Synechocystis

Synechocystis is a genus of unicellular cyanobacteria that inhabit freshwater environments. As photosynthetic bacteria, they use chlorophyll a and the pigment–protein complexes of phycobilisomes (including phycocyanin and allophycocyanin) to harvest light and drive oxygenic photosynthesis.

The best-known species, Synechocystis sp. PCC 6803, is a leading model organism in photosynthesis research and genetic engineering. It is naturally competent, meaning it can take up DNA from its surroundings and be genetically transformed without specialized methods. The genome of this strain has been fully sequenced and extensively annotated, providing a platform for systems biology and metabolic engineering studies.

Physiology and metabolism: Synechocystis cells are typically small and unicellular, often appearing as single cells in liquid cultures. They grow photoautotrophically using light and CO2, but can also utilize organic carbon sources in some conditions. Unlike some cyanobacteria, most Synechocystis strains do not fix atmospheric nitrogen and do not form heterocysts.

Ecology and applications: In nature they occur in freshwater habitats, among biofilms and on moist surfaces. In the laboratory, Synechocystis serves as a versatile chassis for gene function studies, photosynthesis research, and synthetic biology applications, including metabolic engineering and bioproduction. It remains a central reference point for understanding cyanobacterial biology and the evolution of chloroplasts.