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Title: Studies of N2 fixation in batch and continuous cultures of Gloeothece
Author: Du, C.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Continuous cultures of Gloeothece have been established with a dilution rate of 0.015-1. Cell division in continuous cultures grown under alternating light and darkness depended on the length of the light period rather than on light intensity. Patterns of N2 fixation in continuous cultures were different from those in batch cultures when both were grown under alternating 12 hours light of intensity greater than 50 μE/m2/s and 12 hours darkness: continuous cultures fixed N2 mostly during the last half of light period, whilst batch cultures fixed N2 exclusively during the dark phase. In aerobic cultures of Gloeothece, whether N2-fixing or ammonium-grown, the light compensation point responded mainly to the prevailing rate of respiration. In aerobically N2-fixing cultures of Gloeothece, peaks of nitrogenase activity and light compensation point occurred simultaneously. In microaerobically grown N2-fixing cultures of Gloeothece exposed to alternating light and darkness, N2 fixation was exclusively found during the light phase, and was supported by photosynthesis. In vivo inhibition of nitrogenase activity in cultures of Gloeothece by EDTA and heat-shock may be mediated by inhibition of respiration. In aerobic, N2-fixing cultures of Gloeothece, cyanide-sensitive and -insensitive respiration was found: both showed a high rate during the dark phase. However, in ammonium-grown cultures, only cyanide-insensitive respiration was observed. In cyanide-treated N2-fixing and ammonium-grown cultures, the intracellular concentration of O2 did not change throughout a cycle of light and darkness, but in aerobic N2-fixing cultures, the relative intracellular concentration of O2 was close to zero when cultures entered the dark phase.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available