Cyanobacteria

Cyanobacteria are bacteria that perform oxygen-producing photosynthesis, using sunlight to convert carbon dioxide and water into organic matter. They include forms that live as single cells, colonies, or filaments.

Oxygenic photosynthesis: Photosynthesis that uses water as an electron donor and releases oxygen. Cyanobacteria are the only bacteria known to perform this oxygen-producing form of photosynthesis.
Great Oxidation Event: A major rise in atmospheric oxygen around 2.4 billion years ago, following earlier biological oxygen production. Oxygen released by ancient cyanobacteria is widely linked to this transformation of Earth’s atmosphere.
Harmful algal bloom: A rapid increase in algae or cyanobacteria that can harm ecosystems, animals, or people. Cyanobacterial blooms can produce toxins, deplete oxygen, and disrupt water supplies.
Anoxygenic photosynthesis: Photosynthesis that uses electron donors other than water and does not release oxygen. Unlike cyanobacteria, organisms using this form do not split water to power photosynthesis.
Photosystem II: A protein complex that uses light energy to extract electrons from water during photosynthesis. Its water-splitting reaction supplies electrons and releases the oxygen produced by cyanobacteria.
Stromatolite: A layered sedimentary structure built through the growth of microbial communities and the trapping or binding of sediment. Some ancient stromatolites preserve evidence of microbial communities that included cyanobacteria.
Microcystin: A family of toxins produced by some cyanobacteria that can damage the liver. It is a common cyanobacterial toxin monitored during freshwater blooms.
Purple sulfur bacteria: Anoxygenic photosynthetic bacteria that commonly use hydrogen sulfide as an electron donor. They photosynthesize without producing oxygen, unlike cyanobacteria.
Phycobilisome: A light-harvesting complex of pigment-bearing proteins found in many cyanobacteria and red algae. It captures wavelengths that chlorophyll absorbs poorly and transfers the energy to photosystems.
Endosymbiotic theory: The theory that mitochondria and chloroplasts originated as bacteria living inside ancestral eukaryotic cells. Chloroplasts descend from a cyanobacterium incorporated into an ancestral eukaryotic cell.

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