Watkins, Peter Haynes2017-03-102017-03-101951http://hdl.handle.net/10919/76445Industrial waste pollution is a problem of considerable magnitude and of great importance to modern industry. One critical aspect of waste pollution is reduction of dissolved oxygen in natural waters resulting from the oxygen uptake of bacteria while digesting organic wastes. Fundamental information concerning the effect of various physical and chemical factors on the rate of oxygen uptake by bacteria was sought by investigating the rate of oxygen uptake by Pseudomonas fluorescens, a common water organism, as a function of the concentration of substrate and the temperature of environment. The substrates were D-glucose, D-xylose, L-arabinose and acetate, and the temperatures investigated ranged from 15 to 37 ºC. Oxygen uptakes were determined manometrically using the direct Warburg method in conjunction with resting cell techniques. In all tests 3.0 milligrams or Pseudomonas fluorescens (stated as dry bacterial protoplasm) were suspended in 2.5 milliliters of 0.05 molar phosphate buffer of pH 6.8. At 25 °C, for all substrates with the exception of acetate, the rate of oxygen uptake is dependent on concentration in the lower concentration ranges, and follows the Michaelis-Menten equation. Saturation concentrations stated as millimoles per test were 0.0500 for glucose and 0.600 for xylose. Saturation had not been reached in the case or arabinose at the highest concentration tested of 0.8000 millimoles per test. The rate or oxygen uptake increased with acetate concentration up to 0.1000 millimoles per test, and at concentrations above this value a decrease in rate of uptake was observed. A special equation was developed to cover the latter case. When substrate concentrations were held constant and temperature of the environment was varied from 15.0 to 37.0 °C the rate of oxygen uptake increased with temperature in all cases. For glucose the rate of change of the rate of oxygen uptake was 15.8 ± 1.6 microliters per hour per degree centigrade between 15.0 and 20.0 °C, 2.4 ± 0.2 microliters per hour per degree centrigrade between 20.0 and 25.0 °C, and 11.7 ± 1.2 microliters per hour per degree centigrade between 25.0 and 37.0 °C. When glucose concentration was held constant at 0.1000 millimole. For xylose the rate of change of the rate of oxygen uptake was 18.0 ± 1.8 microliters per hour per degree centigrade between 15.0 and 18.0 ºC, 3.9 ± 0.4 microliters per hour per degree centigrade between 18.0 and 35.0 °C, and 16.5 ± 1.6 microliters per hour per degree centigrade between 35.0 and 37.0 ºC when xylose concentration was held constant at 0.400 millimole. For arabinose the rate of change of the rate of oxygen uptake was 10.4 ± 1.0 microliters per hour per degree centigrade between 15.0 and 17.5 °C, 0.4 ± 0.0 microliters per hour per degree centigrade between 17.5 and 30.0 ºC, and 2.4 ± 0.2 microliters per hour per degree centigrade between 30.0 and 37.0 ºC when arabinose concentration was held constant at 0.400 millimole. For acetate the rate of change of the rate of oxygen uptake was 19.7 ± 2.0 microliters per hour per degree centigrade between 15.0 and 18.0 ºC, 2.8 ± 0.3 microliters per hour per degree centigrade between 18.0 and 28.0 °C, and 12.5 ± 1.5 microliters per hour per degree centigrade between 28.0 and 37.0 °C when the acetate concentration was held constant at 0.0500 millimole.175 leavesapplication/pdfen-USIn CopyrightLD5655.V856 1951.W373Pseudomonas fluorescensOxidation, PhysiologicalDissertation