Cryptomycota ('hidden fungi'),Rozellida, orRozellomycota are aclade of micro-organisms that are eitherfungi or asister group to fungi. They differ from classical fungi in that they lackchitinous cell walls at anytrophic stage in their lifecycle, as reported by Jones and colleagues in 2011.[2][3] Despite their unconventional phagocytic feeding habits (typical fungi are osmotrophic), chitin has been observed in the inner layer ofresting spores, and in immature resting spores for some species ofRozella, as indicated withcalcofluor-white stain as well as the presence of a fungal-specificchitin synthase gene.[4]
Rozellida were first detected asDNA sequences retrieved from a freshwater laboratory enclosure.Phylogenetic analysis of these sequences formed a unique terminal clade of then unknown affiliation provisionally called after the first clone in the clade:LKM11.[5]
The term "Rozellida" was coined in 2010, as it was found that the formally described genusRozella, previously considered achytrid, is rather close to LKM11 and other newly-discoveredenvironmental DNA sequences.[6]
Additional members of the group were isolated in 2011 by a team led by Thomas Richards, from theNatural History Museum in London, and also an evolutionary geneticist at theUniversity of Exeter, UK. The team usedDNA techniques to disclose the existence of unknown genetic material dredged from the university pond. Once they had a few unknown sequences theyfluorescently labeled small DNA sequences and let them bind to the matching DNA in the whole sample (fluorescence in situ hybridization). Underfluorescence microscopy, they could see that the possessor cells wereovoid in shape and 3–5micrometres across. They then established that the Cryptomycota were present in other samples taken from further freshwater environments, soils and marine sediments.[7][8]
The common characteristic of the clade members known as of 2011 is that they lack the chitinouscell walls present in almost all previously discovered fungi (includingmicrosporidia) and which are a major feature of the kingdom. Without the chitin the Cryptomycota can bephagotrophic parasites that feed by attaching to, engulfing, or living inside other cells. Most known fungi feed byosmotrophy—taking in nutrients from outside the cell.[7]
Despite their unconventional phagocytic feeding habits (typical fungi are osmotrophic), chitin has been observed in the inner layer ofresting spores, and in immature resting spores for some species ofRozella, as indicated withcalcofluor-white stain as well as the presence of a fungal-specificchitin synthase gene.[4]
In the 2010 article where "Rozellida" was proposed, the authors mentioned that some protein-based analyses suggest that Microsporidia could be closely related to Rozellida. Their own SSUrDNA analysis was unsutiable for this purpose, as Microsporidia is known to have very high mutation rates resulting inlong-branch attraction. An rRNA analysis can only be done after there are more sequences, preferably those close related to both "Rozellida" and Microsporidia, to guide the algorithm into finding the true shape of the tree.[6]
An 2014 rDNA analysis by Karpov et al. considers the group, which they now call "Cryptomycota", sister to Microsporidia. The same article lead to the concept ofOpisthosporidia (Aphelid + Cryptomycota + Microsporidia), which as a whole was found in the analysis to be sister to fungi.[9]
Also in 2014, Corsaro et al. discovered two new endonucleoparasites they termedParamicrosporidium. Their SSU rDNA sequences allowed the authors to find that Microsporidia is nested in the Rozellids (which they call "Rozellomycota").[10] In the same year, they discovered a livingNucleophaga amoebae (described in 1895 and previously also considered a chytrid) and sequenced its SSU rDNA, placing it in Rozellomycota.[11] Both of these genera are shown to branch out in the path connectingRozella and Microsporidia. These two genera show morphological features similar to bothRozella and Microsporidia, and as a result provide some explanation for the large difference between the two.
In 2018, Tedersoo et al. performed a large phylogenetic study on fungi and related taxa to establish a new set of high-ranking taxa. Trees were built using SSU rDNA,RPB1 protein, andRPB2 protein. The study once again confirmed that Microsporidia belongs in Rozellomycota.[12] After the 2020Outline of Fungi and fungus-like taxa has accepted the conclusion (and provided an even bigger SSU rDNA tree), it is generally accepted that Microsporidia does, in fact, belong in the Rozellomycota.[13]
There are some unresolved issues in cutting up the phylogeny. The main question is that sinceRozella branches off early in the phylogeny, some authors elect to give the genus a phylum of its own, giving the rest of the tree ("node 1") a separate "Microsporidiomycota" which would also include LKM11. The relatively authoritativeOutline does not divide in such a way,[1] electing to use one phylum ("node 0") like Tedersoo et al. (2018) and Wijayawardene et al. (2018) have done.[13]: 1378–9
The 2020Outline discusses the related issue of expandingMicrosporidia to includeNucleophaga,Paramicrosporidium,Morellospora andMitosporidium (equivalent to "node 1" above) by Bass et al. (2018),[14] though at that timeOpisthosporidia was still thought to be a clade.[13]: 1378–9
There is also the less radical idea of expanding Microsporidia to include the entire clade sister toNucleophaga. TheOutline currently chooses not to,[1] while Corsaro et al. 2020 does and labels the old clade as "classical Microsporidia". The Corsaro idea is labeled as "Microsporidia s.l." in the above.[15]
The broadest node (node 0; RozellomycotaDoweld 2013 as interpreted byOutline) has also been known as:
RozellidaLara et al. 2010 non Cavalier-Smith 2013[12] – does not specify position of Microsporidia due to known issues with long branches, but does mention the possibility of being closely affiliated to it; choice of type sequences implies inclusion given newer data[6]
CryptomycotaJones & Richards 2011[12] – does not address Microsporidia, but choice of type sequences implies inclusion given newer data[2]
RozellomycotaT. James & Berbee 2011[12] – does not specify position of Microsporidia, scope not clearly defined but implied to be the same as CryptomycotaJones & Richards 2011[4]
RozellomycotaD. Corsaro & R. Michel 2014[12] – first synonym to definitely include Microsporidia[11][10]
RozellomycotinaTedersoo et al. 2018 (same publication as above)[12]
The branch leading toRozella ("node 2") is also known as:
RozellaceaeDoweld 2013
SkirgielliaceaeDoweld 2014
RozellalesCorsaro 2022
(Because there are no named representatives of this branch outside ofRozella, the synonyms listed onRozella also apply here)
The following has unsure placement in the tree:
"Rozellomycetes"Tedersoo 2017 – no citation given[citation needed]
RozellidaCavalier-Smith 2013 non Lara et al. 2010 – considered sister to Aphelids, which would suggest "node 0", but also excluding Microsporidia, which is similar to "node 2"[16]
CryptomycotaJones & Richards 2011 em. Karpov & Aleoshin 2014 – considered sister to the Microsporidia, which translates into a paraphyletic position somewhere between "node 0" and "node 2". Microsporidia is described as having "nonmotile walled spore", while Cryptomycota has "opithokont zoospore".[9]
RozellosporidiaKarpov 2017– considered synonymous in;[12] yet does not specify position of Microsporidia, but wording seems to imply an exclusion[17] and mostly reuses the phylogeny of[9]
Class RozellideaCavalier-Smith 2013: Rozellida + Aphelida. This is similar to theOpisthosporidia discussed inRozellomyceta, though again with the exclusion of Microsporidia.[16]
^Jones MD, Forn I, Gadelha C, Egan MJ, Bass D, Massana R, Richards TA (2011). "Discovery of novel intermediate forms redefines the fungal tree of life".Nature.474 (7350):200–3.doi:10.1038/nature09984.PMID21562490.S2CID4412818.
^abcdeCorsaro, Daniele; Walochnik, Julia; Venditti, Danielle; Hauröder, Bärbel; Michel, Rolf (March 2020). "Solving an old enigma: Morellospora saccamoebae gen. nov., sp. nov. (Rozellomycota), a Sphaerita-like parasite of free-living amoebae".Parasitology Research.119 (3):925–934.doi:10.1007/s00436-020-06623-5.PMID32048025.
^abCavalier-Smith, Thomas (May 2013). "Early evolution of eukaryote feeding modes, cell structural diversity, and classification of the protozoan phyla Loukozoa, Sulcozoa, and Choanozoa".European Journal of Protistology.49 (2):115–178.doi:10.1016/j.ejop.2012.06.001.PMID23085100.
