Neocallimastigomycota
Encyclopedia
Neocallimastigomycota is a phylum
of anaerobic
fungi, found in the digestive tracts of herbivores. It encompasses only one family
.
of the sheep
. Although the cells were first believed to be flagellate
s, it has since been shown that they are fungi related to the core chytrids. Prior to this, the microbial
population of the rumen was believed to consist only of bacteria
and protozoa
. Since their discovery they have been isolated from the digestive
tracts of over 50 herbivore
s, including ruminant
and non-ruminant mammals and herbivorous reptile
s.
s that bears a kinetosome but lacks the nonflagellated centriole
known in most chytrids, and have been known to utilize horizontal gene transfer
in their development of xylanase
(from bacteria) and other glucanases. The nuclear envelopes of their cells
are notable for remaining intact throughout mitosis
.
s to oxidize NADH to NAD+, they release H2
as a product.
. Correction of these names is mandated by the International Code of Botanical Nomenclature, Art. 60. The corrected spelling is used by Index Fungorum. Both spellings occur in the literature and on the WWW as a result of the spelling in the original publication.
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
of anaerobic
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
fungi, found in the digestive tracts of herbivores. It encompasses only one family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
.
Discovery
The fungi in Neocallimastigomycota were first described by Orpin in 1975, based on motile cells present in the rumenRumen
The rumen, also known as a paunch, forms the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. It serves as the primary site for microbial fermentation of ingested feed...
of the sheep
Domestic sheep
Sheep are quadrupedal, ruminant mammals typically kept as livestock. Like all ruminants, sheep are members of the order Artiodactyla, the even-toed ungulates. Although the name "sheep" applies to many species in the genus Ovis, in everyday usage it almost always refers to Ovis aries...
. Although the cells were first believed to be flagellate
Flagellate
Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, some gymnosperms and other closely related plants...
s, it has since been shown that they are fungi related to the core chytrids. Prior to this, the microbial
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
population of the rumen was believed to consist only of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
. Since their discovery they have been isolated from the digestive
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
tracts of over 50 herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s, including ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
and non-ruminant mammals and herbivorous reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s.
Reproduction and growth
These fungi reproduce in the stomach of ruminants through the use of zoosporeZoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some algae, bacteria and fungi to propagate themselves.-Flagella:...
s that bears a kinetosome but lacks the nonflagellated centriole
Centriole
A Centriole is a barrel-shaped cell structure found in most animal eukaryotic cells, though it is absent in higher plants and most fungi. The walls of each centriole are usually composed of nine triplets of microtubules...
known in most chytrids, and have been known to utilize horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
in their development of xylanase
Xylanase
Xylanase is the name given to a class of enzymes which degrade the linear polysaccharide beta-1,4-xylan into xylose, thus breaking down hemicellulose, one of the major components of plant cell walls....
(from bacteria) and other glucanases. The nuclear envelopes of their cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
are notable for remaining intact throughout mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
.
Metabolism
Neocallimastigomycota lack mitochondria. Using hydrogenosomeHydrogenosome
A hydrogenosome is a membrane-enclosed organelle of some anaerobic ciliates, trichomonads and fungi. The hydrogenosomes of trichomonads produce molecular hydrogen, acetate, carbon dioxide and ATP by the combined actions of pyruvate:ferredoxin oxido-reductase, hydrogenase, acetate:succinate CoA...
s to oxidize NADH to NAD+, they release H2
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
as a product.
Polysaccharide-degrading activity
Neocallimastigomycota play an essential role in fibre-digestion in their host species. They are present in large numbers in the digestive tracts of animals which are fed on high fibre diets. The polysaccharide degrading enzymes produced by anaerobic fungi can hydrolyse the most recalcitrant plant polymers and can degrade unlignified plant cell walls entirely. The polysaccharide degrading enzymes are organised into a multiprotein complex, similar to the bacterial cellulosomeSpelling of name
The Greek termination, "-mastix", referring to "whips", i.e. the many flagella on these fungi, is changed to "-mastig-" when combined with additional terminations in Latinized names. The family name Neocallimastigaceae was originally incorrectly published as "Neocallimasticaceae" by the publishing authors which led to the coinage of the misspelled, hence incorrect "Neocallimasticales", an easily forgiven error considering that other "-ix" endings such as Salix goes to SalicaceaeSalicaceae
Salicaceae are a family of flowering plants. Recent genetic studies summarized by the Angiosperm Phylogeny Group has greatly expanded the circumscription of the family to contain 55 genera....
. Correction of these names is mandated by the International Code of Botanical Nomenclature, Art. 60. The corrected spelling is used by Index Fungorum. Both spellings occur in the literature and on the WWW as a result of the spelling in the original publication.