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Passer AR, Coelho MA, Billmyre RB, Nowrousian M, Mittelbach M, Yurkov AM, Averette AF, Cuomo CA, Sun S, Heitman J. Genetic and Genomic Analyses Reveal Boundaries between Species Closely Related to Cryptococcus Pathogens. mBio 2019; 10:e00764-19. [PMID: 31186317 PMCID: PMC6561019 DOI: 10.1128/mbio.00764-19] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 05/08/2019] [Indexed: 12/30/2022] Open
Abstract
Speciation is a central mechanism of biological diversification. While speciation is well studied in plants and animals, in comparison, relatively little is known about speciation in fungi. One fungal model is the Cryptococcus genus, which is best known for the pathogenic Cryptococcus neoformans/Cryptococcus gattii species complex that causes >200,000 new human infections annually. Elucidation of how these species evolved into important human-pathogenic species remains challenging and can be advanced by studying the most closely related nonpathogenic species, Cryptococcus amylolentus and Tsuchiyaea wingfieldii However, these species have only four known isolates, and available data were insufficient to determine species boundaries within this group. By analyzing full-length chromosome assemblies, we reappraised the phylogenetic relationships of the four available strains, confirmed the genetic separation of C. amylolentus and T. wingfieldii (now Cryptococcus wingfieldii), and revealed an additional cryptic species, for which the name Cryptococcus floricola is proposed. The genomes of the three species are ∼6% divergent and exhibit significant chromosomal rearrangements, including inversions and a reciprocal translocation that involved intercentromeric ectopic recombination, which together likely impose significant barriers to genetic exchange. Using genetic crosses, we show that while C. wingfieldii cannot interbreed with any of the other strains, C. floricola can still undergo sexual reproduction with C. amylolentus However, most of the resulting spores were inviable or sterile or showed reduced recombination during meiosis, indicating that intrinsic postzygotic barriers had been established. Our study and genomic data will foster additional studies addressing fungal speciation and transitions between nonpathogenic and pathogenic Cryptococcus lineages.IMPORTANCE The evolutionary drivers of speciation are critical to our understanding of how new pathogens arise from nonpathogenic lineages and adapt to new environments. Here we focus on the Cryptococcus amylolentus species complex, a nonpathogenic fungal lineage closely related to the human-pathogenic Cryptococcus neoformans/Cryptococcus gattii complex. Using genetic and genomic analyses, we reexamined the species boundaries of four available isolates within the C. amylolentus complex and revealed three genetically isolated species. Their genomes are ∼6% divergent and exhibit chromosome rearrangements, including translocations and small-scale inversions. Although two of the species (C. amylolentus and newly described C. floricola) were still able to interbreed, the resulting hybrid progeny were usually inviable or sterile, indicating that barriers to reproduction had already been established. These results advance our understanding of speciation in fungi and highlight the power of genomics in assisting our ability to correctly identify and discriminate fungal species.
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Affiliation(s)
- Andrew Ryan Passer
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Marco A Coelho
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Robert Blake Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Minou Nowrousian
- Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, Bochum, Germany
| | - Moritz Mittelbach
- Geobotany, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Andrey M Yurkov
- Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Anna Floyd Averette
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | | | - Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
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Cryptococcus gattii: An Emerging Cause of Fungal Disease in North America. Interdiscip Perspect Infect Dis 2009; 2009:840452. [PMID: 19503836 PMCID: PMC2686104 DOI: 10.1155/2009/840452] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2008] [Accepted: 01/18/2009] [Indexed: 01/03/2023] Open
Abstract
During the latter half of the twentieth century, fungal pathogens such as
Cryptococcus neoformans were increasingly recognized as a significant threat to the
health of immune compromised populations throughout the world. Until recently, the closely related
species C. gattii was considered to be a low-level endemic pathogen that was confined to
tropical regions such as Australia. Since 1999, C. gattii has emerged in the Pacific Northwest
region of North America and has been responsible for a large disease epidemic among generally
healthy individuals. The changing epidemiology of C. gattii infection is likely to be a consequence of alterations in fungal ecology and biology and illustrates its potential to cause serious human disease.
This review summarizes selected biological and clinical aspects of C. gattii that are
particularly relevant to the recent North American outbreak and compares these to the Australian and South
American experience.
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Sampaio JP, Fell JW, Gadanho M, Bauer R. Kurtzmanomyces insolitus sp. nov., a new anamorphic heterobasidiomycetous yeast species. Syst Appl Microbiol 1999; 22:619-25. [PMID: 10794150 DOI: 10.1016/s0723-2020(99)80015-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
A new anamorphic heterobasidiomycetous yeast species, Kurtzmanomyces insolitus, is described using a polyphasic taxonomic approach. The new species has the salient characteristics of the genus Kurtzmanomyces and, additionally, the ability to produce ballistoconidia. Data derived from comparative micromorphological studies, physiological characterisation, ultrastructure and nucleic acid analyses led to assigning the new species to Kurtzmanomyces rather than to the currently accepted genera of ballistoconidia-forming fungi. An emendation of the genus Kurtzmanomyces is proposed to allow the inclusion of the new species.
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Affiliation(s)
- J P Sampaio
- Lab. Microbiology, Faculty of Sciences and Technology, New University of Lisbon, Caparica, Portugal.
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Spaaij F, Weber G, Roeijmans HJ, van Eijk GW, Oberwinkler F. Fellomyces horovitziae sp. nov., a new basidiomycetous yeast species isolated from a Xenasmatella basidiocarp. Antonie Van Leeuwenhoek 1991; 59:293-8. [PMID: 1883232 DOI: 10.1007/bf00583682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A new species of the genus Fellomyces, F. horovitziae, was isolated from a Xenasmatella basidiocarp. It differs from other accepted species in its carbon assimilation pattern, mol% G + C and low DNA-DNA homology. The delimiting characters are discussed and a key to the genus is provided.
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Affiliation(s)
- F Spaaij
- Institut f. Biologie l, Lehrstuhl f. Spezielle Botanik/Mykologie, Tübingen, Germany
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Sugiyama J, Tokuoka K, Suh SO, Hirata A, Komagata K. Sympodiomycopsis: a new yeast-like anamorph genus with basidiomycetous nature from orchid nectar. Antonie Van Leeuwenhoek 1991; 59:95-108. [PMID: 1854191 DOI: 10.1007/bf00445653] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A description is provided for a new anamorph genus Sympodiomycopsis (Hyphomycetes), which is neither ballistosporogenous nor sterigmatosporogenous. The genus is typified by S. paphiopedili sp. nov. and accommodates one species which was isolated from nectar of Paphiopedilum primurinum in Japan. Phenotypically, the genus shows some similarity to Sympodiomyces because of the presence of a yeast morph with sympodial conidiogenous cell proliferation, but it is distinguished from that genus morphologically by a yeast morph with the enteroblastic-annellidic conidiogenesis and the conspicuous development of a hyphal morph with holoblastic-sympodial conidiogenous cells, and chemotaxonomically by the ubiquinone system Q-10 and 10% difference in the guanine plus cytosine (G + C) content of the nuclear DNA. Phylogenetically, the type of cell wall and septal pore ultrastructure, and the primary biochemical and chemotaxonomic characters of S. paphiopedili indicate a basidiomycetous affinity.
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Affiliation(s)
- J Sugiyama
- Institute of Applied Microbiology, University of Tokyo, Japan
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