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Title: Physiology and biochemistry of the facultatively anaerobic chemolithotroph Thiobacillus denitrificans grown in chemostat culture
Author: Justin, Pauline M. G. S.
ISNI:       0000 0001 3593 6536
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1978
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A continuous culture of T. denitrificans was established in media which had been previously found suitable in latch cultures. The response of the organism to dilution rate was studied in relation to its maximum growth rate, and possible change in the pattern of products from thiosulphate and nitrate as substrates. The organism was grown aerobically and anaerobically with the limitation of thiosulphate tetrathionate or nitrate, and the effect of this on the D crit. and the patterns of substrate use, growth yield and maintenance energy determined. The comparison of growth yield and substrate conversion efficiencies between aerobic and anaerobic conditions provided a unique opportunity to compare a respiratory system in which electrons pass from substrate directly to cytochrome c then to oxygen or nitrate. Anaerobically the Yg was 70% of that aerobically. Prolonged aerobic cultures retained their capacity to grow anaerobically. The use of the chemostat with a limiting oxidant enabled the use of normally toxic substances such as nitrite to be used as growth substrate in the solution phase and nitrous oxide in the gas phase. Nitrate reductase was repressed by oxygen and nitrite j whereas nitrite reductase was fully derepressed by nitrate. The transition between various steady-state limiting substrates was studied to give an idea of the organism's adaptability and substrate turnover when confronted with varying conditions. The presence of a sulphur-oxidizing anti a thiosulphate-oxidizing enzyme was investigated in an attempt to elucidate part of the thiosulphate pathway in this organism. Calculating from the energy requirement for CO2-fixation, the Yg values calculated from chemostat data indicated ATP production to be 4-5 mol/mol thiosulphate and 8-9 mol/mol tetrathionate for anaerobic cultures and 6-7mol/mol thiosulphate for aerobic cultures. Inhibitor experiments with non -growing suspensions indicated oxidative phosphorylation to occur both aerobically and anaerobically.
Supervisor: Not available Sponsor: Natural Environment Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology