protease inhibitor, almost completely inhibited collagen degradation by P. gingivalis cells whereas cathepsin B inhibitor II, a Lys-gingipain inhibitor, did not. A purified preparation of Arg-gingipains A and B hydrolyzed gelatin but did not cleave type I collagen, suggesting that the enzymes must be attached to the cell surface to exert collagenase activity. A number of substances used as adjuncts in periodontal therapy were also tested for their capacity to inhibit collagenase activity of P. gingivalis. Tetracycline, doxycycline, and chlorhexidine strongly inhibited collagenase activity.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Phytochemistry 17 (1978), S. 1037-1042 
    ISSN: 0031-9422
    Keywords: Gramineae ; NAA and NPA binding ; Zea mays ; cell fractionation ; coleoptiles ; cycloartenol-methyltransferase ; cycloeucalenol-obtusifoliol isomerase ; plasmalemma ; sterol glucosyltransferase.
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Activation of the two divergent Escherichia coli cai and fix operons involved in anaerobic carnitine metabolism is co-dependent on the cyclic AMP receptor protein (CRP) and on CaiF, the specific carnitine-sensitive transcriptional regulator. CaiF was overproduced using a phage T7 system, purified on a heparin column and ran as a 15 kDa protein on SDS–PAGE. DNase I footprinting and interference experiments identified two sites, F1 and F2, with apparently comparable affinities for the binding of CaiF in the cai–fix regulatory region. These sites share a common perfect inverted repeat comprising two 11 bp half-sites separated by 13 bp, and centred at −70 and −127 from the fix transcription start site. They were found to overlap the two low-affinity binding sites, CRP2 and CRP3, determined previously for CRP. Gel shift assays and footprinting experiments suggest that CaiF and CRP bind co-operatively to the F1/CRP2 and F2/CRP3 sites of the intergenic cai–fix region. Moreover, they appeared to serve the simultaneous binding of each other, giving rise to an original multiprotein CRP–CaiF complex enabling RNA polymerase recruitment and local DNA untwisting, at least at the fix promoter. Using random mutagenesis, two CaiF mutants impaired in transcription activation were isolated. The N-terminal A27V mutation affected the structural organization of the activator, whereas the central I62N mutation was suggested to interfere with DNA binding.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 9 (1993), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The complete nucleotide sequence of the Escherichia coli nik locus, which has been suggested to encode the specific transport system for nickel, has been determined. It was found to contain five overlapping open reading frames that form a single transcription unit. Deduced amino acid sequence of the nik operon shows that its five gene products, NikA to NikE, are highly homologous to components of oligopeptide-and dipeptide-binding protein-dependent transport systems from several Gram-negative and Gram-positive species. NikA represents the periplasmic binding protein, NikB and NikC are similar to integral membrane components of periplasmic permeases, and NikD and NikE possess typical ATP-binding domains that suggest their energy coupling role to the transport process. Insertion mutations in nik genes totally abolished the nickel-containing hydrogenase activity under nickel limitation and markedly altered the rate of nickel transport. Taken together, these data support the notion that the nik operon encodes a typical periplasmic binding-protein-dependent transport system for nickel.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The sequence encompassing the cai genes of Escherichia coli, which encode the carnitine pathway, has been determined. Apart from the already identified caiB gene coding for the carnitine dehydratase, five additional open reading frames were identified. They belong to the caiTABCDE operon, which was shown to be located at the first minute on the chromosome and transcribed during anaerobic growth in the presence of carnitine. The activity of carnitine dehydratase was dependent on the CRP regulatory protein and strongly enhanced in the absence of a functional H-NS protein, in relation to the consensus sequences detected in the promoter region of the cai operon. In vivo expression studies led to the synthesis of five polypeptides in addition to CaiB, with predicted molecular masses of 56 613 Da (CaiT), 42 564 Da (CaiA), 59311 Da (CaiC), 32 329 Da (CaiD) and 21 930 Da (CaiE). Amino acid sequence similarity or enzymatic analysis supported the function assigned to each protein. CaiT was suggested to be the transport system for carnitine or betaines, CaiA an oxidoreduction enzyme, and CaiC a crotonobetaine/carnitine CoA ligase. CaiD bears strong homology with enoyl hydratases/isomerases. Overproduction of CaiE was shown to stimulate the carnitine racemase activity of the CaiD protein and to markedly increase the basal level of carnitine dehydratase activity. It is inferred that CaiE is an enzyme involved in the synthesis or the activation of the still unknown cofactor required for carnitine dehydratase and carnitine racemase activities. Taken together, these data suggest that the carnitine pathway in E. coli resembles that found in a strain situated between Agrobacterium and Rhizobium.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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