Neocallimastigomycota

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Neocallimastigomycota
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Neocallimastigomycota
M.J. Powell 2007 [1]
Class: Neocallimastigomycetes
M.J. Powell 2007 [1]
Order: Neocallimastigales
J.L. Li, I.B. Heath & L. Packer [2]
Family: Neocallimastigaceae
Type genus
Neocallimastix
(I.B. Heath 1983) Vavra & Joyon
Genera

Aestipascuomyces
Agriosomyces
Aklioshbomyces
Anaeromyces
Buwchfawromyces
Caecomyces
Capellomyces
Cyllamyces
Feramyces
Ghazallomyces
Liebetanzomyces
Joblinomyces
Khoyollomyces
Neocallimastix
Oontomyces
Orpinomyces
Paucimyces
Pecoramyces
Piromyces
Tahromyces

Contents

Neocallimastigomycota is a phylum containing anaerobic fungi, which are symbionts found in the digestive tracts of larger herbivores. Anaerobic fungi were originally placed within phylum Chytridiomycota, within Order Neocallimastigales but later raised to phylum level, [3] a decision upheld by later phylogenetic reconstructions. [4] It encompasses only one family. [3]

Discovery

The fungi in Neocallimastigomycota were first recognised as fungi by Orpin in 1975, [5] based on motile cells present in the rumen of sheep. Their zoospores had been observed much earlier but were believed to be flagellate protists, but Orpin demonstrated that they possessed a chitin cell wall. [6] 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 herbivores, including ruminant and non-ruminant (hindgut-fermenting) mammals and herbivorous reptiles. [7] [8]

Neocallimastigomycota have also been found in humans. [9]

Circumscription

Reproduction and growth

These fungi reproduce in the rumen of ruminants through the formation of zoospores which are released from sporangia. These zoospores bear a kinetosome but lack the nonflagellated centriole known in most chytrids, [1] and have been known to utilize horizontal gene transfer in their development of xylanase (from bacteria) and other glucanases. [10]

The nuclear envelopes of their cells are notable for remaining intact throughout mitosis. [1] Sexual reproduction has not been observed in anaerobic fungi. However, they are known to be able to survive for many months in aerobic environments, [11] a factor which is important in the colonisation of new hosts. In Anaeromyces, the presence of putative resting spores has been observed [12] but the way in which these are formed and germinate remains unknown.

Metabolism

Neocallimastigomycota lack mitochondria but instead contain hydrogenosomes in which the oxidation of NADH to NAD+, leading to formation of H2. [10]

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. [13] The polysaccharide degrading enzymes produced by anaerobic fungi can hydrolyse the most recalcitrant plant polymers and can degrade unlignified plant cell walls entirely. [14] [15] Orpinomyces sp. exhibited the capacity of xylanase, CMCase, lichenase, amylase, β-xylosidase, β-glucosidase, α-Larabinofuranosidase and minor amounts of β-cellobiosidase production by utilizing avicel as the sole energy source. [16] The polysaccharide degrading enzymes are organised into a multiprotein complex, similar to the bacterial cellulosome. [17]

Spelling 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. [18] 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 Salicaceae. Correction of these names is mandated by the International Code of Botanical Nomenclature, Art. 60. The corrected spelling is used by Index Fungorum. [19] Both spellings occur in the literature and on the WWW as a result of the spelling in the original publication.

Related Research Articles

<span class="mw-page-title-main">Chytridiomycota</span> Division of fungi

Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek χυτρίδιον, meaning "little pot", describing the structure containing unreleased zoospores. Chytrids are one of the earliest diverging fungal lineages, and their membership in kingdom Fungi is demonstrated with chitin cell walls, a posterior whiplash flagellum, absorptive nutrition, use of glycogen as an energy storage compound, and synthesis of lysine by the α-amino adipic acid (AAA) pathway.

<span class="mw-page-title-main">Ruminant</span> Hoofed herbivorous grazing or browsing mammals

Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process, which takes place in the front part of the digestive system and therefore is called foregut fermentation, typically requires the fermented ingesta to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ruminare, which means "to chew over again".

<span class="mw-page-title-main">Obligate anaerobe</span> Microorganism killed by normal atmospheric levels of oxygen

Obligate anaerobes are microorganisms killed by normal atmospheric concentrations of oxygen (20.95% O2). Oxygen tolerance varies between species, with some species capable of surviving in up to 8% oxygen, while others lose viability in environments with an oxygen concentration greater than 0.5%.

The rumen, also known as a paunch, is the largest stomach compartment in ruminants and the larger part of the reticulorumen, which is the first chamber in the alimentary canal of ruminant animals. The rumen's microbial favoring environment allows it to serve as the primary site for microbial fermentation of ingested feed. The smaller part of the reticulorumen is the reticulum, which is fully continuous with the rumen, but differs from it with regard to the texture of its lining.

<span class="mw-page-title-main">Dikarya</span> Subkingdom of fungi

Dikarya is a subkingdom of Fungi that includes the divisions Ascomycota and Basidiomycota, both of which in general produce dikaryons, may be filamentous or unicellular, but are always without flagella. The Dikarya are most of the so-called "higher fungi", but also include many anamorphic species that would have been classified as molds in historical literature. Phylogenetically the two divisions regularly group together. In a 1998 publication, Thomas Cavalier-Smith referred to this group as the Neomycota.

<span class="mw-page-title-main">Chytridiales</span> Order of fungi

Fungi of the order Chytridiales, like other members of its division, may either have a monocentric thallus or a polycentric rhizomycelium. When the ribosomal genes of members classified in this order were first examined using molecular techniques, it was discovered that the order contained some species that were not related. With the culture and characterization of Chytridium olla, the type species of this order, the limits of the Chytridiales were established. The Chytridiales is now monophyletic and species such as Polychytrium aggregatum, Chytriomyces angularis and Cladochytrium replicatum have been transferred to other orders.

<span class="mw-page-title-main">Monoblepharidomycetes</span> Class of fungi

Members of the Monoblepharidomycetes have a filamentous thallus that is either extensive or simple and unbranched. They frequently have a holdfast at the base. In contrast to other taxa in their phylum, some reproduce using autospores, although many do so through zoospores. Oogamous sexual reproduction may also occur.

<span class="mw-page-title-main">Exobasidiomycetes</span> Class of fungi

The Exobasidiomycetes are a class of fungi sometimes associated with the abnormal outgrowths of plant tissues known as galls. The class includes Exobasidium camelliae Shirai, the camellia leaf gall and Exobasidium vaccinii Erikss, the leaf and flower gall. There are eight orders in the Exobasidiomycetes, including the Ceraceosorales, Doassansiales, Entylomatales, Exobasidiales, Georgefischeriales, Malasseziales, Microstromatales and the Tilletiales. Four of the eight orders include smut fungi. The families Ceraceosoraceae and Malasseziaceae were formally validated in 2009 for the orders Ceraceosorales and Malasseziales, respectively.

<span class="mw-page-title-main">Fungus</span> Biological kingdom, separate from plants and animals

A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the traditional eukaryotic kingdoms, along with Animalia, Plantae and either Protista or Protozoa and Chromista.

In biology, a phylum is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta.

<span class="mw-page-title-main">Kickxellomycotina</span> Subdivision of fungi

Kickxellomycotina is a fungus grouping. In the subkingdom of Zoopagomyceta Benny, 2007.

Neocallimastix is a genus of obligately anaerobic rumen fungi in the family Neocallimastigaceae. A specialised group of chytrids grow in the rumen of herbivorous animals, where they degrade cellulose and thus play a primary role in the complex microbial ecology of the rumen.

Piromyces is a genus of fungi in the family Neocallimastigaceae.

Butyrivibrio is a genus of bacteria in Class Clostridia. Bacteria of this genus are common in the gastrointestinal systems of many animals. Genus Butyrivibrio was first described by Bryant and Small (1956) as anaerobic, butyric acid-producing, curved rods. Butyrivibrio cells are small, typically 0.4 – 0.6 µm by 2 – 5 µm. They are motile, using a single polar or subpolar monotrichous flagellum. They are commonly found singly or in short chains but it is not unusual for them to form long chains. Despite historically being described as Gram-negative, their cell walls contain derivatives of teichoic acid, and electron microscopy indicates that bacteria of this genus have a Gram-positive cell wall type. It is thought that they appear Gram-negative when Gram stained because their cell walls thin to 12 to 18 nm as they reach stationary phase.

<span class="mw-page-title-main">Glucanase</span>

Glucanases are enzymes that break down large polysaccharides via hydrolysis. The product of the hydrolysis reaction is called a glucan, a linear polysaccharide made of up to 1200 glucose monomers, held together with glycosidic bonds. Glucans are abundant in the endosperm cell walls of cereals such as barley, rye, sorghum, rice, and wheat. Glucanases are also referred to as lichenases, hydrolases, glycosidases, glycosyl hydrolases, and/or laminarinases. Many types of glucanases share similar amino acid sequences but vastly different substrates. Of the known endo-glucanases, 1,3-1,4-β-glucanase is considered the most active.

Neocallimastix patriciarum is a species of fungus that lives in the rumen of sheep and other ruminant species. N. patriciarum is an obligate anaerobe and is an important component of the microbial population within the rumen. Only one of a few rumen fungi, this species is interesting and unique within the fungal world. Originally thought to be a flagellate protists, species within the phylum Neocallimastigomycota were first recognized as a fungus by Colin Orpin in 1975 when he demonstrated that they had cell walls of chitin

Methanogens are a group of microorganisms that produce methane as a byproduct of their metabolism. They play an important role in the digestive system of ruminants. The digestive tract of ruminants contains four major parts: rumen, reticulum, omasum and abomasum. The food with saliva first passes to the rumen for breaking into smaller particles and then moves to the reticulum, where the food is broken into further smaller particles. Any indigestible particles are sent back to the rumen for rechewing. The majority of anaerobic microbes assisting the cellulose breakdown occupy the rumen and initiate the fermentation process. The animal absorbs the fatty acids, vitamins and nutrient content on passing the partially digested food from the rumen to the omasum. This decreases the pH level and initiates the release of enzymes for further breakdown of the food which later passes to the abomasum to absorb remaining nutrients before excretion. This process takes about 9–12 hours.

<span class="mw-page-title-main">Saccharomyceta</span> Clade of fungi

Saccharomyceta is a clade of fungi containing Pezizomycotina and Saccharomycotina, or all Ascomycete fungi except Taphrinomycotina according to the 2007 fungal phylogeny "The Mycota: A Comprehensive Treatise on Fungi as Experimental Systems for Basic and Applied Research" and Tedersoo et al. 2018.

<i>Anaeromyces robustus</i> Fungus living in the gut of cows and sheep

Anaeromyces robustus is a fungal microorganism that lives in the gut rumen of many ruminant herbivores such as cows and sheep. Previously thought to be protozoa from their flagellated zoospores, they are biomass degraders and help the animal by breaking down carbohydrates and plant materials from the food the animal ingests. This fungus, therefore, is anaerobic and lives without oxygen. Gut fungi are dramatically outnumbered by other organisms in the microbiome; however, they are important members of the gut microbiome in ruminants and hind-gut fermenters and play a key role in digestion.

Anthony "Tony" Peter John Trinci was a British mycologist, botanist, and microbiologist. He was a leading expert on fungi.

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