An akinete is an enveloped, thick-walled, non-motile, dormant cell formed by both

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

and

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

. Cyanobacterial akinetes are mainly formed by filamentous, heterocyst-forming members under the order

Nostocales The Nostocales are an order of cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (c ...

and Stigonematales.

Eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

microalgae also produce akinetes, such as '' Haematococcus''. During akinete formation, cells accumulate and store various essential material, allowing the akinete to serve as a survival structure for up to many years. The cell akinetes are resistant to cold and

desiccation Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...

. However, akinetes are not resistant to heat. Once conditions become more favorable for growth, the akinete can then germinate back into a vegetative cell. Increased light intensity, nutrients availability, oxygen availability, and changes in salinity are important triggers for

germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, ...

. In cyanobacteria, akinetes usually develop in strings with each cell differentiating after another and this occurs next to heterocysts if they are present. Development usually occurs during stationary phase and is triggered by unfavorable conditions such as insufficient light or nutrients, temperature, and saline levels in the environment. In comparison to vegetative cells, akinetes are generally larger. This is associated with the accumulation of

nucleic acids Nucleic acids are large biomolecules that are crucial in all cells and viruses. They are composed of nucleotides, which are the monomer components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main classes of nucleic a ...

which is important for both dormancy and germination of the akinete. Despite being a resting cell, it is still capable of some metabolic activities such as

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

, protein synthesis, and

carbon fixation Biological carbon fixation, or сarbon assimilation, is the Biological process, process by which living organisms convert Total inorganic carbon, inorganic carbon (particularly carbon dioxide, ) to Organic compound, organic compounds. These o ...

, albeit at significantly lower levels. Akinetes can remain dormant for extended periods of time. Studies have shown that some species could be cultured that from akinetes were 18 and 64 years old.David Livingstone & G.H.M. Jaworski (1980) The viability of akinetes of blue-green algae recovered from the sediments of Rostherne Mere, British Phycological Journal, 15:4, 357-364, DOI: 10.1080/00071618000650361 Akinete formation also influences the perennial blooms of cyanobacteria. In algae, akinetes form when environmental signals indicate impending change unfavorable to growth, such as the arrival of winter. Like cyanobacterial akinetes, they accumulate storage materials, but also develop thick

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

s and suspend active metabolism. When conditions improve, the akinete germinates via the cell wall breaking open.

References

Cell biology Cyanobacterial cells Cyanobacteria Cyanobacteria stubs Algae {{cell-biology-stub