Nostocaceae
Encyclopedia
The Nostocaceae is a family of cyanobacteria that forms filament
-shaped colonies
enclosed in mucus
or a gelatinous sheath. Some genera
in this family are found primarily in fresh water (such as Nostoc
), while others are found primarily in salt water (such as Nodularia
). Other genera (e.g. Anabaena
) may be found in both fresh and salt water.
Like other cyanobacteria, these bacteria sometimes contain photosynthetic pigment
s in their cytoplasm to perform photosynthesis
. The particular pigments they contain gives the cells a bluish-green color.
Species of the Nostocaceae are particularly known for their nitrogen fixing
abilities, and they form symbiotic
relationships with certain plant
s, such as the mosquito fern
, cycad
s, and hornwort
s. The cyanobacteria provides nitrogen to its host. Certain species of Anabaena have been used on rice paddy fields. Mosquito ferns carrying the cyanobacteria grow on the water in the fields during the growing season. They and the nitrogen they contain are then plowed into the soil following the harvest, which has proved to be an effective natural fertilizer.
The family Nostocaceae belongs to the order Nostocales
. Members of the family can be distinguished from those in other families by their (1) unbranched filaments of cells arranged end-to-end, and (2) development of heterocyst
s among the cells of the filaments.
Filament
-In physics and electrical engineering:* An electrical filament used to emit light in an Incandescent light bulb* Similarly, a thin heating element* Current filament* Filament propagation, diffractionless propagation of a light beam...
-shaped colonies
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
enclosed in mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
or a gelatinous sheath. Some genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
in this family are found primarily in fresh water (such as Nostoc
Nostoc
Nostoc is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells in a gelatinous sheath.The name "Nostoc" was invented by Paracelsus...
), while others are found primarily in salt water (such as Nodularia
Nodularia
Nodularia is a genus of filamentous nitrogen-fixing cyanobacteria, or blue-green algae. They occur mainly in brackish or salinic waters, such as the hypersaline Makgadikgadi Pans, the Peel-Harvey Estuary in Western Australia or the Baltic Sea. Nodularia cells occasionally form heavy algal blooms...
). Other genera (e.g. Anabaena
Anabaena
Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its 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...
) may be found in both fresh and salt water.
Like other cyanobacteria, these bacteria sometimes contain photosynthetic pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
s in their cytoplasm to perform photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. The particular pigments they contain gives the cells a bluish-green color.
Species of the Nostocaceae are particularly known for their nitrogen fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
abilities, and they form symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
relationships with certain plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, such as the mosquito fern
Mosquito fern
Azolla is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, looking nothing like conventional ferns but more resembling duckweed or some mosses.-Selected species:Azolla caroliniana Willd. [ Poss. synon...
, cycad
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s, and hornwort
Hornwort
Hornworts are a group of bryophytes, or non-vascular plants, comprising the division Anthocerotophyta. The common name refers to the elongated horn-like structure, which is the sporophyte. The flattened, green plant body of a hornwort is the gametophyte plant.Hornworts may be found worldwide,...
s. The cyanobacteria provides nitrogen to its host. Certain species of Anabaena have been used on rice paddy fields. Mosquito ferns carrying the cyanobacteria grow on the water in the fields during the growing season. They and the nitrogen they contain are then plowed into the soil following the harvest, which has proved to be an effective natural fertilizer.
The family Nostocaceae belongs to the order Nostocales
Nostocales
The Nostocales order contains most of the species of cyanobacteria. It includes filamentous forms, both simple or branched, and both those occurring as single strands or multiple strands within a sheath. Some but not all members show a decrease in width from the base...
. Members of the family can be distinguished from those in other families by their (1) unbranched filaments of cells arranged end-to-end, and (2) development of heterocyst
Heterocyst
Heterocysts are specialized nitrogen-fixing cells formed by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale and Anabaena sphaerica, during nitrogen starvation. They fix nitrogen from dinitrogen in the air using the enzyme nitrogenase, in order to provide the...
s among the cells of the filaments.
Sources
- Bold, Harold C., Alexopoulos, Constantine J., & Delevoryas, Theodore. (1987). Morphology of Plants and Fungi (5th ed.). New York: Harper & Row. ISBN 0-06-040839-1.
- Drouet, Francis. (1973). Revision of the Nostocaceae with Cylindrical Trichomes (formerly Scytonemataceae and Rivulariaceae). New York: Hafner Press. ISBN 0028440609
- Drouet, Francis. (1981). Revision of the Stigonemataceae with a Summary of the Classification of the Blue-green Algae. Vaduz: J. Cramer. Nova Hedwigia: Heft 66.