Cryptomycota ('hidden fungi'), Rozellida, or Rozellomycota are a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

of micro-organisms that are either

fungi A fungus ( : fungi or funguses) 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 a kingdom, separately fr ...

or a

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to fungi. They differ from classical fungi in that they lack

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

ous cell walls at any

trophic Trophic, from Ancient Greek τροφικός (''trophikos'') "pertaining to food or nourishment", may refer to: * Trophic cascade * Trophic coherence * Trophic egg * Trophic function * Trophic hormone * Trophic level index * Trophic level ...

stage in their lifecycle, as reported by Jones and colleagues in 2011. Despite their unconventional feeding habits, chitin has been observed in the inner layer of

resting spore A resting spore is a resistant cell, used to survive adverse environmental conditions. Resting spore is a term commonly applied to both diatoms and fungi. In fungi A resting spore can be a spore created by fungi which is thickly encysted (has a ...

s, and in immature resting spores for some species of ''

Rozella ''Rozella'' is a fungal genus of obligate endoparasites of a variety of hosts, including Oomycota, Chytridiomycota, and Blastocladiomycota. ''Rozella'' was circumscribed by French mycologist Marie Maxime Cornu in 1872. Considered one of the ear ...

'', as indicated with calcofluor-white stain as well as the presence of a fungal-specific

chitin synthase In enzymology, a chitin synthase () is an enzyme that catalyzes the chemical reaction :UDP-N-acetyl-D-glucosamine + ,4-(N-acetyl-beta-D-glucosaminyl) \rightleftharpoons UDP + ,4-(N-acetyl-beta-D-glucosaminyl)+1 Thus, the two substrates of this ...

gene. Rozellida were first detected as

DNA sequence DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. T ...

s retrieved from a freshwater laboratory enclosure.

Phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

analysis of these sequences formed a unique terminal clade of then unknown affiliation provisionally called after the first clone in the clade: LKM11. The only formally described genus in the clade is ''Rozella'', which was previously considered a

chytrid Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zoöspores. Chytrid ...

. The existence of related organisms was known from

environmental DNA Environmental DNA or eDNA is DNA that is collected from a variety of environmental samples such as soil, seawater, snow or air, rather than directly sampled from an individual organism. As various organisms interact with the environment, DNA ...

sequences. Additional members of the group were isolated in 2011 by a team led by Thomas Richards, from the

Natural History Museum in London The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum an ...

, and also an evolutionary geneticist at the

University of Exeter , mottoeng = "We Follow the Light" , established = 1838 - St Luke's College1855 - Exeter School of Art1863 - Exeter School of Science 1955 - University of Exeter (received royal charter) , type = Public , ...

, UK. The team used DNA techniques to disclose the existence of unknown genetic material dredged from the university pond. Once they had a few unknown sequences they fluorescently labeled small DNA sequences and let them bind to the matching DNA in the whole sample ( fluorescence in situ hybridization). Under

fluorescence microscopy A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. "Fluorescence microscop ...

, they could see that the possessor cells were

ovoid An oval () is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas ( projective geometry, technical drawing, etc.) it is given a more precise definition, which may include either o ...

in shape and 3–5

micrometre The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American and British English spelling differences# ...

s across. They then established that the cryptomycota were present in other samples taken from further freshwater environments, soils and marine sediments. The common characteristic of the clade members is that they lack the chitinous

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...

s present in almost all previously discovered fungi (including

microsporidia Microsporidia are a group of spore-forming unicellular parasites. These spores contain an extrusion apparatus that has a coiled polar tube ending in an anchoring disc at the apical part of the spore. They were once considered protozoans or pr ...

) and which are a major feature of the kingdom. Without the chitin the cryptomycota can be

phagotrophic Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is c ...

parasites that feed by attaching to, engulfing, or living inside other cells. Most known fungi feed by osmotrophy—taking in nutrients from outside the cell.

Taxonomy

* Phylum Rozellomycota ** Class Rozellidea Cavalier-Smith 2013 s.s. *** Order Rozellida Cavalier-Smith 2013 s.s. **** Genus '' Mitosporidium'' Haag et al. 2014 **** Genus '' Morellospora'' Corsaro et al. 2020 **** Genus ''

Nucleophaga Nucleophaga is a genus of eukaryotic microorganisms that are internal parasites of amoeba, flagellates, and ciliates. Morphology and life cycle ''Nucleophaga'' grows within the nucleus of its host cell. Its spores are ingested by the host and ...

'' Dangeard 1895 **** Genus '' Paramicrosporidium'' Corsaro et al. 2014 **** Genus ''

'' Cornu 1872

References

{{Taxonbar, from=Q1142300 Opisthokont orders Holomycota