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.[1] Cyanobacteria such as Aphanizomenon are known for using photosynthesis to create energy and therefore use sunlight as their energy source.[2] Aphanizomenon bacteria also play a big role in the Nitrogen cycle since they can perform nitrogen fixation. Studies on the species Aphanizomenon flos-aquae have shown that it can regulate buoyancy through light-induced changes in turgor pressure.[3] It is also able to move by means of gliding, though the specific mechanism by which this is possible is not yet known.
| Aphanizomenon | |
|---|---|
| |
| Aphanizomenon flos-aquae | |
Scientific classification 
| |
| Domain: | Bacteria |
| Phylum: | Cyanobacteria |
| Class: | Cyanophyceae |
| Order: | Nostocales |
| Family: | Aphanizomenonaceae |
| Genus: | Aphanizomenon A.Morren ex Bornet & Flahault, 1888 |
| Species | |
|
Aphanizomenon flos-aquae Aphanizomenon gracile Aphanizomenon issatschenkoi Aphanizomenon ovalisporum | |
Ecology
editOvercoming phosphate limitation
editAphanizomenon 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.[4] The cylindrospermopsin 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
editAll species in the cyanobacteria phylum can perform photosynthesis. They use a similar photosynthesis to plants, using two photosystems which is called the Z-scheme. 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.[5]
Nitrogen fixation
editAphanizomenon are a special type of cyanobacteria called heterocysts, which are capable of producing biologically useful nitrogen (ammonium) by the process of nitrogen fixation 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.[6][7] 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 an area will suddenly increase.[8]
Algal blooms
editAphanizomenon can produce algal blooms 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.[9]
Toxin production
editAphanizomenon species may produce cyanotoxins including cylindrospermospin (CYN), lipopolysaccharides (LPS), anatoxin-a, saxitoxin and BMAA.[10][11] 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 5 mg.[12] 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 an 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.[13]
Colony formation
edit
Aphanizomenon may form large colonies as a defense against herbivore grazing, especially Daphnia in freshwater. [14]
See also
editReferences
edit- ^ "Phycokey - Aphanizomenon". cfb.unh.edu. Retrieved 2021-04-22.
- ^ "Life History and Ecology of Cyanobacteria". ucmp.berkeley.edu. Retrieved 2021-04-27.
- ^ Konopka, A.; T. D. Brock; A. E. Walsby (1978). "Buoyancy regulation by planktonic blue-green algae in Lake Mendota, Wisconsin". Arch. Hydrobiol. 83: 524–537.
- ^ Yehonathan Bar-Yosef; Assaf Sukenik; Ora Hadas; Yehudit Viner-Mozzini & Aaron Kaplan (2010). "Enslavement in the Water Body by Toxic Aphanizomenon ovalisporum, Inducing Alkaline Phosphatase in Phytoplanktons". Current Biology. 20 (17): 1557–1561. doi:10.1016/j.cub.2010.07.032. PMID 20705465.
- ^ Mullineaux, Conrad W. (2014-01-21). "Electron transport and light-harvesting switches in cyanobacteria". Frontiers in Plant Science. 5: 7. doi:10.3389/fpls.2014.00007. ISSN 1664-462X. PMC 3896814. PMID 24478787.
- ^ Adam, B.; Klawonn, I.; Svedén, J. B.; Bergkvist, J.; Nahar, N.; Walve, J.; Littmann, S.; Whitehouse, M. J.; Lavik, G.; Kuypers, M. M.; Ploug, H. (2015). "N2-fixation, ammonium release and N-transfer to the microbial and classical food web within a plankton community". The ISME Journal. 10 (2): 450–459. doi:10.1038/ismej.2015.126. PMC 4737936. PMID 26262817.
- ^ Ploug, Helle; Musat, Niculina; Adam, Birgit; Moraru, Christina L.; Lavik, Gaute; Vagner, Tomas; Bergman, Birgitta; Kuypers, Marcel M. M. (2010). "Carbon and nitrogen fluxes associated with the cyanobacterium Aphanizomenon sp. in the Baltic Sea". The ISME Journal. 4 (9): 1215–1223. doi:10.1038/ismej.2010.53. hdl:21.11116/0000-0001-CAC0-2. PMID 20428225.
- ^ "Bacterial Bloom, Cloudy Water, Ammonia/Nitrite Spike - What do I do?". the fishroom. 2019-12-09. Retrieved 2021-04-27.
- ^ US EPA, OW (2013-06-03). "Harmful Algal Blooms". US EPA. Retrieved 2021-05-10.
- ^ "Cyanobacteria/Cyanotoxins". US EPA. 2015. Archived from the original on 2015-10-17. Retrieved 2015-10-25.
- ^ "Aphanizomenon (cyanoScope) · iNaturalist". iNaturalist. Retrieved 2021-04-27.
- ^ Minnesota Department of Health. "Anatoxin-a and Drinking Water" (PDF). Archived (PDF) from the original on 2020-10-20. Retrieved 2021-05-07.
- ^ "Saxitoxin - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2021-05-08.
- ^ "Aphanizomenon blooms: alternate control and cultivation by Daphnia pulex" (PDF). American Society of Limnology and Oceanography Special Symposium No. 3: 299-304. 1980.
Guiry, M.D.; Guiry, G.M. "Aphanizomenon". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.