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Title: Studies on N2-fixing Gloeothece grown under alternating light and darkness
Author: Perry, S. M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1988
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When Gloeothece, a unicellular cyanobacterium, is grown under a cycle of alternating light and darkness, it fixes N2 predominantly in the dark, thereby effecting a temporal separation of N2 fixation and photosynthesis. Similar diurnal variations in N2 fixation have been reported in Synechococcus sp. BG 43511, in which it has been proposed that the pattern is an endogenous property of the cell cycle. However, in Gloeothece it appears that this pattern is imposed by metabolic events unrelated to the cell cycle. Thus in Gloeothece, diurnal variations in the rate of N2 fixation almost parallel variations in the rate of nitrogenase synthesis, which is detectable only during that part of the light/dark cycle during which nitrogenase activity is rising or about to rise (i.e. the first 6-8h of darkness). During this period, the energy needed for nitrogenase synthesis and activity is provided by the oxidation of glucan synthesized in the preceding light period. Cessation of nitrogenase synthesis after 8h darkness coincides with depletion of glucan reserves and a sharp rise in the intracellular ratio of ADP to ATP. Subsequent restoration of nitrogenase synthesis requires a lag period of 12-16h, including at least 4h of light. These events are repeated every 24h and do not relate to the doubling time of Gloeothece (55-70h).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available