Genomic and phenotypic insights into the expanding phylogenetic landscape of the Cryptococcus genus.
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2025-11
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The fungal genus Cryptococcus includes several life-threatening human pathogens as well as diverse saprobic species whose genome architecture, ecology, and evolutionary history remain less well characterized. Understanding how some lineages evolved into major pathogens remains a central challenge and may be advanced by comparisons with their nonpathogenic counterparts. Integrative approaches have become essential for delimiting species and reconstructing evolutionary relationships, particularly in lineages with cryptic diversity or extensive chromosomal rearrangements. Here, we formally characterize six Cryptococcus species representing distinct evolutionary lineages, comprising both newly discovered and previously recognized but unnamed taxa, through a combination of phylogenomic analyses, divergence metrics, chromosomal comparisons, mating assays, and phenotypic profiling. Among pathogenic taxa, we formally name Cryptococcus hyracis sp. nov., corresponding to the previously characterized VGV lineage within the C. gattii complex. In parallel, we describe five saprobic, nonpathogenic species isolated from fruit, soil, and bark beetle galleries, spanning four phylogenetic clades. We identify a strong ecological association with bark beetles for Cryptococcus porticicola sp. nov., the only newly described nonpathogenic species with multiple sequenced strains from diverse sites. In this species, we detect strain-level chromosomal variation and evidence of sexual reproduction, along with population-level signatures of recombination. Across the genus, chromosome-level comparisons reveal extensive structural variation, including species- and strain-specific rearrangements that may restrict gene flow. We also identify multiple instances of chromosome number reduction, often accompanied by genomic signatures consistent with centromere inactivation or loss of centromeric identity. Comparative metabolic profiling with Biolog phenotype microarrays reveals clade-level differentiation and distinct substrate preferences, which may reflect metabolic divergence and habitat-specific diversification. Notably, we confirm that thermotolerance is restricted to clinically relevant taxa. These findings refine the species-level taxonomy of Cryptococcus, broaden its known genomic and ecological diversity, and strengthen the framework for investigating speciation, adaptation, and the emergence of pathogenicity within the genus.
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Coelho, Marco A, Márcia David-Palma, Aleksey V Kachalkin, Miroslav Kolařík, Benedetta Turchetti, José Paulo Sampaio, Michael J Wingfield, Matthew C Fisher, et al. (2025). Genomic and phenotypic insights into the expanding phylogenetic landscape of the Cryptococcus genus. PLoS genetics, 21(11). p. e1011945. 10.1371/journal.pgen.1011945 Retrieved from https://hdl.handle.net/10161/33768.
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Joseph Heitman
Joseph Heitman was an undergraduate at the University of Chicago (1980-1984), graduating from the BS-MS program with dual degrees in chemistry and biochemistry with general and special honors. He then matriculated as an MD-PhD student at Cornell and Rockefeller Universities and worked with Peter Model and Norton Zinder on how restriction enzymes recognize specific DNA sequences and how bacteria respond to and repair DNA breaks and nicks. Dr. Heitman moved as an EMBO long-term fellow to the Biocenter in Basel Switzerland where, in studies with Mike Hall and Rao Movva, pioneered the use of yeast as a model for studies of immunosuppressive drug action. Their studies elucidated the central role of FKBP12 in forming complexes with FK506 and rapamycin that inhibit cell signaling and growth, discovered Tor1 and Tor2 as the targets of rapamycin, and contributed to the appreciation that immunosuppressive drugs inhibit signal transduction cascades that are conserved from yeasts to humans.
Dr. Heitman moved to Duke University in 1992, and is a member of the Department of Molecular Genetics and Microbiology where his studies focus on microorganisms addressing fundamental biological questions and unmet medical needs. Dr. Heitman and colleagues focus on model and pathogenic yeasts including Cryptococcus neoformans and other diverse species from the fungal kingdom. Their studies with fungi as genetic models have revealed biological and genetic principles that can be generalized as models for eukaryotic cell and organism function. These include discovering FKBP12 and Tor1/2 as the targets of the immunosuppressive anti-proliferative natural product rapamycin, elucidating central roles of the calcium activated phosphatase calcineurin governing fungal virulence and morphogenesis and antifungal drug action, deciphering how cells sense and respond to nutrients via permeases, G protein coupled receptors, and the Tor signaling cascade, and illustrating how both model and pathogenic fungi sense both the environment and the infected host. In parallel, their studies address the evolution, structure, and function of fungal mating type loci as models for gene cluster and sex chromosome evolution. The discovery of an ancestral sex determining locus in the basal fungal lineages involving two HMG domain proteins, SexM and SexP, homologous to the mammalian Sry sex determinant provides insights into both the origins of sex specification and its plasticity throughout the radiation of the fungal and metazoan kingdoms from their last shared common ancestor. Their discovery of unisexual mating in fungi and subsequent analysis of its impact on the evolution of eukaryotic microbial pathogens provides insights into both microbial evolution and pathogenesis and how sexual reproduction may have first evolved. Recent studies have unveiled novel mechanisms of antimicrobial drug resistance involving epimutations that silence drug-target genes via RNAi, functions of RNAi in genomic integrity of microbial pathogens, and loss of RNAi in hypervirulent outbreak lineages.
Dr. Heitman is a recipient of the Burroughs Wellcome Scholar Award in Molecular Pathogenic Mycology (1998-2005), the 2002 ASBMB AMGEN award for significant contributions using molecular biology to our understanding of human disease, and the 2003 Squibb Award from the Infectious Diseases Society of America (IDSA) for outstanding contributions to infectious disease research, the 2018 Korsmeyer Award from the American Society for Clinical Investigation, and the 2018 Rhoda Benham Award from the Medical Mycological Society of the Americas. He is the recipient of an NIH/NIAID MERIT award 2011-2021 in support of studies on fungal unisexual reproduction in microbial pathogen evolution, a Duke University translational research mentoring award in 2012, and a Dean’s Award for Excellence in Mentoring from the Duke Graduate School in 2018. He has served as an instructor in residence since 1998 for the Molecular Mycology Course at the Marine Biological Laboratory at Woods Hole, MA. Dr. Heitman is an editor for the journals PLOS Genetics, Genetics (2012-2017), PLOS Pathogens (Pearls review editor), Current Genetics (2001-2014), mBio, and Fungal Genetics and Biology; a member of the editorial boards of PLOS Biology, Current Biology, Cell Host and Microbe, and PeerJ; former editor for PLOS Pathogens (mycology section editor, 2008-2011) and Eukaryotic Cell (2002-2012); an advisory board member for the Fungal Genome Initiative at the Broad Institute, the Fungal Kingdom Genome Project at the Department of Energy Joint Genome Institute, the NIAID Genomic Sequencing Centers for Infectious Diseases, and for the Integrated Microbial Biodiversity Program at the Canadian Institute for Advanced Research (CIFAR); co-chair for the Duke Chancellor’s Science Advisory Council (2009-2010); and co-chair/chair for the FASEB summer conference on Microbial Pathogenesis: Mechanisms of Infectious Disease (2011, 2013). He was elected a member of the American Society for Clinical Investigation (ASCI) in 2003, a fellow of the Infectious Diseases Society of America (IDSA) in 2003, a fellow of the American Academy of Microbiology in 2004, a fellow of the American Association for the Advancement of Science (AAAS) in 2004, a member of the Association of American Physicians (AAP) in 2006, and a member of the American Academy of Arts & Sciences in 2020. Dr. Heitman was an investigator with the Howard Hughes Medical Institute from 1992 to 2005. Dr. Heitman served as the director for the Duke University Program in Genetics and Genomics (UPGG) from 2002-2009 (including writing two funded competitive renewals for the T32 NIH training grant and establishing the annual program retreat). He was the founding director for the Center for Microbial Pathogenesis (now called the Center for Host-Microbial Interactions, CHoMI) and served in this capacity January 2002-October 2014. He is currently the director of the Tri-institutional (Duke, UNC-CH, NC State) Molecular Mycology and Pathogenesis Training Program (MMPTP) (since July 1, 2012), and Chair of the Department of Molecular Genetics and Microbiology (since September 1, 2009).
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