P. van Alphen
W. van Grondelle
- Culturing Synechocystis sp. Strain PCC 6803 with N2 and CO2 in a Diel Regime Reveals Multiphase Glycogen Dynamics with Low Maintenance Costs
- Applied and Environmental Microbiology
- Volume | Issue number
- 82 | 14
- Pages (from-to)
- Document type
- Faculty of Science (FNWI)
- Swammerdam Institute for Life Sciences (SILS)
Investigating the physiology of cyanobacteria cultured under a diel light regime is relevant for a better understanding of the resulting growth characteristics and for specific biotechnological applications that are foreseen for these photosynthetic organisms.Here, we present the results of a multi-omics study of the model cyanobacterium Synechocystis sp. PCC 6803, cultured in a lab-scale photobioreactor in physiological conditions relevant for large-scale culturing. The culture is sparged with N2 and CO2, leading to an anoxic environment during the dark period.Growth follows the availability of light. Metabolite analysis performed with 1H Nuclear Magnetic Resonance analysis, shows that amino acids involved in nitrogen and sulfur assimilation show elevated levels in the light. Most protein levels, analyzed through mass spectrometry, remain rather stable. However, several high-light-response proteins and stress-response proteins show distinct changes at the onset of the light period.Microarray-based transcript analysis finds common patterns of approximately 56 % of the transcriptome following the diel regime. These oscillating transcripts can be grouped coarsely into genes that are up-regulated and down-regulated in the dark period, respectively.The accumulated glycogen is degraded in the anaerobic environment in the dark. A small part is degraded gradually, reflecting basic maintenance requirements of the cells in darkness. Surprisingly, the largest part is degraded rapidly in a short time span at the end of the dark period. This degradation could allow rapid formation of metabolic intermediates at the end of the dark period, preparing the cells for the resumption of growth at the start of the light period. IMPORTANCE: Industrial scale biotechnological applications are anticipated for cyanobacteria. We simulated large-scale high cell-density culturing of Synechocystis sp. PCC 6803 under a diel light regime in a lab-scale photobioreactor. In BG-11 medium, Synechocystis grows only in the light. Metabolite analysis groups the collected samples according to the light and dark condition, respectively. Proteome analysis suggests that the majority of enzyme-activity regulation is not hierarchical, but rather through enzyme activity regulation. An abrupt light-on condition induces high-light-stress proteins. Transcript analysis shows distinct patterns for the light and dark periods.Glycogen gradually accumulates in the light and is rapidly consumed in the last quarter of the dark period. This suggests that the circadian clock primes the cellular machinery for immediate resumption of growth in the light.
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