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Eukaryotic Cell, March 2009, p. 353-361, Vol. 8, No. 3
1535-9778/09/$08.00+0     doi:10.1128/EC.00373-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Phylogeny and Phenotypic Characterization of Pathogenic Cryptococcus Species and Closely Related Saprobic Taxa in the Tremellales {triangledown} ,{dagger}

Keisha Findley,1 Marianela Rodriguez-Carres,1 Banu Metin,1 Johannes Kroiss,2 Álvaro Fonseca,3 Rytas Vilgalys,4 and Joseph Heitman1*

Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710,1 Department of Zoology, University of Regensburg, 93040 Regensburg, Germany,2 Centro de Recursos Microbiológicos, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal,3 Department of Biology, Duke University, Durham, North Carolina 277084

Received 24 November 2008/ Accepted 10 January 2009

The basidiomycetous yeasts Cryptococcus neoformans and Cryptococcus gattii are closely related sibling species that cause respiratory and neurological disease in humans and animals. Within these two recognized species, phylogenetic analysis reveals at least six cryptic species defined as molecular types (VNI/II/B, VNIV, VGI, VGII, VGIII, and VGIV) that comprise the pathogenic Cryptococcus species complex. These pathogenic species are clustered in the Filobasidiella clade within the order Tremellales. Previous studies have shown that the Filobasidiella clade also includes several saprobic fungi isolated from insect frass, but information evaluating the relatedness of the saprobes and pathogens within this cluster is limited. Here, the phylogeny encompassing a subset of species in the Tremellales lineage that clusters closely with the pathogenic Cryptococcus species complex was resolved by employing a multilocus sequencing approach for phylogenetic analysis. Six highly conserved genomic loci from 15 related basidiomycete species were sequenced, and the alignments from the concatenated gene sequences were evaluated with different tree-building criteria. Furthermore, these 15 species were subjected to virulence and phenotype assays to evaluate their pathogenic potential. These studies revealed that Cryptococcus amylolentus and Tsuchiyaea wingfieldii, two nonpathogenic sibling species, are the taxa most closely related to the pathogens C. neoformans and C. gattii and together with Filobasidiella depauperata form a Cryptococcus sensu stricto group. Five other saprobic yeast species form the Kwoniella clade, which appears to be a part of a more distantly related sensu lato group. This study establishes a foundation for future comparative genomic approaches that will provide insight into the structure, function, and evolution of the mating type locus, the transitions in modes of sexual reproduction, and the emergence of human pathogenic species from related or ancestral saprobic species.

* Corresponding author. Mailing address: Room 322, CARL Building, Box 3546, Research Drive, Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710. Phone: (919) 684-2824. Fax: (919) 684-5458. E-mail: heitm001{at}duke.edu

{triangledown} Published ahead of print on 16 January 2009.

{dagger} Supplemental material for this article may be found at http://ec.asm.org/.

Eukaryotic Cell, March 2009, p. 353-361, Vol. 8, No. 3
1535-9778/09/$08.00+0     doi:10.1128/EC.00373-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



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