Anabaena

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Template:Short description Script error: No such module "Hatnote". Template:Automatic taxobox

Anabaena is a genus of filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to local wildlife, as well as farm animals and pets. Production of these neurotoxins is assumed to be an input into its symbiotic relationships, protecting the plant from grazing pressure.

A DNA sequencing project was undertaken by the United States Department of Energy between 1999 and 2005. This project mapped the complete genome of model organism Anabaena variabilis ATCC 29413, which is 7.2 million base pairs long.[1][2] A paper detailing the process was published in 2014.[3] The study focused on heterocysts, which convert nitrogen into ammonia. Certain species of Anabaena have been used on rice paddy fields, proving to be an effective natural fertilizer.

Species

List of current (C), unverified (U), and preliminary (P) species from AlgaeBase:[4]

<templatestyles src="Div col/styles.css"/>

Script error: No such module "Check for unknown parameters".

List of synonimized species from AlgaeBase:[4]

<templatestyles src="Div col/styles.css"/>

Script error: No such module "Check for unknown parameters".

Recent changes

The genus has significant overlap with Aphanizomenon. Despite An. variabilis having been removed from the genus to form a new Trichormus 1988, it seems to be phylogenetically placed in Anabaena (between the "planktic" main-group and the group formed by An. augstumalis and An. oscillarioides). As a result the position of T. variabilis and the two species of benthic Anabaena may be subject to change.[5] The group around Trichormus variabilis is better-supported by data than grouping it together with main-group Anabaena/Aphanizomenon, so it's more likely for the two species to be split out. In addition, the position of Trichormus azollae needs change.[6]

  • In 2009, a 42-species group under the "planktic" main-group, determined by 16S rRNA or gas vesicle morphotype, were transferred to Dolichospermum.[7]
  • In 2010, the genus Sphaerospermopsis was created, moving away 3 species. 3 more were moved to this genus later.
  • In 2012, 3 species were moved to the new genus Chrysosporum. One was later moved to Umezakia.

Many of sequenced the morphospecies in Anabaena, Dolichospermum, and Aphanizomenon (ADA clade) are not monophyletic. Work is underway to sequence more genomes from these genera to produce a species classification based on genetic branching.[8]

Nitrogen fixation by Anabaena

File:Necklace of Mermaid.tif
Anabaena sp.
Script error: No such module "Check for unknown parameters".

Under nitrogen-limiting conditions, vegetative cells differentiate into heterocysts at semiregular intervals along the filaments. Heterocyst cells are terminally specialized for nitrogen fixation. The interior of these cells is micro-oxic as a result of increased respiration, inactivation of O2-producing photosystem (PS) II, and formation of a thickened envelope outside of the cell wall. Nitrogenase, sequestered within these cells, transforms dinitrogen into ammonia at the expense of ATP and reductant—both generated by carbohydrate metabolism, a process supplemented, in the light, by the activity of PS I. Carbohydrate, probably in the form of glucose, is synthesized in vegetative cells and moves into heterocysts. In return, nitrogen fixed in heterocysts moves into the vegetative cells, at least in part in the form of amino acids.[9]

The fern Azolla forms a symbiotic relationship with the cyanobacterium Anabaena azollae, which fixes atmospheric nitrogen, giving the plant access to this essential nutrient. This has led to the plant being dubbed a "super-plant", as it can readily colonise areas of freshwater, and grow at great speed - doubling its biomass in as little as 1.9 days.[10] The typical limiting factor on its growth is phosphorus, abundance of which, due to chemical runoff, often leads to Azolla blooms. Unlike other known plants, the symbiotic microorganism is transferred directly from one generation to the next. This has made Anabaena azollae completely dependent on its host, as several of its genes are either lost or have been transferred to the nucleus in Azolla's cells.[11]

Primitive vision pigments studied in Anabaena

Anabaena is used as a model organism to study simple vision. The process in which light changes the shape of molecules in the retina, thereby driving the cellular reactions and signals that cause vision in vertebrates, is studied in Anabaena. Anabaena sensory rhodopsin, a specific light-sensitive membrane protein, is central to this research.[12]

DNA repair

Double strand breaks (DSBs) are a type of DNA damage that can be repaired by homologous recombination. This enzymatic repair process occurs in several enzymatic steps including an early step catalyzed by RecN protein.[13] A study of the dynamics of RecN in DSB repair in Anabaena indicated differential regulation of DSB repair so that it is active in vegetative cells but absent in mature heterocysts that are terminal cells.[14]

References

<templatestyles src="Reflist/styles.css" />

  1. ↑ Script error: No such module "citation/CS1".
  2. ↑ Script error: No such module "citation/CS1".
  3. ↑ Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "citation/CS1".Script error: No such module "Unsubst".
  10. ↑ Script error: No such module "Citation/CS1".
  11. ↑ The Arctic Azolla event - The Geological Society
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ Hu S, Wang J, Wang L, Zhang CC, Chen WL. Dynamics and Cell-Type Specificity of the DNA Double-Strand Break Repair Protein RecN in the Developmental Cyanobacterium Anabaena sp. Strain PCC 7120. PLoS One. 2015 Oct 2;10(10):e0139362. doi: 10.1371/journal.pone.0139362. PMID 26431054; PMCID: PMC4592062

Script error: No such module "Check for unknown parameters".

Further reading

  • Script error: No such module "Citation/CS1".
  • Eduardo Romero-Vivas, Fernando Daniel Von Borstel, Claudia Perez-Estrada, Darla Torres-Ariño, Francisco Juan Villa-Medina, Joaquin Gutierrez (2015) On-water remote monitoring robotic system for estimating patch coverage of Anabaena sp. filaments in shallow water; Environ. Sci.: Processes Impacts 04/2015; DOI:10.1039/C5EM00097A

External links

Template:Taxonbar

Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Anabaena&oldid=2058588"