Extracellular Fibrils of Pathogenic Yeast Cryptococcus gattii Are Important for Ecological Niche, Murine Virulence and Human Neutrophil Interactions

ABSTRACTCryptococcus gattiiis a primary pathogenic yeast that causes disease in both animals and humans. It is closely related toCryptococcus neoformansand diverged from a common ancestor ∼40 million years ago. WhileC. gattiihas a characterized sexual cycle dependent upon a dimorphic region of the genome known as the MAT locus, mating has rarely been observed in this species. In this study, we identify for the first time clinical (both human and veterinary) and environmental isolates from Australia that retain sexual fecundity. A collection of 120 isolates from a variety of geographic locations was analyzed for molecular type, mating type, and the ability to develop mating structures when cocultured with fertile tester strains. Nine isolates produced dikaryotic filaments with paired nuclei, fused clamp connections, and basidiospores. DNA sequence analysis of three genes (URA5, the MATα-specificSXI1α gene, and the MATa-specificSXI2agene) revealed little or no variability inURA5andSXI2a, respectively. However across the 108 MATα strains sequenced, theSXI1α gene was found to exist as 11 different alleles. Phylogenetic analysis found most variation to occur in the more fertile genotypes. Although some lineages of AustralianC. gattiihave retained the ability to mate, the majority of isolates were sterile, suggesting that asexuality is the dominant mode of propagation in these populations.

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Transcription Factor STE12α Has Distinct Roles in Morphogenesis, Virulence, and Ecological Fitness of the Primary Pathogenic Yeast Cryptococcus gattii

Eukaryotic Cell ◽

10.1128/ec.00009-06 ◽

2006 ◽

Vol 5 (7) ◽

pp. 1065-1080 ◽

Cited By ~ 37

Author(s):

Ping Ren ◽

Deborah J. Springer ◽

Melissa J. Behr ◽

William A. Samsonoff ◽

Sudha Chaturvedi ◽

...

Keyword(s):

Transcription Factor ◽

Gene Knockout ◽

Natural Habitat ◽

Cryptococcus Gattii ◽

Human Neutrophils ◽

Knockout Mutant ◽

Pathogenic Yeast ◽

Ecological Fitness

ABSTRACT Cryptococcus gattii is a primary pathogenic yeast, increasingly important in public health, but factors responsible for its host predilection and geographical distribution remain largely unknown. We have characterized C. gattii STE12α to probe its role in biology and pathogenesis because this transcription factor has been linked to virulence in many human and plant pathogenic fungi. A full-length STE12α gene was cloned by colony hybridization and sequenced using primer walk and 3′ rapid amplification of cDNA ends strategies, and a ste12αΔ gene knockout mutant was created by URA5 insertion at the homologous site. A semiquantitative analysis revealed delayed and poor mating in ste12αΔ mutant; this defect was not reversed by exogenous cyclic AMP. C. gattii parent and mutant strains showed robust haploid fruiting. Among putative virulence factors tested, the laccase transcript and enzymatic activity were down regulated in the ste12αΔ mutant, with diminished production of melanin. However, capsule, superoxide dismutase, phospholipase, and urease were unaffected. Similarly, Ste12 deficiency did not cause any auxotrophy, assimilation defects, or sensitivity to a large panel of chemicals and antifungals. The ste12αΔ mutant was markedly attenuated in virulence in both BALB/c and A/Jcr mice models of meningoencephalitis, and it also exhibited significant in vivo growth reduction and was highly susceptible to in vitro killing by human neutrophils (polymorphonuclear leukocytes). In tests designed to simulate the C. gattii natural habitat, the ste12αΔ mutant was poorly pigmented on wood agar prepared from two tree species and showed poor survival and multiplication in wood blocks. Thus, STE12α plays distinct roles in C. gattii morphogenesis, virulence, and ecological fitness.

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Ecological niche of Cryptococcus neoformans var. grubii and Cryptococcus gattii in decaying wood of trunk hollows of living trees in Jabalpur City of Central India

Mycopathologia ◽

10.1007/s11046-007-9039-2 ◽

2007 ◽

Vol 164 (4) ◽

pp. 159-170 ◽

Cited By ~ 31

Author(s):

N. Grover ◽

Shesh Rao Nawange ◽

J. Naidu ◽

S. M. Singh ◽

Archana Sharma

Keyword(s):

Cryptococcus Neoformans ◽

Ecological Niche ◽

Central India ◽

Cryptococcus Gattii ◽

Decaying Wood

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Cryptococcus gattii: Emergence in Western North America: Exploitation of a Novel Ecological Niche

Interdisciplinary Perspectives on Infectious Diseases ◽

10.1155/2009/176532 ◽

2009 ◽

Vol 2009 ◽

pp. 1-8 ◽

Cited By ~ 34

Author(s):

Kausik Datta ◽

Karen H. Bartlett ◽

Kieren A. Marr

Keyword(s):

North America ◽

Pacific Northwest ◽

Ecological Niche ◽

Ecological Niche Modeling ◽

Cryptococcus Gattii ◽

Host Susceptibility ◽

Emerging Pathogens ◽

Animal Populations ◽

The Pacific ◽

Recent Emergence

The relatively uncommon fungal pathogenCryptococcus gattiirecently emerged as a significant cause of cryptococcal disease in human and animals in the Pacific Northwest of North America. Although genetic studies indicated its possible presence in the Pacific Northwest for more than 30 years,C. gattiias an etiological agent was largely unknown in this region prior to 1999. The recent emergence may have been encouraged by changing conditions of climate or land use and/or host susceptibility, and predictive ecological niche modeling indicates a potentially wider spread.C. gattiican survive wide climatic variations and colonize the environment in tropical, subtropical, temperate, and dry climates. Long-term climate changes, such as the significantly elevated global temperature in the last 100 years, influence patterns of disease among plants and animals and create niche microclimates habitable by emerging pathogens.C. gattiimay have exploited such a hitherto unrecognized but clement environment in the Pacific Northwest to provide a wider exposure and risk of infection to human and animal populations.

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The Trehalose Synthesis Pathway Is an Integral Part of the Virulence Composite for Cryptococcus gattii

Infection and Immunity ◽

10.1128/iai.00565-09 ◽

2009 ◽

Vol 77 (10) ◽

pp. 4584-4596 ◽

Cited By ~ 67

Author(s):

Popchai Ngamskulrungroj ◽

Uwe Himmelreich ◽

Julia A. Breger ◽

Christabel Wilson ◽

Methee Chayakulkeeree ◽

...

Keyword(s):

Cryptococcus Gattii ◽

Growth Defect ◽

Central Importance ◽

Outbreak Strain ◽

Pathogenic Yeast ◽

Yeast Extract Peptone Dextrose ◽

Capsule Production ◽

Trehalose Biosynthesis ◽

Highly Virulent ◽

Trehalose Synthesis

ABSTRACT The trehalose pathway is essential for stress tolerance and virulence in fungi. We investigated the importance of this pathway for virulence of the pathogenic yeast Cryptococcus gattii using the highly virulent Vancouver Island, Canada, outbreak strain R265. Three genes putatively involved in trehalose biosynthesis, TPS1 (trehalose-6-phosphate [T6P] synthase) and TPS2 (T6P phosphatase), and degradation, NTH1 (neutral trehalose), were deleted in this strain, creating the R265tps1Δ, R265tps2Δ, and R265nth1Δ mutants. As in Cryptococcus neoformans, cellular trehalose was reduced in the R265tps1Δ and R265tps2Δ mutants, which could not grow and died, respectively, at 37°C on yeast extract-peptone-dextrose agar, suggesting that T6P accumulation in R265tps2Δ is directly toxic. Characterizations of the cryptococcal hexokinases and trehalose mutants support their linkage to the control of glycolysis in this species. However, unlike C. neoformans, the C. gattii R265tps1Δ mutant demonstrated, in addition, defects in melanin and capsule production, supporting an influence of T6P on these virulence pathways. Attenuated virulence of the R265tps1Δ mutant was not due solely to its 37°C growth defect, as shown in worm studies and confirmed by suppressor mutants. Furthermore, an intact trehalose pathway controls protein secretion, mating, and cell wall integrity in C. gattii. Thus, the trehalose synthesis pathway plays a central role in the virulence composites of C. gattii through multiple mechanisms. Deletion of NTH1 had no effect on virulence, but inactivation of the synthesis genes, TPS1 and TPS2, has profound effects on survival of C. gattii in the invertebrate and mammalian hosts. These results highlight the central importance of this pathway in the virulence composites of both pathogenic cryptococcal species.

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Dishwashers as an Extreme Environment of Potentially Pathogenic Yeast Species

Pathogens ◽

10.3390/pathogens10040446 ◽

2021 ◽

Vol 10 (4) ◽

pp. 446

Author(s):

Kamila Kulesza ◽

Anna Biedunkiewicz ◽

Karolina Nowacka ◽

Maria Dynowska ◽

Monika Urbaniak ◽

...

Keyword(s):

Ecological Niche ◽

Candida Parapsilosis ◽

Yeast Species ◽

Tap Water ◽

Extreme Environment ◽

Rhodotorula Mucilaginosa ◽

Pathogenic Yeast ◽

Exophiala Dermatitidis ◽

Yeast Strains ◽

Standard Procedures

The study aimed to compare the yeast species diversity in the specific environment of dishwashers, taking into account the potential risk for users. Yeasts were isolated from ten dishwashers and from tap water supplied to the appliances. Samples were collected for mycological analyses at the beginning of each month, from February to May 2016. Four dishwasher sites (rubber seals, detergent dispensers, sprinklers, and water drains) were analyzed. The microfungi were identified by the standard procedures applied in mycological diagnostics. To confirm species identification, molecular analysis was performed based on the sequences of the D1/D2 region. The presence of microfungi was detected in 70% of the investigated appliances. Rubber seals, detergent dispensers, and water drains were the most frequently colonized elements. Thirty-five yeast strains were isolated in this study, of which twenty-seven were obtained from dishwashers and eight from tap water. The strains belonged to six genera and six species (Candida parapsilosis, Clavispora lusitaniae, Dipodascus capitatus, Exophiala dermatitidis, Meyerozyma guilliermondii, and Rhodotorula mucilaginosa). Most of the strains came from rubber seals. In this way, it was demonstrated that the dishwashers’ condition is sufficient as an ecological niche for microfungi.

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Cryptococcus neoformans Mates on Pigeon Guano: Implications for the Realized Ecological Niche and Globalization

Eukaryotic Cell ◽

10.1128/ec.00097-07 ◽

2007 ◽

Vol 6 (6) ◽

pp. 949-959 ◽

Cited By ~ 110

Author(s):

Kirsten Nielsen ◽

Anna L. De Obaldia ◽

Joseph Heitman

Keyword(s):

Cryptococcus Neoformans ◽

Growth And Development ◽

Ecological Niche ◽

Ecological Niches ◽

Brown Pigment ◽

Pathogenic Yeast ◽

Realized Niche ◽

Fundamental Niche ◽

Physical Conditions ◽

Resource Requirements

ABSTRACT The ecological niche that a species can occupy is determined by its resource requirements and the physical conditions necessary for survival. The niche to which an organism is most highly adapted is the realized niche, whereas the complete range of habitats that an organism can occupy represents the fundamental niche. The growth and development of Cryptococcus neoformans and Cryptococcus gattii on pigeon guano were examined to determine whether these two species occupy the same or different ecological niches. C. neoformans is a cosmopolitan pathogenic yeast that infects predominantly immunocompromised individuals, exists in two varieties (grubii [serotype A] and neoformans [serotype D]), and is commonly isolated from pigeon guano worldwide. By contrast, C. gattii often infects immunocompetent individuals and is associated with geographically restricted environments, most notably, eucalyptus trees. Pigeon guano supported the growth of both species, and a brown pigment related to melanin, a key virulence factor, was produced. C. neoformans exhibited prolific mating on pigeon guano, whereas C. gattii did not. The observations that C. neoformans completes the life cycle on pigeon guano but that C. gattii does not indicates that pigeon guano could represent the realized ecological niche for C. neoformans. Because C. gattii grows on pigeon guano but cannot sexually reproduce, pigeon guano represents a fundamental but not a realized niche for C. gattii. Based on these studies, we hypothesize that an ancestral Cryptococcus strain gained the ability to sexually reproduce in pigeon guano and then swept the globe.

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Clonality and Recombination in Genetically Differentiated Subgroups of Cryptococcus gattii

Eukaryotic Cell ◽

10.1128/ec.4.8.1403-1409.2005 ◽

2005 ◽

Vol 4 (8) ◽

pp. 1403-1409 ◽

Cited By ~ 98

Author(s):

Leona T. Campbell ◽

Bart J. Currie ◽

Mark Krockenberger ◽

Richard Malik ◽

Wieland Meyer ◽

...

Keyword(s):

Papua New Guinea ◽

Eucalyptus Camaldulensis ◽

New Guinea ◽

Life Cycles ◽

Cryptococcus Gattii ◽

Pathogenic Yeast ◽

Sexual Exchange ◽

Population Structures ◽

Two Populations ◽

Epidemiological Link

ABSTRACTCryptococcus gattiiis a pathogenic yeast that together withCryptococcus neoformanscauses cryptococcosis in humans and animals. High numbers of viableC. gattiipropagules can be obtained from certain species of AustralianEucalyptus camaldulensistrees, and an epidemiological link betweenEucalyptuscolonization and human exposure has been proposed. However, the highest prevalence ofC. gattiicryptococcosis occurs in Papua New Guinea and in regions of Australia where the eucalypt species implicated to date are not endemic. This study investigated the population structure of three geographically distinct clinical and veterinary populations ofC. gattiifrom Australia and Papua New Guinea. All populations that consisted of a genotype found frequently in Australia (VGI) were strongly clonal and were highly differentiated from one another. Two populations of the less common VGII genotype from Sydney and the Northern Territory had population structures inferring recombination. In addition, there was some evidence of reduced genetic differentiation between these geographically remote regions. In a companion study presented in this issue, VGII isolates were overwhelmingly more fertile than those of the VGI genotype, giving biological support to the indirect assessment of sexual exchange. It appears that the VGI genotype propagates clonally on eucalypts in Australia and on an unknown substrate in Papua New Guinea, with infection initiated by an unidentified infectious propagule. VGII isolates are completing their life cycles and may be dispersed via sexually produced basidiospores, which are also likely to initiate respiratory infection.

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Evidence of Recombination in Mixed-Mating-Type and α-Only Populations of Cryptococcus gattii Sourced from Single Eucalyptus Tree Hollows

Eukaryotic Cell ◽

10.1128/ec.00020-08 ◽

2008 ◽

Vol 7 (4) ◽

pp. 727-734 ◽

Cited By ~ 60

Author(s):

Nathan Saul ◽

Mark Krockenberger ◽

Dee Carter

Keyword(s):

Mating Type ◽

Strong Association ◽

Eucalyptus Camaldulensis ◽

Cryptococcus Gattii ◽

Mixed Mating ◽

Pathogenic Yeast ◽

Individual Tree ◽

Tree Hollows ◽

Large Numbers ◽

Widespread Phenomenon

ABSTRACT Disease caused by the pathogenic yeast Cryptococcus gattii begins with the inhalation of an infectious propagule. As C. gattii is heavily encapsulated, this propagule is most likely to be a basidiospore. However, most C. gattii strains are infertile in laboratory crosses, and population studies indicate that recombination and dispersal are very restricted. In addition, strains of the α mating type predominate, which would not be expected in a mating population. C. gattii comprises four genetically distinct molecular genotypes, designated VGI to VGIV. C. gattii molecular type VGI has a strong association with Eucalyptus camaldulensis and can be found in high numbers in E. camaldulensis hollows. Previous work on isolates obtained from E. camaldulensis suggested that environmental populations of C. gattii are highly fragmented, have limited ability to disperse, and are confined to individual tree hollows. In the current study, we examined large numbers of isolates from three separate hollows for evidence of recombination. In two hollows, the α and a mating types were present in approximately equal numbers. The third hollow had α cells only and was from a region where a isolates have never been found. Statistical analysis of multilocus genotypes revealed recombining subpopulations in the three Eucalyptus hollows. Recombination was equally present in the α-a and α-only populations. This is consistent with recent studies that have found evidence suggestive of α-α mating in C. gattii and Cryptococcus neoformans and raises the possibility this may be a widespread phenomenon, allowing these fungi to recombine despite a paucity of a mating partners.

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