Anabaena is a genus of filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities, and they form symbiosis relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce , 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.
Species
List of current (C), unverified (U), and preliminary (P) species from AlgaeBase:
List of synonimized species from AlgaeBase:
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Anabaena affinis S →
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An. akankoensis S →
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Anabaena ambigua S →
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An. anisococca S →
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Anabaena anomala S →
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An. antarctica S →
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An. aphanizomenoides S →
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Anabaena arctica S →
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Anabaena azollae S → Trichormus azollae
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An. ballygungii S →
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Anabaena baltica S →
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An. berezowskii S →
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Anabaena bergii S →
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Anabaena bituri S →
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Anabaena bothae S →
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Anabaena botulus S →
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Anabaena bullosa S →
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An. calcicola S →
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An. californica S →
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Anabaena caspica S →
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An. chalybea S →
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An. circinalis S →
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An. circularis S →
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An. citrispora S →
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An. compacta S →
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An. compacta S →
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An. constricta S →
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Anabaena crassa S →
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Anabaena curva S →
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An. cycadearum S →
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An. cylindrospermoides S →
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An. cylindrospora S →
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Anabaena danica S →
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An. decorticans S →
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An. delicatula S →
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An. desikacharyensis S →
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An. doliolum S →
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An. ellipsoides S →
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An. ellipsospora S →
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An. eucompacta S →
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Anabaena fallax S →
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An. farciminiformis S →
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An. fertilissima S →
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An. flos-aquae S →
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An. fragilis S →
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An. fuellebornii S →
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Anabaena fusca S →
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An. gelatinicola S →
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An. gelatinosa S →
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An. gelatinosa S →
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Anabaena globosa S →
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An. halbfassii S →
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An. hallensis S →
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An. hansgirgii S →
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An. hassallii S →
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An. helicoidea S →
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An. heterospora S →
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An. hoshiarpurensis S →
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An. humicola S →
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An. impalpabilis S →
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An. impalpebralis S →
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An. impalpebralis S →
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An. incrassata S →
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Anabaena indica S →
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An. infusionum S →
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An. intricata S →
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An. isocystoides S →
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An. issatschenkoi S →
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An. jacutica S →
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An. kashiensis S →
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Anabaena khannae S →
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An. kisseleviana S →
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An. knipowitschii S →
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An. lemmermannii S →
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An. limicola S →
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An. limicola S →
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An. limnetica S →
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An. longicellularis S →
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Anabaena lutea S →
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An. macrospora S →
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Anabaena major S →
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An. manguinii S →
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Anabaena maxima S →
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An. membranina S →
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An. mendotae S →
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An. minispora S →
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Anabaena minuta S →
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Anabaena mollis S →
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Anabaena mucosa S →
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An. mysorensis S →
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Anabaena nathii S →
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An. naviculoides S →
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An. nygaardii S →
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Anabaena oryzae S →
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Anabaena oumiana S →
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Anabaena parva S →
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An. perturbata S →
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An. planctonica S →
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An. polysperma S →
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An. polyspora S →
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An. portoricensis S →
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An. propinqua S →
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An. pseudocompacta S →
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An. pseudoscillatoria S →
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An. pseudovariabilis S →
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An. raciborskii S →
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An. randhawae S →
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An. reniformis S →
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An. reverdattoana S →
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An. rufescens S →
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An. scheremetieviae S →
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An. siamensis S →
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An. sibirica S →
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An. sigmoidea S →
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An. skujaelaxum S →
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Anabaena smithii S →
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An. solitaria S →
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An. spiralis S →
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An. spiroides S →
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An. stagnalis S →
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An. steloides S →
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An. subcylindrica S →
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An. subtropica S →
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An. tanganyikae S →
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An. tenericaulis S →
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Anabaena tenuis S →
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An. thermalis S →
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An. torquesreginae S →
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An. ucrainica S →
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An. unispora S →
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An. utermoehlii S →
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An. vaginicola S →
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An. variabilis S → Trichormus variabilis
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An. viguieri S →
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Anabaena volzii S →
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Anabaena werneri S →
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An. zinserlingii S →
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.
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.
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In 2009, a 42-species group under the "planktic" main-group, determined by 16S rRNA or gas vesicle morphotype, were transferred to Dolichospermum.
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In 2010, the genus Sphaerospermopsis was created, moving away 3 species. 3 more were moved to this genus later.
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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.
Nitrogen fixation by Anabaena
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 O
2-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
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The fern Azolla forms a symbiosis 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.[ The Arctic Azolla event - The Geological Society]
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.
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.
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.
[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]
Further reading
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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
