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  • 1
    Digitale Medien
    Digitale Medien
    Enzymic and molecular analysis of microbial communities associated with lotic particulate organic matter (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 28 (1992), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Most allochthonous plant detritus moves through stream ecosystems as fine particulate organic matter (FPOM), whose associated microbial communities, unlike those of coarse detritus, have received little scrutiny.2. Benthic POM was collected from a fourth-order boreal river and two first-order tributaries in northern New York during July 1991, sorted it into eight size fractions ranging from 38 to 〉4000 μm, and assayed each fraction for ergosterol, DNA, and the activity of nine extracellular enzymes: β-1, 4-glucosidase, endocellulase, cellobiohydrolase, phenol oxidase, peroxidase, β-N-acetylglucosaminidase, acid phosphatase, alkaline phosphatase, and aryl sulphatase. In addition, DNA-DNA hybridization was used to investigate the structural similarity of the microbial communities associated with the FPOM fractions.3. Various enzymes showed distinct activity patterns in relation to particle size as well as among sites. Half of the possible pairwise correlations among enzyme variables were statistically significant, but no enzyme activities were correlated with biomass indices (DNA and ergosterol concentration). DNA-DNA dot-blot hybridizations suggested extensive structural similarity among the microbial communities associated with FPOM fractions.4. Cluster analysis was used to compare microbial functional similarity, measured by enzyme assays, and structural similarity, measured by DNA—DNA hybridization. Comparison of cluster coefficients showed a weak correlation between community structural similarity and functional similarity (r= 0.51) with fifteen of eighteen fractions grouped within a narrow range of distance.5. The results suggest a convergence in microbially mediated FPOM processing despite system-level differences in litter and water quality.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1992.tb00597.x
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  • 2
    Digitale Medien
    Digitale Medien
    Enzymic and chemical analysis of particulate organic matter from a boreal river (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 23 (1990), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY. 1. Benthic particulate organic matter (POM) was collected from a shallow pool of a fourth order boreal stream and sorted into seven size fractions ranging from 63 to 〉4000μm. Each size fraction was analysed for fibre, total phosphorus, and total Kjeldahl nitrogen. Microbial activity was measured by oxygen consumption and characterized by assaying for eleven classes of exoenzymes including cellulase, phenol oxidase, peroxidase, phosphatase and sulphatase.2. Indices of detritus quality such as C/N, C/P, percent lignin, and microbial respiration showed improvement with decreasing particle size. Three covarying exoenzyme groups were identified: a carbohydrase-phosphatase group that included eight enzymes, a phenol oxidase-peroxidase group, and sulphatase. The activity of the carbohydrase-phosphatase group, was significantly correlated with microbial respiration and the carbohydrate content of the POM. Phenol oxidase-peroxidase activity was correlated with lignin content for POM greater than 250 μm, but activity increased markedly in the two smallest size fractions even though the lignin content of the POM continued to decline, Sulphatase activity was inversely related to particle size over the entire range.3. The changes in microbial activity with particle size were attributed to the increasing surface area to volume ratio of smaller particles and to an ecological succession in the microbial community.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1990.tb00273.x
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  • 3
    Digitale Medien
    Digitale Medien
    Comparison of epilithic and epixylic biofilm development in a boreal river (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 25 (1991), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY. 1. We assessed substratum effects on lotic biofilm development by placing glass and white pine sampling units in a fourth-order boreal river, and analysing, at 6-week intervals, upper-surface biofilms for ATP, chlorophyll, ergosterol, and the activities of nine exoenzymes.2. All parameters, except chlorophyll standing stock (range 80–320 μg dm−2) and β-xylosidase activity (range 0.4–4.8 μmol h−1 dm−2), were significantly greater for epixylic biofilms than for epilithic ones, but the magnitude of the increases varied from 2 to 5 fold, showing that, even under similar hydrodynamic conditions, epilithic and epixylic biofilms are structurally and functionally distinct. For example, ergosterol concentrations ranged from undetectable to 0.93 μg dm−2 for epilithon and from 11–49 μg dm−2 for epixylon; corresponding ranges for ATP were 1.6–3.7 (epilithon) and 4.2–7.7 μg dm−2 (epixylon), for acid phosphatase activity: 2.3–4.9 and 20–41 μmolh−1dm−2, and for alkaline phosphatase activity: 1.9–8.1 and 29–150 μmol h−1dm−2, respectively.3. The more extensive epixylic development was attributed to utilization of the wood substratum as a supplemental carbon source and to a higher density of microbial attachment sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1991.tb00483.x
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  • 4
    Digitale Medien
    Digitale Medien
    The root surface phosphatases ofEriophorum vaginatum: Effects of temperature, pH, substrate concentration and inorganic phosphorus (1988)
    Springer
    Plant and soil 105 (1988), S. 3-10 
    Details
    ISSN: 1573-5036
    Schlagwort(e): arctic ; Eriophorum ; pH ; phosphatases ; phosphorus ; PNPPase ; root enzymes ; temperature ; tundra
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Eriophorum vaginatum L. subsp.spissum (Fern.) Hult., a dominant plant in arctic tundra ecosystems, has acid phosphatase activity evenly distributed along its root surface from the root tip to a distance at least 16 cm from the tip. These root surface phosphatases have optimal activity from pH 3.5 to 4.0; mean soil pH for soil samples collected with roots was 3.69. Apparent energy of activation and Q10 values (14.0 kcal mol−1 and 2.2, respectively) do not provide evidence for temperature acclimation, but substantial phosphatase activity was measured at 1°C. Kinetic parameters determined for this root surface phosphatase were as follows: Km=9.23 mM, Vmax=1.61×10−3 μmoles mm−2h−1. The presence of inorganic phosphorus in the assay medium did not inhibit root surface phosphatase activity except at very high concentrations (100 mM); even then, only slight inhibition was detected (7 to 19%). A comparison of hydrolysis rates with inorganic phosphate assimilation rates measured forE. vaginatum indicates that organic phosphate hydrolysis may occur at approximately one third the rate of inorganic phosphate absorption. Calculations show that inorganic phosphate produced by root surface phosphatase activity may satisfy 65% of the annual phosphate demand ofE. vaginatum. Since arctic tundra soils are typically higher in dissolved organic phosphorus compounds than in inorganic phosphate, root surface phosphatase activity may make a considerable contribution to the phosphate nutrition of this widespread and abundant arctic plant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02371136
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  • 5
    Digitale Medien
    Digitale Medien
    Carbon and nitrogen dynamics along the decay continuum: Plant litter to soil organic matter (1989)
    Springer
    Plant and soil 115 (1989), S. 189-198 
    Details
    ISSN: 1573-5036
    Schlagwort(e): carbon ; cellulose ; decomposition ; δ13C ; δ15N ; lignin ; nitrogen ; stable isotopes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Decay processes in an ecosystem can be thought of as a continuum beginning with the input of plant litter and leading to the formation of soil organic matter. As an example of this continuum, we review a 77-month study of the decay of red pine (Pinus resinosa Ait.) needle litter. We tracked the changes in C chemistry and the N pool in red pine (Pinus resinosa Ait.) needle litter during the 77-month period using standard chemical techniques and stable isotope, analyses of C and N. Mass loss is best described by a two-phase model: an initial phase of constant mass loss and a phase of very slow loss dominated by degradation of ‘lignocellulose’ (acid soluble sugars plus acid insoluble C compounds). As the decaying litter enters the second phase, the ratio of lignin to lignin and cellulose (the lignocellulose index, LCI) approaches 0.7. Thereafter, the LCI increases only slightly throughout the decay continuum indicating that acid insoluble materials (‘lignin’) dominate decay in the latter part of the continuum. Nitrogen dynamics are also best described by a two-phase model: a phase of N net immobilization followed by a phase of N net mineralization. Small changes in C and N isotopic composition were observed during litter decay. Larger changes were observed with depth in the soil profile. An understanding of factors that control ‘lignin’ degradation is key to predicting the patterns of mass loss and N dynamics late in decay. The hypothesis that labile C is needed for ‘lignin’ degradation must be evaluated and the sources of this C must be identified. Also, the hypothesis that the availability of inorganic N slows ‘lignin’ decay must be evaluated in soil systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02202587
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  • 6
    Digitale Medien
    Digitale Medien
    Exoenzyme accumulation in epilithic biofilms (1991)
    Springer
    Hydrobiologia 222 (1991), S. 29-37 
    Details
    ISSN: 1573-5117
    Schlagwort(e): biofilm ; epilithon ; exoenzyme activity ; community structure ; stream ecology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Although exoenzyme accumulation is often proposed as an explanation for the high metabolic activity of biofilms, little is known about the abundance, distribution and turnover rates of exoenzymes within these communities. To assess accumulation, epilithic biofilm samples were collected from a fourth-order boreal river and homogenized. The resulting particles were fractionated by size and each fraction was assayed for nine exoenzyme activities, chlorophyll, and ATP. In general, carbohydrase activities were not correlated with microbial biomass indicators; the largest pool of activity was in the aqueous phase (〈 0.2 µm). Phenol oxidase, peroxidase, and phosphatase activities were largely particle-bound and often correlated with microbial biomass distribution. It was concluded that the epilithic biofilm matrix was effective at accumulating carbohydrase activity and that this accumulation may partially account for the metabolic resistance of epilithic biofilms to dissolved organic matter fluctuations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00017497
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