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Title: Studies on carbon metabolism and nitrogen fixation by Gloeothece
Author: Rajab, T. M. A.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1985
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When cultures of Gloeothece grown under constant light, were transferred to dark anerobic conditions, the rate of acetylene reduction dropped within 1h to 25-30% of that in the light, and reached a minimum after 10-12h. The only source at ATP for nitrogenase, under such conditions, is substrate level phosphorylation utilising endogenous material. All attempts to support N2-fixation by an exogenous source of energy proved unsuccessful. Although Gloeothecewas able to fix nitrogen under dark anaerobic conditions, no nitrogenase synthesis was observed. Gloeothece survived under dark anaerobic conditions for at least 96h, but they appeared to lose the ability to protect nitrogenase against inactivation by O2 over this period. Thus, when cultures of Gloeothece maintained under dark anaerobic conditions for more than 12h, were transferred to the light under anaerobic conditions, the nitrogenase activity which subsequently appeared was oxygen-sensitive. ATP is a necessary source of energy for N2-fixation. On the other hand, ADP inhibits nitrogenase activity. Therefore, the relative amounts of ADP and ATP may control nitrogenase activity. A routine method for measuring adenine nucleotides in Gloeothece, based on the luciferin-luciferase technique, was developed as existing methodology was found unsuitable. Under constant illumination, the observed fluctuations in nitrogenase activity in Gloeothece were not found to be related to changes in the ADP/ATP ratio. However, the ADP/ATP ratio had an indirect effect, possibly via synthesis, on the nitrogenase activity in Gloeothece grown under an alternating cycle of 12h light and 12h darkness. On the other hand, acetylene reduction was inversely related to the ADP/ATP ratio when cultures of Gloeothece were transferred from dark anaerobic conditions to dark aerobic and then to light aerobic conditions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available