Cyanobacteria in a colony. Photo:

Cohen MF, Meeks JC, Cai Y and Wolk CP (1998) Transposon mutagenesis of heterocyst‐forming filamentous cyanobacteria. In: McIntosh L (ed.) Photosynthesis: Molecular Biology of Energy Capture. Methods in Enzymology, Vol. 297, pp. 3–17. New York: Academic Press.

cyanobacteria; differentiation; nitrogen fixation; pattern formation; cell communication

Black K, Buikema WJ and Haselkorn R (1995) The hglK gene is required for localization of heterocyst‐specific glycolipids in the cyanobacterium Anabaena sp. strain PCC 7120. Journal of Bacteriology 177: 6440–6448.

Cyanobacteria may be immotile, or they move by

Zehr JP (2011) Nitrogen fixation by marine cyanobacteria. Trends in Microbiology 19: 162–173.

The most common cyanobacterial structures in the fossil record are the mound-producing stromatolites and related oncolites. Indeed, these fossil colonies are so common that paleobiology, micropaleontology and paleobotany cite the Pre-Cambrian and Cambrian period as an "age of stromatolites" and an "age of algae."

Cyanobacteria can fix atmospheric nitrogen in anaerobic ..

The pattern of spaced heterocysts is regulated by inhibitor gradients that promote the decay of HetR, confirming mathematical models of two‐dimensional pattern formation in heterocystous cyanobacteria.

Cyanobacteria | Cyanobacteria | Photosynthesis

Nitrogen is an element vital to all life processes on Earth. Nitrogen is very important in our biosphere, where nitrogen comprises 78% of the atmosphere, and is part of every living tissue. It is a component of amino acids, proteins and nucleic acids. With the exception of carbon, nitrogen is the most universal element of life. Life could not exist without nitrogen. .
Nitrogen is essential for organic development; nitrogenous compounds are also required by some organisms for metabolic functions and respiration. Unfortunately, free nitrogen in the atmosphere is not in a form that is usable by plants or animals. Because of its stable structural formula, it is relatively inert and does not combine readily with other elements.

All living organisms, from fish to plants, have great quantities of assimilated nitrogen in their tissues. Nitrogen is a fundamental ingredient for the formation of proteins and nucleic acids. Every organism you place in your aquarium adds nitrogen based compounds; from fish to coral, to live rock, to plants.
The introduction of food also adds nitrogen. Dead or alive, they are organic masses, and possess the same nitrogenous attributes as the fish, plants, invertebrates you added to your aquarium.
Inorganic nitrogen is added two ways: the atmosphere and new water. Atmospheric nitrogen (N2) is incorporated into our aquarium water by way of nitrogen fixing bacteria and by Cyanobacteria (bacteria that obtain their energy through photosynthesis) as ammonia (NH3). Some Cyanobacteria fix nitrogen gas, which cannot be used by plants, into ammonia, nitrites (NO2-) or nitrates (NO3-). Nitrates can then be utilized by plants and converted to nucleic acids and protein.
Inorganic nitrogenous compounds from our tap or well water also enter our aquarium, often as Nitrites or Nitrates. Reverse Osmosis can remove much of this.
For more about tap water, please see this article:

Photosynthetic Organisms - Plants, Algae, Cyanobacteria

Cyanobacteria are oxygenic photosynthetic bacteria that are widespread in marine, freshwater and terrestrial environments, and many of them are capable of fixing atmospheric nitrogen. However, ironically, nitrogenase, the enzyme that is responsible for the reduction of N2, is extremely sensitive to O2. Therefore, oxygenic photosynthesis and N2 fixation are not compatible. Hence, cyanobacteria had to evolve a variety of strategies circumventing this paradox, allowing them to grow at the expense of N2, a ubiquitous source of nitrogen. Some filamentous cyanobacteria differentiate heterocysts. These cells lack the oxygenic photosystem and possess a glycolipid cell wall that keeps the oxygen concentration sufficiently low for nitrogen fixation to take place. This strategy is known as spatial separation of oxygenic photosynthesis and nitrogen fixation. Nonheterocystous cyanobacteria may temporally separate these processes by fixing nitrogen during the night. Again others use a combination of these strategies.

Mini-review Nitrogen fixation and photosynthetic oxygen ..

typically have an S-layer, a layer of proteins fitted together like a mosaic, which covers the outer membrane and
on top of this is another layer of protein fibrils, called oscillin fibrils, wound around the cell in a helix.