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Cyanobacteria are a very large and diverse phylum of photosynthetic prokaryotes. [19] They are defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis. They often live in colonial aggregates that can take on a multitude of forms. [20]
Cyanobacterial cell division and cell growth mutant phenotypes in Synechocystis, Synechococcus, and Anabaena.Stars indicate gene essentiality in the respective organism. While one gene can be essential in one cyanobacterial organism/morphotype, it does not necessarily mean it is essential in all other cyanobacteria.
Cyanothece’s nucleoids are spread loosely throughout the cell, with a net-like appearance. [2] [3] Instead of concentric thylakoid membranes that share a center or axis, Cyanothece’s exhibit short, wavy and radially arranged., [3] [7] All Cyanothece had nitrogenase activity at one time; although some strains have lost the necessary genes. [5]
Cyanobacteria are photosynthetic prokaryotes that have existed on Earth for an estimated 2.7 billion years. The ability of cyanobacteria to produce oxygen initiated the transition from a planet consisting of high levels of carbon dioxide and little oxygen, to what has been called the Great Oxygenation Event where large amounts of oxygen gas were produced. [4]
They do not contain chloroplasts; rather, they bear a striking resemblance to chloroplasts themselves. This suggests that organisms resembling cyanobacteria were the evolutionary precursors of chloroplasts. One imagines primitive eukaryotic cells taking up cyanobacteria as intracellular symbionts in a process known as endosymbiosis.
Reproduction takes place asexually by fragmentation. Usually the filament breaks into a number of fragments called hormogonia. Each hormogonium consist of one or more cells and grows into a filament by cell division in one direction. [1] As a result of recent genetic analyses, several new genera were erected from this genus, e.g. Tenebriella. [3]
The following sequences take place in formation of heterocysts from a vegetative cell: The cell enlarges. Granular inclusions decrease. Photosynthetic lammel reorients. The wall finally becomes triple-layered. These three layers develop outside the cell's outer layer. The middle layer is homogeneous. The inner layer is laminated.
Each photosystem II contains at least 99 cofactors: 35 chlorophyll a, 12 beta-carotene, two pheophytin, two plastoquinone, two heme, one bicarbonate, 20 lipids, the Mn 4 CaO 5 cluster (including two chloride ions), one non heme Fe 2+ and two putative Ca 2+ ions per monomer. [4] There are several crystal structures of photosystem II. [5]