Chytrid Species Research Articles

Infection strategies of different chytrids in a diatom spring bloom

Abstract Diatom blooms are often accompanied by an increase in parasitic chytrids that kill the host cells, which they are infecting, and can contribute to the decline of the bloom. However, host specificity and range of these chytrids are currently poorly understood. Low host specificity would enable the parasites to opportunistically infect any diatom species, while specialisation on infecting specific high‐biomass species could result in high prevalence and rapid spread of infection. We investigated such host–parasite interactions by monitoring the diverse diatom spring bloom in lake Erken using amplicon sequencing. We also performed infection experiments with two different, newly isolated chytrid species and several diatom cultures from the bloom. Chytridiomycota displayed the highest relative abundance of all parasitic lineages and were probably physically attached to larger organisms. Since the chytrids reached maximum abundance shortly after a peak in diatom reads, they were probably infecting these important primary producers. Phylogenetic analyses of the isolated chytrid strains identified them as members of the classes Rhizophydiales and Lobulomycetales. The infection experiments revealed high host specificity in these two chytrids targeting different diatom species. The experimental results supported statistical analyses of the environmental sequencing data, which suggested the presence of two different infection strategies: the most abundant chytrid species were specialised on infecting dominant diatom genera (i.e. Stephanodiscus, Aulacoseira, Asterionella), while rarer chytid species infected a range of less abundant diatoms.

National eDNA-based monitoring of Batrachochytrium dendrobatidis and amphibian species in Norway

Freshwaters represent the most threatened environments with regard to biodiversity loss and, therefore, there is a need for national monitoring programs to effectively document species distribution and evaluate potential risks for vulnerable species. The monitoring of species for effective management practices is, however, challenged by insufficient data acquisition when using traditional methods. Here we present the application of environmental DNA (eDNA) metabarcoding of amphibians in combination with quantitative PCR (qPCR) assays for an invasive pathogenic chytrid species (Batrachochytrium dendrobatidis -Bd), a potential threat to endemic and endangered amphibian species. Statistical comparison of amphibian species detection using either traditional or eDNA-based approaches showed weak correspondence. By tracking the distribution of Bd over three years, we concluded that the risk for amphibian extinction is low since Bd was only detected at five sites where multiple amphibians were present over the sampled years. Our results show that eDNA-based detection can be used for simultaneous monitoring of amphibian diversity and the presence of amphibian pathogens at the national level in order to assess potential species extinction risks and establish effective management practices. As such our study represents suggestions for a national monitoring program based on eDNA.

Coinfection of Chytrid Fungi in Urodeles during an Outbreak of Chytridiomycosis in Spain.

Chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), has had an unprecedented impact on amphibian biodiversity. Although Bd is globally widespread, Bsal is currently spreading, increasing the probability that these pathogens will co-occur in individual amphibians. Interactions among coinfecting parasites can have significant outcomes on disease dynamics and impact and, therefore, may have important consequences for amphibian conservation. We analyzed the patterns of Bd-Bsal coinfections in two species of free-ranging urodeles during an outbreak of chytridiomycosis in Spain. Our goals were to assess 1) the probability of co-occurrence of both chytrid species and 2) the correlation of pathogen loads in coinfected hosts. We detected coinfections in 81.58% of Triturus marmoratus (n=38) and in 18.75% of Ichthyosaura alpestris (n=16). Histopathologic lesions of chytridiomycosis were observed only in T. marmoratus. Our results demonstrate a positive relationship between Bd and Bsal loads in T. marmoratus, whereas the co-occurrence analysis showed a random association among pathogens in both urodele species. Overall, we show that Bd-Bsal coinfections intensify pathogen load in T. marmoratus and could, therefore, increase disease severity and have important consequences for the conservation of some amphibian species.

Plant Gender Affects Soil Fungal Microbiota Associated with Welwitschia mirabilis, an Unusual Desert Gymnosperm.

In a recent study, we found a distinct soil bacterial community associated with male and female plants of the desert gymnosperm Welwitschia mirabilis. In this subsequent study, we also found that the soil fungal community associated with Welwitschia differs between male and female plants, and between unvegetated areas and the soil under plants. Site location, pH, and soil moisture also had an important influence on the composition of the fungal community. A number of Ascomycota and Chytrid species were found to be distinct indicators of male and female plants, respectively, but there was no overall difference at the phylum level or in terms of diversity. The unvegetated areas between plants also differed in terms of several Ascomycota OTUs. Network connectivity of the fungal communities was found to be higher under both male and female Welwitschia plants than in unvegetated control areas. As with the bacterial community, it is unclear what processes produce the gender-distinct fungal community, and also the more general plant-associated community, and also what the effects on the biology of the plants are. One possibility behind the gender-related difference in fungal community is that there are differences in the production of pollen or nectar between the two plant genders, affecting the below-ground soil community.

The Effects of Nitrogen and Phosphorus on Colony Growth and Zoospore Characteristics of Soil Chytridiomycota.

The Chytridiomycota phylum contributes to nutrient cycling and the flow of energy between trophic levels in terrestrial and aquatic ecosystems yet remains poorly described or absent from publications discussing fungal communities in these environments. This study contributes to the understanding of three species of soil chytrids in vitro—Gaertneriomyces semiglobifer, Spizellomyces sp. and Rhizophlyctis rosea—in the presence of elevated concentrations of nitrogen and phosphorus and with different sources of nitrogen. Colony growth was measured after 4 weeks as dry weight and total protein. To determine the impacts on zoospore reproduction, motility, lipid content, and attachment to organic substrates, 4- and 8-week incubation times were investigated. Whilst all isolates were able to assimilate ammonium as a sole source of nitrogen, nitrate was less preferred or even unsuitable as a nutrient source for G. semiglobifer and R. rosea, respectively. Increasing phosphate concentrations led to diverse responses between isolates. Zoospore production was also variable between isolates, and the parameters for zoospore motility appeared only to be influenced by the phosphate concentration for Spizellomyces sp. and R. rosea. Attachment rates increased for G. semiglobifer in the absence of an inorganic nitrogen source. These findings highlight variability between the adaptive responses utilised by chytrids to persist in a range of environments and provide new techniques to study soil chytrid biomass and zoospore motility by total protein quantification and fluorescent imaging respectively.

Cilium axoneme internalization and degradation in chytrid fungi.

Loss of the cilium is important for cell cycle progression and certain developmental transitions. Chytrid fungi are a group of basal fungi that have retained centrioles and cilia, and they can disassemble their cilia via axoneme internalization as part of the transition from free-swimming spores to sessile sporangia. While this type of cilium disassembly has been observed in many single-celled eukaryotes, it has not been well characterized because it is not observed in common model organisms. To better characterize cilium disassembly via axoneme internalization, we focused on chytrids Rhizoclosmatium globosum and Spizellomyces punctatus to represent two lineages of chytrids with different motility characteristics. Our results show that each chytrid species can reel in its axoneme into the cell body along its cortex on the order of minutes, while S. punctatus has additional faster ciliary compartment loss and lash-around mechanisms. S. punctatus retraction can also occur away from the cell cortex and is partially actin dependent. Post-internalization, the tubulin of the axoneme is degraded in both chytrids over the course of about 2 hr. Axoneme disassembly and axonemal tubulin degradation are both partially proteasome dependent. Overall, chytrid cilium disassembly is a fast process that separates axoneme internalization and degradation.

High-efficiency electroporation of chytridfungi

Two species of parasitic fungi from the phylum Chytridiomycota (chytrids)are annihilating global amphibian populations. These chytrid species—Batrachochytrium dendrobatidis and B. salamandrivorans—have high rates of mortality and transmission. Uponestablishing infection in amphibians, chytrids rapidly multiply within the skin anddisrupt their hosts’ vital homeostasis mechanisms. Current disease models suggest thatchytrid fungi locate and infect their hosts during a motile, unicellular ‘zoospore’ lifestage. Moreover, other chytrid species parasitize organisms from across the tree oflife, making future epidemics in new hosts a likely possibility. Efforts to mitigate thedamage and spread of chytrid disease have been stymied by the lack of knowledge aboutbasic chytrid biology and tools with which to test molecular hypotheses about diseasemechanisms. To overcome this bottleneck, we have developed high-efficiency delivery ofmolecular payloads into chytrid zoospores using electroporation. Our electroporationprotocols result in payload delivery to between 75 and 97% of living cells of threespecies: B. dendrobatidis, B. salamandrivorans, and anon-pathogenic relative, Spizellomyces punctatus.This method lays the foundation for molecular genetic tools needed to establishecological mitigation strategies and answer broader questions in evolutionary and cellbiology.

New species of aquatic chytrids from Oman

ABSTRACT Oman is a desert country in the south of the Middle East. Springs and other water sources that harbor aquatic organisms can be separated by hundreds of kilometers. In Oct 2019, we isolated four freshwater aquatic fungi (Chytridiomycota) from benthic detritus baited with pine pollen on a general nutrient medium near Salalah, Oman. Database queries of nuc 28S rRNA (28S) and internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) revealed that one of these strains was Dinochytrium kinnereticum, a recently described algal pathogen from the Sea of Galilee. The other three strains had low molecular identity to available ITS sequences. These unknown strains varied in size and released endogenously swarming zoospores through papillae from mature zoosporangia. Zoospore ultrastructure was consistent with described species in the Rhizophydiales, and molecular phylogenetic results grouped these three strains into a clade in the genus Rhizophydium. We circumscribe these three strains as a sp. nov., thereby expanding the diversity within Rhizophydium described as the new species R. jobii. In doing so, we provide the first report of Chytridiomycota from Oman.

Comparative genomics of chytrid fungi reveal insights into the obligate biotrophic and pathogenic lifestyle of Synchytrium endobioticum

Synchytrium endobioticum is an obligate biotrophic soilborne Chytridiomycota (chytrid) species that causes potato wart disease, and represents the most basal lineage among the fungal plant pathogens. We have chosen a functional genomics approach exploiting knowledge acquired from other fungal taxa and compared this to several saprobic and pathogenic chytrid species. Observations linked to obligate biotrophy, genome plasticity and pathogenicity are reported. Essential purine pathway genes were found uniquely absent in S. endobioticum, suggesting that it relies on scavenging guanine from its host for survival. The small gene-dense and intron-rich chytrid genomes were not protected for genome duplications by repeat-induced point mutation. Both pathogenic chytrids Batrachochytrium dendrobatidis and S. endobioticum contained the largest amounts of repeats, and we identified S. endobioticum specific candidate effectors that are associated with repeat-rich regions. These candidate effectors share a highly conserved motif, and show isolate specific duplications. A reduced set of cell wall degrading enzymes, and LysM protein expansions were found in S. endobioticum, which may prevent triggering plant defense responses. Our study underlines the high diversity in chytrids compared to the well-studied Ascomycota and Basidiomycota, reflects characteristic biological differences between the phyla, and shows commonalities in genomic features among pathogenic fungi.

An Alternative Bioassay for Synchytrium endobioticum Demonstrates the Expression of Potato Wart Resistance in Aboveground Plant Parts.

The obligate biotrophic chytrid species Synchytrium endobioticum is the causal agent of potato wart disease. Currently, 39 pathotypes have been described based on their interaction with a differential set of potato varieties. Wart resistance and pathotyping is performed using bioassays in which etiolated tuber sprouts are inoculated. Here, we describe an alternative method in which aboveground plant parts are inoculated. Susceptible plants produced typical wart symptoms in developing but not in fully expanded aboveground organs. Colonization of the host by S. endobioticum was verified by screening for resting spores by microscopy and by molecular techniques using TaqMan polymerase chain reaction and RNAseq analysis. When applied to resistant plants, none of these symptoms were detectable. Recognition of S. endobioticum pathotypes by differentially resistant potato varieties was identical in axillary buds and the tuber-based bioassays. This suggests that S. endobioticum resistance genes are expressed in both etiolated "belowground" sprouts and green aboveground organs. RNAseq analysis demonstrated that the symptomatic aboveground materials contain less contaminants compared with resting spores extracted from tuber-based assays. This reduced microbial contamination in the aboveground bioassay could be an important advantage to study this obligate biotrophic plant-pathogen interaction. Because wart resistance is active in both below- and aboveground organs, the aboveground bioassay can potentially speed up screening for S. endobioticum resistance in potato breeding programs because it omits the requirement for tuber formation. In addition, possibilities arise to express S. endobioticum effectors in potato leaves through agroinfiltration, thereby providing additional phenotyping tools for research and breeding. Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

New Member of Gromochytriales (Chytridiomycetes)-Apiochytrium granulosporum nov. gen. et sp.

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, appears 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 a S943 group I intron that carries a homing endonuclease pseudogene.

The linear mitochondrial genome of the quarantine chytrid Synchytrium endobioticum; insights into the evolution and recent history of an obligate biotrophic plant pathogen

BackgroundChytridiomycota species (chytrids) belong to a basal lineage in the fungal kingdom. Inhabiting terrestrial and aquatic environments, most are free-living saprophytes but several species cause important diseases: e.g. Batrachochytrium dendrobatidis, responsible for worldwide amphibian decline; and Synchytrium endobioticum, causing potato wart disease. S. endobioticum has an obligate biotrophic lifestyle and isolates can be further characterized as pathotypes based on their virulence on a differential set of potato cultivars. Quarantine measures have been implemented globally to control the disease and prevent its spread. We used a comparative approach using chytrid mitogenomes to determine taxonomical relationships and to gain insights into the evolution and recent history of introductions of this plant pathogen.ResultsWe assembled and annotated the complete mitochondrial genome of 30 S. endobioticum isolates and generated mitochondrial genomes for five additional chytrid species. The mitochondrial genome of S. endobioticum is linear with terminal inverted repeats which was validated by tailing and PCR amplifying the telomeric ends. Surprisingly, no conservation in organisation and orientation of mitochondrial genes was observed among the Chytridiomycota except for S. endobioticum and its sister species Synchytrium microbalum. However, the mitochondrial genome of S. microbalum is circular and comprises only a third of the 72.9 Kbp found for S. endobioticum suggesting recent linearization and expansion. Four mitochondrial lineages were identified in the S. endobioticum mitochondrial genomes. Several pathotypes occur in different lineages, suggesting that these have emerged independently. In addition, variations for polymorphic sites in the mitochondrial genome of individual isolates were observed demonstrating that S. endobioticum isolates represent a community of different genotypes. Such communities were shown to be complex and stable over time, but we also demonstrate that the use of semi-resistant potato cultivars triggers a rapid shift in the mitochondrial haplotype associated with increased virulence.ConclusionsMitochondrial genomic variation shows that S. endobioticum has been introduced into Europe multiple times, that several pathotypes emerged multiple times, and that isolates represent communities of different genotypes. Our study represents the most comprehensive dataset of chytrid mitogenomes, which provides new insights into the extraordinary dynamics and evolution of mitochondrial genomes involving linearization, expansion and reshuffling.

Inventory of chytrid diversity in two temporary forest ponds using a multiphasic approach

ABSTRACTFood webs in temporary forest ponds are driven by decomposition of terrestrial inputs. Chytrid fungi are important components of the fungal community, degrading leaf litter in streams reliant on terrestrial inputs and in lake ecosystems where they may stabilize the food web. However, little is known about chytrid fungi in temporary forest ponds. We inventoried the chytrid diversity present in two temporary forest ponds via light microscopy of baited samples and ion semiconductor (Ion Torrent) sequencing of environmental DNA. We quantified trends of chytrid alpha and beta diversity as a function of spatial and temporal factors. A total of 59 chytrid taxa were detected throughout the study. Beta diversity exhibited variation across the sampled months for both the entire fungal community as well as for chytrids alone. Shifts in community composition were also apparent, although diversity metrics and composition patterns did not meet adjusted P values. The results of this study highlight the diversity of chytrid fungi in temporary forest ponds and the need for further studies on the spatial and temporal dynamics of chytrid species.

Diversity and Hidden Host Specificity of Chytrids Infecting Colonial Volvocacean Algae.

Chytrids are zoosporic fungi that play an important, but yet understudied, ecological role in aquatic ecosystems. Many chytrid species have been morphologically described as parasites on phytoplankton. However, the majority of them have rarely been isolated and lack DNA sequence data. In this study we isolated and cultivated three parasitic chytrids, infecting a common volvocacean host species, Yamagishiella unicocca. To identify the chytrids, we characterized morphology and life cycle, and analyzed phylogenetic relationships based on 18S and 28S rDNA genes. Host range and specificity of the chytrids was determined by cross-infection assays with host strains, characterized by rbcL and ITS markers. We were able to confirm the identity of two chytrid strains as Endocoenobium eudorinae Ingold and Dangeardia mamillata Schröder and described the third chytrid strain as Algomyces stechlinensis gen. et sp. nov. The three chytrids were assigned to novel and phylogenetically distant clades within the phylum Chytridiomycota, each exhibiting different host specificities. By integrating morphological and molecular data of both the parasitic chytrids and their respective host species, we unveiled cryptic host-parasite associations. This study highlights that a high prevalence of (pseudo)cryptic diversity requires molecular characterization of both phytoplankton host and parasitic chytrid to accurately identify and compare host range and specificity, and to study phytoplankton-chytrid interactions in general.

Diverse fungal lineages in subtropical ponds are altered by sediment-bound copper

Ponds represent a black box for fungal ecology. Compared to terrestrial environments, the fungal ecology of aquatic environments is rarely studied, and the few published studies have tended to be of lotic habitats in the northern hemisphere. We explored fungal communities and their responses to a gradient of copper in five year old artificial, replicated ponds in Australia. Ponds were subject to natural variations in temperature, precipitation and biotic colonisation. To explore the fungal communities, we amplified the ITS1 region of rDNA from samples of the water column, the sediment and cellulose baits (analogues to leaf fall) alone and in the presence of a gradient of copper. Fungal amplicon data revealed almost 800 fungal species from these habitats within the ponds. Interestingly, no chytrids from the Cladochytriales and Rhizophlyctidales were detected on cellulose baits, instead, putatively novel zoosporic taxa in the Chytridiomycota and the Rozellomycota were observed. Given the keystone role zoosporic fungi are thought to play in aquatic food webs, along with their role as primary decomposers of plant material, improved knowledge of their diversity and distribution is vital for understanding ecosystem function in standing water habitats. In aquatic environments copper tends to be bound to sediment and is not especially mobile in the water phase. The presence of copper in our sediment samples was correlated with repeatable and profound shifts in the fungal community, with chytrid species appearing to be the most sensitive, suggesting that they may be useful indicator organisms. Indirect effects of copper on fungal communities living on leaf analogues and in the water column were also explored.

A New Parasitic Chytrid, Staurastromyces oculus (Rhizophydiales, Staurastromycetaceae fam. nov.), Infecting the Freshwater Desmid Staurastrum sp.

Chytrids are a diverse group of ubiquitous true zoosporic fungi. The recent molecular discovery of a large diversity of undescribed chytrids has raised awareness on their important, but so far understudied ecological role in aquatic ecosystems. In the pelagic zone, of both freshwater and marine ecosystems, many chytrid species have been morphologically described as parasites on almost all major groups of phytoplankton. However, the majority of these parasitic chytrids has rarely been isolated and lack DNA sequence data, resulting in a large proportion of "dark taxa" in databases. Here, we report on the isolation and in-depth morphological, molecular and host range characterization of a chytrid infecting the common freshwater desmid Staurastrum sp. We provide first insights on the metabolic activity of the different chytrid development stages by using the vital dye FUN®-1 (2-chloro-4-[2,3-dihydro-3-methyl-[benzo-1,3-thiazol-2-yl]-methylidene]-1-phenylquinolinium iodide). Cross infection experiments suggest that this chytrid is an obligate parasite and specific for the genus Staurastrum sp. Phylogenetic analysis, based on ITS1-5.8S-ITS2 and 28S rDNA sequences, placed it in the order Rhizophydiales. Based on the unique zoospore ultrastructure, combined with thallus morphology, and molecular phylogenetic placement, we describe this parasitic chytrid as a new genus and species Staurastromyces oculus, within a new family Staurastromycetaceae.

A survey for Batrachochytrium salamandrivorans in Chinese amphibians

Abstract For the last decade, chytridiomycosis was considered to be caused by a single species of fungus, Batrachochytrium dendrobatidis (Bd), but a second chytrid species, Batrachochytrium salamandrivorans (Bs), was recently isolated from an infected Salamandra salamandra in the Netherlands. To date, Bs has only been found in the Netherlands. To assess whether Bs is present in China, we analyzed a total of 665 samples, including 425 wild samples, 41 preserved specimens, and 199 captive samples, from 30 different species, including both urodeles and anurans. Our sample sites covered 15 provinces in China. All of the samples tested negative for Bs, resulting in a 95% confidence limit for a prevalence of 0.6%. The absence of Bs observed in this large-scale survey in China has significant implications for amphibian conservation and for border trade management strategies intended to control amphibian diseases. We strongly recommend the continued close monitoring of Bs to verify the status of this potentially devastating amphibian fungus in China.

Phylogeny of Powellomycetaceae fam. nov. and description of Geranomyces variabilis gen. et comb. nov.

The genus Powellomyces was described to accommodate two monocentric chytrid species from soil that develop exogenously and possess zoosporic ultrastructure similar to other members of the order Spizellomycetales. Despite Powellomyces-like chytrids being commonly observed in gross culture, the genus contained only two species. To determine diversity in this group I amassed 49 isolates of Powellomyces-like chytrids, including the cultures upon which species types were based and new isolates from pollen-baited water cultures of soils, plant detritus and manure. I sequenced portions of nucSSU and nucLSU rDNA regions and the EF-1α-like gene from each isolate to produce a molecular phylogeny. This phylogeny supports monophyly of spizellomycetalean chytrids with exogenous development and suggests that multiple distinct lineages exist within this group. This phylogeny, along with a reevaluation of the ultra-structural features of the two described species, supports the recognition of a new family, Powellomycetaceae, and genus, Geranomyces, which contains 31 isolates of G. variabilis comb. nov.

Oomycetes and fungi: important parasites on marine algae

Considering that the field is largely unexplored and its importance to aquaculture, outline of oomycetes and fungi parasiting on marine algae was provided in this paper, including 15 species of oomycetes, six species of chytrids, 31 Ascomycota species and one species of mitosporic fungi. In natrue, both the oomycetes and chytrids frequently occurred and induced prevalences of disease which could destroy the populations of host plants greatly. However, the parasites in Ascomycota on algae have never occurred as epidemics so far. Some issues relating to the field were discussed such as performing tests to satisfy Koch’s postulates, investigations of host specificity, interactions between host and parasite and the potential effects of environmental factors on occurrence of a disease, which are urgent in need of further investigations.

Microsporidia Evolved from Ancestral Sexual Fungi

Microsporidia are obligate, intracellular eukaryotic pathogens that infect animal cells, including humans [1]. Previous studies suggested microsporidia share a common ancestor with fungi [2-7]. However, the exact nature of this phylogenetic relationship is unclear because of unusual features of microsporidial genomes, which are compact with fewer and highly divergent genes [8]. As a consequence, it is unclear whether microsporidia evolved from a specific fungal lineage, or whether microsporidia are a sister group to all fungi. Here, we present evidence addressing this controversial question that is independent of sequence-based phylogenetic reconstruction, but rather based on genome structure. In the zygomycete basal fungal lineage, the sex locus is a syntenic gene cluster governing sexual reproduction in which a high mobility group (HMG) transcription-factor gene is flanked by triose-phosphate transporter (TPT) and RNA helicase genes [9]. Strikingly, microsporidian genomes harbor a sex-related locus with the same genes in the same order. Genome-wide synteny analysis reveals multiple other loci conserved between microsporidia and zygomycetes to the exclusion of all other fungal lineages with sequenced genomes. These findings support the hypothesis that microsporidia are true fungi that descended from a zygomycete ancestor and suggest microsporidia may have an extant sexual cycle.