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  • 1
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 325 (1987), S. 346-348 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The Gulf of Mexico mussels appear to belong to a new species of mytilid different from the hydrothermal vent species (R. D. Turner, personal communication). The abnormally low 513C values3 for the mussel tissue has fuelled speculation that biogeni-cally produced methane (513C of -60 to -90%〉)6 ...
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 49 (2004), S. 0 
    ISSN: 1574-6941
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: To determine whether repeated, long-term NH4+ fertilization alters the enzymatic function of the atmospheric CH4 oxidizer community in soil, we examined CH4 uptake kinetics in temperate pine and hardwood forest soils amended with 150 kg N ha−1 y−1 as NH4NO3 for more than a decade. The highest rates of atmospheric CH4 consumption occurred in the upper 5 cm mineral soil of the control plots. In contrast to the results of several previous studies, surface organic soils in the control plots also exhibited high consumption rates. Fertilization decreased in situ CH4 consumption in the pine and hardwood sites relative to the control plots by 86% and 49%, respectively. Fertilization increased net N mineralization and relative nitrification rates and decreased CH4 uptake most dramatically in the organic horizon, which contributed substantially to the overall decrease in field flux rates. In all cases, CH4 oxidation followed Michaelis–Menten kinetics, with apparent Km (Km(app)) values typical of high-affinity soil CH4 oxidizers. Both Km(app) and Vmax(app) were significantly lower in fertilized soils than in unfertilized soils. The physiology of the methane consumer community in the fertilized soils was distinct from short-term responses to NH4+ addition. Whereas the immediate response to NH4+ was an increase in Km(app), resulting from apparent enzymatic substrate competition, the long-term response to fertilization was a community-level shift to a lower Km(app), a possible adaptation to diminish the competitiveness of NH4+ for enzyme active sites.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Solemya borealis Totten was collected from anoxic sediments in Buzzards Bay, Massachusetts in April and July 1989 and examined for the presence of symbiotic, chemoautotrophic bacteria. In addition, sediment cores collected at the same site were analyzed throughout the year, to provide a detailed description of the S. borealis habitat. Here we present structural, enzymatic, biochemical, and stable isotope data which suggests that S. borealis, like the related species Solemya velum Say and Solemya reidi Bernard, contains high concentrations of symbiotic chemoautotrophic bacteria in gill bacteriocytes which play a significant role in nutrition. Transmission electron microscopy revealed the presence of rod-shaped cells, which resemble Gram-negative bacteria, within gill epithelial cells. Ribulose-1,5-bisphosphate carboxylase activity in cell-free extracts of S. borealis gill tissue was comparable with that found in other invertebrate-chemoautotroph symbioses. Very negative δ34S ratios (-32.6 to-15.7‰) suggest the utilization of porewater sulfides as both an energy and a sulfur source for the symbionts. Carbon and nitrogen stable isotope ratios were extremely negative (δ13C=-32 to-34.6‰, δ15N=-9.7 to-8.6‰), similar to those of other bivalve-chemoautotroph symbioses. High concentrations of cis-vaccenic acid, a fatty acid previously found in other invertebrate-chemoautotroph symbioses, were found in all the major lipid classes of the gills of S. borealis. The stable isotope ratios and lipid composition of S. borealis suggest that most of this bivalve's nutritional requirements are supplied by bacterial endosymbionts. High levels of taurine in the free amino acid pool of S. borealis suggest the existence of unusual amino acid metabolic pathways which may be the result of endosymbiont activity. The S. borealis specimens were found in relatively shallow water sediments dominated by silts and clays. The sediments contain high concentrations of organic carbon and nitrogen, exhibit limited oxygen penetration, and have high rates of ammonium and sulfide input from the anaerobic microbial community. Sediment C and N stable isotope ratios reflect the input of algal-derived nutrients to the sediments (δ13C=-20.7 to-20.9‰, δ15N=+7.7 to +20.8‰). Sediment δ34S ratios ranged from-18.7 to-25.1‰ demonstrating the presence of sulfur produced by bacterial dissimilatory sulfate reduction processes.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 302 (1983), S. 58-61 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Two Atlantic coast bivalves were analysed for the presence and activity of chemoautotrophic bacteria by: (1) assaying for ribulose-l,5-bisphosphate carboxylase (RuBPCase) activity; (2) transmission electron microscopy; (3) epifluorescent microscopy; (4) assays of lipopolysaccharide content; and (5) ...
    Materialart: Digitale Medien
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  • 5
    ISSN: 1432-0843
    Schlagwort(e): Key words Ondansetron ; Cyclophosphamide ; Pharmacokinetics ; Bone marrow transplant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Purpose: Both ondansetron and cyclophosphamide are thought to be metabolized by hepatic microsomal processes. The purpose of this study was to evaluate the potential pharmacokinetic interactions between ondansetron and high-dose alkylating agent chemotherapy. Methods: A total of 54 breast cancer patients receiving high-dose cyclophosphamide, cisplatin and carmustine were treated prospectively in four sequential cohorts. Cohorts I and II received continuous infusions of both ondansetron and prochlorperazine, and cohorts III and IV received a continuous infusion of ondansetron alone at the same doses. All patients received lorazepam every 4 h. A group of 75 matched historical controls had received a continuous infusion of prochlorperazine with lorazepam. Pharmacokinetic monitoring of each drug used in the high-dose chemotherapy regimen was conducted. Results: Median AUCs of cyclophosphamide in patients receiving ondansetron (73.6 mg/ml · min) were lower than those of the control patients (88.3 mg/ml · min, n = 75, P = 0.0004), but the median cisplatin AUC was approximately 10% higher and no difference in the disposition of carmustine was demonstrated. Patients treated with ondansetron displayed a higher frequency of headaches than the controls. The frequency of achieving complete emetic control was greater in the ondansetron + prochlorperazine groups compared to the ondansetron alone groups and was greater in both these groups than in the prochlorperazine alone group on the first day of therapy only. Conclusion: Ondansetron altered the systemic exposure to cyclophosphamide when these agents were administered concomitantly. Ondansetron did not substantially improve overall emetic control when used alone but may improve control in combination with prochlorperazine. Future randomized studies are needed to delineate the effect of ondansetron on the disposition of the active cyclophosphamide metabolites so that clinical implications can be addressed.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [s.l.] : Macmillan Magazines Ltd.
    Nature 403 (2000), S. 725-726 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Symbiont-containing mussels (Mytilidae) are found at hydrothermal vents and cold seeps on the ocean floor, but it is not known whether these taxa represent an ancient lineage endemic to these surroundings or are more recent invaders. Here we show that several small and poorly known mussels, ...
    Materialart: Digitale Medien
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  • 7
    Publikationsdatum: 2022-05-25
    Beschreibung: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS ONE 8 (2013): e56993, doi:10.1371/journal.pone.0056993.
    Beschreibung: The mxaF gene, coding for the large (α) subunit of methanol dehydrogenase, is highly conserved among distantly related methylotrophic species in the Alpha-, Beta- and Gammaproteobacteria. It is ubiquitous in methanotrophs, in contrast to other methanotroph-specific genes such as the pmoA and mmoX genes, which are absent in some methanotrophic proteobacterial genera. This study examined the potential for using the mxaF gene as a functional and phylogenetic marker for methanotrophs. mxaF and 16S rRNA gene phylogenies were constructed based on over 100 database sequences of known proteobacterial methanotrophs and other methylotrophs to assess their evolutionary histories. Topology tests revealed that mxaF and 16S rDNA genes of methanotrophs do not show congruent evolutionary histories, with incongruencies in methanotrophic taxa in the Methylococcaceae, Methylocystaceae, and Beijerinckiacea. However, known methanotrophs generally formed coherent clades based on mxaF gene sequences, allowing for phylogenetic discrimination of major taxa. This feature highlights the mxaF gene’s usefulness as a biomarker in studying the molecular diversity of proteobacterial methanotrophs in nature. To verify this, PCR-directed assays targeting this gene were used to detect novel methanotrophs from diverse environments including soil, peatland, hydrothermal vent mussel tissues, and methanotroph isolates. The placement of the majority of environmental mxaF gene sequences in distinct methanotroph-specific clades (Methylocystaceae and Methylococcaceae) detected in this study supports the use of mxaF as a biomarker for methanotrophic proteobacteria.
    Beschreibung: This work was supported in part by grants from the U.S. National Science Foundation Ecosystems Studies program (awards # DEB9708092 and DEB0089738).
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/msword
    Format: application/pdf
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  • 8
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Society for Microbiology, 2001. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 67 (2001): 4726-4733, doi:10.1128/AEM.67.10.4726-4733.2001.
    Beschreibung: Methanotrophic bacteria play a major role in the global carbon cycle, degrade xenobiotic pollutants, and have the potential for a variety of biotechnological applications. To facilitate ecological studies of these important organisms, we developed a suite of oligonucleotide probes for quantitative analysis of methanotroph-specific 16S rRNA from environmental samples. Two probes target methanotrophs in the family Methylocystaceae (type II methanotrophs) as a group. No oligonucleotide signatures that distinguish between the two genera in this family, Methylocystis and Methylosinus, were identified. Two other probes target, as a single group, a majority of the known methanotrophs belonging to the family Methylococcaceae (type I/X methanotrophs). The remaining probes target members of individual genera of the Methylococcaceae, including Methylobacter, Methylomonas, Methylomicrobium, Methylococcus, and Methylocaldum. One of the family-level probes also covers all methanotrophic endosymbionts of marine mollusks for which 16S rRNA sequences have been published. The two known species of the newly described genus Methylosarcina gen. nov. are covered by a probe that otherwise targets only members of the closely related genus Methylomicrobium. None of the probes covers strains of the newly proposed genera Methylocella and "Methylothermus," which are polyphyletic with respect to the recognized methanotrophic families. Empirically determined midpoint dissociation temperatures were 49 to 57°C for all probes. In dot blot screening against RNA from positive- and negative-control strains, the probes were specific to their intended targets. The broad coverage and high degree of specificity of this new suite of probes will provide more detailed, quantitative information about the community structure of methanotrophs in environmental samples than was previously available.
    Beschreibung: This work was supported by the U.S. National Science Foundation (award DEB9708092).
    Schlagwort(e): Methanotrophic bacteria
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: 212958 bytes
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  • 9
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Society for Microbiology, 2002. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 68 (2002): 316-325, doi:10.1128/AEM.68.1.316-325.2002.
    Beschreibung: A coastal marine sulfide-oxidizing autotrophic bacterium produces hydrophilic filamentous sulfur as a novel metabolic end product. Phylogenetic analysis placed the organism in the genus Arcobacter in the epsilon subdivision of the Proteobacteria. This motile vibrioid organism can be considered difficult to grow, preferring to grow under microaerophilic conditions in flowing systems in which a sulfide-oxygen gradient has been established. Purified cell cultures were maintained by using this approach. Essentially all 4',6-diamidino-2-phenylindole dihydrochloride-stained cells in a flowing reactor system hybridized with Arcobacter-specific probes as well as with a probe specific for the sequence obtained from reactor-grown cells. The proposed provisional name for the coastal isolate is "Candidatus Arcobacter sulfidicus." For cells cultured in a flowing reactor system, the sulfide optimum was higher than and the CO2 fixation activity was as high as or higher than those reported for other sulfur oxidizers, such as Thiomicrospira spp. Cells associated with filamentous sulfur material demonstrated nitrogen fixation capability. No ribulose 1,5-bisphosphate carboxylase/oxygenase could be detected on the basis of radioisotopic activity or by Western blotting techniques, suggesting an alternative pathway of CO2 fixation. The process of microbial filamentous sulfur formation has been documented in a number of marine environments where both sulfide and oxygen are available. Filamentous sulfur formation by "Candidatus Arcobacter sulfidicus" or similar strains may be an ecologically important process, contributing significantly to primary production in such environments.
    Beschreibung: This work was supported by National Science Foundation grant IBN-9630054.
    Schlagwort(e): Sulfide-oxidizing autotrophic bacterium ; Hydrophilic filamentous sulfur
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: 1027760 bytes
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  • 10
    Publikationsdatum: 2022-08-02
    Beschreibung: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Gomaa, F., Utter, D. R., Loo, W., Lahr, D. J. G., & Cavanaugh, C. M. Exploring the protist microbiome: the diversity of bacterial communities associated with Arcella spp. (Tubulina: Amoebozoa). European Journal of Protistology, 82, (2022): 125861, https://doi.org/10.1016/j.ejop.2021.125861.
    Beschreibung: Research on protist-bacteria interactions is increasingly relevant as these associations are now known to play important roles in ecosystem and human health. Free-living amoebae are abundant in all environments and are frequent hosts for bacterial endosymbionts including pathogenic bacteria. However, to date, only a small fraction of these symbionts have been identified, while the structure and composition of the total symbiotic bacterial communities still remains largely unknown. Here, we use the testate amoeba Arcella spp. as model organisms to investigate the specificity and diversity of Arcella-associated microbial communities. High-throughput amplicon sequencing from the V4 region of the 16S rRNA gene revealed high diversity in the bacterial communities associated with the wild Arcella spp. To investigate the specificity of the associated bacterial community with greater precision, we investigated the bacterial communities of two lab-cultured Arcella species, A. hemispherica and A. intermedia, grown in two different media types. Our results suggest that Arcella-bacteria associations are species-specific, and that the associated bacterial community of lab-cultured Arcella spp. remains distinct from that of the surrounding media. Further, each host Arcella species could be distinguished based on its bacterial composition. Our findings provide insight into the understanding of eukaryotic-bacterial symbiosis.
    Beschreibung: This project was funded by National Science Foundation Postdoctoral Research Fellowship in Biology to F. Gomaa, Grant Number: PRFB1611514. Support was provided to D.R.U. from the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1745303 to D.R.U and by Harvard University’s Department of Organismic and Evolutionary Biology program.
    Schlagwort(e): Arcella- associated microbiome ; Intracellular bacterial diversity ; Heterotrophic amoebae ; Amoeba-resistant bacteria
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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