Immunosuppression in vitro by a metabolite of a human pathogenic fungus.

ABSTRACT A library of more than 4,500 signature-tagged insertion mutants of the human pathogenic fungus Cryptococcus neoformans was generated, and a subset was screened in a murine inhalation model to identify genes required for virulence. New genes that regulate aspects of C. neoformans virulence were also identified by screening the entire library for in vitro phenotypes related to the ability to cause disease, including melanin production, growth at high temperature, and growth under conditions of nutrient limitation. A screen of 10% of the strain collection in mice identified an avirulent mutant strain with an insertion in the ENA1 gene, which is predicted to encode a fungus-specific sodium or potassium P-type ATPase. The results of the deletion of the gene and complementation experiments confirmed its key role in mammalian virulence. ena1 mutant strains exhibited no change in sensitivity to high salt concentrations but were sensitive to alkaline pH conditions, providing evidence that the fungus may have to survive at elevated pH during infection of the mammalian host. The mutation of the well-characterized virulence factor calcineurin (CNA1) also rendered C. neoformans strains sensitive to elevated pH. ENA1 transcripts in wild-type and cna1 mutant strains were upregulated in response to high pH, and cna1 ena1 double mutant strains exhibited increased sensitivity to elevated pH, indicating that at least two pathways in the fungus mediate survival under alkaline conditions. Signature-tagged mutagenesis is an effective strategy for the discovery of new virulence genes in fungal pathogens of animals.

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In vitro antifungal and demelanizing activity of Nepeta rtanjensis essential oil against the human pathogen Bipolaris spicifera

Archives of Biological Sciences ◽

10.2298/abs1103897g ◽

2011 ◽

Vol 63 (3) ◽

pp. 897-905 ◽

Cited By ~ 2

Author(s):

Milica Ljaljevic-Grbic ◽

M. Stupar ◽

Jelena Vukojevic ◽

D. Grubisic

Keyword(s):

Essential Oil ◽

Pathogenic Fungus ◽

Pathogenic Fungi ◽

Positive Control ◽

Alternative Source ◽

Conidia Germination ◽

Growth Assay ◽

Human Pathogenic Fungus ◽

Bipolaris Spicifera

The antifungal activity of Nepeta rtanjensis Diklic & Milojevic essential oil was tested against the human pathogenic fungus Bipolaris spicifera (Bainier) Subramanian via mycelial growth assay and conidia germination assay. The minimally inhibitory concentration (MIC) of the oil was determined at 1.0 ?g ml-1, while the MIC for the antifungal drug Bifonazole in a positive control was determined at 10.0 ?g ml-1. The maximum of conidia germination inhibition was accomplished at 0.6 ?g ml-1. In addition, at 0.6 ?g ml-1 and 0.8 ?g ml-1 the oil was able to cause morphophysiological changes in B. spicifera. The most significant result is the bleaching effect of the melanized conidial apparatus of the test fungi, since the melanin is the virulence factor in human pathogenic fungi. These results showed the strong antifungal properties of N. rtanjensis essential oil, supporting its possible rational use as an alternative source of new antifungal compounds.

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Hgc1 Mediates Dynamic Candida albicans-Endothelium Adhesion Events during Circulation

Eukaryotic Cell ◽

10.1128/ec.00307-09 ◽

2009 ◽

Vol 9 (2) ◽

pp. 278-287 ◽

Cited By ~ 29

Author(s):

Duncan Wilson ◽

Bernhard Hube

Keyword(s):

Blood Pressure ◽

Endothelial Cells ◽

Candida Albicans ◽

Pathogenic Fungus ◽

Interaction Model ◽

Serum Factors ◽

Content Type ◽

Disseminated Candidiasis ◽

Human Pathogenic Fungus

ABSTRACT Common iatrogenic procedures can result in translocation of the human pathogenic fungus Candida albicans from mucosal surfaces to the bloodstream. Subsequent disseminated candidiasis and infection of deep-seated organs may occur if the fungus is not eliminated by blood cells. In these cases, fungal cells adhere to the endothelial cells of blood vessels, penetrate through endothelial layers, and invade deeper tissue. In this scenario, endothelial adhesion events must occur during circulation under conditions of physiological blood pressure. To investigate the fungal and host factors which contribute to this essential step of disseminated candidiasis, we have developed an in vitro circulatory C. albicans-endothelium interaction model. We demonstrate that both C. albicans yeast and hyphae can adhere under flow at a pressure similar to capillary blood pressure. Serum factors significantly enhanced the adhesion potential of viable but not killed C. albicans cells to endothelial cells. During circulation, C. albicans cells produced hyphae and the adhesion potential first increased, then decreased with time. We provide evidence that a specific temporal event in the yeast-to-hyphal transition, regulated by the G1 cyclin Hgc1, is critical for C. albicans-endothelium adhesion during circulation.

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Urease as a Virulence Factor in Experimental Cryptococcosis

Infection and Immunity ◽

10.1128/iai.68.2.443-448.2000 ◽

2000 ◽

Vol 68 (2) ◽

pp. 443-448 ◽

Cited By ~ 336

Author(s):

Gary M. Cox ◽

Jean Mukherjee ◽

Garry T. Cole ◽

Arturo Casadevall ◽

John R. Perfect

Keyword(s):

Pathogenic Fungus ◽

Single Copy ◽

Genomic Locus ◽

Phenoloxidase Activity ◽

Infection Models ◽

Experimental Cryptococcosis ◽

Human Pathogenic Fungus ◽

Hydrolysis Of ◽

Capsule Size

ABSTRACT Urease catalyzes the hydrolysis of urea to ammonia and carbamate and has been found to be an important pathogenic factor for certain bacteria. Cryptococcus neoformans is a significant human pathogenic fungus that produces large amounts of urease; thus we wanted to investigate the importance of urease in the pathogenesis of cryptococcosis. We cloned and sequenced the genomic locus containing the single-copy C. neoformans urease gene (URE1) and used this to disrupt the native URE1in the serotype A strain H99. The ure1 mutant strains were found to have in vitro growth characteristics, phenoloxidase activity, and capsule size similar to those of the wild type. Comparison of aure1 mutant with H99 after intracisternal inoculation into corticosteroid-treated rabbits revealed no significant differences in colony counts recovered from the cerebrospinal fluid. However, when these two strains were compared in both the murine intravenous and inhalational infection models, there were significant differences in survival. Mice infected with a ure1 strain lived longer than mice infected with H99 in both models. The ure1 strain was restored to urease positivity by complementation withURE1, and two resulting transformants were significantly more pathogenic than the ure1 strain. Our results suggest that urease activity is involved in the pathogenesis of cryptococcosis but that the importance may be species and/or infection site specific.

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Expression Patterns in Reductive Iron Assimilation and Functional Consequences during Phagocytosis of Lichtheimia corymbifera, an Emerging Cause of Mucormycosis

Journal of Fungi ◽

10.3390/jof7040272 ◽

2021 ◽

Vol 7 (4) ◽

pp. 272

Author(s):

Felicia Adelina Stanford ◽

Nina Matthias ◽

Zoltán Cseresnyés ◽

Marc Thilo Figge ◽

Mohamed I. Abdelwahab Hassan ◽

...

Keyword(s):

Gene Expression ◽

Iron Uptake ◽

Intracellular Transport ◽

Pathogenic Fungus ◽

Expression Patterns ◽

Iron Depletion ◽

Iron Assimilation ◽

Human Pathogenic Fungus ◽

Hyphal Formation ◽

Yeast Mutants

Iron is an essential micronutrient for most organisms and fungi are no exception. Iron uptake by fungi is facilitated by receptor-mediated internalization of siderophores, heme and reductive iron assimilation (RIA). The RIA employs three protein groups: (i) the ferric reductases (Fre5 proteins), (ii) the multicopper ferroxidases (Fet3) and (iii) the high-affinity iron permeases (Ftr1). Phenotyping under different iron concentrations revealed detrimental effects on spore swelling and hyphal formation under iron depletion, but yeast-like morphology under iron excess. Since access to iron is limited during pathogenesis, pathogens are placed under stress due to nutrient limitations. To combat this, gene duplication and differential gene expression of key iron uptake genes are utilized to acquire iron against the deleterious effects of iron depletion. In the genome of the human pathogenic fungus L. corymbifera, three, four and three copies were identified for FRE5, FTR1 and FET3 genes, respectively. As in other fungi, FET3 and FTR1 are syntenic and co-expressed in L. corymbifera. Expression of FRE5, FTR1 and FET3 genes is highly up-regulated during iron limitation (Fe-), but lower during iron excess (Fe+). Fe- dependent upregulation of gene expression takes place in LcFRE5 II and III, LcFTR1 I and II, as well as LcFET3 I and II suggesting a functional role in pathogenesis. The syntenic LcFTR1 I–LcFET3 I gene pair is co-expressed during germination, whereas LcFTR1 II- LcFET3 II is co-expressed during hyphal proliferation. LcFTR1 I, II and IV were overexpressed in Saccharomyces cerevisiae to represent high and moderate expression of intracellular transport of Fe3+, respectively. Challenge of macrophages with the yeast mutants revealed no obvious role for LcFTR1 I, but possible functions of LcFTR1 II and IVs in recognition by macrophages. RIA expression pattern was used for a new model of interaction between L. corymbifera and macrophages.

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Deletion of pksA attenuates the melanogenesis, growth and sporulation ability and causes increased sensitivity to stress response and antifungal drugs in the human pathogenic fungus Fonsecaea monophora

Microbiological Research ◽

10.1016/j.micres.2020.126668 ◽

2021 ◽

Vol 244 ◽

pp. 126668

Author(s):

Xing Xiao ◽

Yu Li ◽

Yu Lan ◽

Jing Zhang ◽

Ya He ◽

...

Keyword(s):

Stress Response ◽

Pathogenic Fungus ◽

Antifungal Drugs ◽

Fonsecaea Monophora ◽

Increased Sensitivity ◽

Human Pathogenic Fungus

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Comparative Genomics Suggests That the Human Pathogenic Fungus Pneumocystis jirovecii Acquired Obligate Biotrophy through Gene Loss

Genome Biology and Evolution ◽

10.1093/gbe/evu155 ◽

2014 ◽

Vol 6 (8) ◽

pp. 1938-1948 ◽

Cited By ~ 31

Author(s):

Ousmane H. Cissé ◽

Marco Pagni ◽

Philippe M. Hauser

Keyword(s):

Comparative Genomics ◽

Gene Loss ◽

Pathogenic Fungus ◽

Pneumocystis Jirovecii ◽

Human Pathogenic Fungus

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Three sympatrically occurring species of Metarhizium show plant rhizosphere specificity

Microbiology ◽

10.1099/mic.0.051102-0 ◽

2011 ◽

Vol 157 (10) ◽

pp. 2904-2911 ◽

Cited By ~ 88

Author(s):

Michael Wyrebek ◽

Cristina Huber ◽

Ramanpreet Kaur Sasan ◽

Michael J. Bidochka

Keyword(s):

Tree Species ◽

Acer Saccharum ◽

Panicum Virgatum ◽

Sugar Maple ◽

Root Exudate ◽

Pathogenic Fungus ◽

Plant Roots ◽

Metarhizium Robertsii ◽

Grass Roots

Here we tested the hypothesis that species of the soil-inhabiting insect-pathogenic fungus Metarhizium are not randomly distributed in soils but show plant-rhizosphere-specific associations. We isolated Metarhizium from plant roots at two sites in Ontario, Canada, sequenced the 5′ EF-1α gene to discern Metarhizium species, and developed an RFLP test for rapid species identification. Results indicated a non-random association of three Metarhizium species (Metarhizium robertsii, Metarhizium brunneum and Metarhizium guizhouense) with the rhizosphere of certain types of plant species (identified to species and categorized as grasses, wildflowers, shrubs and trees). M. robertsii was the only species that was found associated with grass roots, suggesting a possible exclusion of M. brunneum and M. guizhouense. Supporting this, in vitro experiments showed that M. robertsii conidia germinated significantly better in Panicum virgatum (switchgrass) root exudate than did M. brunneum or M. guizhouense. M. guizhouense and M. brunneum only associated with wildflower rhizosphere when co-occurring with M. robertsii. With the exception of these co-occurrences, M. guizhouense was found to associate exclusively with the rhizosphere of tree species, predominantly Acer saccharum (sugar maple), while M. brunneum was found to associate exclusively with the rhizosphere of shrubs and trees. These associations demonstrate that different species of Metarhizium associate with specific plant types.

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What Are the Best Parents for Hybrid Progeny? An Investigation into the Human Pathogenic Fungus Cryptococcus

Journal of Fungi ◽

10.3390/jof7040299 ◽

2021 ◽

Vol 7 (4) ◽

pp. 299

Author(s):

Man You ◽

Jianping Xu

Keyword(s):

Pathogenic Fungus ◽

Sequence Divergence ◽

Hybrid Vigor ◽

Phenotypic Trait ◽

Hybrid Progeny ◽

Melanin Production ◽

Fluconazole Resistance ◽

Human Pathogenic Fungus ◽

Two Temperatures ◽

The Relationship

Hybridization between more divergent organisms is likely to generate progeny with more novel genetic interactions and genetic variations. However, the relationship between parental genetic divergence and progeny phenotypic variation remains largely unknown. Here, using strains of the human pathogenic Cryptococcus, we investigated the patterns of such a relationship. Twenty-two strains with up to 15% sequence divergence were mated. Progeny were genotyped at 16 loci. Parental strains and their progeny were phenotyped for growth ability at two temperatures, melanin production at seven conditions, and susceptibility to the antifungal drug fluconazole. We observed three patterns of relationships between parents and progeny for each phenotypic trait, including (i) similar to one of the parents, (ii) intermediate between the parents, and (iii) outside the parental phenotypic range. We found that as genetic distance increases between parental strains, progeny showed increased fluconazole resistance and growth at 37 °C but decreased melanin production under various oxidative and nitrosative stresses. Our findings demonstrate that, depending on the traits, both evolutionarily more similar strains and more divergent strains may be better parents to generate progeny with hybrid vigor. Together, the results indicate the enormous potential of Cryptococcus hybrids in their evolution and adaptation to diverse conditions.

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The CDC42 Homolog of the Dimorphic FungusPenicillium marneffei Is Required for Correct Cell Polarization during Growth but Not Development

Journal of Bacteriology ◽

10.1128/jb.183.11.3447-3457.2001 ◽

2001 ◽

Vol 183 (11) ◽

pp. 3447-3457 ◽

Cited By ~ 63

Author(s):

Kylie J. Boyce ◽

Michael J. Hynes ◽

Alex Andrianopoulos

Keyword(s):

Cell Shape ◽

Pathogenic Fungus ◽

Cell Polarization ◽

Dominant Negative ◽

Yeast Cells ◽

Polarized Growth ◽

Temperature Dependent ◽

Human Pathogenic Fungus ◽

Rho Family

ABSTRACT The opportunistic human pathogenic fungus Penicillium marneffei is dimorphic and is thereby capable of growth either as filamentous multinucleate hyphae or as uninucleate yeast cells which divide by fission. The dimorphic switch is temperature dependent and requires regulated changes in morphology and cell shape. Cdc42p is a Rho family GTPase which in Saccharomyces cerevisiae is required for changes in polarized growth during mating and pseudohyphal development. Cdc42p homologs in higher organisms are also associated with changes in cell shape and polarity. We have cloned a highly conserved CDC42 homolog from P. marneffeinamed cflA. By the generation of dominant-negative and dominant-activated cflA transformants, we have shown that CflA initiates polarized growth and extension of the germ tube and subsequently maintains polarized growth in the vegetative mycelium. CflA is also required for polarization and determination of correct cell shape during yeast-like growth, and active CflA is required for the separation of yeast cells. However, correct cflAfunction is not required for dimorphic switching and does not appear to play a role during the generation of specialized structures during asexual development. In contrast, heterologous expression ofcflA alleles in Aspergillus nidulansprevented conidiation.

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