Physiological studies to optimize growth of the prototype biosolar cell factory Synechocystis sp. PCC6803

The oxygenic photoautotroph Synechocystis sp. PCC6803 is a present-day cyanobacterium, a lineage with billions of years of history. In this thesis, we explore ways to optimize the use of Synechocystis for the realization of a sustainable society, in which the carbon cycle is closed by using sunlight to produce fuel and chemical feedstock out of CO2. A deeper understanding of metabolism in Synechocystis is required to be able to reach this goal in the future.
State-of-the-art photobioreactors were used to precisely control and measure parameters of growth and develop a new medium, as described in chapter 2. This chapter explores the limits of growth of Synechocystis and exposes nutrient limitations.
In chapters 3 and 4, the photosynthetic apparatus itself is closely investigated with special emphasis on the role of the light-harvesting complexes typically found in cyanobacteria, revealing a remarkable flexibility in coping with varying light intensities.
Because of the desire to use sunlight to fuel the assimilation of CO2, it is of paramount importance to be able to deal with the steady rhythm of day and night, as well as varying light intensities during the day. Chapters 5 to 7 cover the circadian clock of Synechocystis, an essential mechanism to time gene expression and metabolism. The clock of Synechocystis was shown to be robust and in control of large number of cellular processes, crucial for coping with the night and allowing for additional regulation to enhance production of compounds of interest.
Chapter 8 discusses all findings in a broader context.