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2010): Phylogenetic position of the genus Mesochytrium (Chytridiomycota) based on zoospore ultrastructure and sequences from the 18S and 28S rRNA gene. -Nova Hedwigia 90: 81–94. Abstract: Ultrastructural features and a molecular phylogeny of Mesochytrium penetrans (strain X-10 CALU) based on 18S and 28S rRNA gene sequences were investigated for the...
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... (Figs 10, 13). The veil consists of a thin fibrillar circle around the proximal end of the centriole, with several waved treads passing to the cell surface at sharp angles to the centriole (Fig. 10). It appears that each veil tread corresponds to the centriole doublet (triplet). A general schematic of zoospore ultrastructure is illustrated (Fig. ...
Citations
... In some cases, sequences from clades that were readily recovered with metabarcoding were not detected. The most striking case is Gromochytriales and Mesochytriales, together containing a total of three described species, all of which are obligate parasites (20,69,70). Despite limited described species, Mesochytriales is represented by numerous environmental DNA sequences (20). ...
Environmental DNA analyses of fungal communities typically reveal a much larger diversity than can be ascribed to known species. Much of this hidden diversity lies within undescribed fungal lineages, especially the early diverging fungi (EDF). Although these EDF often represent new lineages even at the phylum level, they have never been cultured, making their morphology and ecology uncertain. One of the methods to characterize these uncultured fungi is a single-cell DNA sequencing approach. In this study, we established a large data set of single-cell sequences of EDF by manually isolating and photographing parasitic fungi on various hosts such as algae, protists, and micro-invertebrates, combined with subsequent long-read sequencing of the ribosomal DNA locus (rDNA). We successfully obtained rDNA sequences of 127 parasitic fungal cells, which clustered into 71 phylogenetic lineages belonging to seven phylum-level clades of EDF: Blastocladiomycota, Chytridiomycota, Aphelidiomycota, Rozellomycota, and three unknown phylum-level clades. Most of our single cells yielded novel sequences distinguished from both described taxa and existing metabarcoding data, indicating an expansive and hidden diversity of parasitic taxa of EDF. We also revealed an unexpected diversity of endobiotic Olpidium -like chytrids and hyper-parasitic lineages. Overall, by combining photographs of parasitic fungi with phylogenetic analyses, we were able to better understand the ecological function and morphology of many of the branches on the fungal tree of life known only from DNA sequences.
IMPORTANCE
Much of the diversity of microbes from natural habitats, such as soil and freshwater, comprise species and lineages that have never been isolated into pure culture. In part, this stems from a bias of culturing in favor of saprotrophic microbes over the myriad symbiotic ones that include parasitic and mutualistic relationships with other taxa. In the present study, we aimed to shed light on the ecological function and morphology of the many undescribed lineages of aquatic fungi by individually isolating and sequencing molecular barcodes from 127 cells of host-associated fungi using single-cell sequencing. By adding these sequences and their photographs into the fungal tree, we were able to understand the morphology of reproductive and vegetative structures of these novel fungi and to provide a hypothesized ecological function for them. These individual host-fungal cells revealed themselves to be complex environments despite their small size; numerous samples were hyper-parasitized with other zoosporic fungal lineages such as Rozellomycota.
... The chytrid-host relationship has been studied mainly in freshwater models, which evaluated the dynamics between chytrids and phytoplankton (Kagami et al., 2014). Chytrid infections have been reported in diatoms (Canter, 1969;Seto & Degawa, 2018), chlorophytes (Karpov et al., 2010;Vélez et al., 2011), cyanobacteria (Agha et al., 2016), and dinoflagellates (Leshem et al., 2016). In marine ecosystems, the few studies conducted on chytrids showed that chytrid biomass correlates positively with phytoplankton (Gutiérrez et al., 2016;Lepère et al., 2016). ...
The interactions of parasitic fungi with their phytoplankton hosts in the marine environment is mostly unknown. In this study, we evaluated the diversity of Chytridiomycota in phytoplankton communities dominated by dinoflagellates at several coastal locations in the NW Mediterranean Sea and demonstrated the most prominent interactions of these parasites with their hosts. The protist community in seawater differed from that in sediment, with the latter characterized by a greater heterogeneity of putative hosts, such as dinoflagellates and diatoms, as well as a chytrid community more diverse in its composition and with a higher relative abundance. Chytrids accounted for 77 amplicon sequence variants, of which 70 were found exclusively among different blooming host species. The relative abundance of chytrids was highest in samples dominated by the dinoflagellate genera Ostreopsis and Alexandrium, clearly indicating the presence of specific chytrid communities. The establishment of parasitoid‐host co‐cultures of chytrids and dinoflagellates allowed the morphological identification and molecular characterization of three species of Chytridiomycota, including Dinomyces arenysensis, as one of the most abundant environmental sequences, and the discovery of two other species not yet described.
... The cp begins near the distal end of the spiral fibre; the true TP must be at this level as in Monoblepharis (Fig. 20B) but no micrograph showed the cp/ TP junction. A 2-gene rDNA tree showed Caulochytrium as a deep isolated branch (Karpov et al. 2010) and a multiprotein tree using 29,255 amino acid positions (Ahrendt et al. 2018) firmly placed it within Chytridiomycota as sister to Rhizoclosmatium, so is closer to Chytridiales than Spizellomycetales [Naranjo-Ortiz and Gabaldón 2019 wrongly said its phylogeny is unstudied; Powell in Adl et al. 2019 correctly put it within Chytridomycetes (as order Caulochytriales) but Wijayawardene et al. 2018 unwisely treated it as a separate phylum]. ...
I thoroughly discuss ciliary transition zone (TZ) evolution, highlighting many overlooked evolutionarily significant ultrastructural details. I establish fundamental principles of TZ ultrastructure and evolution throughout eukaryotes, inferring unrecognised ancestral TZ patterns for Fungi, opisthokonts, and Corticata (i.e., kingdoms Plantae and Chromista). Typical TZs have a dense transitional plate (TP), with a previously overlooked complex lattice as skeleton. I show most eukaryotes have centriole/TZ junction acorn-V filaments (whose ancestral function was arguably supporting central pair microtubule-nucleating sites; I discuss their role in centriole growth). Uniquely simple malawimonad TZs (without TP, simpler acorn) pinpoint the eukaryote tree's root between them and TP-bearers, highlighting novel superclades. I integrate TZ/ciliary evolution with the best multiprotein trees, naming newly recognised major eukaryote clades and revise megaclassification of basal kingdom Protozoa. Recent discovery of non-photosynthetic phagotrophic flagellates with genome-free plastids (Rhodelphis), the sister group to phylum Rhodophyta (red algae), illuminates plant and chromist early evolution. I show previously overlooked marked similarities in cell ultrastructure between Rhodelphis and Picomonas, formerly considered an early diverging chromist. In both a nonagonal tube lies between their TP and an annular septum surrounding their 9+2 ciliary axoneme. Mitochondrial dense condensations and mitochondrion-linked smooth endomembrane cytoplasmic partitioning cisternae further support grouping Picomonadea and Rhodelphea as new plant phylum Pararhoda. As Pararhoda/Rhodophyta form a robust clade on site-heterogeneous multiprotein trees, I group Pararhoda and Rhodophyta as new infrakingdom Rhodaria of Plantae within subkingdom Biliphyta, which also includes Glaucophyta with fundamentally similar TZ, uniquely in eukaryotes. I explain how biliphyte TZs generated viridiplant stellate-structures.
... willei is adjacent to the kinetosome, in contrast to a typical fenestrated cisterna in chytrids belonging to Chytridiales , Rhizophydiales and some other orders, where it closely associates with the plasma membrane at the lateral side of the zoospore. The plant parasitic chytrid Synchytrium macrosporum (Synchytriales), green algal parasite Mesochytrium penetrans (Mesochytriales), and chitinophilic saprotrophic chytrid Arkaya serpentina (Polychytriales) also have the fenestrated cisterna facing the kinetosome (Montecillo et al. 1980, Karpov et al. 2010, Longcore & Simmons 2012. However, in all these species, the fenestrated cisterna is near the kinetosome but separated from it. ...
During the last decade, the classification system of chytrids has dramatically changed based on zoospore ultrastructure and molecular phylogeny. In contrast to well-studied saprotrophic chytrids, most parasitic chytrids have thus far been only morphologically described by light microscopy, hence they hold great potential for filling some of the existing gaps in the current classification of chytrids. The genus Zygorhizidium is characterized by an operculate zoosporangium and a resting spore formed as a result of sexual reproduction in which a male thallus and female thallus fuse via a conjugation tube. All described species of Zygorhizidium are parasites of algae and their taxonomic positions remain to be resolved. Here, we examined morphology, zoospore ultrastructure, host specificity, and molecular phylogeny of seven cultures of Zygorhizidium spp. Based on thallus morphology and host specificity, one culture was identified as Z. willei parasitic on zygnematophycean green algae, whereas the others were identified as parasites of diatoms, Z. asterionellae on Asterionella, Z. melosirae on Aulacoseira, and Z. planktonicum on Ulnaria (formerly Synedra). According to phylogenetic analysis, Zygorhizidium was separated into two distinct order-level novel lineages; one lineage was composed singly of Z. willei, which is the type species of the genus, and the other included the three species of diatom parasites. Zoospore ultrastructural observation revealed that the two lineages can be distinguished from each other and both possess unique characters among the known orders within the Chytridiomycetes. Based on these results, we accommodate the three diatom parasites, Z. asterionellae, Z. melosirae, and Z. planktonicum in the distinct genus Zygophlyctis, and propose two new orders: Zygorhizidiales and Zygophlyctidales.
... Together these sequences form a new phylogenetic group. Among the described organisms, the closest relative of this group is Mesochytrium penetrans, which was classified in the Chytridiomycetes incertae sedis (Karpov et al. 2010). Meso chytrium penetrans is the only described species of a diverse group of uncultured fungi from soil, freshwater and hydrobiont gut samples collected from temperate zone of Eurasia and North America (Table 2). ...
... Molecular phylogeny places the strain x-51 far from Rhizophy diales, as a sister to 'clade I' -a cluster containing many environmental sequences of the Chytridiomycetes (Lefèvre et al. 2008, Jobard et al. 2012) besides a formally described species Mesochytrium penetrans, which was earlier shown to have a rather isolated position among the Chytridiomycetes (Karpov et al. 2010). The features that distinguish Mesochytrium are the partial penetration of the host cell by the sporangium and a zoospore with a unique ultrastructural organization. ...
... Thus, we have to compare the zoospore structure of strain x-51 with that of M. penetrans. Two strains of M. penetrans (x-10 and x-46 CALU) were studied by electron microscopy, and 18S and 28S rRNA genes were sequenced for x-10 (Gromov et al. 2000, Karpov et al. 2010. Their general organization differs from that of x-51; unlike x-51 the M. penetrans has no ribosomal aggregation, its mitochondrion with MLC is enclosed by ER, a fenestrated cisterna faces the posterior of the cell, and a vacuole is present (Fig. 5b). ...
Molecular phylogenetic analysis of 18S rRNA gene sequences of nearly any species of Chytridiomycota has typically challenged traditional classification and triggered taxonomic revision. This has often led to the establishment of new taxa which, normally, appear well supported by zoospore ultrastructure, which provides diagnostic characters. To construct a meaningful and comprehensive classification of Chytridiomycota, the combination of molecular phylogenies and morphological studies of traditionally defined chytrid species is needed. In this work, we have studied morphological and ultrastructural features based on light and transmission electron microscopy as well as molecular phylogenetic analysis of a parasite (strain X‐124 CCPP ZIN RAS) morphologically similar to Rhizophydium granulosporum living on the yellow‐green alga Tribonema gayanum. Phylogenetic analysis of the 18S rRNA gene sequence of this strain supports that it represents a new genus and species affiliated to the recently established order Gromochytriales. The ultrastructure of X‐124 confirms its phylogenetic position sister to Gromochytrium and serves as the basis for the description of the new genus and species Apiochytrium granulosporum. The 18S rRNA gene of A. granulosporum contains S943 intron carries a homing endonuclease pseudogene.
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... Kochiomyces D.J.S. Barr 1980, Spizellomycetaceae, Spizellomycetales, Spizellomycetes, Chytridiomycota, one species, type: K. dichotomus (Umphlett) D.J.S. Barr, saprobes, USA, see Wakefield et al. (2010;phylogeny), Kirk et al. (2013;genus accepted), Letcher and Powell (2017;phylogeny), cultures and sequences are available. Lacustromyces Longcore 1993, Polychytriaceae, Polychytriales, Polychytriomycetes, Chytridiomycota, one species, type: L. hiemalis Longcore, from soil, USA, see Karpov et al. (2010;relationship with Mesochytrium), Kirk et al. (2013;genus accepted), cultures and sequences are available. Loborhiza A.M. Hanson 1944, Chytridiomycetes genera incertae sedis, Chytridiomycota, one species, type: L. metzneri A.M. Hanson, saprobes, see Kirk et al. (2013; genus accepted), cultures and sequences are unavailable. ...
... Maunachytrium D.R. Simmons 2009, Lobulomycetaceae, Lobulomycetales, Lobulomycetes, Chytridiomycota, one species, type: M. keaense D.R. Simmons, from soil, Hawaii, see Simmons et al. (2009taxonomy, phylogeny), cultures and sequences are available. Megachytrium Sparrow 1931, Chytridiomycetes genera incertae sedis, Chytridiomycota, one species, type: M. westonii Sparrow, saprobes, North America, see Kirk et al. (2013;genus Karpov et al. (2010Karpov et al. ( , 2014phylogeny), cultures and sequences are available. Micromyces P.A. Dang. ...
Compared to the higher fungi (Dikarya), taxonomic and evolutionary studies on the basal clades of fungi are fewer in number. Thus, the generic boundaries and higher ranks in the basal clades of fungi are poorly known. Recent DNA based taxonomic studies have provided reliable and accurate information. It is therefore necessary to compile all available information since basal clades genera lack updated checklists or outlines. Recently, Tedersoo et al. (MycoKeys 13:1–20, 2016) accepted Aphelidiomycota and Rozellomycota in Fungal clade. Thus, we regard both these phyla as members in Kingdom Fungi. We accept 16 phyla in basal clades viz. Aphelidiomycota, Basidiobolomycota, Blastocladiomycota, Calcarisporiellomycota, Caulochytriomycota, Chytridiomycota, Entomophthoromycota, Glomeromycota, Kickxellomycota, Monoblepharomycota, Mortierellomycota, Mucoromycota, Neocallimastigomycota, Olpidiomycota, Rozellomycota and Zoopagomycota. Thus, 611 genera in 153 families, 43 orders and 18 classes are provided with details of classification, synonyms, life modes, distribution, recent literature and genomic data. Moreover, Catenariaceae Couch is proposed to be conserved, Cladochytriales Mozl.-Standr. is emended and the family Nephridiophagaceae is introduced.
... Recent taxonomic studies on chytrids based on molecular phylogeny and zoospore ultrastructure were conducted primarily using isolates of saprotrophic chytrids (Letcher et al., 2008;Simmons, 2011;V elez et al., 2013). However, there are a large number of described species of parasitic chytrids (Sparrow, 1960) but only a few parasitic chytrid species have been sequenced and their phylogenetic positions clarified (Karpov et al., , 2010Küpper, Maier, Müller, Loiseaux-de Goer, & Guillou, 2006;Lepelletier et al., 2014;Seto, Kagami, & Degawa, 2017;Sønstebø & Rohrlack, 2011;V elez et al., 2011). Karpov et al. (2014) examined the molecular phylogeny and zoospore ultrastructure of two parasitic chytrids on algae and proposed two new orders: Gromochytriales and Mesochytriales. ...
... Generally, parasitic chytrids are considered to be host specific, but host range differs according to the taxa (Ibelings et al., 2004;Sparrow, 1960). Some chytrids are highly host-specific at species level (Canter & Jaworski, 1978;Karpov, Letcher, Mamkaeva, & Mamkaeva, 2010). In contrast, other chytrids can infect a broader range of hosts (Gromov, Plujusch, & Mamkaeva, 1999;Lepelletier et al., 2014). ...
During the last decade, our concept of chytrid systematics has dramatically changed based on molecular phylogeny and zoospore ultrastructure. In contrast with well-studied saprotrophic chytrids, only a few obligate parasitic chytrids have been investigated with modern methods. Here, we investigate the novel chytrid culture KS93 that is parasitic on the diatom Aulacoseira granulata. Thallus morphology of KS93 was characterized by a spherical, stalked zoosporangium with a single, apical inoperculate discharge pore and zoospore discharge as a mass in a vesicle. A cross-inoculation experiment revealed that the infection of KS93 was specific to A. granulata. Zoospores of KS93 possessed the characters of the Group I type zoospore of the Chytriomycetaceae in the Chytridiales, but does not appear to have a paracrystalline inclusion. Additionally, KS93 also possessed a globule-type KAS (kinetosome-associated structure), first reported here for members of Chytriomycetaceae. In our molecular phylogeny, KS93 was placed in the basal position of the Chytriomycetaceae and was distinguished from any known species in the family. Morphological features of KS93 were distinct from those of any other taxa in the Chytriomycetaceae and from any described chytrids. Based on these results, we describe this chytrid as Pendulichytrium sphaericum gen. et sp. nov. in the family Chytriomycetaceae.
... The Rhizophydiales, Lobulomycetales, Cladochytriales, Polychytriales, and Synchytriales have been separated from the Chytridiales. The Mesochytriales and Gromochytriales are newly discovered sister lineages which include no previously described chytrid species 8. Gromochytriales (Karpov et al. 2014a) 9. Mesochytriales (Karpov et al. 2010(Karpov et al. , 2014a 10. Synchytriales (Lange and Olson 1978b;Longcore et al. 2016;Montecillo et al. 1980;Smith et al. 2014) Several species of chytrids have been examined ultrastructurally, but their molecular phylogenetic placement is uncertain, and these remain as incertae sedis: Caulochytrium (Powell 1981b); Entophlyctis apiculate (Shin et al. 2001); Polyphagus euglenae (Powell 1981a); Rhizophydium planktonicum (Beakes et al. 1993); and Zygorhizidium (Beakes et al. 1988). ...
The Chytridiomycota is a group of fungi characterized by the production of zoospores with a single posteriorly directed flagellum. The thalli of these fungi are typically microscopic and varied. The advent of molecular phylogenetics combined with analyses of zoospore ultrastructural characters has transformed our understanding of the relationship of these fungi and has revealed greater genetic diversity than expected. What was once the single order Chytridiales is now ten monophyletic orders. Rozella, Olpidium, and the Blastocladiomycota, organisms once thought to be within the Chytridiomycota, diverge in separate lineages and are no longer included in the Chytridiomycota. The Neocallimastigomycota are sister to Chytridiomycota, but they are distinct in their zoospore ultrastructure, behavior of nuclear envelope during mitosis, and specific adaptation as anaerobes to digestive systems of herbivores. Molecular characterization of environmental samples demonstrates that zoosporic fungi are widespread and can survive in a range of habitats, from oceans to freshwater and even harsh environments including under artic snow or in exposed soils in alpine regions. The importance of these organisms as parasites, saprotrophs of refractory materials, and components in food webs is discussed. Ways to collect, culture, and characterize these organisms are highlighted. Current classification based on molecular and ultrastructural analyses is described.
... eschweizerbart_xxx D.R. Simmons & Longcore) . As provisionally placed in Spizellomycetales (Barr 1980), Rhizophlyctis A.Fisch., Rozella Cornu, Olpidium (A.Braun) J.Schröt., and Caulochytrium Voos & L.S.Olive are now excluded (James et al. 2006, James & Berbee 2011, Karpov et al. 2010. ...
Spizellomycetaceae is a family of soil-inhabiting chytrids that presently contains four genera – Spizellomyces, Triparticalcar, Kochiomyces, and Gaertneriomyces – that were delineated on the basis of unique zoospore ultrastructure. A recent molecular phylogeny of Spizellomycetaceae revealed Triparticalcar and Kochiomyces to be monophyletic, Spizellomyces and Gaertneriomyces to occur in multiple lineages, and several lineages of unidentified strains. To define better the uncharacterized strains, here we closely replicate that recent phylogeny and incorporate several new strains. Molecular phylogenetic and ultrastructural analyses revealed three lineages with unique zoospore ultrastructure, which we delineate as three new genera Brevicalcar, Bulbosomyces, and Gallinipes. Our results demonstrate greater molecular and ultrastructural diversity in Spizellomycetaceae than was previously realized and reveal ultrastructural features not exhibited in other taxa in Chytridiomycota. © 2017 J. Cramer in Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany.
... Recent taxonomic studies on chytrids based on molecular phylogenies and zoospore ultrastructures were mainly conducted using isolates of saprophytic chytrids (Letcher et al. 2008;Simmons 2011). Although there are a large number of described species of parasitic chytrids (Sparrow 1960), only a few parasitic chytrid species have been sequenced and their phylogenetic positions clarified (Karpov et al. 2010K€ upper et al. 2006;Lepelletier et al. 2014;V elez et al. 2011). Some chytrids that are parasitic on algae were found to be closely related to the environmental sequences of uncultured chytrids, and have sometimes been classified into novel clades (Ishida et al. 2015;Karpov et al. 2014). ...
Chytrids are true fungi that reproduce with posteriorly uniflagellate zoospores. In the last decade, environmental DNA surveys revealed a large number of uncultured chytrids as well as undescribed order-level novel clades in Chytridiomycota. Although many species have been morphologically described, only some DNA sequence data of parasitic chytrids are available from the database. We herein discuss five cultures of parasitic chytrids on diatoms Aulacoseira spp. and Asterionella formosa. In order to identify the chytrids examined, thallus morphologies were observed using light microscopy. We also conducted a phylogenetic analysis using 18S, 5.8S, and 28S rDNA sequences to obtain their phylogenetic positions. Based on their morphological characteristics, two cultures parasitic on As. formosa were identified as Rhizophydium planktonicum and Zygorhizidium planktonicum. The other three cultures infecting Aulacoseira spp. (two on Au. ambigua and the other on Au. granulata) were regarded as Zygorhizidium aff. melosirae. The results of the molecular phylogenetic analysis revealed that R. planktonicum belonged to the known order Chytridiales, while the two species of Zygorhizidium were placed in a novel clade that was previously reported as an undescribed clade composed of only the environmental sequences of uncultured chytrids. This article is protected by copyright. All rights reserved.
