Browsing by Author "Robinson, J. A."

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Activity of Pseudomonas aeruginosa in Biofilms: Steady State
(1984-12) Bakke, Rune; Trulear, Michael Gerald; Robinson, J. A.; Characklis, William G.
Aerobic glucose metabolism by Pseudomonas aeruginosa in steady-state biofilms at various substrate loading rates and reactor dilution rates was investigated. Variables monitored were substrate (glucose), biofilm cellular density, biofilm extracellular polymeric substance (EPS) density, and suspended cellular and EPS concentrations. A mathematical model developed to describe the system was compared to experimental data. Intrinsic yield and rate coefficients included in the model were obtained from suspended continuous culture studies of glucose metabolism by P. aeruginosa. Experimental data compared well with the mathematical model, suggesting that P. aeruginosa does not behave differently in steady-state biofilm cultures, where diffusional resistance is negligible, than in suspended cultures. This implies that kinetic and stoichiometric coefficients for P. aeruginosa derived in suspended continuous culture can be used to describe steady-state biofilm processes.
Bacterial adsorption to smooth surfaces: Rate, extent, and spatial pattern
(1985-12) Nelson, Christopher H.; Robinson, J. A.; Characklis, William G.
The influence of bulk-water bacterial cell concentration and specific growth rate history on bacterial adsorption rates to surfaces was investigated using response surface analysis. A pure culture of Pseudomonas sp. 224s was grown in a chemostat and pumped into a continuous flow reactor where the bacteria were exposed to clean, glass surfaces under turbulent flow conditions for a periodof six hours. Adsorption rate decreased approximately linearly with increasing specific growth rate history. Glass surfaces became saturated with 2248 at ca. 0.1% coverage and the resulting spatial pattern of the adsorbed cells deviated from random in the direction of uniformity.
Cellular reproduction and extracellular polymer formation by pseudonomas aeruginosa in continuous culture
(1984-12) Robinson, J. A.; Trulear, Michael Gerald; Characklis, William G.
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.
Simultaneous estimation of Vmax, Km, and the rate of endogenous substrate production (R) from substrate depletion data
(1984-06) Robinson, J. A.; Characklis, William G.
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 (So) is not error-free. Of the 3 linearized forms, the one where t/(So - S) is regressed against ln(S0/S)/(So - S) gave estimates of Vmax and Km closest to the true population means of these parameters. Further, this linearization was the least sensitive of the 3 to errors (Â±1%) in So. 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 So 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 estimate Vmax and Km when substrafe 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 which Vmax, 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