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  • 1
    ISSN: 1432-0789
    Keywords: Genetically modified microorganisms ; Population dynamics ; Earthworm gut ; Pseudomonas fluorescens ; Lumbricus terrestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A laboratory microcosm study was used to investigate the survival and population dynamics of genetically modified microorganisms (GMM) in the gut of Lumbricus terrestris. Three methods of axenic earthworm production were investigated. An antibiotic mixture of streptomycin and cycloheximide was introduced either passively, mixed with sterile soil or cellulose, or actively, by teflon catheter. Worms treated by all methods lost weight but this was least for the catheter method which was also the only method to produce axenic earthworms. Axenic earthworms were used to determine the effect of competition with indigenous gut bacteria on ingested GMM. The GMM used was Pseudomonas fluorescens, strain 10586/FAC510, with chromosomally inserted Lux genes for bioluminescence, and chromosomal resistance to rifampicin. The bacteria were grown up to the mid-exponential phase before inoculation into earthworms. Bacteria in faecal material were enumerated by dilution plate counting using selective agar. The GMM were re-isolated from the casts of both antibiotic-treated and untreated earthworms. Lower concentrations of GMM and higher concentrations of indigenous bacteria in the casts of untreated compared to antibiotic-treated earthworms suggested that competition is a fundamental control on population dynamics of the introduced bacterial inocula ingested by earthworms. The catheter method, developed in this study, is proposed as a technique to contribute to the risk assessment of environmental release of GMM.
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  • 2
    ISSN: 1432-0789
    Keywords: Bacterial inocula lux modified ; Pseudomonas fluorescens ; Repacked soil microcosms ; Earthworms ; Lumbricus terrestris ; Leaching patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two laboratory experiments were used to investigate the effect of the earthworm Lumbricus terrestris on transport of genetically marked Pseudomonas fluorescens inocula through soil microcosms. The microcosms comprised cylindrical cores of repacked soil with or without earthworms. Late log-phase cells of P. fluorescens, chromosomally marked with lux genes encoding bioluminescence, were applied to the surface of soil cores as inoculated filter paper discs. In one experiment, 5 and 10 days after inoculation, cores were destructively harvested to determine concentrations of marked pseudomonads with depth relative to the initial inoculum applied. Transport of the bacteria occurred only in the presence of earthworms. In a second experiment cores were subjected to simulated rainfall events 18 h after inoculation with lux-marked bacteria at 3-day intervals over a 24-day period. Resulting leachates were analysed for the appearance of the marked bacteria, and after 28 days cores were destructively harvested. Although some marked cells (less than 0.1% of the inoculum applied) were leached through soil in percolating water, particularly in the presence of earthworms, the most important effect of earthworms on cell transport was through burial of inoculated litter rather than an increase in bypass flow due to earthworm channels.
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  • 3
    ISSN: 1432-0789
    Keywords: Key words Bacterial inocula lux modified ; Pseudomonas fluorescens ; Repacked soil microcosms ; Earthworms ; Lumbricus terrestris ; Leaching patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two laboratory experiments were used to investigate the effect of the earthworm Lumbricus terrestris on transport of genetically marked Pseudomonas fluorescens inocula through soil microcosms. The microcosms comprised cylindrical cores of repacked soil with or without earthworms. Late log-phase cells of P. fluorescens, chromosomally marked with lux genes encoding bioluminescence, were applied to the surface of soil cores as inoculated filter paper discs. In one experiment, 5 and 10 days after inoculation, cores were destructively harvested to determine concentrations of marked pseudomonads with depth relative to the initial inoculum applied. Transport of the bacteria occurred only in the presence of earthworms. In a second experiment cores were subjected to simulated rainfall events 18 h after inoculation with lux-marked bacteria at 3-day intervals over a 24-day period. Resulting leachates were analysed for the appearance of the marked bacteria, and after 28 days cores were destructively harvested. Although some marked cells (less than 0.1% of the inoculum applied) were leached through soil in percolating water, particularly in the presence of earthworms, the most important effect of earthworms on cell transport was through burial of inoculated litter rather than an increase in bypass flow due to earthworm channels.
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Company
    Nature biotechnology 10 (1992), S. 830-831 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: PROSAMO (Planned Release of Selected and Modified Organisms) is a three-year plant and microbial research programme operating as a partnership between the U.K. government (DTI), AFRC, industry (a consortium often major biotechnology companies), and four leading academic research ...
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  • 5
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The survival characteristics of Escherichia coli O157:H7 in private drinking water wells were investigated to assess the potential for human exposure. A non-toxigenic, chromosomally lux-marked strain of E. coli O157:H7 was inoculated into well water from four different sites in the North East of Scotland. These waters differed significantly in their heavy metal contents as well as nutrient and bacterial grazer concentrations. Grazing and other biological factors were studied using filtered (3 and 0.2 μm) and autoclaved water. The survival of E. coli O157:H7 was primarily decreased by elevated copper concentrations. This hypothesis was supported by acute toxicity assay data. In addition, significant protozoan predation effects were observed in untreated water when compared with survival rates in filtered water. The combination of these two factors in particular determines the survival time of the pathogen in a private water well. It therefore appears that wells with higher water quality as assessed using the European Union Drinking Water Directive standards will also allow survival of E. coli O157:H7 for much longer periods.
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  • 6
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of temperature, light and pH on mycelial growth and luminescence of four naturally bioluminescent fungi were investigated. Cultures of Armillaria mellea, Mycena citricolor, Omphalotus olearius and Panellus stipticus were grown at 5°C, 15°C, 22°C and 30°C, under 24 h light, 12 h light/12 h dark and 24 h dark, and at a pH ranging from 3.5 to 7 in three separate experiments. Temperature and pH had a significant effect on mycelial growth and bioluminescence, however light did not. Bioluminescence and mycelial growth were optimum at 22°C and pH 3–3.5, the exception being M. citricolor for which bioluminescence and growth were optimum at pH 5–6 and pH 4, respectively. With the exception of M. citricolor, bioluminescence and mycelial growth were greater under 24 h darkness. An understanding of the effect of culture conditions on mycelial growth and luminescence is necessary for the future application of bioluminescent fungi as biosensors.
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  • 7
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plant-derived carbon is the substrate which drives the rate of microbial assimilation and turnover of nutrients, in particular N and P, within the rhizosphere. To develop a better understanding of rhizosphere dynamics, a tripartite reporter gene system has been developed. We used three lux-marked Pseudomonas fluorescens strains to report on soil (1) assimilable carbon, (2) N-status, and (3) P-status. In vivo studies using soil water, spiked with C, N and P to simulate rhizosphere conditions, showed that the tripartite reporter system can provide real-time assessment of carbon and nutrient status. Good quantitative agreement for bioluminescence output between reference material and soil water samples was found for the C and P reporters. With regard to soil nitrate, the minimum bioavailable concentration was found to be greater than that analytically detectable in soil water. This is the first time that bioavailable soil C, N and P have been quantified using a tripartite reporter gene system.
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  • 8
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A mini-Tn5 transposon was modified to introduce a promoterless luxCDABE cassette from Vibrio fischeri into environmentally relevant bacterial strains in order to develop bioluminescence-based biosensors for toxicity testing. The mini-Tn5 luxCDABE transposon was chromosomally integrated downstream from an active promoter into two Pseudomonas strains (Pseudomonas fluorescens 8866 and Pseudomonas putida F1). Characterisation of the bioluminescent transconjugants demonstrated that the transposon integration was stable and had no effect on growth rate. Both P. fluorescens 8866 Tn5 luxCDABE and P. putida F1 Tn5 luxCDABE were used to assess the toxicity of standard solutions (Cu, Zn and 3,5-DCP) as well as Cu- and 3,5-DCP-spiked groundwater samples. They were successfully used for bioluminescence-based bioassays and the potential value of using different bacterial biosensors for ecotoxicity testing was shown.
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  • 9
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Lux-marked bacterial biosensors and a commercial toxicity testing bacterial strain (Microtox™) were exposed to 2,4-dichlorophenol (DCP) and the light output response measured. Increasing DCP concentrations caused a decrease in light output in all three biosensors with an order of sensitivity (in terms of luminescence decrease over the DCP concentration range) of Pseudomonas fluorescens〈Escherichia coli〈Microtox™. Adsorption of DCP to E. coli was measured using uniformly ring labelled [14C]DCP and found to be very rapid. The effect of pH on toxicity and adsorption was also investigated. Low pH values increased the amount of DCP adsorbed to the cell and increased the toxicity of DCP.
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  • 10
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Plant responses to increasing atmospheric CO2 concentrations have received considerable interest. However, major uncertainties in relation to interactive effects of CO2 with above- and below-ground conditions remain. This microcosm study investigated the impacts of CO2 concentration on plant growth, dry matter partitioning and rhizodeposition as affected by: (i) photon flux density (PFD), and (ii) growth matrix. Plants were grown in a sandy loam soil for 28 d under two photon flux densities: 350 (low PFD) and 1000 μmol m–2 s–1 (high PFD) and two CO2 concentrations: 450 (low CO2) and 720 μmol mol–1 (high CO2). Partitioning of recent assimilate amongst plant and rhizosphere C-pools was determined by use of 14CO2 pulse-labelling. In treatments with high PFD and/or high CO2, significant (P 〈 0.05) increases in dry matter production were found in comparison with the low PFD/low CO2 treatment. In addition, significant (P 〈 0.05) reductions in shoot %N and SLA were found in treatments imposing high PFD and/or high CO2. Root weight ratio (RWR) was unaffected by CO2 concentration, however, partitioning of 14C to below ground pools was significantly (P 〈 0.05) increased. In a separate study, L. perenne was grown for 28 d in microcosms percolated with nutrient solution, in either a sterile sand matrix or nonsterile soil, under high or low CO2. Dry matter production was significantly (P 〈 0.01) increased for both sand and soil grown seedlings. Dry matter partitioning was affected by matrix type. 14C-allocation below ground was increased for sand grown plants. Rhizodeposition was affected by CO2 concentration for growth in each matrix, but was increased for plants grown in the soil matrix, and decreased for those in sand. The results illustrate that plant responses to CO2 are potentially affected by (i) PFD, and (ii) by feedbacks from the growth matrix. Such feedbacks are discussed in relation to soil nutrient status and interactions with the rhizosphere microbial biomass.
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