Anabaena is a
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of
filament-In physics and electrical engineering:* Electrical filament* Current filament* Filament propagation, diffractionless propagation of a light beam* Hot cathode, a filament in a vacuum tube that emits electrons-In astronomy:* Galaxy filament...
ous
cyanobacteriaCyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria = blue)...
, or blue-green
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in...
, found as
planktonPlankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification...
. It is known for its nitrogen fixing abilities, and they form
symbioticThe term symbosis commonly describes close and often long-term interactions between different biological species...
relationships with certain plants, such as the
mosquito fernAzolla is a genus of seven species of aquatic ferns, the only genus in the family Azollaceae...
. They are one of four genera of cyanobacteria that produce
neurotoxinA neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels.Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
s, 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
grazingGrazing generally describes a type of predation in which an herbivore feeds on plants , and also on other multicellular autotrophs...
pressure.
A
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
sequencingIn genetics and biochemistry, sequencing means to determine the primary structure of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succinctly summarizes much of the atomic-level structure of the sequenced molecule.-DNA sequencing:DNA...
project was undertaken in 1999, which mapped the complete
genomeIn modern molecular biology the genome refers to all of its hereditary information encoded in DNA .The genome includes both the genes and the non-coding sequences of the DNA. The term was adapted in 1920 by Hans Winkler, Professor of Botany at the University of Hamburg, Germany...
of
Anabaena, which is 7.2 million base pairs long.
Anabaena is a
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of
filament-In physics and electrical engineering:* Electrical filament* Current filament* Filament propagation, diffractionless propagation of a light beam* Hot cathode, a filament in a vacuum tube that emits electrons-In astronomy:* Galaxy filament...
ous
cyanobacteriaCyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria = blue)...
, or blue-green
algaeAlgae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in...
, found as
planktonPlankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification...
. It is known for its nitrogen fixing abilities, and they form
symbioticThe term symbosis commonly describes close and often long-term interactions between different biological species...
relationships with certain plants, such as the
mosquito fernAzolla is a genus of seven species of aquatic ferns, the only genus in the family Azollaceae...
. They are one of four genera of cyanobacteria that produce
neurotoxinA neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels.Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
s, 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
grazingGrazing generally describes a type of predation in which an herbivore feeds on plants , and also on other multicellular autotrophs...
pressure.
A
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information...
sequencingIn genetics and biochemistry, sequencing means to determine the primary structure of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succinctly summarizes much of the atomic-level structure of the sequenced molecule.-DNA sequencing:DNA...
project was undertaken in 1999, which mapped the complete
genomeIn modern molecular biology the genome refers to all of its hereditary information encoded in DNA .The genome includes both the genes and the non-coding sequences of the DNA. The term was adapted in 1920 by Hans Winkler, Professor of Botany at the University of Hamburg, Germany...
of
Anabaena, which is 7.2 million base pairs long. The study focused on
heterocystHeterocysts are specialized nitrogen-fixing cells formed by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale and Anabaena sperica, during nitrogen starvation. They fix nitrogen from dinitrogen in the air using the enzyme nitrogenase, in order to provide the...
s, which convert
nitrogenNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
into
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
. Certain species of
Anabaena have been used on
riceRice is the seed of a monocot plant Oryza sativa, of the grass family . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East, South, Southeast Asia, the Middle East, Latin America, and the West Indies...
paddy fieldA paddy field is a flooded parcel of arable land used for growing rice and other semiaquatic crops. Rice can also be grown in dry-fields, but from the twentieth century paddy field agriculture became the dominant form of growing rice...
s, proving to be an effective natural
fertilizerFertilizers are chemical compounds applied to promote plant and fruit growth. Fertilizers are usually applied either through the soil or by foliar feeding...
.
Species
- Anabaena aequalis
- Anabaena affinis
- Anabaena angstumalis
- Anabaena angstumalis angstumalis
- Anabaena angstumalis marchica
- Anabaena aphanizomendoides
- Anabaena azollae
- Anabaena bornetiana
- Anabaena catenula
- Anabaena circinalis
Anabaena circinalis is species of cyanobacteria of genus Anabaena. It is capable of producing saxitoxin, which is poisonous to both human and animals....
- Anabaena confervoides
- Anabaena constricta
- Anabaena cyanobacterium
- Anabaena cycadeae
- Anabaena cylindrica
- Anabaena echinispora
- Anabaena felisii
- Anabaena flosaquae
- Anabaena flosaquae flosaquae
- Anabaena flosaquae minor
- Anabaena flosaquae treleasei
- Anabaena helicoidea
- Anabaena inaequalis
- Anabaena lapponica
- Anabaena laxa
- Anabaena lemmermannii
- Anabaena levanderi
- Anabaena limnetica
- Anabaena macrospora
- Anabaena macrospora macrospora
- Anabaena macrospora robusta
- Anabaena monticulosa
- Anabaena nostoc
- Anabaena oscillarioides
- Anabaena planctonica
- Anabaena raciborskii
- Anabaena scheremetievi
- Anabaena sphaerica
- Anabaena spiroides
- Anabaena spiroides crassa
- Anabaena spiroides spiroides
- Anabaena subcylindrica
- Anabaena torulosa
- Anabaena unispora
- Anabaena variabilis
- Anabaena verrucosa
- Anabaena viguieri
- Anabaena wisconsinense
- Anabaena zierlingii
Nitrogen Fixation by Anabaena
Under nitrogen-limiting conditions, vegetative cells differentiate into heterocysts at semi-regular intervals along the filaments. Heterocysts are cells that are terminally specialized for
nitrogen fixationNitrogen fixation usually refers to the biological process by which nitrogen in the atmosphere is converted into ammonia. This process is essential for life because fixed nitrogen is required to biosynthesize a basic building block of life, e.g. nucleotides for DNA and amino acids for proteins...
. The interior of these cells is microoxic 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.
NitrogenaseNitrogenase is the enzyme used by some organisms to fix atmospheric nitrogen gas . It is the only known family of enzymes which accomplishes this process. Dinitrogen is quite inert because of the strength of its N-N triple bond...
, sequestered within these cells, transforms dinitrogen into
ammoniumThe ammonium cation is a positively charged polyatomic cation of the chemical formula NH. It has a formula weight of 18.05 and is formed by the protonation of ammonia...
at the expense of ATP and reductant—both generated by carbohydrate metabolism, a process that is supplemented, in the light, by the activity of PS I. Carbohydrate, probably in the form of sucrose, 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 acidAmino acids are molecules containing an amine group, a carboxylic acid group and one of the twenty R-groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H
2NCHRCOOH, where R is an organic substituent...
s.
External links