''Aphanizomenon'' is a genus of cyanobacteria that inhabits freshwater lakes and can cause dense blooms. They are unicellular organisms that consolidate into linear (non-branching) chains called trichomes. Parallel trichomes can then further unite into aggregates called rafts. Since Aphanizomenon is a genus in the cyanobacteria phylum. Bacteria in the Cyanobacteria phylum are known for using photosynthesis to create energy and therefore use sunlight as their energy source. Aphanizomenon bacteria also play a big role in the Nitrogen cycle since they can perform

nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

. Studies on the species ''Aphanizomenon flos-aquae'' have shown that it can regulate buoyancy through light-induced changes in

turgor Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilibri ...

pressure. It is also able to move by means of gliding, though the specific mechanism by which this is possible is not yet known.

Ecology

Overcoming phosphate limitation

''Aphanizomenon'' may become dominant in a water body partially due to their ability to induce phosphate-limitation in other phytoplankton while also increasing phosphate availability to itself through release of

cylindrospermopsin Cylindrospermopsin (abbreviated to CYN, or CYL) is a cyanotoxin produced by a variety of freshwater cyanobacteria. CYN is a polycyclic uracil derivative containing guanidino and sulfate groups. It is also zwitterionic, making it highly water ...

. The

causes other phytoplankton to increase their alkaline phosphatase activity, increasing inorganic phosphate availability in the water to ''Aphanizomenon'' during times when phosphate becomes limiting.

Photosynthesis

All species in the cyanobacteria phylum can perform photosynthesis. They use a similar photosynthesis to plants, using two photosystems which is called the

Z-scheme Light-dependent reactions is jargon for certain photochemical reactions that are involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions, the first occurs at photosystem II (PSII) and ...

. This is different from other photosynthetic bacteria that only use one photosystem and do not have thylakoids. Cyanobacteria species such as Aphanizomenon also use Oxygen as their final electron acceptor in the Electron Transport Chain, which is also different from other photosynthetic bacteria, which perform a type of photosynthesis called

anoxygenic photosynthesis Bacterial anoxygenic photosynthesis differs from the better known oxygenic photosynthesis in plants by the reductant used (e.g. hydrogen sulfide instead of water) and the byproduct generated (e.g. elemental sulfur instead of molecular oxygen). Ba ...

Nitrogen fixation

''Aphanizomenon are a special type of cyanobacteria called

heterocyst Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as '' Nostoc punctiforme'', ''Cylindrospermum stagnale'', and ''Anabaena sphaerica''. They fix nitrogen fr ...

s,'' which are capable of producing biologically useful nitrogen ( ammonium) by the process of

from atmospheric nitrogen. A large proportion (between 35 and 50%) of fixed nitrogen may be released into the surrounding water, providing an important source of biologically available nitrogen to the ecosystem. Since Aphanizomenon are one of the few species of bacteria that can perform nitrogen fixation, other bacterial species that use nitrogen ions as a reactant will start to rely on the species as a source of usable nitrogen. This will cause a bacterial bloom to form, which is a condition under which the number of bacterial colonies in a area will suddenly increase.

Algal Blooms

Aphanizomenon can produce

algal bloom An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term ''algae'' encompass ...

s from producing usable nitrogen causing other bacterial species to form colonies around the Aphanizomenon. Algal Blooms formed from Aphanizomenon species tend to be very toxic and create a variety of toxins. These blooms may also create dead zones in the water. This ends up being bad for the ecosystem, since it can hurt many of the plants and animals living around it.

Toxin production

''Aphanizomenon'' species may produce

cyanotoxins Cyanotoxins are toxins produced by cyanobacteria (also known as blue-green algae). Cyanobacteria are found almost everywhere, but particularly in lakes and in the ocean where, under high concentration of phosphorus conditions, they reproduce exp ...

including cylindrospermospin (CYN),

lipopolysaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer ...

s (LPS),

anatoxin-a Anatoxin-a, also known as Very Fast Death Factor (VFDF), is a secondary, bicyclic amine alkaloid and cyanotoxin with acute neurotoxicity. It was first discovered in the early 1960s in Canada, and was isolated in 1972. The toxin is produced by mu ...

saxitoxin Saxitoxin (STX) is a potent neurotoxin and the best-known paralytic shellfish toxin (PST). Ingestion of saxitoxin by humans, usually by consumption of shellfish contaminated by toxic algal blooms, is responsible for the illness known as paralyt ...

and

BMAA β-Methylamino--alanine, or BMAA, is a non-proteinogenic amino acid produced by cyanobacteria. BMAA is a neurotoxin and its potential role in various neurodegenerative disorders is the subject of scientific research. Structure and properti ...

. Though not all Aphanizomenon produce cyanotoxins, many do. CYNs are a toxin that is especially toxic for the liver and kidney, thought to inhibit protein synthesis. LPSs are found in the cellular membrane of gram-negative bacterial cells and is released when the cellular membrane is degraded. The releasing of LPSs in animals can cause a severe immune response causing it to be very toxic for animals. Anatoxin-a is a type of anatoxin, it is normally released during algal blooms in lakes, causing exposure to animals around it. Anatoxin-a is toxic to the nerves in animals and is very lethal to humans with a lethal dose thought to be less than 5mg. Similarly to anatoxin-a, BMAAs are another type of neurotoxin that lingers inside animals for longer than anatoxin-a. It will keep affecting animals even after a algal bloom dies down. Last, saxitoxins is yet another type of neurotoxin known to be released by a species of Aphanizomenon. It interrupts nerve transmissions to and from the brain, causing it to be very toxic.

Colony formation

Aphanizomenon_Bloom_Upper_Klamath_Lake_USGS

''Aphanizomenon'' may form large colonies as a defense against herbivore grazing, especially ''

Daphnia ''Daphnia'' is a genus of small planktonic crustaceans, in length. ''Daphnia'' are members of the order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembl ...

'' in freshwater.

References

Nostocales Cyanobacteria genera {{cyanobacteria-stub