| Abstract |
The results described in this thesis reveal that unicellular diazotrophic cyanobacteria are unable to fix N2 under fully aerobic conditions. This suggests that in their natural environment these organisms must be exposed to O2 concentrations well below air saturation at least during the periods that they actively fix N2 (i.e. during the dark). Furthermore, temperature is identified as an important factor for dinitrogen fixation in cyanobacteria. It is found that the O2 flux into the heterocyst is dynamically regulated by temperature.
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