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  • 1
    Electronic Resource
    Electronic Resource
    The world's largest landfill (1992)
    s.l. : American Chemical Society
    Environmental science & technology 26 (1992), S. 1486-1495 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00032a002
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  • 2
    Electronic Resource
    Electronic Resource
    In situ rumen hydrogen concentrations in steers fed eight times daily, measured using a mercury reduction detector (1988)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 53 (1988), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Dissolved hydrogen was measured in the bovine rumen using an in situ hydrogen probe coupled to a mercury reduction detector. The probe can quantitate dissolved hydrogen from low nM concentrations to saturation. In the rumen of steers fed every 3 h, basal hydrogen concentrations averaged 1.38 μM ± 0.26, and the basal level remained stable throughout an 18–25 h period. In contrast, a steer fed once a day had a basal hydrogen concentration of 1.40 μM, but the level was not stable between feedings. For the steers fed every 3 h, the reticulum displayed the most dramatic fluctuations in the hydrogen concentration after the feeding event. Hydrogen spikes (10–20 μM) in the reticulum were detected 2 min after feed ingestion, and lasted for 30 min. In the center of the rumen the feeding response was observed 30 min after feeding and typically lasted 1 h. The magnitude of hydrogen spikes in the center of the rumen was reduced in comparison to the reticulum. The magnitude of the hydrogen spikes indicates that feeding steers as frequently as eight times a day does not establish a steady-state with respect to hydrogen concentration. However, frequent feedings do minimize drift from the basal hydrogen level. Assuming Michaelis-Menten kinetics our data predict that methane production from hydrogen proceeds at 22% of its maximal velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1988.tb02652.x
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  • 3
    Electronic Resource
    Electronic Resource
    Competition between sulfate-reducing and methanogenic bacteria for H2 under resting and growing conditions (1984)
    Springer
    Archives of microbiology 137 (1984), S. 26-32 
    Details
    ISSN: 1432-072X
    Keywords: Desulfovibrio ; Methanospirillum ; Methanobacterium ; Methanosarcina ; Hydrogen kinetics ; Competition ; Monod kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The basis for the outcome of competition between sulfidogens and methanogens for H2 was examined by comparing the kinetic parameters of representatives of each group separately and in co-culture. Michaelis-Menten parameters (V max and K m) for four methanogens and five sulfate-reducing bacteria were determined from H2-depletion data. Further, Monod growth parameters (μmax, K s, Y H2) for Desulfovibrio sp. G11 and Methanospirillum hungatei JF-1 were similarly estimated. H2 K m values for the methanogenic bacteria ranged from 2.5 μM (Methanospirillum PM1) to 13 μM for Methanosarcina barkeri MS; Methanospirillum hungatei JF-1 and Methanobacterium PM2 had intermediate H2 K m estimates of 5 μM. Average H2 K m estimates for the five sulfidogens was 1.2 μM. No consistent difference among the V max estimates for the above sulfidogens (mean=100 nmol H2 min-1 mg-1 protein) and methanogens (mean=110 nmol H2 min-1 mg-1 protein) was found. A two-term Michaelis-Menten equation accurately predicted the apparent H2 K m values and the fate of H2 by resting co-cultures of sulfate-reducers and methanogens. Half-saturation coefficients (K s) for H2-limited growth of Desulfovibrio sp. G11 (2–4 μM) and Methanospirillum JF-1 (6–7 μM) were comparable to H2 K m estimates obtained for these organisms. Maximum specific growth rates for Desulfovibrio sp. G11 (0.05 h-1) were similar to those of Methanospirillum JF-1 (0.05–0.06 h-1); whereas G11 had an average yield coefficient 4 x that of JF-1. Calculated μmax and V max/K m values for the methanogens and sulfidogens studied predict that the latter bacterial group will process more H2 whether these organisms are in a growing or resting state, when the H2 concentration is in the first-order region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425803
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  • 4
    Electronic Resource
    Electronic Resource
    Simultaneous estimation ofV max, Km, and the rate of endogenous substrate production (R) from substrate depletion data (1984)
    Springer
    Microbial ecology 10 (1984), S. 165-178 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nonlinear and 3 linearized forms of the integrated Michaelis-Menten equation were evaluated for their ability to provide reliable estimates of uptake kinetic parameters, when the initial substrate concentration (S0) is not error-free. Of the 3 linearized forms, the one where t/(S0−S) is regressed against ln(S0/S)/(S0−S) gave estimates ofV max and Km closest to the true population means of these parameters. Further, this linearization was the least sensitive of the 3 to errors (±1%) in S0. Our results illustrate the danger of relying on r2 values for choosing among the 3 linearized forms of the integrated Michaelis-Menten equation. Nonlinear regression analysis of progress curve data, when S0 is not free of error, was superior to even the best of the 3 linearized forms. The integrated Michaelis-Menten equation should not be used to estimateV max and Km when substrate production occurs concomitant with consumption of added substrate. We propose the use of a new equation for estimation of these parameters along with a parameter describing endogenous substrate production (R) for kinetic studies done with samples from natural habitats, in which the substrate of interest is an intermediate. The application of this new equation was illustrated for both simulated data and previously obtained H2 depletion data. The only means by whichV max, Km, and R may be evaluated from progress curve data using this new equation is via nonlinear regression, since a linearized form of this equation could not be derived. Mathematical components of computer programs written for fitting data to either of the above nonlinear models using nonlinear least squares analysis are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02011423
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  • 5
    Electronic Resource
    Electronic Resource
    Denitrification: ecological niches, competition and survival (1983)
    Springer
    Antonie van Leeuwenhoek 48 (1983), S. 569-583 
    Details
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Organisms with the denitrification capacity are widely distributed and in high density in nature. It is not well understood why they are so successful. A survey of denitrifying enzyme content of various habitats is presented which indicates a role of carbon and oxygen, but not nitrate, in affecting denitrifier populations. It is suggested that organic carbon is more important than oxygen status in determining denitrifying enzyme content of habitats. In low oxygen environments, denitrifiers compete with organisms that dissimilate nitrate to ammonium, a process which conserves nitrogen. The energetic and kinetic parameters that affect this competition are evaluated. The latter is examined using Michaelis-Menten theoretical models by varying Vmax, Km, and So (substrate concentration) for the two competing populations. The outcome predicted by these models is presented and discussed in relation to previous data on population densities and Km values for representatives of these competing groups. These models suggest the conditions required to achieve changes in partitioning between the two fates of nitrate. These considerations are important if one is to be able to evaluate and successfully “manage” the fate of nitrate in any habitat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00399542
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  • 6
    Electronic Resource
    Electronic Resource
    Cellular reporoduction and extracellular polymer formation by Pseudomonas aeruginosa in continuous culture (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1409-1417 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of cellular reproduction and the rate and extent of synthesis of extracellular polymeric substances (EPS) were investigated for P. aeruginosa growing in glucose-limited chemostats. μmax and Ks estimates of 0.4 h-1 and 2 mg glucose C/L, respectively, at 25°C were obtained for this bacterium. The extent of EPS formation was inversely related to the growth rate of P. aeruginosa. The rate of EPS formation had both growth- and non-growth-associated components. The growth-associated polymer formation rate coefficient (k) was 0.3 mg polymer C/mg cellular C and the non-growth-associated polymer formation rate coefficient (k′) was 0.04 mg polymer C/mg cellular C/h. The values for k and k′ must be regarded as provisional since the product formation data were quite variable at low dilution rates. Estimates of the cellular (Yx/s) and polymer (Yp/s) yield coefficients were 0.3 mg cellular C/mg glucose C and 0.6 mg polymer C/mg glucose C, respectively. Most of the non-growth-associated consumption of glucose detected was due to exopolymer formation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260261203
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