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Santi L, Berger M, Guimarães JA, Calegari-Alves YP, Vainstein MH, Yates JR, Beys-da-Silva WO. Proteomic profile of Cryptococcus gattii biofilm: Metabolic shift and the potential activation of electron chain transport. J Proteomics 2024; 290:105022. [PMID: 37838096 DOI: 10.1016/j.jprot.2023.105022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 09/22/2023] [Accepted: 10/03/2023] [Indexed: 10/16/2023]
Abstract
Cryptococcus gattii is a primary pathogenic fungus that causes pneumonia. This species is also responsible for an outbreak in Vancouver, Canada, and spreading to the mainland and United States. The use of medical devices is often complicated by infections with biofilm-forming microbes with increased resistance to antimicrobial agents and host defense mechanisms. This study investigated the comparative proteome of C. gattii R265 (VGIIa) grown under planktonic and biofilm conditions. A brief comparison with C. neoformans H99 biofilm and the use of different culture medium and surface were also evaluated. Using Multidimensional Protein Identification Technology (MudPIT), 1819 proteins were identified for both conditions, where 150 (8.2%) were considered differentially regulated (up- or down-regulated and unique in biofilm cells). Overall, the proteomic approach suggests that C. gattii R265 biofilm cells are maintained by the induction of electron transport chain for reoxidation, and by alternative energy metabolites, such as succinate and acetate. SIGNIFICANCE: Since C. gattii is considered a primary pathogen and is one of the most virulent and less susceptible to antifungals, understanding how biofilms are maintained is fundamental to search for new targets to control this important mode of growth that is difficult to eradicate.
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Affiliation(s)
- Lucélia Santi
- Faculty of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil; Post-Graduation Program of Cellular and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil; Center of Experimental Research, Clinical Hospital of Porto Alegre, Porto Alegre, RS, Brazil.
| | - Markus Berger
- Center of Experimental Research, Clinical Hospital of Porto Alegre, Porto Alegre, RS, Brazil; Tick-Pathogen Transmission Unit, Laboratory of Bacteriology, National Institute of Allergy and Infectious Diseases, Hamilton, MT, United States
| | - Jorge A Guimarães
- Center of Experimental Research, Clinical Hospital of Porto Alegre, Porto Alegre, RS, Brazil
| | - Yohana Porto Calegari-Alves
- Post-Graduation Program of Cellular and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Marilene H Vainstein
- Post-Graduation Program of Cellular and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - John R Yates
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, United States
| | - Walter O Beys-da-Silva
- Faculty of Pharmacy, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil; Post-Graduation Program of Cellular and Molecular Biology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil; Center of Experimental Research, Clinical Hospital of Porto Alegre, Porto Alegre, RS, Brazil
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Vanherp L, Poelmans J, Govaerts K, Hillen A, Lagrou K, Vande Velde G, Himmelreich U. In vivo assessment of differences in fungal cell density in cerebral cryptococcomas of mice infected with Cryptococcus neoformans or Cryptococcus gattii. Microbes Infect 2023; 25:105127. [PMID: 36940783 DOI: 10.1016/j.micinf.2023.105127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 03/07/2023] [Accepted: 03/15/2023] [Indexed: 03/22/2023]
Abstract
In cerebral cryptococcomas caused by Cryptococcus neoformans or Cryptococcus gattii, the density of fungal cells within lesions can contribute to the overall brain fungal burden. In cultures, cell density is inversely related to the size of the cryptococcal capsule, a dynamic polysaccharide layer surrounding the cell. Methods to investigate cell density or related capsule size within fungal lesions of a living host are currently unavailable, precluding in vivo studies on longitudinal changes. Here, we assessed whether intravital microscopy and quantitative magnetic resonance imaging techniques (diffusion MRI and MR relaxometry) would enable non-invasive investigation of fungal cell density in cerebral cryptococcomas in mice. We compared lesions caused by type strains C. neoformans H99 and C. gattii R265 and evaluated potential relations between observed imaging properties, fungal cell density, total cell and capsule size. The observed inverse correlation between apparent diffusion coefficient and cell density permitted longitudinal investigation of cell density changes. Using these imaging methods, we were able to study the multicellular organization and cell density within brain cryptococcomas in the intact host environment of living mice. Since the MRI techniques are also clinically available, the same approach could be used to assess fungal cell density in brain lesions of patients.
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Affiliation(s)
- Liesbeth Vanherp
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Jennifer Poelmans
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Kristof Govaerts
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Amy Hillen
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Katrien Lagrou
- Laboratory of Clinical Bacteriology and Mycology, Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium; National Reference Centre for Mycosis, Department of Laboratory Medicine, University Hospitals Leuven, Leuven, Belgium
| | - Greetje Vande Velde
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium
| | - Uwe Himmelreich
- Biomedical MRI, Department of Imaging and Pathology, KU Leuven, Leuven, Belgium.
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Silva TC, de Ávila RI, Zara ALSA, Santos AS, Ataídes F, Freitas VAQ, Costa CR, Valadares MC, Silva MDRR. Punicalagin triggers ergosterol biosynthesis disruption and cell cycle arrest in Cryptococcus gattii and Candida albicans : Action mechanisms of punicalagin against yeasts. Braz J Microbiol 2020; 51:1719-1727. [PMID: 32856241 DOI: 10.1007/s42770-020-00364-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 08/08/2020] [Indexed: 01/22/2023] Open
Abstract
Punicalagin is a phenolic compound extracted from Lafoensia pacari A. St.-Hil (Lythraceae) leaves. It has demonstrated interesting activity against pathogenic fungi, e.g., Cryptococcus gattii and Candida albicans, by inhibiting fungi growth in a minimum inhibitory concentration (MIC) at 4 μg/mL. However, the mechanisms behind its antifungal action are not well understood. In this study, certain parameters were investigated, by transmission electron microscopy, ergosterol synthesis inhibition, and flow cytometry analyses, to gain insight into the possible biological targets of punicalagin (4 or 16 μg/mL) against yeast cells. Data showed that, in contrast to untreated cells, punicalagin triggered severe ultrastructural changes in C. gattii and C. albicans, such as disorganization of cytoplasmic content and/or thickened cell walls. In addition, it caused a decrease in yeast plasma membrane ergosterol content in a concentration-dependent manner. However, it was unable to bring about significant fungal cell membrane rupture. On the other hand, punicalagin (16 μg/mL) significantly arrested C. albicans and C. gattii cells at the G0/G1 phase, with a consequent reduction in cells at the G2/M phase in both fungi isolates, and thereby prevented progression of the normal yeast cell cycle. However, these alterations showed no involvement of reactive oxygen species overproduction in C. albicans and C. gattii cells, although punicalagin triggered a significant loss of mitochondrial membrane potential in C. albicans. These findings suggest that punicalagin is a promising plant-derived compound for use in developing new antifungal therapies.
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Affiliation(s)
- Thaísa Cristina Silva
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | - Renato Ivan de Ávila
- Laboratório de Ensino e Pesquisa em Toxicologia In Vitro - Tox In, Faculdade de Farmácia, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | | | - Andressa Santana Santos
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | - Fábio Ataídes
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | | | - Carolina Rodrigues Costa
- Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | - Marize Campos Valadares
- Laboratório de Ensino e Pesquisa em Toxicologia In Vitro - Tox In, Faculdade de Farmácia, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
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Vu K, Thompson GR, Roe CC, Sykes JE, Dreibe EM, Lockhart SR, Meyer W, Engelthaler DM, Gelli A. Flucytosine resistance in Cryptococcus gattii is indirectly mediated by the FCY2-FCY1-FUR1 pathway. Med Mycol 2018; 56:857-867. [PMID: 29554336 PMCID: PMC10905989 DOI: 10.1093/mmy/myx135] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 10/12/2017] [Indexed: 11/14/2022] Open
Abstract
Cryptococcosis is an opportunistic fungal infection caused by members of the two sibling species complexes: Cryptococcus neoformans and Cryptococcus gattii. Flucytosine (5FC) is one of the most widely used antifungals against Cryptococcus spp., yet very few studies have looked at the molecular mechanisms responsible for 5FC resistance in this pathogen. In this study, we examined 11 C. gattii clinical isolates of the major molecular type VGIII based on differential 5FC susceptibility and asked whether there were genomic changes in the key genes involved in flucytosine metabolism. Susceptibility assays and sequencing analysis revealed an association between a point mutation in the cytosine deaminase gene (FCY1) and 5FC resistance in two of the studied 5FC resistant C. gattii VGIII clinical isolates, B9322 and JS5. This mutation results in the replacement of arginine for histidine at position 29 and occurs within a variable stretch of amino acids. Heterologous expression of FCY1 and spot sensitivity assays, however, demonstrated that this point mutation did not have any effect on FCY1 activities and was not responsible for 5FC resistance. Comparative sequence analysis further showed that no changes in the amino acid sequence and no genomic alterations were observed within 1 kb of the upstream and downstream sequences of either cytosine permeases (FCY2-4) or uracil phosphoribosyltransferase (FUR1) genes in 5FC resistant and 5FC susceptible C. gattii VGIII isolates. The herein obtained results suggest that the observed 5FC resistance in the isolates B9322 and JS5 is due to changes in unknown protein(s) or pathway(s) that regulate flucytosine metabolism.
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Affiliation(s)
- Kiem Vu
- Department of Pharmacology, University of California, Davis, California, USA
| | - George R Thompson
- Department of Medical Microbiology and Immunology, University of California, Davis, California, USA
- Department of Internal Medicine, Division of Infectious Diseases, University of California Davis Medical Center, Davis, California, USA
| | - Chandler C Roe
- Translational Genomics Research Institute, Flagstaff, Arizona, USA
| | - Jane E Sykes
- Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California, USA
| | | | - Shawn R Lockhart
- Mycotic Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia USA
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Center for Infectious Diseases and Microbiology, Marie Bashir Institute for Emerging Infectious Diseases and Biosecurity, Westmead Clinical School, Sydney Medical School, Westmead Hospital, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
| | | | - Angie Gelli
- Department of Pharmacology, University of California, Davis, California, USA
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Chang M, Sionov E, Khanal Lamichhane A, Kwon-Chung KJ, Chang YC. Roles of Three Cryptococcus neoformans and Cryptococcus gattii Efflux Pump-Coding Genes in Response to Drug Treatment. Antimicrob Agents Chemother 2018; 62:e01751-17. [PMID: 29378705 PMCID: PMC5913978 DOI: 10.1128/aac.01751-17] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 01/22/2018] [Indexed: 12/14/2022] Open
Abstract
Cryptococcus neoformans and Cryptococcus gattii species complexes are the etiologic agents of cryptococcosis. We have deciphered the roles of three ABC transporters, Afr1, Afr2, and Mdr1, in the representative strains of the two species, C. neoformans H99 and C. gattii R265. Deletion of AFR1 in H99 and R265 drastically reduced the levels of resistance to three xenobiotics and three triazoles, suggesting that Afr1 is the major drug efflux pump in both strains. Fluconazole susceptibility was not affected when AFR2 or MDR1 was deleted in both strains. However, when these genes were deleted in combination with AFR1, a minor additive effect in susceptibility toward several drugs was observed. Deletion of all three genes in both strains caused further increases in susceptibility toward fluconazole and itraconazole, suggesting that Afr2 and Mdr1 augment Afr1 function in pumping these triazoles. Intracellular accumulation of Nile Red significantly increased in afr1Δ mutants of both strains, but rhodamine 6G accumulation increased only in the mdr1Δ mutant of H99. Thus, the three efflux pumps play different roles in the two strains when exposed to different azoles and xenobiotics. AFR1 and AFR2 expression was upregulated in H99 and R265 when treated with fluconazole. However, MDR1 expression was upregulated only in R265 under the same conditions. We screened a library of transcription factor mutants and identified several mutants that manifested either altered fluconazole sensitivity or an increase in the frequency of fluconazole heteroresistance. Gene expression analysis suggests that the three efflux pumps are regulated independently by different transcription factors in response to fluconazole exposure.
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Affiliation(s)
- Miwha Chang
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Edward Sionov
- Department of Food Quality and Safety, Institute for Postharvest and Food Sciences, The Volcani Center, Agricultural Research Organization, Rishon LeZion, Israel
| | - Ami Khanal Lamichhane
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Kyung J Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Yun C Chang
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Chang YC, Khanal Lamichhane A, Bradley J, Rodgers L, Ngamskulrungroj P, Kwon-Chung KJ. Differences between Cryptococcus neoformans and Cryptococcus gattii in the Molecular Mechanisms Governing Utilization of D-Amino Acids as the Sole Nitrogen Source. PLoS One 2015; 10:e0131865. [PMID: 26132227 PMCID: PMC4489021 DOI: 10.1371/journal.pone.0131865] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 06/08/2015] [Indexed: 12/03/2022] Open
Abstract
The ability to grow on media containing certain D-amino acids as a sole nitrogen source is widely utilized to differentiate Cryptococcus gattii from C. neoformans. We used the C. neoformans H99 and C. gattii R265 strains to dissect the mechanisms of D-amino acids utilization. We identified three putative D-amino acid oxidase (DAO) genes in both strains and showed that each DAO gene plays different roles in D-amino acid utilization in each strain. Deletion of DAO2 retarded growth of R265 on eleven D-amino acids suggesting its prominent role on D-amino acid assimilation in R265. All three R265 DAO genes contributed to growth on D-Asn and D-Asp. DAO3 was required for growth and detoxification of D-Glu by both R265 and H99. Although growth of H99 on most D-amino acids was poor, deletion of DAO1 or DAO3 further exacerbated it on four D-amino acids. Overexpression of DAO2 or DAO3 enabled H99 to grow robustly on several D-amino acids suggesting that expression levels of the native DAO genes in H99 were insufficient for growth on D-amino acids. Replacing the H99 DAO2 gene with a single copy of the R265 DAO2 gene also enabled its utilization of several D-amino acids. Results of gene and promoter swaps of the DAO2 genes suggested that enzymatic activity of Dao2 in H99 might be lower compared to the R265 strain. A reduction in virulence was only observed when all DAO genes were deleted in R265 but not in H99 indicating a pathobiologically exclusive role of the DAO genes in R265. These results suggest that C. neoformans and C. gattii divergently evolved in D-amino acid utilization influenced by their major ecological niches.
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Affiliation(s)
- Yun C. Chang
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD, United States of America
- * E-mail:
| | - Ami Khanal Lamichhane
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD, United States of America
| | - James Bradley
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD, United States of America
| | - Laura Rodgers
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD, United States of America
| | - Popchai Ngamskulrungroj
- Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Kyung J. Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, NIAID, NIH, Bethesda, MD, United States of America
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Dylag M. Etiological factors of cryptococcosis - what makes them pathogens ? Med Dosw Mikrobiol 2015; 67:221-231. [PMID: 27019916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A significant participation in the growing prevalence of fungal infections have basidiomycete yeasts of the genus of Cryptococcus. Among about seventy actually known species belonging to Cryptococcus genus there are only two: Cryptococcus neoformans and Cryptococcus gattii, which as anamorphs in parasitic stage of its life fully evolved the mechanisms predisposing them to be a human and animal pathogens. Specific attributes important in the pathogenesis of cryptococcosis called virulence factors allow them to colonize the mammalian tissues. Undoubtedly, the most important role in the pathogenesis play: the presence of polysaccharide capsule, synthesis of melanin, and the ability to grow in the range of temperatures 35-40°C.
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Chong HS, Campbell L, Padula MP, Hill C, Harry E, Li SS, Wilkins MR, Herbert B, Carter D. Time-course proteome analysis reveals the dynamic response of Cryptococcus gattii cells to fluconazole. PLoS One 2012; 7:e42835. [PMID: 22880118 PMCID: PMC3412811 DOI: 10.1371/journal.pone.0042835] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/11/2012] [Indexed: 01/16/2023] Open
Abstract
Cryptococcus gattii is an encapsulated fungus capable of causing fatal disease in immunocompetent humans and animals. As current antifungal therapies are few and limited in efficacy, and resistance is an emerging issue, the development of new treatment strategies is urgently required. The current study undertook a time-course analysis of the proteome of C. gattii during treatment with fluconazole (FLC), which is used widely in prophylactic and maintenance therapies. The aims were to analyze the overall cellular response to FLC, and to find fungal proteins involved in this response that might be useful targets in therapies that augment the antifungal activity of FLC. During FLC treatment, an increase in stress response, ATP synthesis and mitochondrial respiratory chain proteins, and a decrease in most ribosomal proteins was observed, suggesting that ATP-dependent efflux pumps had been initiated for survival and that the maintenance of ribosome synthesis was differentially expressed. Two proteins involved in fungal specific pathways were responsive to FLC. An integrative network analysis revealed co-ordinated processes involved in drug response, and highlighted hubs in the network representing essential proteins that are required for cell viability. This work demonstrates the dynamic cellular response of a typical susceptible isolate of C. gattii to FLC, and identified a number of proteins and pathways that could be targeted to augment the activity of FLC.
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Affiliation(s)
- Hin Siong Chong
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia
| | - Leona Campbell
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia
| | - Matthew P. Padula
- ithree institute, University of Technology, Broadway, New South Wales, Australia
| | - Cameron Hill
- School of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, New South Wales, Australia
| | - Elizabeth Harry
- ithree institute, University of Technology, Broadway, New South Wales, Australia
| | - Simone S. Li
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, New South Wales, Australia
| | - Marc R. Wilkins
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, New South Wales, Australia
| | - Ben Herbert
- School of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, New South Wales, Australia
| | - Dee Carter
- School of Molecular Bioscience, University of Sydney, Sydney, New South Wales, Australia
- * E-mail:
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Ngamskulrungroj P, Chang Y, Roh J, Kwon-Chung KJ. Differences in nitrogen metabolism between Cryptococcus neoformans and C. gattii, the two etiologic agents of cryptococcosis. PLoS One 2012; 7:e34258. [PMID: 22479580 PMCID: PMC3313984 DOI: 10.1371/journal.pone.0034258] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 02/24/2012] [Indexed: 12/23/2022] Open
Abstract
Two members of the Cryptococcus neoformans-gattii species complex, the etiologic agents of cryptococcosis, can be differentiated by biological, biochemical, serological and molecular typing techniques. Based on their differences in carbon and nitrogen utilization patterns, cost effective and very specific diagnostic tests using D-proline and canvanine-glycine-bromthymol blue (CGB) media have been formulated and are widely used for identification of the two species. However, these methods have yet to be tested for strains with confirmed molecular types to assess the degree of specificity for each molecular type in the two species. We collected global isolates of every major molecular type available and tested their patterns of nitrogen utilization. We confirmed specificity of the CGB test to be 100% regardless of molecular type while the D-proline test yielded 8–38% false negative results in three of the four C. gattii molecular types, VGI–VGIII. The utilization pattern of a new set of amino acids: D-alanine, L-tryptophan and L-phenylalanine, showed species specificity comparable to that of D-proline. We discovered that the transcription factor Gat1 (Are1) regulates the utilization of nitrogen differently between C. neoformans and C. gattii strains. Unlike in C. neoformans, expression of the genes encoding glycine decarboxylase complex in C. gatti was only partially suppressed by nitrogen catabolite repression in the presence of ammonium. GAT1 in C. neoformans controlled the induction of three of the four genes encoding the glycine decarboxylase complex when glycine was used as the sole nitrogen source while in C. gattii its regulation of these genes was less stringent. Moreover, while virulence of C. neoformans strains in mice was not affected by Gat1, the transcription factor positively influenced the virulence of C. gattii strain.
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Affiliation(s)
- Popchai Ngamskulrungroj
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Yun Chang
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jamin Roh
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Kyung J. Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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