Synechocystis sp. PCC6803 is a freshwater cyanobacterium capable of both phototrophic growth by oxygenic photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

 in sunlight and heterotrophic growth by glycolysis

Glycolysis

Glycolysis is the metabolic pathway that converts glucose C6H12O6, into pyruvate, CH3COCOO− + H+...

 and oxidative phosphorylation

Oxidative phosphorylation

Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate . Although the many forms of life on earth use a range of different nutrients, almost all aerobic organisms carry out oxidative phosphorylation to produce ATP,...

 during dark periods. Transitions of light and dark phases are effectively anticipated by a circadian clock.

Overview

Cyanobacteria are model microorganisms for the study of photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

, carbon and nitrogen assimilation

Nitrogen assimilation

Nitrogen assimilation is a fundamental biological process that occurs in plants and algae that are incapable of independent nitrogen fixation. The assimilation of nitrogen has marked effects on plant productivity, biomass, and crop yield, and nitrogen deficiency leads to a decrease in structural...

, evolution of plant plastids, and adaptability to environmental stresses.
Synechocystis sp. PCC 6803 is one of the most highly studied cyanobacteria as it can grow both autotrophically or heterotrophically in the absence of light. It was isolated from a freshwater lake in 1968 and is easily transformed by exogenous DNA. The photosynthetic apparatus is very similar to the one found in plants. This organism also exhibits phototactic movement.

Light-activated heterotrophy

It can live completely heterotrophically in the dark, but for yet unknown reasons requires a minimum of 5 to 15 minutes (blue) light per day. This regulatory role of light is intact in both PSI and PSII deficient strains.

NDH-2 is a regulatory quinone:NAD(P)H oxidoreductase global analysis of circadian gene expression indicates that translation genes are expressed at the early subjective day.

Some glycolytic genes are regulated by sll1330 under light and glucose-supplemented conditions. One of the most important glycolytic genes is fructose-1,6-bisphosphate aldolase

Fructose-bisphosphate aldolase

In molecular biology, fructose-bisphosphate aldolase , is a glycolytic enzyme that catalyses the reversible aldol cleavage or condensation of fructose-1,6-bisphosphate into dihydroxyacetone-phosphate and glyceraldehyde 3-phosphate...

(fbaA). The mRNA level of fbaA is increased under light and glucose-supplemented conditions. But in Δsll1330, fbaA is not increased under same conditions.

Databases

• SynechoNET: integrated protein-protein interaction database of a model cyanobacterium Synechocystis sp. PCC 6803. SynechoNET is a specialized cyanobacterial protein-protein interaction database. It shows feasible cyanobacterial domain-domain interactions, as well as their protein level interactions using the model cyanobacterium, Synechocystis sp. PCC 6803. Additionally, SynechoNET provides transmembrane topology and domain information, as well as the interaction networks in graphical web interfaces.
• CyanoBase: Cyanobacteria carry a complete set of genes for oxygenic photosynthesis, which is the most fundamental life process on the earth. This organism is also interesting from an evolutional viewpoint, for it was born in a very ancient age and has survived in various environments. Chloroplast is believed to have evolved from cyanobacterial ancestors which developed an endosymbiontic relationship with a eukaryotic host cell. CyanoBase provides an easy way of accessing the sequences and all-inclusive annotation data on the structures of the cyanobacterial genomes. This database was originally developed by Makoto Hirosawa, Takakazu Kaneko and Satoshi Tabata, and the current version of CyanoBase has been developed and maintained by Yasukazu Nakamura, Takakazu Kaneko, and Satoshi Tabata at Kazusa DNA Research Institute.
• STRING: STRING is a database of known and predicted protein-protein interactions.The interactions include direct (physical) and indirect (functional) associations; they are derived from four sources: Genomic Context, High-throughpot Experiments, (Conserved) Coexpression, and Previous Knowledge. The database currently contains 1,513,782 proteins in 373 species. Especially, the database provides interactions for Synechocystis sp. PCC 6803.
• cTFbase: cTFbase contains 1288 putative TFs identified from 21 fully sequenced cyanobacterial genomes. Through its user-friendly interactive interface, users can employ various criteria to retrieve all TF sequences and their detailed annotation information, including sequence features, domain architecture and sequence similarity against the linked databases. Furthermore, cTFbase also provides phylogenetic trees of individual TF family, multiple sequence alignments of the DNA-binding domain and ortholog identification from any selected genomes.