Characterization of Synechocystis sp. PCC 6803 under mixotrophic conditions
Organisms that belong to the phytoplankton are able to perform photosynthesis and can thus live photoautotrophically. However, if they are provided with organic carbon sources some of them can switch to a mixotrophic lifestyle. The ability to switch between autotrophy and mixotrophy gives these organisms a selective advantage. In this thesis the glucose tolerant strain of the cyanobacterium Synechocystis sp. PCC 6803 was characterized under mixotrophic growth conditions. Special attention was paid to the glucose degradation pathways and to the reaction that converts pyruvate to acetyl-CoA. This reaction can be catalyzed either by the PDH-complex or alternatively by the pyruvate:ferredoxin/flavodoxin oxidoreductase (PFOR). The latter enzyme is tightly connected to the bidirectional NiFe-hydrogenase, which is directly reduced by ferredoxin. It could be shown that the bidirectional hydrogenase is essential under mixotrophic, nitrate limited conditions.