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Lohse MB, Ziv N, Johnson AD. Variation in transcription regulator expression underlies differences in white-opaque switching between the SC5314 reference strain and the majority of Candida albicans clinical isolates. Genetics 2023; 225:iyad162. [PMID: 37811798 PMCID: PMC10627253 DOI: 10.1093/genetics/iyad162] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 08/26/2023] [Indexed: 10/10/2023] Open
Abstract
Candida albicans, a normal member of the human microbiome and an opportunistic fungal pathogen, undergoes several morphological transitions. One of these transitions is white-opaque switching, where C. albicans alternates between 2 stable cell types with distinct cellular and colony morphologies, metabolic preferences, mating abilities, and interactions with the innate immune system. White-to-opaque switching is regulated by mating type; it is repressed by the a1/α2 heterodimer in a/α cells, but this repression is lifted in a/a and α/α mating type cells (each of which are missing half of the repressor). The widely used C. albicans reference strain, SC5314, is unusual in that white-opaque switching is completely blocked when the cells are a/α; in contrast, most other C. albicans a/α strains can undergo white-opaque switching at an observable level. In this paper, we uncover the reason for this difference. We show that, in addition to repression by the a1/α2 heterodimer, SC5314 contains a second block to white-opaque switching: 4 transcription regulators of filamentous growth are upregulated in this strain and collectively suppress white-opaque switching. This second block is missing in the majority of clinical strains, and, although they still contain the a1/α2 heterodimer repressor, they exhibit a/α white-opaque switching at an observable level. When both blocks are absent, white-opaque switching occurs at very high levels. This work shows that white-opaque switching remains intact across a broad group of clinical strains, but the precise way it is regulated and therefore the frequency at which it occurs varies from strain to strain.
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Affiliation(s)
- Matthew B Lohse
- Department of Microbiology and Immunology, University of California - San Francisco, San Francisco, CA 94143, USA
| | - Naomi Ziv
- Department of Microbiology and Immunology, University of California - San Francisco, San Francisco, CA 94143, USA
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California - San Francisco, San Francisco, CA 94143, USA
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2
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Paulo EA, de Souza CM, Perini HF, de Almeida RSC, Costa IC, Pavanelli WR, Furlaneto-Maia L, Furlaneto MC. Altered phagocytosis and morphogenesis of phenotypic switching-derived strains of the pathogenic Candida tropicalis co-cultured with phagocytic cells. Microb Pathog 2023:106186. [PMID: 37269878 DOI: 10.1016/j.micpath.2023.106186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/05/2023]
Abstract
BACKGROUND AND OBJECTIVE Candida tropicalis is among the most prevalent human pathogenic yeast species. Switch states of C. tropicalis differ in virulence traits. Here, we evaluate the effect of phenotypic switching on phagocytosis and yeast-hyphae transition in C. tropicalis. METHODS C. tropicalis morphotypes included clinical strain and two switch strains (rough variant and rough revertant). In vitro phagocytosis assay was performed using peritoneal macrophages and hemocytes. The proportion of hyphal cells was ascertained by scoring morphology using optical microscopy. Expression of the WOR1 (White-opaque regulator 1) and EFG1 (Enhanced filamentous growth protein 1) was determined by quantitative PCR. RESULTS The rough variant was more resistant to in vitro phagocytosis by peritoneal macrophages than that observed for the clinical strain, while hemocytes phagocytosed clinical and rough variant to the same extent. The rough revertant was more phagocytosed than the clinical strain by both phagocytes. During co-incubation with phagocytic cells, the clinical strain of C. tropicalis exists mainly as blastoconidia. The co-culture of the rough variant with macrophages resulted in a higher percentage of hyphae than blastoconidia cells, while in co-culture with hemocytes no differences were observed between the percentage of hyphae and blastoconidia. The expression levels of WOR1 in the rough variant co-cultured with phagocytes were significantly higher than they were in the clinical strain. CONCLUSIONS Differences on phagocytosis and hyphal growth between switch states cells of C. tropicalis co-cultured with phagocytic cells were observed. The pronounced hyphal growth may affect the complex host-pathogen relationship and favor the pathogen to scape phagocytosis. The pleiotropic effects of phenotypic switching suggest that this event may contribute to the success of infection associated with C. tropicalis.
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Affiliation(s)
- Eloiza A Paulo
- Department of Microbiology, Paraná State University of Londrina, University Campus, C.P. 6001, Paraná, Brazil
| | - Cassia M de Souza
- Department of Microbiology, Paraná State University of Londrina, University Campus, C.P. 6001, Paraná, Brazil
| | - Hugo F Perini
- Department of Microbiology, Paraná State University of Londrina, University Campus, C.P. 6001, Paraná, Brazil
| | - Ricardo S Couto de Almeida
- Department of Microbiology, Paraná State University of Londrina, University Campus, C.P. 6001, Paraná, Brazil
| | - Ivete C Costa
- Department of Pathology, Paraná State University of Londrina, Paraná, Brazil
| | - Wander R Pavanelli
- Department of Pathology, Paraná State University of Londrina, Paraná, Brazil
| | - Luciana Furlaneto-Maia
- Department of Food Technology, Technological Federal University of Paraná, Londrina, Paraná, Brazil
| | - Marcia C Furlaneto
- Department of Microbiology, Paraná State University of Londrina, University Campus, C.P. 6001, Paraná, Brazil.
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3
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Guan G, Tao L, Li C, Xu M, Liu L, Bennett RJ, Huang G. Glucose depletion enables Candida albicans mating independently of the epigenetic white-opaque switch. Nat Commun 2023; 14:2067. [PMID: 37045865 PMCID: PMC10097730 DOI: 10.1038/s41467-023-37755-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 03/30/2023] [Indexed: 04/14/2023] Open
Abstract
The human fungal pathogen Candida albicans can switch stochastically and heritably between a "white" phase and an "opaque" phase. Opaque cells are the mating-competent form of the species, whereas white cells are thought to be essentially "sterile". Here, we report that glucose depletion, a common nutrient stress, enables C. albicans white cells to undergo efficient sexual mating. The relative expression levels of pheromone-sensing and mating-associated genes (including STE2/3, MFA1, MFα1, FIG1, FUS1, and CEK1/2) are increased under glucose depletion conditions, while expression of mating repressors TEC1 and DIG1 is decreased. Cph1 and Tec1, factors that act downstream of the pheromone MAPK pathway, play opposite roles in regulating white cell mating as TEC1 deletion or CPH1 overexpression promotes white cell mating. Moreover, inactivation of the Cph1 repressor Dig1 increases white cell mating ~4000 fold in glucose-depleted medium relative to that in the presence of glucose. Our findings reveal that the white-to-opaque epigenetic switch may not be a prerequisite for sexual mating in C. albicans in nature.
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Affiliation(s)
- Guobo Guan
- Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Shanghai Institute of Infectious Disease and Biosecurity and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Li Tao
- Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Shanghai Institute of Infectious Disease and Biosecurity and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Chao Li
- Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Shanghai Institute of Infectious Disease and Biosecurity and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ming Xu
- Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Shanghai Institute of Infectious Disease and Biosecurity and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China
| | - Ling Liu
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Richard J Bennett
- Molecular Microbiology and Immunology Department, Brown University, Providence, RI, 02912, USA
| | - Guanghua Huang
- Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Shanghai Institute of Infectious Disease and Biosecurity and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China.
- Shanghai Engineering Research Center of Industrial Microorganisms, Shanghai, 200438, China.
- Shanghai Huashen Institute of Microbes and Infections, Shanghai, 200052, China.
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4
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Yadav V, Sun S, Heitman J. On the evolution of variation in sexual reproduction through the prism of eukaryotic microbes. Proc Natl Acad Sci U S A 2023; 120:e2219120120. [PMID: 36867686 PMCID: PMC10013875 DOI: 10.1073/pnas.2219120120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 01/23/2023] [Indexed: 03/05/2023] Open
Abstract
Almost all eukaryotes undergo sexual reproduction to generate diversity and select for fitness in their population pools. Interestingly, the systems by which sex is defined are highly diverse and can even differ between evolutionarily closely related species. While the most commonly known form of sex determination involves males and females in animals, eukaryotic microbes can have as many as thousands of different mating types for the same species. Furthermore, some species have found alternatives to sexual reproduction and prefer to grow clonally and yet undergo infrequent facultative sexual reproduction. These organisms are mainly invertebrates and microbes, but several examples are also present among vertebrates suggesting that alternative modes of sexual reproduction evolved multiple times throughout evolution. In this review, we summarize the sex-determination modes and variants of sexual reproduction found across the eukaryotic tree of life and suggest that eukaryotic microbes provide unique opportunities to study these processes in detail. We propose that understanding variations in modes of sexual reproduction can serve as a foundation to study the evolution of sex and why and how it evolved in the first place.
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Affiliation(s)
- Vikas Yadav
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC27710
| | - Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC27710
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC27710
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5
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Brenes LR, Johnson AD, Lohse MB. Farnesol and phosphorylation of the transcriptional regulator Efg1 affect Candida albicans white-opaque switching rates. PLoS One 2023; 18:e0280233. [PMID: 36662710 PMCID: PMC9858334 DOI: 10.1371/journal.pone.0280233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/24/2022] [Indexed: 01/21/2023] Open
Abstract
Candida albicans is a normal member of the human microbiome and an opportunistic fungal pathogen. This species undergoes several morphological transitions, and here we consider white-opaque switching. In this switching program, C. albicans reversibly alternates between two cell types, named "white" and "opaque," each of which is normally stable across thousands of cell divisions. Although switching under most conditions is stochastic and rare, certain environmental signals or genetic manipulations can dramatically increase the rate of switching. Here, we report the identification of two new inputs which affect white-to-opaque switching rates. The first, exposure to sub-micromolar concentrations of (E,E)-farnesol, reduces white-to-opaque switching by ten-fold or more. The second input, an inferred PKA phosphorylation of residue T208 on the transcriptional regulator Efg1, increases white-to-opaque switching ten-fold. Combining these and other environmental inputs results in a variety of different switching rates, indicating that a given rate represents the integration of multiple inputs.
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Affiliation(s)
- Lucas R. Brenes
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Alexander D. Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America
| | - Matthew B. Lohse
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
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Khan A, Moni SS, Ali M, Mohan S, Jan H, Rasool S, Kamal MA, Alshahrani S, Halawi M, Alhazmi HA. Antifungal Activity of Plant Secondary Metabolites on Candida albicans: An Updated Review. Curr Mol Pharmacol 2023; 16:15-42. [PMID: 35249516 DOI: 10.2174/1874467215666220304143332] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 11/24/2021] [Accepted: 12/06/2021] [Indexed: 11/22/2022]
Abstract
Fungal infections have been increasing continuously worldwide, especially in immunocompromised individuals. Fungi, regarded as eukaryotic pathogens, have many similarities to the host cells, which inhibit anti-fungal drug development progress. Various fungal model systems have been studied, and it was concluded that Candida spp. is the most common disease-causing fungus. Candida species are well known to cause infections not only in our mouth, skin, and vagina, but they are also a frequent cause of life-threatening hospital bloodstream infections. The morphological and developmental pathways of Candida have been studied extensively, providing insight into the fungus development. Candida albicans is known to be the most pathogenic species responsible for a variety of infections in humans. Conventional anti-fungal drugs, mainly azoles drugs available in the market, have been used for years developing resistance in C. albicans. Hence, the production of new anti-fungal drugs, which require detailed molecular knowledge of fungal pathogenesis, needs to be encouraged. Therefore, this review targets the new approach of "Green Medicines" or the phytochemicals and their secondary metabolites as a source of novel anti-fungal agents to overcome the drug resistance of C. albicans, their mechanism of action, and their combined effects with the available anti-fungal drugs.
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Affiliation(s)
- Andleeb Khan
- Department of Pharmacology and Toxicology, College of Pharmacy, Jazan University, Jazan, 45142, Saudi Arabia
| | | | - M Ali
- Department of Pharmacognosy, College of Pharmacy, Jazan University, Jazan, 45142, Saudi Arabia
| | - Syam Mohan
- Substance Abuse and Toxicology Research Center, Jazan University, Jazan, 45142, Saudi Arabia
- School of Health Sciences, University of Petroleum and Energy Studies, Dehradun, Uttarakhand, India
| | - Huma Jan
- Department of Clinical Biochemistry, University of Kashmir, Hazratbal, Srinagar -190006, J&K, India
| | - Saiema Rasool
- Department of School Education, Govt. of Jammu & Kashmir, Srinagar, 190001 J&K, India
| | - Mohammad A Kamal
- Institutes for Systems Genetics, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu 610041, Sichuan, China
- King Fahd Medical Research Center, King Abdulaziz University, P. O. Box 80216, Jeddah 21589. Saudi Arabia
- Department of Pharmacy, Faculty of Allied Health Sciences, Daffodil International University, Dhaka 1207, Bangladesh
- Enzymoics, 7 Peterlee place, Hebersham, NSW 2770; Novel Global Community Educational Foundation, Australia
| | - Saeed Alshahrani
- Department of Pharmacology and Toxicology, College of Pharmacy, Jazan University, Jazan, 45142, Saudi Arabia
| | - Maryam Halawi
- Department of Clinical Pharmacy, College of Pharmacy, Jazan University, Jazan, 45142, Saudi Arabia
| | - Hassan A Alhazmi
- Substance Abuse and Toxicology Research Center, Jazan University, Jazan, 45142, Saudi Arabia
- Department of Pharmaceutical Chemistry, College of Pharmacy, Jazan University, Jazan, 45142, Saudi Arabia
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7
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Du H, Zheng Q, Bennett RJ, Huang G. Ploidy changes in human fungal pathogens: Going beyond sexual reproduction. PLoS Pathog 2022; 18:e1010954. [PMID: 36480532 PMCID: PMC9731408 DOI: 10.1371/journal.ppat.1010954] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Han Du
- Shanghai Institute of Infectious Disease and Biosecurity, Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- College of Pharmaceutical Sciences, Southwest University, Chongqing, China
| | - Qiushi Zheng
- Shanghai Institute of Infectious Disease and Biosecurity, Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, China
| | - Richard J. Bennett
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, United States of America
| | - Guanghua Huang
- Shanghai Institute of Infectious Disease and Biosecurity, Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, State Key Laboratory of Genetic Engineering, School of Life Science, Fudan University, Shanghai, China
- Shanghai Engineering Research Center of Industrial Microorganisms, Fudan University, Shanghai, China
- Shanghai Huashen Institute of Microbes and Infections, Shanghai, China
- * E-mail:
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8
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Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris. Cell Microbiol 2022. [DOI: 10.1155/2022/2599136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.
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9
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de Souza CM, Moralez ATP, Dos Santos MM, Mantovani MS, Furlaneto-Maia L, Furlaneto MC. Deciphering Colonies of Phenotypic Switching-Derived Morphotypes of the Pathogenic Yeast Candida tropicalis. Mycopathologia 2022; 187:509-516. [PMID: 36057915 DOI: 10.1007/s11046-022-00663-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 08/18/2022] [Indexed: 11/29/2022]
Abstract
BACKGROUND Phenotypic switching generates fungal colonies with altered morphology and allows pathogens to adapt to changing environments. OBJECTIVE This study investigated the structure and genetic factors of switched morphotypes colonies in Candida tropicalis. METHODS Morphotypes of C. tropicalis comprised the clinical strain 49.07 that exhibited smooth colony phenotype and switched (crepe and rough) morphotypes that showed colonies with marked structural variations, including wrinkled surface, depressions areas, and irregular edges (structured morphology). The morphotypes were analyzed for the presence and distribution of the extracellular matrix (ECM) at the ultrastructural level-SEM. The composition of the ECM and the percentage of hyphae in colonies were evaluated. The expression of EFG1 (Enhanced filamentous growth protein 1), WOR1 (White-opaque regulator 1), and BCR1 (Biofilm and cell wall regulator 1) in the morphotypes was measured by RT-qPCR. RESULTS Colonies of the switched variants exhibited distinct arrangements of ECM compared to the smooth phenotype (clinical strain). In addition, rough variant colonies showed higher amounts of total carbohydrates and proteins in ECM (p < 0.05). Switched (crepe and rough) colonies exhibited a higher percentage of hyphae throughout their development (p < 0.05). The mRNA expression levels of EFG1, WOR1, and BCR1 in the rough morphotype were significantly higher than they were in the smooth morphotype. In addition, there was a positive correlation between the expression of these genes and filamentation (hyphae formation) of the rough morphotype (r2 > 0.9472, p < 0.05). CONCLUSION Structural variations in switched morphotypes colonies of C. tropicalis seem to be associated with increased hyphae growth and the amount and distribution of ECM. Switched colonies have distinct expressions of the EFG1, WOR1, and BCR1 master regulators genes.
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Affiliation(s)
- Cássia Milena de Souza
- Department of Microbiology, Center of Biological Sciences, Paraná State University of Londrina, Rodovia Celso Garcia Cid, Pr 445 Km 380, C.P. 6001, Londrina, Paraná, 86051990, Brazil
| | - Alane Tatiana Pereira Moralez
- Department of Microbiology, Center of Biological Sciences, Paraná State University of Londrina, Rodovia Celso Garcia Cid, Pr 445 Km 380, C.P. 6001, Londrina, Paraná, 86051990, Brazil
| | - Murilo Moreira Dos Santos
- Department of Microbiology, Center of Biological Sciences, Paraná State University of Londrina, Rodovia Celso Garcia Cid, Pr 445 Km 380, C.P. 6001, Londrina, Paraná, 86051990, Brazil
| | | | | | - Marcia Cristina Furlaneto
- Department of Microbiology, Center of Biological Sciences, Paraná State University of Londrina, Rodovia Celso Garcia Cid, Pr 445 Km 380, C.P. 6001, Londrina, Paraná, 86051990, Brazil.
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10
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Lima R, Ribeiro FC, Colombo AL, de Almeida JN. The emerging threat antifungal-resistant Candida tropicalis in humans, animals, and environment. FRONTIERS IN FUNGAL BIOLOGY 2022; 3:957021. [PMID: 37746212 PMCID: PMC10512401 DOI: 10.3389/ffunb.2022.957021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 07/28/2022] [Indexed: 09/26/2023]
Abstract
Antifungal resistance in humans, animals, and the environment is an emerging problem. Among the different fungal species that can develop resistance, Candida tropicalis is ubiquitous and causes infections in animals and humans. In Asia and some Latin American countries, C. tropicalis is among the most common species related to candidemia, and mortality rates are usually above 40%. Fluconazole resistance is especially reported in Asian countries and clonal spread in humans and the environment has been investigated in some studies. In Brazil, high rates of azole resistance have been found in animals and the environment. Multidrug resistance is still rare, but recent reports of clinical multidrug-resistant isolates are worrisome. The molecular apparatus of antifungal resistance has been majorly investigated in clinical C. tropicalis isolates, revealing that this species can develop resistance through the conjunction of different adaptative mechanisms. In this review article, we summarize the main findings regarding antifungal resistance and Candida tropicalis through an "One Health" approach.
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Affiliation(s)
- Ricardo Lima
- Special Mycology Laboratory, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Felipe C. Ribeiro
- Special Mycology Laboratory, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Arnaldo L. Colombo
- Special Mycology Laboratory, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
| | - Joăo N. de Almeida
- Special Mycology Laboratory, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, Brazil
- Clinical Laboratory, Hospital Israelita Albert Einstein, São Paulo, Brazil
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11
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Jafarian H, Hardani AK, Asnafi AA, Mahmoudabadi AZ. Population structure, susceptibility profile, phenotypic and mating properties of Candida tropicalis isolated from pediatric patients. Microb Pathog 2022; 170:105690. [PMID: 35917988 DOI: 10.1016/j.micpath.2022.105690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 07/15/2022] [Accepted: 07/19/2022] [Indexed: 10/16/2022]
Abstract
BACKGROUND Candida tropicalis is one of the most frequently isolated species and is commonly associated with nosocomial infections, hematological malignancy, neutropenia, and urinary tract infections. AIMS This study aims to genotype C. tropicalis strains isolated from pediatric patients admitted to two hospitals in Ahvaz, Iran. We provide a vision of the genotypes, mating types, enzymatic activity, phenotypes, and antifungal susceptibility profile of these isolates. METHODS Candida tropicalis isolates were collected from various clinical (Oral, urine, wound, and bronchoalveolar lavage) and environmental sources between November 2020 and November 2021. Primitively, samples were cultured on CHROMagar Candida. All isolates were identified by sequencing the Internal Transcribed Spacer (ITS) region for precise identification. Isolates were genotyped by six microsatellite markers specific for C. tropicalis. Antifungal susceptibility profiles were determined against eight antifungal agents according to CLSI M27 standards. The phenotype of each C. tropicalis isolate was assessed using yeast peptone dextrose agar supplemented with phloxine B. Mating types of C. tropicalis isolates were determined using MTLa1 and MTL2 specific primers. RESULTS Species identification revealed 46 C. tropicalis strains. Among them, 39 different genotypes were detected that have split into 34 singletons and five clusters. Twenty isolates were the non-wild type for itraconazole and posaconazole. Four isolates were multidrug-resistant. The activity of hemolysin and esterase enzyme was very strong among all isolates. Mating type and phenotype were not significantly correlated with genotypes (p = 0.721 and p = 0.135, respectively). CONCLUSIONS To conclude, tested populations were moderately differentiated with high gene flow. One cluster of isolates among different hospitals was identified, and three clusters were from different cities.
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Affiliation(s)
- Hadis Jafarian
- Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Department of Medical Mycology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Amir Kamal Hardani
- Department of Pediatrics, School of Medicine, Abuzar Children Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Ali Amin Asnafi
- Thalassemia and Hemoglobinopathy Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Ali Zarei Mahmoudabadi
- Infectious and Tropical Diseases Research Center, Health Research Institute, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran; Department of Medical Mycology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
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12
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Mating-Type Switching in Budding Yeasts, from Flip/Flop Inversion to Cassette Mechanisms. Microbiol Mol Biol Rev 2022; 86:e0000721. [PMID: 35195440 PMCID: PMC8941940 DOI: 10.1128/mmbr.00007-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mating-type switching is a natural but unusual genetic control process that regulates cell identity in ascomycete yeasts. It involves physically replacing one small piece of genomic DNA by another, resulting in replacement of the master regulatory genes in the mating pathway and hence a switch of cell type and mating behavior. In this review, we concentrate on recent progress that has been made on understanding the origins and evolution of mating-type switching systems in budding yeasts (subphylum Saccharomycotina). Because of the unusual nature and the complexity of the mechanism in Saccharomyces cerevisiae, mating-type switching was assumed until recently to have originated only once or twice during yeast evolution. However, comparative genomics analysis now shows that switching mechanisms arose many times independently-at least 11 times in budding yeasts and once in fission yeasts-a dramatic example of convergent evolution. Most of these lineages switch mating types by a flip/flop mechanism that inverts a section of a chromosome and is simpler than the well-characterized 3-locus cassette mechanism (MAT/HML/HMR) used by S. cerevisiae. Mating-type switching (secondary homothallism) is one of the two possible mechanisms by which a yeast species can become self-fertile. The other mechanism (primary homothallism) has also emerged independently in multiple evolutionary lineages of budding yeasts, indicating that homothallism has been favored strongly by natural selection. Recent work shows that HO endonuclease, which makes the double-strand DNA break that initiates switching at the S. cerevisiae MAT locus, evolved from an unusual mobile genetic element that originally targeted a glycolytic gene, FBA1.
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13
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Ziv N, Brenes LR, Johnson A. Multiple molecular events underlie stochastic switching between 2 heritable cell states in fungi. PLoS Biol 2022; 20:e3001657. [PMID: 35594297 PMCID: PMC9162332 DOI: 10.1371/journal.pbio.3001657] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 06/02/2022] [Accepted: 05/04/2022] [Indexed: 02/07/2023] Open
Abstract
Eukaryotic transcriptional networks are often large and contain several levels of feedback regulation. Many of these networks have the ability to generate and maintain several distinct transcriptional states across multiple cell divisions and to switch between them. In certain instances, switching between cell states is stochastic, occurring in a small subset of cells of an isogenic population in a seemingly homogenous environment. Given the scarcity and unpredictability of switching in these cases, investigating the determining molecular events is challenging. White-opaque switching in the fungal species Candida albicans is an example of stably inherited cell states that are determined by a complex transcriptional network and can serve as an experimentally accessible model system to study characteristics important for stochastic cell fate switching in eukaryotes. In standard lab media, genetically identical cells maintain their cellular identity (either "white" or "opaque") through thousands of cell divisions, and switching between the states is rare and stochastic. By isolating populations of white or opaque cells, previous studies have elucidated the many differences between the 2 stable cell states and identified a set of transcriptional regulators needed for cell type switching and maintenance of the 2 cell types. Yet, little is known about the molecular events that determine the rare, stochastic switching events that occur in single cells. We use microfluidics combined with fluorescent reporters to directly observe rare switching events between the white and opaque states. We investigate the stochastic nature of switching by beginning with white cells and monitoring the activation of Wor1, a master regulator and marker for the opaque state, in single cells and throughout cell pedigrees. Our results indicate that switching requires 2 stochastic steps; first an event occurs that predisposes a lineage of cells to switch. In the second step, some, but not all, of those predisposed cells rapidly express high levels of Wor1 and commit to the opaque state. To further understand the rapid rise in Wor1, we used a synthetic inducible system in Saccharomyces cerevisiae into which a controllable C. albicans Wor1 and a reporter for its transcriptional control region have been introduced. We document that Wor1 positive autoregulation is highly cooperative (Hill coefficient > 3), leading to rapid activation and producing an "all or none" rather than a graded response. Taken together, our results suggest that reaching a threshold level of a master regulator is sufficient to drive cell type switching in single cells and that an earlier molecular event increases the probability of reaching that threshold in certain small lineages of cells. Quantitative molecular analysis of the white-opaque circuit can serve as a model for the general understanding of complex circuits.
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Affiliation(s)
- Naomi Ziv
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail: (NZ); (AJ)
| | - Lucas R. Brenes
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Alexander Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- * E-mail: (NZ); (AJ)
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14
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Abstract
CRISPR-Cas9 technology radically changed the approach to genetic manipulation of both medically and industrially relevant Candida species, as attested by the ever-increasing number of applications to the study of pathogenesis, drug resistance, gene expression, and host pathogen interaction and drug discovery. Here, we describe the use of plasmid-based systems for high efficiency CRISPR-Cas9 gene editing into any strain of four non-albicans Candida species, namely, Candida parapsilosis, Candida orthopsilosis, Candida metapsilosis, and Candida tropicalis. The plasmids pCP-tRNA and pCT-tRNA contain all the elements necessary for expressing the CRISPR-Cas9 machinery, and they can be used in combination with a repair template for disrupting gene function by insertion of a premature stop codon or by gene deletion. The plasmids are easily lost in the absence of selection, allowing scarless gene editing and minimizing detrimental effects of prolonged Cas9 expression.
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Affiliation(s)
- Lisa Lombardi
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin, Ireland.
| | - Geraldine Butler
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin, Ireland
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15
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Mishra A, Forche A, Anderson MZ. Parasexuality of Candida Species. Front Cell Infect Microbiol 2021; 11:796929. [PMID: 34966696 PMCID: PMC8711763 DOI: 10.3389/fcimb.2021.796929] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 11/19/2021] [Indexed: 12/03/2022] Open
Abstract
While most fungi have the ability to reproduce sexually, multiple independent lineages have lost meiosis and developed parasexual cycles in its place. Emergence of parasexual cycles is particularly prominent in medically relevant fungi from the CUG paraphyletic group of Candida species. Since the discovery of parasex in C. albicans roughly two decades ago, it has served as the model for Candida species. Importantly, parasex in C. albicans retains hallmarks of meiosis including genetic recombination and chromosome segregation, making it a potential driver of genetic diversity. Furthermore, key meiotic genes play similar roles in C. albicans parasex and highlights parallels between these processes. Yet, the evolutionary role of parasex in Candida adaptation and the extent of resulting genotypic and phenotypic diversity remain as key knowledge gaps in this facultative reproductive program. Here, we present our current understanding of parasex, the mechanisms governing its regulation, and its relevance to Candida biology.
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Affiliation(s)
- Abhishek Mishra
- Department of Microbiology, The Ohio State University, Columbus, OH, United States
| | - Anja Forche
- Department of Biology, Bowdoin College, Brunswick, ME, United States
| | - Matthew Z Anderson
- Department of Microbiology, The Ohio State University, Columbus, OH, United States.,Department of Microbial Infection and Immunity, The Ohio State University, Columbus, OH, United States
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16
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Xu J. Is Natural Population of Candida tropicalis Sexual, Parasexual, and/or Asexual? Front Cell Infect Microbiol 2021; 11:751676. [PMID: 34760719 PMCID: PMC8573272 DOI: 10.3389/fcimb.2021.751676] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 10/12/2021] [Indexed: 01/04/2023] Open
Abstract
Candida tropicalis is one of the most common opportunistic yeast pathogens of humans, especially prevalent in tropical and subtropical regions. This yeast has broad ecological distributions, can be found in both terrestrial and aquatic ecosystems, including being associated with a diversity of trees, animals, and humans. Evolutionary theory predicts that organisms thriving in diverse ecological niches likely have efficient mechanisms to generate genetic diversity in nature. Indeed, abundant genetic variations have been reported in natural populations (both environmental and clinical) of C. tropicalis. However, at present, our understanding on how genetic diversity is generated in natural C. tropicalis population remains controversial. In this paper, I review the current understanding on the potential modes of reproduction in C. tropicalis. I describe expectations of the three modes of reproduction (sexual, parasexual, and asexual) and compare them with the observed genotypic variations in natural populations. Though sexual and parasexual reproduction cannot be excluded, the analyses suggest asexual reproduction alone could explain all the observations reported so far. The results here have implications for understanding the evolution and epidemiology of C. tropicalis and other related human fungal pathogens.
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Affiliation(s)
- Jianping Xu
- Institute of Bast Fiber Crops and Center of Southern Economic Crops, Chinese Academy of Agricultural Sciences, Changsha, China.,Department of Biology, McMaster University, Hamilton, ON, Canada
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17
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Qiu L, Zhang TS, Song JZ, Zhang J, Li Z, Wang JJ. BbWor1, a Regulator of Morphological Transition, Is Involved in Conidium-Hypha Switching, Blastospore Propagation, and Virulence in Beauveria bassiana. Microbiol Spectr 2021; 9:e0020321. [PMID: 34319134 PMCID: PMC8552717 DOI: 10.1128/spectrum.00203-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 07/07/2021] [Indexed: 12/16/2022] Open
Abstract
Morphological transition is an important adaptive mechanism in the host invasion process. Wor1 is a conserved fungal regulatory protein that controls the phenotypic switching and pathogenicity of Candida albicans. By modulating growth conditions, we simulated three models of Beauveria bassiana morphological transitions, including CTH (conidia to hyphae), HTC (hyphae to conidia), and BTB (blastospore to blastospore). Disruption of BbWor1 (an ortholog of Wor1) resulted in a distinct reduction in the time required for conidial germination (CTH), a significant increase in hyphal growth, and a decrease in the yield of conidia (HTC), indicating that BbWor1 positively controls conidium production and negatively regulates hyphal growth in conidium-hypha switching. Moreover, ΔBbWor1 prominently decreased blastospore yield, shortened the G0/G1 phase, and prolonged the G2/M phase under the BTB model. Importantly, BbWor1 contributed to conidium-hypha switching and blastospore propagation via different genetic pathways, and yeast one-hybrid testing demonstrated the necessity of BbWor1 to control the transcription of an allergen-like protein gene (BBA_02580) and a conidial wall protein gene (BBA_09998). Moreover, the dramatically weakened virulence of ΔBbWor1 was examined by immersion and injection methods. Our findings indicate that BbWor1 is a vital participant in morphological transition and pathogenicity in entomopathogenic fungi. IMPORTANCE As a well-known entomopathogenic fungus, Beauveria bassiana has a complex life cycle and involves transformations among single-cell conidia, blastospores, and filamentous hyphae. This study provides new insight into the regulation of the fungal cell morphological transitions by simulating three models. Our research identified BbWor1 as a core transcription factor of morphological differentiation that positively regulates the production of conidia and blastospores but negatively regulates hyphal growth. More importantly, BbWor1 affects fungal pathogenicity and the global transcription profiles within three models of growth stage transformation. The present study lays a foundation for the exploration of the transition mechanism of entomopathogenic fungi and provides material for the morphological study of fungi.
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Affiliation(s)
- Lei Qiu
- School of Biological Science and Technology, University of Jinan, Jinan, China
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China
| | - Tong-Sheng Zhang
- School of Biological Science and Technology, University of Jinan, Jinan, China
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China
| | - Ji-Zheng Song
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China
| | - Jing Zhang
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China
| | - Ze Li
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan, China
| | - Juan-Juan Wang
- School of Biological Science and Technology, University of Jinan, Jinan, China
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18
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Han C, Kwon H, Park G, Jang M, Lee HJ, Seo S, Kwon M, Jeon W, Lee H, Lee H, Ahn J. Enhanced mating-type switching and sexual hybridization in heterothallic yeast Yarrowia lipolytica. FEMS Yeast Res 2021; 20:5762678. [PMID: 32105315 DOI: 10.1093/femsyr/foaa011] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 02/26/2020] [Indexed: 12/12/2022] Open
Abstract
Yarrowia lipolytica is a non-conventional, heterothallic, oleaginous yeast with wide range of industrial applications. Increasing ploidy can improve advantageous traits for industrial applications including genetic stability, stress resistance, and productivity, but the construction of knockout mutant strains from polyploid cells requires significant effort due to the increased copy numbers of target genes. The goal of this study was to evaluate the effectiveness of a mating-type switching strategy by single-step transformation without a genetic manipulation vestige, and to optimize the conventional method for increasing ploidy (mating) in Y. lipolytica. In this study, mating-type genes in haploid Y. lipolytica cells were scarlessly converted into the opposite type genes by site-specific homologous recombination, and the resulting MATB-type cells were mated at low temperature (22°C) with addition of sodium citrate with each MATA-type haploid cell to yield a MATA/MATB-type diploid strain with genetic information from both parental strains. The results of this study can be used to increase ploidy and for whole genome engineering of a yeast strain with unparalleled versatility for industrial application.
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Affiliation(s)
- Changpyo Han
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea.,Interdisciplinary Program for Bioengineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
| | - Heeun Kwon
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea
| | - Gyuyeon Park
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea.,KRIBB School of Biotechnology, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
| | - Minjeong Jang
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea
| | - Hye-Jeong Lee
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea
| | - Sunghwa Seo
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea
| | - Mincheol Kwon
- Anticancer Agent Research Center, Korea Research Institute of Bioscience and Biotechnology, Cheongju 28116, Republic of Korea.,Department of Biomolecular Science, KRIBB School of Bioscience, University of Science and Technology, Daejeon 34141, Republic of Korea
| | - Wooyoung Jeon
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea
| | - Heeseok Lee
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea.,KRIBB School of Biotechnology, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
| | - Hongweon Lee
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea.,KRIBB School of Biotechnology, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
| | - Jungoh Ahn
- Biotechnology Process Engineering Center, Korea Research Institute of Bioscience and Biotechnology, 30 Yeongudanji-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 28116, Republic of Korea.,KRIBB School of Biotechnology, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
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19
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Mancera E, Nocedal I, Hammel S, Gulati M, Mitchell KF, Andes DR, Nobile CJ, Butler G, Johnson AD. Evolution of the complex transcription network controlling biofilm formation in Candida species. eLife 2021; 10:e64682. [PMID: 33825680 PMCID: PMC8075579 DOI: 10.7554/elife.64682] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 04/06/2021] [Indexed: 12/30/2022] Open
Abstract
We examine how a complex transcription network composed of seven 'master' regulators and hundreds of target genes evolved over a span of approximately 70 million years. The network controls biofilm formation in several Candida species, a group of fungi that are present in humans both as constituents of the microbiota and as opportunistic pathogens. Using a variety of approaches, we observed two major types of changes that have occurred in the biofilm network since the four extant species we examined last shared a common ancestor. Master regulator 'substitutions' occurred over relatively long evolutionary times, resulting in different species having overlapping but different sets of master regulators of biofilm formation. Second, massive changes in the connections between the master regulators and their target genes occurred over much shorter timescales. We believe this analysis is the first detailed, empirical description of how a complex transcription network has evolved.
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Affiliation(s)
- Eugenio Mancera
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad IrapuatoIrapuatoMexico
| | - Isabel Nocedal
- Department of Microbiology and Immunology, University of California, San FranciscoSan FranciscoUnited States
| | - Stephen Hammel
- School of Biomolecular and Biomedical Science, Conway Institute, University College DublinDublinIreland
| | - Megha Gulati
- Department of Molecular and Cell Biology, University of California, MercedMercedUnited States
| | - Kaitlin F Mitchell
- Department of Medical Microbiology and Immunology, University of WisconsinMadisonUnited States
| | - David R Andes
- Department of Medical Microbiology and Immunology, University of WisconsinMadisonUnited States
| | - Clarissa J Nobile
- Department of Molecular and Cell Biology, University of California, MercedMercedUnited States
| | - Geraldine Butler
- School of Biomolecular and Biomedical Science, Conway Institute, University College DublinDublinIreland
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California, San FranciscoSan FranciscoUnited States
- Microbiome Initiative, Chan Zuckerberg BiohubSan FranciscoUnited States
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20
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O’Brien CE, Oliveira-Pacheco J, Ó Cinnéide E, Haase MAB, Hittinger CT, Rogers TR, Zaragoza O, Bond U, Butler G. Population genomics of the pathogenic yeast Candida tropicalis identifies hybrid isolates in environmental samples. PLoS Pathog 2021; 17:e1009138. [PMID: 33788904 PMCID: PMC8041210 DOI: 10.1371/journal.ppat.1009138] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 04/12/2021] [Accepted: 03/15/2021] [Indexed: 01/02/2023] Open
Abstract
Candida tropicalis is a human pathogen that primarily infects the immunocompromised. Whereas the genome of one isolate, C. tropicalis MYA-3404, was originally sequenced in 2009, there have been no large-scale, multi-isolate studies of the genetic and phenotypic diversity of this species. Here, we used whole genome sequencing and phenotyping to characterize 77 isolates of C. tropicalis from clinical and environmental sources from a variety of locations. We show that most C. tropicalis isolates are diploids with approximately 2-6 heterozygous variants per kilobase. The genomes are relatively stable, with few aneuploidies. However, we identified one highly homozygous isolate and six isolates of C. tropicalis with much higher heterozygosity levels ranging from 36-49 heterozygous variants per kilobase. Our analyses show that the heterozygous isolates represent two different hybrid lineages, where the hybrids share one parent (A) with most other C. tropicalis isolates, but the second parent (B or C) differs by at least 4% at the genome level. Four of the sequenced isolates descend from an AB hybridization, and two from an AC hybridization. The hybrids are MTLa/α heterozygotes. Hybridization, or mating, between different parents is therefore common in the evolutionary history of C. tropicalis. The new hybrids were predominantly found in environmental niches, including from soil. Hybridization is therefore unlikely to be associated with virulence. In addition, we used genotype-phenotype correlation and CRISPR-Cas9 editing to identify a genome variant that results in the inability of one isolate to utilize certain branched-chain amino acids as a sole nitrogen source.
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Affiliation(s)
- Caoimhe E. O’Brien
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
| | - João Oliveira-Pacheco
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
| | - Eoin Ó Cinnéide
- School of Medicine, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
| | - Max A. B. Haase
- Laboratory of Genetics, Center for Genomic Science Innovation, Wisconsin Energy Institute, DOE Great Lakes Bioenergy Research Center, J.F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Chris Todd Hittinger
- Laboratory of Genetics, Center for Genomic Science Innovation, Wisconsin Energy Institute, DOE Great Lakes Bioenergy Research Center, J.F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Thomas R. Rogers
- Department of Clinical Microbiology, Trinity College Dublin, Dublin, Ireland; Department of Microbiology, St James’s Hospital, Dublin, Ireland
| | - Oscar Zaragoza
- Mycology Reference Laboratory, National Centre for Microbiology, Instituto de Salud Carlos III, Carretera Majadahonda-Pozuelo, Km2, Majadahonda, Madrid, Spain
| | - Ursula Bond
- Department of Microbiology, School of Genetics and Microbiology, Trinity College Dublin, Ireland
| | - Geraldine Butler
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Belfield, Dublin, Ireland
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21
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Beekman CN, Cuomo CA, Bennett RJ, Ene IV. Comparative genomics of white and opaque cell states supports an epigenetic mechanism of phenotypic switching in Candida albicans. G3 (BETHESDA, MD.) 2021; 11:6108101. [PMID: 33585874 PMCID: PMC8366294 DOI: 10.1093/g3journal/jkab001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 12/28/2020] [Indexed: 01/08/2023]
Abstract
Several Candida species can undergo a heritable and reversible transition from a 'white' state to a mating proficient 'opaque' state. This ability relies on highly interconnected transcriptional networks that control cell-type-specific gene expression programs over multiple generations. Candida albicans, the most prominent pathogenic Candida species, provides a well-studied paradigm for the white-opaque transition. In this species, a network of at least eight transcriptional regulators controls the balance between white and opaque states that have distinct morphologies, transcriptional profiles, and physiological properties. Given the reversible nature and the high frequency of white-opaque transitions, it is widely assumed that this switch is governed by epigenetic mechanisms that occur independently of any changes in DNA sequence. However, a direct genomic comparison between white and opaque cells has yet to be performed. Here, we present a whole-genome comparative analysis of C. albicans white and opaque cells. This analysis revealed rare genetic changes between cell states, none of which are linked to white-opaque switching. This result is consistent with epigenetic mechanisms controlling cell state differentiation in C. albicans and provides direct evidence against a role for genetic variation in mediating the switch.
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Affiliation(s)
- Chapman N Beekman
- Department of Molecular Microbiology and Immunology,
Brown University, Providence, RI 02912, USA
| | - Christina A Cuomo
- Infectious Disease and Microbiome Program, Broad
Institute, Cambridge, MA 02142, USA
| | - Richard J Bennett
- Department of Molecular Microbiology and Immunology,
Brown University, Providence, RI 02912, USA
| | - Iuliana V Ene
- Department of Molecular Microbiology and Immunology,
Brown University, Providence, RI 02912, USA
- Corresponding author:
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22
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Lew SQ, Lin CH. N-acetylglucosamine-mediated morphological transition in Candida albicans and Candida tropicalis. Curr Genet 2021; 67:249-254. [PMID: 33388851 DOI: 10.1007/s00294-020-01138-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 10/22/2022]
Abstract
Morphological transitions in Candida species are key factors in facilitating invasion and adapting to environmental changes. N-acetylglucosamine (GlcNAc) is a monosaccharide signalling molecule that can regulate morphological transitions in Candida albicans and Candida tropicalis. Interestingly, although the uptake and metabolic pathways of GlcNAc and GlcNAc-mediated white-to-opaque cell switching are similar between the two Candida species, GlcNAc induces hyphal development in C. albicans, whereas it suppresses hyphal development in C. tropicalis. These findings indicate that the characteristics of C. albicans and C. tropicalis in response to GlcNAc are remarkably different. Here, we compare the conserved and divergent GlcNAc-mediated signalling pathways and catabolism between the two Candida species. Deletion of NGT1, a GlcNAc transportation gene, inhibited hyphal formation in C. albicans but promoted hyphal development in C. tropicalis. To further understand these opposite effects on filamentous growth in response to GlcNAc in the two Candida species, the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) signalling pathways in both C. albicans and C. tropicalis were compared. Interestingly, GlcNAc activated the cAMP/PKA signalling pathway of the two Candida species, suggesting that the hyphal development-regulated circuit is remarkably diverse between the two species. Indeed, the Ndt80-like gene REP1, which is critical for regulating GlcNAc catabolism, exhibits distinct roles in the hyphal development of C. albicans and C. tropicalis. These data suggest possible reasons for the divergent hyphal growth response in C. albicans and C. tropicalis upon GlcNAc induction.
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Affiliation(s)
- Shi Qian Lew
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan
| | - Ching-Hsuan Lin
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan.
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23
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Lohse MB, Brenes LR, Ziv N, Winter MB, Craik CS, Johnson AD. An Opaque Cell-Specific Expression Program of Secreted Proteases and Transporters Allows Cell-Type Cooperation in Candida albicans. Genetics 2020; 216:409-429. [PMID: 32839241 PMCID: PMC7536846 DOI: 10.1534/genetics.120.303613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 08/20/2020] [Indexed: 11/18/2022] Open
Abstract
An unusual feature of the opportunistic pathogen Candida albicans is its ability to switch stochastically between two distinct, heritable cell types called white and opaque. Here, we show that only opaque cells, in response to environmental signals, massively upregulate a specific group of secreted proteases and peptide transporters, allowing exceptionally efficient use of proteins as sources of nitrogen. We identify the specific proteases [members of the secreted aspartyl protease (SAP) family] needed for opaque cells to proliferate under these conditions, and we identify four transcriptional regulators of this specialized proteolysis and uptake program. We also show that, in mixed cultures, opaque cells enable white cells to also proliferate efficiently when proteins are the sole nitrogen source. Based on these observations, we suggest that one role of white-opaque switching is to create mixed populations where the different phenotypes derived from a single genome are shared between two distinct cell types.
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Affiliation(s)
- Matthew B Lohse
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143
| | - Lucas R Brenes
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143
| | - Naomi Ziv
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143
| | - Michael B Winter
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143
| | - Charles S Craik
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, California 94143
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24
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A Set of Diverse Genes Influence the Frequency of White-Opaque Switching in Candida albicans. G3-GENES GENOMES GENETICS 2020; 10:2593-2600. [PMID: 32487674 PMCID: PMC7407467 DOI: 10.1534/g3.120.401249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The fungal species Candida albicans is both a member of the human microbiome and a fungal pathogen. C. albicans undergoes several different morphological transitions, including one called white-opaque switching. Here, cells reversibly switch between two states, “white” and “opaque,” and each state is heritable through many cell generations. Each cell type has a distinct cellular and colony morphology and they differ in many other properties including mating, nutritional specialization, and interactions with the innate immune system. Previous genetic screens to gain insight into white-opaque switching have focused on certain classes of genes (for example transcriptional regulators or chromatin modifying enzymes). In this paper, we examined 172 deletion mutants covering a broad range of cell functions. We identified 28 deletion mutants with at least a fivefold effect on switching frequencies; these cover a wide variety of functions ranging from membrane sensors to kinases to proteins of unknown function. In agreement with previous reports, we found that components of the pheromone signaling cascade affect white-to-opaque switching; however, our results suggest that the major effect of Cek1 on white-opaque switching occurs through the cell wall damage response pathway. Most of the genes we identified have not been previously implicated in white-opaque switching and serve as entry points to understand new aspects of this morphological transition.
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25
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Moralez AP, Perini HF, Paulo EA, Furlaneto-Maia L, Furlaneto MC. Effect of phenotypic switching on biofilm traits in Candida tropicalis. Microb Pathog 2020; 149:104346. [PMID: 32562809 DOI: 10.1016/j.micpath.2020.104346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 06/02/2020] [Accepted: 06/11/2020] [Indexed: 10/24/2022]
Abstract
Candida tropicalis can undergo multiple forms of phenotypic switching. We have reported a switching system in C. tropicalis that is associated with changes in virulence attributes. We aimed to assess biofilm formation by distinct switch states of C. tropicalis and evaluate whether their sessile cells exhibit altered virulence traits. C. tropicalis strains included the parental phenotype (a clinical isolate) and four switch phenotypes (crepe, rough, revertant of crepe and revertant of rough). Biofilm formation and adhesion capability of sessile cells on polystyrene were assessed through quantification of total biomass. Filamentous forms were characterized by direct counting of sessile cells. A virulence assay was conducted using the Galleria mellonella infection model. Switch variants (crepe and rough) and their revertant counterparts produced higher biofilm biomass (P < 0.05) than the parental strain. Additionally, filamentous forms were enriched among sessile cells of switched strains compared to those observed for sessile cells of the parental strain, with the exception of the revertant of rough. Sessile cells of switched strains showed higher adhesion to polystyrene compared to the parental strain. Sessile cells of the crepe variant and its revertant strain (RC) exhibited higher virulence against G. mellonella larvae than sessile cells of the parental strain. Our findings indicate that switching events in C. tropicalis affect biofilm development and that sessile cells of distinct switch states may exhibit increased adhesion ability and enhanced virulence towards G. mellonella larvae.
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Affiliation(s)
- AlaneT P Moralez
- Department of Microbiology, Paraná State University of Londrina, Paraná, Brazil
| | - Hugo F Perini
- Department of Microbiology, Paraná State University of Londrina, Paraná, Brazil
| | - Eloiza A Paulo
- Department of Microbiology, Paraná State University of Londrina, Paraná, Brazil
| | - Luciana Furlaneto-Maia
- Department of Food Technology, Technological Federal University of Paraná, Londrina, Paraná, Brazil
| | - Marcia C Furlaneto
- Department of Microbiology, Paraná State University of Londrina, Paraná, Brazil.
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26
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Guin K, Chen Y, Mishra R, Muzaki SRBM, Thimmappa BC, O'Brien CE, Butler G, Sanyal A, Sanyal K. Spatial inter-centromeric interactions facilitated the emergence of evolutionary new centromeres. eLife 2020; 9:e58556. [PMID: 32469306 PMCID: PMC7292649 DOI: 10.7554/elife.58556] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 05/22/2020] [Indexed: 12/12/2022] Open
Abstract
Centromeres of Candida albicans form on unique and different DNA sequences but a closely related species, Candida tropicalis, possesses homogenized inverted repeat (HIR)-associated centromeres. To investigate the mechanism of centromere type transition, we improved the fragmented genome assembly and constructed a chromosome-level genome assembly of C. tropicalis by employing PacBio sequencing, chromosome conformation capture sequencing (3C-seq), chromoblot, and genetic analysis of engineered aneuploid strains. Further, we analyzed the 3D genome organization using 3C-seq data, which revealed spatial proximity among the centromeres as well as telomeres of seven chromosomes in C. tropicalis. Intriguingly, we observed evidence of inter-centromeric translocations in the common ancestor of C. albicans and C. tropicalis. Identification of putative centromeres in closely related Candida sojae, Candida viswanathii and Candida parapsilosis indicates loss of ancestral HIR-associated centromeres and establishment of evolutionary new centromeres (ENCs) in C. albicans. We propose that spatial proximity of the homologous centromere DNA sequences facilitated karyotype rearrangements and centromere type transitions in human pathogenic yeasts of the CUG-Ser1 clade.
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Affiliation(s)
- Krishnendu Guin
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific ResearchBangaloreIndia
| | - Yao Chen
- School of Biological Sciences, Nanyang Technological UniversitySingaporeSingapore
| | - Radha Mishra
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific ResearchBangaloreIndia
| | | | - Bhagya C Thimmappa
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific ResearchBangaloreIndia
| | - Caoimhe E O'Brien
- School Of Biomolecular & Biomed Science, Conway Institute of Biomolecular and Biomedical Research, University College DublinDublinIreland
| | - Geraldine Butler
- School Of Biomolecular & Biomed Science, Conway Institute of Biomolecular and Biomedical Research, University College DublinDublinIreland
| | - Amartya Sanyal
- School of Biological Sciences, Nanyang Technological UniversitySingaporeSingapore
| | - Kaustuv Sanyal
- Molecular Mycology Laboratory, Molecular Biology and Genetics Unit, Jawaharlal Nehru Centre for Advanced Scientific ResearchBangaloreIndia
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27
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Phenotypic switching in Candida tropicalis alters host-pathogen interactions in a Galleria mellonella infection model. Sci Rep 2019; 9:12555. [PMID: 31467372 PMCID: PMC6715636 DOI: 10.1038/s41598-019-49080-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 08/16/2019] [Indexed: 11/08/2022] Open
Abstract
Candida tropicalis is a human pathogen associated with high mortality rates. We have reported a switching system in C. tropicalis consisting of five morphotypes – the parental, switch variant (crepe and rough), and revertant (crepe and rough) strains, which exhibited altered virulence in a Galleria mellonella model. Here, we evaluate whether switching events may alter host-pathogen interactions by comparing the attributes of the innate responses to the various states. All switched strains induced higher melanization in G. mellonella larvae than that induced by the parental strain. The galiomicin expression was higher in the larvae infected with the crepe and rough morphotypes than that in the larvae infected with the parental strain. Hemocytes preferentially phagocytosed crepe variant cells over parental cells in vitro. In contrast, the rough variant cells were less phagocytosed than the parental strain. The hemocyte density was decreased in the larvae infected with the crepe variant compared to that in the larvae infected with the parental strain. Interestingly, larvae infected with the revertant of crepe restored the hemocyte density levels that to those observed for larvae infected with the parental strain. Most of the switched strains were more resistant to hemocyte candidacidal activity than the parental strain. These results indicate that the switch states exhibit similarities as well as important differences during infection in a G. mellonella model.
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28
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Kim S, Lee J, Sung BH. Isolation and Characterization of the Stress-Tolerant Candida tropicalis YHJ1 and Evaluation of Its Xylose Reductase for Xylitol Production From Acid Pre-treatment Wastewater. Front Bioeng Biotechnol 2019; 7:138. [PMID: 31338365 PMCID: PMC6626919 DOI: 10.3389/fbioe.2019.00138] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 05/22/2019] [Indexed: 11/13/2022] Open
Abstract
A stress-tolerant yeast was isolated from honey using acid hydrolysate generated from sequential acid-/alkali-pretreatment of empty palm fruit bunch fiber (EPFBF). The isolated yeast was identified molecularly, taxonomically, and morphologically as Candida tropicalis YHJ1, and analyzed for application in xylitol production. The isolated yeast showed stress tolerance toward various chemical reagents and could grow with up to 600 g/L xylose in the culture medium. This yeast also had a broad carbohydrate utilization spectrum, and its xylitol yield was greatest in medium supplemented with xylose as the sole carbon source. In batch fermentation for xylitol production, the yeast could convert xylose prepared from acidic EPFBF pretreatment wastewater into xylitol. Interestingly, C. tropicalis YHJ1 xylose reductase, containing a Ser279 residue, exhibited more effective xylitol conversion compared to orthologous Candida enzymes containing Leu279 or Asn279; this improvement was associated with NADPH binding, as predicted through homologous structure modeling and enzyme kinetic analysis. Taken together, these results show a novel stress-tolerant yeast strain that may be applicable to xylitol production from toxic lignocellulosic byproducts.
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Affiliation(s)
- Seonghun Kim
- Jeonbuk Branch Institute, Korea Research Institute of Bioscience and Biotechnology, Jeongeup, South Korea.,Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon, South Korea
| | - Jinhyuk Lee
- Genome Editing Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.,Department of Bioinformatics, KRIBB School of Bioscience, University of Science and Technology, Daejeon, South Korea
| | - Bong Hyun Sung
- Synthetic Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.,Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon, South Korea
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29
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A natural histone H2A variant lacking the Bub1 phosphorylation site and regulated depletion of centromeric histone CENP-A foster evolvability in Candida albicans. PLoS Biol 2019; 17:e3000331. [PMID: 31226107 PMCID: PMC6613695 DOI: 10.1371/journal.pbio.3000331] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 07/08/2019] [Accepted: 06/03/2019] [Indexed: 12/24/2022] Open
Abstract
Eukaryotes have evolved elaborate mechanisms to ensure that chromosomes segregate with high fidelity during mitosis and meiosis, and yet specific aneuploidies can be adaptive during environmental stress. Here, we identify a chromatin-based system required for inducible aneuploidy in a human pathogen. Candida albicans utilizes chromosome missegregation to acquire tolerance to antifungal drugs and for nonmeiotic ploidy reduction after mating. We discovered that the ancestor of C. albicans and 2 related pathogens evolved a variant of histone 2A (H2A) that lacks the conserved phosphorylation site for kinetochore-associated Bub1 kinase, a key regulator of chromosome segregation. Using engineered strains, we show that the relative gene dosage of this variant versus canonical H2A controls the fidelity of chromosome segregation and the rate of acquisition of tolerance to antifungal drugs via aneuploidy. Furthermore, whole-genome chromatin precipitation analysis reveals that Centromere Protein A/ Centromeric Histone H3-like Protein (CENP-A/Cse4), a centromeric histone H3 variant that forms the platform of the eukaryotic kinetochore, is depleted from tetraploid-mating products relative to diploid parents and is virtually eliminated from cells exposed to aneuploidy-promoting cues. We conclude that genetically programmed and environmentally induced changes in chromatin can confer the capacity for enhanced evolvability via chromosome missegregation.
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30
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de Jong AW, Hagen F. Attack, Defend and Persist: How the Fungal Pathogen Candida auris was Able to Emerge Globally in Healthcare Environments. Mycopathologia 2019; 184:353-365. [PMID: 31209693 DOI: 10.1007/s11046-019-00351-w] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 05/28/2019] [Indexed: 12/25/2022]
Abstract
Within a decade after its first description, the multidrug-resistant yeast Candida auris has emerged globally as a nosocomial pathogen causing difficult to control outbreaks. This, together with the alarmingly high mortality rate of up to 66% associated with C. auris candidemia, calls for a better understanding of its virulence traits and routes of transmission. Unlike other clinically relevant Candida species, C. auris seems to have the unique ability to be easily transmitted between patients. Although initially thought to express fewer virulence traits than Candida albicans, recent genomic insights suggest C. auris to possess these traits to a much more similar extent. This review highlights the virulence traits C. auris expresses to attack the host, defend itself against antimicrobial agents and to persist within the healthcare environment.
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Affiliation(s)
- Auke W de Jong
- Department of Medical Mycology, Westerdijk Fungal Biodiversity Institute, Utrecht, The Netherlands
| | - Ferry Hagen
- Department of Medical Mycology, Westerdijk Fungal Biodiversity Institute, Utrecht, The Netherlands.
- Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, The Netherlands.
- Laboratory of Medical Mycology, Jining No. 1 People's Hospital, Jining, Shandong, People's Republic of China.
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31
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Mancera E, Frazer C, Porman AM, Ruiz-Castro S, Johnson AD, Bennett RJ. Genetic Modification of Closely Related Candida Species. Front Microbiol 2019; 10:357. [PMID: 30941104 PMCID: PMC6433835 DOI: 10.3389/fmicb.2019.00357] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 02/11/2019] [Indexed: 11/25/2022] Open
Abstract
Species from the genus Candida are among the most important human fungal pathogens. Several of them are frequent commensals of the human microbiota but are also able to cause a variety of opportunistic infections, especially when the human host becomes immunocompromised. By far, most of the research to understand the molecular underpinnings of the pathogenesis of these species has focused on Candida albicans, the most virulent member of the genus. However, epidemiological data indicates that related Candida species are also clinically important. Here, we describe the generation of a set of strains and plasmids to genetically modify C. dubliniensis and C. tropicalis, the two pathogenic species most closely related to C. albicans. C. dubliniensis is an ideal model to understand C. albicans pathogenesis since it is the closest species to C. albicans but considerably less virulent. On the other hand, C. tropicalis is ranked among the four most common causes of infections by Candida species. Given that C. dubliniensis and C. tropicalis are obligate diploids with no known conventional sexual cycle, we generated strains that are auxotrophic for at least two amino acids which allows the tandem deletion of both alleles of a gene by complementing the two auxotrophies. The strains were generated in two different genetic backgrounds for each species — one for which the genomic sequence is available and a second clinically important one. In addition, we have adapted plasmids developed to delete genes and epitope/fluorophore tag proteins in C. albicans so that they can be employed in C. tropicalis. The tools generated here allow for efficient genetic modification of C. dubliniensis and C. tropicalis, and thus facilitate the study of the molecular basis of pathogenesis in these medically relevant fungi.
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Affiliation(s)
- Eugenio Mancera
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Irapuato, Irapuato, Mexico.,Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, United States
| | - Corey Frazer
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
| | - Allison M Porman
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
| | - Susana Ruiz-Castro
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Irapuato, Irapuato, Mexico
| | - Alexander D Johnson
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, United States
| | - Richard J Bennett
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI, United States
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32
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Abstract
Candida species are a major cause of infection worldwide. The species associated with infection vary with geographical location and with patient population. Infection with Candida tropicalis is particularly common in South America and Asia, and Candida parapsilosis infections are more common in the very young. Molecular methods for manipulating the genomes of these species are still lacking. We describe a simple and efficient CRISPR-based gene editing system that can be applied in the C. parapsilosis species group, including the sister species Candida orthopsilosis and Candida metapsilosis. We have also constructed a separate system for gene editing in C. tropicalis. Many Candida species that cause infection have diploid genomes and do not undergo classical meiosis. The application of clustered regularly interspaced short palindromic repeat-Cas9 (CRISPR-Cas9) gene editing systems has therefore greatly facilitated the generation of gene disruptions and the introduction of specific polymorphisms. However, CRISPR methods are not yet available for all Candida species. We describe here an adaption of a previously developed CRISPR system in Candida parapsilosis that uses an autonomously replicating plasmid. Guide RNAs can be introduced in a single cloning step and are released by cleavage between a tRNA and a ribozyme. The plasmid also contains CAS9 and a selectable nourseothricin SAT1 marker. It can be used for markerless editing in C. parapsilosis, C. orthopsilosis, and C. metapsilosis. We also show that CRISPR can easily be used to introduce molecular barcodes and to reintroduce wild-type sequences into edited strains. Heterozygous mutations can be generated, either by careful selection of the distance between the polymorphism and the Cas9 cut site or by providing two different repair templates at the same time. In addition, we have constructed a different autonomously replicating plasmid for CRISPR-Cas9 editing in Candida tropicalis. We show that editing can easily be carried out in multiple C. tropicalis isolates. Nonhomologous end joining (NHEJ) repair occurs at a high level in C. metapsilosis and C. tropicalis. IMPORTANCECandida species are a major cause of infection worldwide. The species associated with infection vary with geographical location and with patient population. Infection with Candida tropicalis is particularly common in South America and Asia, and Candida parapsilosis infections are more common in the very young. Molecular methods for manipulating the genomes of these species are still lacking. We describe a simple and efficient CRISPR-based gene editing system that can be applied in the C. parapsilosis species group, including the sister species Candida orthopsilosis and Candida metapsilosis. We have also constructed a separate system for gene editing in C. tropicalis.
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33
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Tek EL, Sundstrom JF, Gardner JM, Oliver SG, Jiranek V. Evaluation of the ability of commercial wine yeasts to form biofilms (mats) and adhere to plastic: implications for the microbiota of the winery environment. FEMS Microbiol Ecol 2019; 94:4831476. [PMID: 29394344 DOI: 10.1093/femsec/fix188] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/30/2018] [Indexed: 12/16/2022] Open
Abstract
Commercially available active dried wine yeasts are regularly used by winemakers worldwide to achieve reliable fermentations and obtain quality wine. This practice has led to increased evidence of traces of commercial wine yeast in the vineyard, winery and uninoculated musts. The mechanism(s) that enables commercial wine yeast to persist in the winery environment and the influence to native microbial communities on this persistence is poorly understood. This study has investigated the ability of commercial wine yeasts to form biofilms and adhere to plastic. The results indicate that the biofilms formed by commercial yeasts consist of cells with a combination of different lifestyles (replicative and non-replicative) and growth modes including invasive growth, bud elongation, sporulation and a mat sectoring-like phenotype. Invasive growth was greatly enhanced on grape pulp regardless of strain, while adhesion on plastic varied between strains. The findings suggest a possible mechanism that allows commercial yeast to colonise and survive in the winery environment, which may have implications for the indigenous microbiota profile as well as the population profile in uninoculated fermentations if their dissemination is not controlled.
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Affiliation(s)
- Ee Lin Tek
- Department of Wine and Food Science, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
| | - Joanna F Sundstrom
- Department of Wine and Food Science, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
| | - Jennifer M Gardner
- Department of Wine and Food Science, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia
| | - Stephen G Oliver
- Department of Biochemistry & Cambridge Systems Biology Centre, University of Cambridge, Cambridge CB2 1GA, UK
| | - Vladimir Jiranek
- Department of Wine and Food Science, School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, South Australia 5064, Australia.,Australian Research Council Training Centre for Innovative Wine Production, University of Adelaide, Waite Campus, Australia
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34
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Frazer C, Hernday AD, Bennett RJ. Monitoring Phenotypic Switching in Candida albicans and the Use of Next-Gen Fluorescence Reporters. ACTA ACUST UNITED AC 2019; 53:e76. [PMID: 30747494 DOI: 10.1002/cpmc.76] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Candida albicans is an opportunistic human fungal pathogen that is able to cause both mucosal and systemic infections. It is also a frequent human commensal, where it is typically found inhabiting multiple niches including the gastrointestinal tract. One of the most remarkable features of C. albicans biology is its ability to undergo heritable and reversible switching between different phenotypic states, a phenomenon known as phenotypic switching. This is best exemplified by the white-opaque switch, in which cells undergo epigenetic transitions between two alternative cellular states. Here, we describe assays to quantify the frequency of switching between states, as well as methods to help identify cells in different phenotypic states. We also describe the use of environmental cues that can induce switching into either the white or opaque state. Finally, we introduce the use of mNeonGreen and mScarlet fluorescent proteins that have been optimized for use in C. albicans and which outperform commonly used fluorescent proteins for both fluorescence microscopy and flow cytometry. © 2019 by John Wiley & Sons, Inc.
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Affiliation(s)
- Corey Frazer
- Molecular Microbiology and Immunology Department, Brown University, Providence, Rhode Island
| | - Aaron D Hernday
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, Merced, California.,Quantitative and Systems Biology Graduate Program, School of Natural Sciences, University of California, Merced, Merced, California
| | - Richard J Bennett
- Molecular Microbiology and Immunology Department, Brown University, Providence, Rhode Island
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35
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Abstract
Fungi are prone to phenotypic instability, that is, the vegetative phase of these organisms, be they yeasts or molds, undergoes frequent switching between two or more behaviors, often with different morphologies, but also sometime having different physiologies without any obvious morphological outcome. In the context of industrial utilization of fungi, this can have a negative impact on the maintenance of strains and/or on their productivity. Instabilities have been shown to result from various mechanisms, either genetic or epigenetic. This chapter will review different types of instabilities and discuss some lesser-known ones, mostly in filamentous fungi, while it will direct readers to additional literature in the case of well-known phenomena such as the amyloid prions or fungal senescence. It will present in depth the "white/opaque" switch of Candida albicans and the "crippled growth" degeneration of the model fungus Podospora anserina. These are two of the most thoroughly studied epigenetic phenotypic switches. I will also discuss the "sectors" presented by many filamentous ascomycetes, for which a prion-based model exists but is not demonstrated. Finally, I will also describe intriguing examples of phenotypic instability for which an explanation has yet to be provided.
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36
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Galán-Ladero MÁ, Blanco-Blanco MT, Fernández-Calderón MC, Lucio L, Gutiérrez-Martín Y, Blanco MT, Pérez-Giraldo C. Candida tropicalis biofilm formation and expression levels of the CTRG ALS-like genes in sessile cells. Yeast 2018; 36:107-115. [PMID: 30477048 DOI: 10.1002/yea.3370] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 11/19/2018] [Accepted: 11/22/2018] [Indexed: 02/06/2023] Open
Abstract
Candida tropicalis is an emergent pathogen with a high rate of mortality associated with it; however, less is known about its pathogenic capacity. Biofilm formation (BF) has important clinical repercussions, and it begins with adherence to a substrate. The adherence capacity depends principally on the cell surface hydrophobicity (CSH) and, at a later stage, on specific adherence due to adhesins. The ALS family in C. tropicalis, implicated in adhesion and BF, is represented in several CTRG genes. In this study, we determined the biofilm-forming ability, the primary adherence, and the CSH of C. tropicalis, including six isolates from blood and seven from urine cultures. We also compared the expression of four CTRG ALS-like genes (CTRG_01028, CTRG_02293, CTRG_03786, and CTRG_03797) in sessile versus planktonic cells, selected for their possible contribution to BF. All the C. tropicalis strains were biofilm producers, related to its filamentation capacity; all the strains displayed a high adherence ability correlated to the CSH, and all the strains expressed the CTRG genes in both types of growth. Urine isolates present, although not significantly, higher CSH, adherence, and biofilm formation than blood isolates. This study reveals that three CTRG ALS-like genes-except CTRG_03797-were more upregulated in biofilm cells, although with a considerable variation in expression across the strains studied and between the CTRG genes. C. tropicalis present a high biofilm capacity, and the overexpression of several CTRG ALS-like genes in the sessile cells suggests a role by the course of the biofilm formation.
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Affiliation(s)
| | | | - María Coronada Fernández-Calderón
- Area of Microbiology, Faculty of Medicine, University of Extremadura, Badajoz, Spain.,Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, CIBER BBN, Badajoz, Spain
| | - Leopoldo Lucio
- Area of Microbiology, Faculty of Medicine, University of Extremadura, Badajoz, Spain.,Laboratorio de Salud Pública Badajoz, Servicio Extremeño de Salud, Badajoz, Spain
| | - Yolanda Gutiérrez-Martín
- Bioscience Applied Techniques Services, Servicio de Apoyo a la Investigación UEx, Badajoz, Spain
| | - María Teresa Blanco
- Area of Microbiology, Faculty of Medicine, University of Extremadura, Badajoz, Spain.,Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, CIBER BBN, Badajoz, Spain
| | - Ciro Pérez-Giraldo
- Area of Microbiology, Faculty of Medicine, University of Extremadura, Badajoz, Spain.,Centro de Investigación Biomédica en Red de Bioingeniería, Biomateriales y Nanomedicina, CIBER BBN, Badajoz, Spain
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Abstract
Microbial colonizers of humans have evolved to adapt to environmental cues and to sense nutrient availability. Oxygen is a constantly changing environmental parameter in different host tissues and in different types of infection. We describe how Candida albicans, an opportunistic fungal pathogen, can modulate the host response under hypoxia and anoxia. We found that high infiltration of polymorphonuclear leukocytes (PMNs) to the site of infection contributes to a low oxygen milieu in a murine subdermal abscess. A persistent hypoxic environment did not affect viability or metabolism of PMNs. Under oxygen deprivation, however, infection with C. albicans disturbed specific PMN responses. PMNs were not able to efficiently phagocytose, produce ROS, or release extracellular DNA traps. Failure to launch an adequate response was caused by C. albicans cell wall masking of β-glucan upon exposure to low oxygen levels which hindered PAMP sensing by Dectin-1 on the surfaces of PMNs. This in turn contributed to immune evasion and enhanced fungal survival. The cell wall masking effect is prolonged by the accumulation of lactate produced by PMNs under low oxygen conditions. Finally, adaptation to oxygen deprivation increased virulence of C. albicans which we demonstrated using a Caenorhabditis elegans infection model.IMPORTANCE Successful human colonizers have evolved mechanisms to bypass immune surveillance. Infiltration of PMNs to the site of infection led to the generation of a low oxygen niche. Exposure to low oxygen levels induced fungal cell wall masking, which in turn hindered pathogen sensing and antifungal responses by PMNs. The cell wall masking effect was prolonged by increasing lactate amounts produced by neutrophil metabolism under oxygen deprivation. In an invertebrate infection model, C. albicans was able to kill infected C. elegans nematodes within 2 days under low oxygen conditions, whereas the majority of uninfected controls and infected worms under normoxic conditions survived. These results suggest that C. albicans benefited from low oxygen niches to increase virulence. The interplay of C. albicans with innate immune cells under these conditions contributed to the overall outcome of infection. Adaption to low oxygen levels was in addition beneficial for C. albicans by reducing susceptibility to selected antifungal drugs. Hence, immunomodulation of host cells under low oxygen conditions could provide a valuable approach to improve current antifungal therapies.
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Huang G, Huang Q, Wei Y, Wang Y, Du H. Multiple roles and diverse regulation of the Ras/cAMP/protein kinase A pathway in Candida albicans. Mol Microbiol 2018; 111:6-16. [PMID: 30299574 DOI: 10.1111/mmi.14148] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2018] [Indexed: 01/15/2023]
Abstract
Candida albicans is a major fungal pathogen of humans, causing both superficial and life-threatening systemic infections in immunocompromised people. The conserved Ras/cAMP/PKA pathway plays a key role in regulating multiple traits important for the virulence of C. albicans such as cell growth, yeast-hyphal transition, white-opaque switching, sexual reproduction and biofilm development. Diverse external signals influence cell physiology by activating this signaling pathway. The key components of the Ras/cAMP/PKA pathway include two Ras GTPases (Ras1 and Ras2), an adenylyl cyclase (Cyr1, also known as Cdc35), two cyclic nucleotide phosphodiesterases (Pde1 and Pde2) and the catalytic (Tpk1 and Tpk2) and regulatory (Bcy1) subunits of PKA kinase. Activation of this pathway dramatically alters the gene expression profile via several transcription factors, leading to the activation of specific biological processes. Here, we review the progress made in the past two decades to elucidate the molecular mechanisms by which the Ras/cAMP/PKA pathway senses diverse environmental cues and controls specific cellular responses and its connection with other signaling pathways in C. albicans.
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Affiliation(s)
- Guanghua Huang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China.,State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Qian Huang
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, 550025, China
| | - Yujia Wei
- Department of Dermatology, Affiliated Hospital of Guizhou Medical University, Guiyang, 550025, China
| | - Yue Wang
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore, 138673, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
| | - Han Du
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200438, China.,Institutes of Biomedical Sciences, Fudan University, Shanghai, 200032, China
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39
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Fukui K, Nakamura K, Kuwashima H, Majima T. White-to-opaque switching is involved in the phospholipase B production of Candida dubliniensis on Price's egg yolk agar. Odontology 2018; 107:174-185. [PMID: 30083973 DOI: 10.1007/s10266-018-0382-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 07/20/2018] [Indexed: 01/12/2023]
Abstract
Measuring the production of Candida dubliniensis (C. dubliniensis) phospholipase B (PLase B) by the Price's method has long been considered to be unattainable because the levels of PLase produced are undetectable. In this study, C. dubliniensis, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis and C. tropicalis were shown to produce PLase B and form clear white zones around their colonies when peptone, a component of the original Price's egg yolk (OP) agar, is replaced with a yeast nitrogen base (YNB). This new medium is named modified Price's (MP) agar. Based on this finding, we propose a new modified Price's (NMP) agar containing 0.75% peptone and 0.25% YNB, which enabled measurement of PLase B production by C. dubliniensis and C. albicans with results consistent with those obtained for C. albicans grown on OP agar. We strongly believe that the MP and NMP agars are very useful for screening PLase B production by C. dubliniensis and non-albicans Candida spp. Moreover, the addition of several bioactive agents (the proteinase inhibitors pepstatin A and saquinavir, the calcineurin inhibitors cyclosporine A and tacrolimus, the cell-permeable cAMP analog dBcAMP, and the quorum-sensing molecule farnesol) to the OP agar enhanced PLase B production by C. dubliniensis. During the course of our study to clarify the reason why PLase B was not produced, we found that C. dubliniensis cells grown on OP agar undergo a white-to-opaque transition, which may explain why they showed minimal production of PLase B on this medium.
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Affiliation(s)
- Kayoko Fukui
- Department of Pharmacology, The Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan
| | - Kenjirou Nakamura
- Department of Pharmacology, The Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan.
| | - Haruhiro Kuwashima
- Department of Pharmacology, The Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan
| | - Toshiro Majima
- Department of Pharmacology, The Nippon Dental University School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Chuo-ku, Niigata, 951-8580, Japan
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40
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Lin CJ, Chen YL. Conserved and Divergent Functions of the cAMP/PKA Signaling Pathway in Candida albicans and Candida tropicalis. J Fungi (Basel) 2018; 4:E68. [PMID: 29890663 PMCID: PMC6023519 DOI: 10.3390/jof4020068] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 05/28/2018] [Accepted: 06/07/2018] [Indexed: 01/03/2023] Open
Abstract
Fungal species undergo many morphological transitions to adapt to changing environments, an important quality especially in fungal pathogens. For decades, Candida albicans has been one of the most prevalent human fungal pathogens, and recently, the prevalence of Candida tropicalis as a causative agent of candidiasis has increased. In C. albicans, the ability to switch between yeast and hyphal forms is thought to be a key virulence factor and is regulated by multiple signaling cascades—including the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA), calcineurin, high-osmolarity glycerol (HOG), and mitogen-activated protein kinases (MAPK) signaling pathways—upon receiving environmental cues. The cAMP/PKA signaling pathway also triggers white-opaque switching in C. albicans. However, studies on C. tropicalis morphogenesis are limited. In this minireview, we discuss the regulation of the yeast-hypha transition, virulence, and white-opaque switching through the cAMP/PKA pathway in the closely related species C. albicans and C. tropicalis.
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Affiliation(s)
- Chi-Jan Lin
- Department of Plant Pathology and Microbiology, National Taiwan University, 10617 Taipei, Taiwan.
| | - Ying-Lien Chen
- Department of Plant Pathology and Microbiology, National Taiwan University, 10617 Taipei, Taiwan.
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41
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Du H, Zheng Q, Bing J, Bennett RJ, Huang G. A coupled process of same- and opposite-sex mating generates polyploidy and genetic diversity in Candida tropicalis. PLoS Genet 2018; 14:e1007377. [PMID: 29734333 PMCID: PMC5957450 DOI: 10.1371/journal.pgen.1007377] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 05/17/2018] [Accepted: 04/24/2018] [Indexed: 01/04/2023] Open
Abstract
Sexual reproduction is a universal mechanism for generating genetic diversity in eukaryotes. Fungi exhibit diverse strategies for sexual reproduction both in nature and in the laboratory. In this study, we report the discovery of same-sex (homothallic) mating in the human fungal pathogen Candida tropicalis. We show that same-sex mating occurs between two cells carrying the same mating type (MTLa/a or α/α) and requires the presence of pheromone from the opposite mating type as well as the receptor for this pheromone. In ménage à trois mating mixes (i.e., “a x a + α helper” or “α x α + a helper” mixes), pheromone secreted by helper strains promotes diploid C. tropicalis cells to undergo same-sex mating and form tetraploid products. Surprisingly, however, the tetraploid mating products can then efficiently mate with cells of the opposite mating type to generate hexaploid products. The unstable hexaploid progeny generated from this coupled process of same- and opposite-sex mating undergo rapid chromosome loss and generate extensive genetic variation. Phenotypic analysis demonstrated that the mating progeny-derived strains exhibit diverse morphologies and phenotypes, including differences in secreted aspartic proteinase (Sap) activity and susceptibility to the antifungal drugs. Thus, the coupling of same- and opposite-sex mating represents a novel mode to generate polyploidy and genetic diversity, which may facilitate the evolution of new traits in C. tropicalis and adaptation to changing environments. The fungal pathogen Candida tropicalis not only lives as a commensal in humans but is also widely distributed in diverse environments. Until recently, C. tropicalis was thought to be an asexual diploid organism. In this study, we report the discovery of same-sex mating and reveal an unusual process in which same- and opposite-sex mating are coupled in this fungus. The coupling process represents a novel mode of mating which produces unstable polyploid products and results in a high level of genetic and phenotypic diversity. This biological process may benefit the adaptation of C. tropicalis to a variety of ecological niches and promotes survival under stressful conditions. Our study expands the repertoire of mating strategies in fungi and sheds new lights on the generation of polyploidy and genomic flexibility.
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Affiliation(s)
- Han Du
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
- Institutes of Biomedical Sciences, Fudan University, Shanghai, China
- * E-mail:
| | - Qiushi Zheng
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jian Bing
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Richard J. Bennett
- Department of Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, United States of America
| | - Guanghua Huang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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42
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Hennig S, Wenzel M, Haas C, Hoffmann A, Weber J, Rödel G, Ostermann K. New approaches in bioprocess-control: Consortium guidance by synthetic cell-cell communication based on fungal pheromones. Eng Life Sci 2018; 18:387-400. [PMID: 32624919 DOI: 10.1002/elsc.201700181] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 02/08/2018] [Accepted: 03/13/2018] [Indexed: 01/02/2023] Open
Abstract
Bioconversions in industrial processes are currently dominated by single-strain approaches. With the growing complexity of tasks to be carried out, microbial consortia become increasingly advantageous and eventually may outperform single-strain fermentations. Consortium approaches benefit from the combined metabolic capabilities of highly specialized strains and species, and the inherent division of labor reduces the metabolic burden for each strain while increasing product yields and reaction specificities. However, consortium-based designs still suffer from a lack of available tools to control the behavior and performance of the individual subpopulations and of the entire consortium. Here, we propose to implement novel control elements for microbial consortia based on artificial cell-cell communication via fungal mating pheromones. Coupling to the desired output is mediated by pheromone-responsive gene expression, thereby creating pheromone-dependent communication channels between different subpopulations of the consortia. We highlight the benefits of artificial communication to specifically target individual subpopulations of microbial consortia and to control e.g. their metabolic profile or proliferation rate in a predefined and customized manner. Due to the steadily increasing knowledge of sexual cycles of industrially relevant fungi, a growing number of strains and species can be integrated into pheromone-controlled sensor-actor systems, exploiting their unique metabolic properties for microbial consortia approaches.
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Affiliation(s)
- Stefan Hennig
- Institute of Genetics Technische Universität Dresden Dresden Germany
| | - Mandy Wenzel
- Institute of Genetics Technische Universität Dresden Dresden Germany
| | - Christiane Haas
- Institute of Natural Materials Technology Technische Universität Dresden Dresden Germany
| | - Andreas Hoffmann
- Institute of Natural Materials Technology Technische Universität Dresden Dresden Germany
| | - Jost Weber
- Institute of Natural Materials Technology Technische Universität Dresden Dresden Germany.,Evolva Biotec A/S Lersø Parkallé 42 Copenhagen Denmark
| | - Gerhard Rödel
- Institute of Genetics Technische Universität Dresden Dresden Germany
| | - Kai Ostermann
- Institute of Genetics Technische Universität Dresden Dresden Germany
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43
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Scordino F, Giuffrè L, Barberi G, Marino Merlo F, Orlando MG, Giosa D, Romeo O. Multilocus Sequence Typing Reveals a New Cluster of Closely Related Candida tropicalis Genotypes in Italian Patients With Neurological Disorders. Front Microbiol 2018; 9:679. [PMID: 29696003 PMCID: PMC5904457 DOI: 10.3389/fmicb.2018.00679] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 03/22/2018] [Indexed: 01/12/2023] Open
Abstract
Candida tropicalis is a pathogenic yeast that has emerged as an important cause of candidemia especially in elderly patients with hematological malignancies. Infections caused by this species are mainly reported from Latin America and Asian-Pacific countries although recent epidemiological data revealed that C. tropicalis accounts for 6-16.4% of the Candida bloodstream infections (BSIs) in Italy by representing a relevant issue especially for patients receiving long-term hospital care. The aim of this study was to describe the genetic diversity of C. tropicalis isolates contaminating the hands of healthcare workers (HCWs) and hospital environments and/or associated with BSIs occurring in patients with different neurological disorders and without hematological disease. A total of 28 C. tropicalis isolates were genotyped using multilocus sequence typing analysis of six housekeeping (ICL1, MDR1, SAPT2, SAPT4, XYR1, and ZWF1) genes and data revealed the presence of only eight diploid sequence types (DSTs) of which 6 (75%) were completely new. Four eBURST clonal complexes (CC2, CC10, CC11, and CC33) contained all DSTs found in this study and the CC33 resulted in an exclusive, well-defined, clonal cluster from Italy. In conclusion, C. tropicalis could represent an important cause of BSIs in long-term hospitalized patients with no underlying hematological disease. The findings of this study also suggest a potential horizontal transmission of a specific C. tropicalis clone through hands of HCWs and expand our understanding of the molecular epidemiology of this pathogen whose population structure is still far from being fully elucidated as its complexity increases as different categories of patients and geographic areas are examined.
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Affiliation(s)
- Fabio Scordino
- Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Centro Neurolesi "Bonino-Pulejo", Messina, Italy
| | - Letterio Giuffrè
- Department of Veterinary Sciences, Division of Animal Production, University of Messina, Messina, Italy
| | - Giuseppina Barberi
- Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Centro Neurolesi "Bonino-Pulejo", Messina, Italy
| | - Francesca Marino Merlo
- Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Centro Neurolesi "Bonino-Pulejo", Messina, Italy
| | - Maria Grazia Orlando
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
| | - Domenico Giosa
- Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Centro Neurolesi "Bonino-Pulejo", Messina, Italy
| | - Orazio Romeo
- Scientific Institute for Research, Hospitalization and Health Care (IRCCS), Centro Neurolesi "Bonino-Pulejo", Messina, Italy.,Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy
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44
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Dominguez E, Zarnowski R, Sanchez H, Covelli AS, Westler WM, Azadi P, Nett J, Mitchell AP, Andes DR. Conservation and Divergence in the Candida Species Biofilm Matrix Mannan-Glucan Complex Structure, Function, and Genetic Control. mBio 2018; 9:e00451-18. [PMID: 29615504 PMCID: PMC5885036 DOI: 10.1128/mbio.00451-18] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 03/01/2018] [Indexed: 01/18/2023] Open
Abstract
Candida biofilms resist the effects of available antifungal therapies. Prior studies with Candida albicans biofilms show that an extracellular matrix mannan-glucan complex (MGCx) contributes to antifungal sequestration, leading to drug resistance. Here we implement biochemical, pharmacological, and genetic approaches to explore a similar mechanism of resistance for the three most common clinically encountered non-albicansCandida species (NAC). Our findings reveal that each Candida species biofilm synthesizes a mannan-glucan complex and that the antifungal-protective function of this complex is conserved. Structural similarities extended primarily to the polysaccharide backbone (α-1,6-mannan and β-1,6-glucan). Surprisingly, biochemical analysis uncovered stark differences in the branching side chains of the MGCx among the species. Consistent with the structural analysis, similarities in the genetic control of MGCx production for each Candida species also appeared limited to the synthesis of the polysaccharide backbone. Each species appears to employ a unique subset of modification enzymes for MGCx synthesis, likely accounting for the observed side chain diversity. Our results argue for the conservation of matrix function among Candida spp. While biogenesis is preserved at the level of the mannan-glucan complex backbone, divergence emerges for construction of branching side chains. Thus, the MGCx backbone represents an ideal drug target for effective pan-Candida species biofilm therapy.IMPORTANCECandida species, the most common fungal pathogens, frequently grow as a biofilm. These adherent communities tolerate extremely high concentrations of antifungal agents, due in large part, to a protective extracellular matrix. The present studies define the structural, functional, and genetic similarities and differences in the biofilm matrix from the four most common Candida species. Each species synthesizes an extracellular mannan-glucan complex (MGCx) which contributes to sequestration of antifungal drug, shielding the fungus from this external assault. Synthesis of a common polysaccharide backbone appears conserved. However, subtle structural differences in the branching side chains likely rely upon unique modification enzymes, which are species specific. Our findings identify MGCx backbone synthesis as a potential pan-Candida biofilm therapeutic target.
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Affiliation(s)
- Eddie Dominguez
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Robert Zarnowski
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Hiram Sanchez
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Antonio S Covelli
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - William M Westler
- National Magnetic Resonance Facility, University of Wisconsin-Madison, Wisconsin, USA
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, USA
| | - Jeniel Nett
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Aaron P Mitchell
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - David R Andes
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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45
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Defosse TA, Le Govic Y, Courdavault V, Clastre M, Vandeputte P, Chabasse D, Bouchara JP, Giglioli-Guivarc'h N, Papon N. [Yeasts from the CTG clade (Candida clade): Biology, impact in human health, and biotechnological applications]. J Mycol Med 2018; 28:257-268. [PMID: 29545121 DOI: 10.1016/j.mycmed.2018.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 02/05/2018] [Accepted: 02/12/2018] [Indexed: 11/29/2022]
Abstract
Among the subdivision of Saccharomycotina (ascomycetes budding yeasts), the CTG clade (formerly the Candida clade) includes species that display a particular genetic code. In these yeasts, the CTG codon is predominantly translated as a serine instead of a leucine residue. It is now well-known that some CTG clade species have a major impact on human and its activities. Some of them are recognized as opportunistic agents of fungal infections termed candidiasis. In addition, another series of species belonging to the CTG clade draws the attention of some research groups because they exhibit a strong potential in various areas of biotechnology such as biological control, bioremediation, but also in the production of valuable biocompounds (biofuel, vitamins, sweeteners, industrial enzymes). Here we provide an overview of recent advances concerning the biology, clinical relevance, and currently tested biotechnological applications of species of the CTG clade. Future directions for scientific research on these particular yeasts are also discussed.
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Affiliation(s)
- T A Defosse
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France; EA 2106, université de Tours, biomolécules et biotechnologies végétales, Tours, France
| | - Y Le Govic
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France; Laboratoire de parasitologie - mycologie, centre hospitalier universitaire d'Angers, Angers, France
| | - V Courdavault
- EA 2106, université de Tours, biomolécules et biotechnologies végétales, Tours, France
| | - M Clastre
- EA 2106, université de Tours, biomolécules et biotechnologies végétales, Tours, France
| | - P Vandeputte
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France; Laboratoire de parasitologie - mycologie, centre hospitalier universitaire d'Angers, Angers, France
| | - D Chabasse
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France; Laboratoire de parasitologie - mycologie, centre hospitalier universitaire d'Angers, Angers, France
| | - J-P Bouchara
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France; Laboratoire de parasitologie - mycologie, centre hospitalier universitaire d'Angers, Angers, France
| | - N Giglioli-Guivarc'h
- EA 2106, université de Tours, biomolécules et biotechnologies végétales, Tours, France
| | - N Papon
- Groupe d'étude des interactions Hôte-Pathogène (EA 3142), SFR interactions cellulaires et applications thérapeutiques, université d'Angers, 49933 Angers, France.
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Epigenetic control of pheromone MAPK signaling determines sexual fecundity in Candida albicans. Proc Natl Acad Sci U S A 2017; 114:13780-13785. [PMID: 29255038 DOI: 10.1073/pnas.1711141115] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Several pathogenic Candida species are capable of heritable and reversible switching between two epigenetic states, "white" and "opaque." In Candida albicans, white cells are essentially sterile, whereas opaque cells are mating-proficient. Here, we interrogate the mechanism by which the white-opaque switch regulates sexual fecundity and identify four genes in the pheromone MAPK pathway that are expressed at significantly higher levels in opaque cells than in white cells. These genes encode the β subunit of the G-protein complex (STE4), the pheromone MAPK scaffold (CST5), and the two terminal MAP kinases (CEK1/CEK2). To define the contribution of each factor to mating, C. albicans white cells were reverse-engineered to express elevated, opaque-like levels of these factors, either singly or in combination. We show that white cells co-overexpressing STE4, CST5, and CEK2 undergo mating four orders of magnitude more efficiently than control white cells and at a frequency approaching that of opaque cells. Moreover, engineered white cells recapitulate the transcriptional and morphological responses of opaque cells to pheromone. These results therefore reveal multiple bottlenecks in pheromone MAPK signaling in white cells and that alleviation of these bottlenecks enables efficient mating by these "sterile" cell types. Taken together, our findings establish that differential expression of several MAPK factors underlies the epigenetic control of mating in C. albicans We also discuss how fitness advantages could have driven the evolution of a toggle switch to regulate sexual reproduction in pathogenic Candida species.
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47
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Zheng Q, Zhang Q, Bing J, Ding X, Huang G. Environmental and genetic regulation of white-opaque switching inCandida tropicalis. Mol Microbiol 2017; 106:999-1017. [DOI: 10.1111/mmi.13862] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2017] [Indexed: 02/05/2023]
Affiliation(s)
- Qiushi Zheng
- State Key Laboratory of Mycology; Institute of Microbiology, Chinese Academy of Sciences; Beijing 100101 China
- College of life sciences, University of Chinese Academy of Sciences; Beijing 100049 China
| | - Qiuyu Zhang
- State Key Laboratory of Mycology; Institute of Microbiology, Chinese Academy of Sciences; Beijing 100101 China
- College of life sciences, University of Chinese Academy of Sciences; Beijing 100049 China
| | - Jian Bing
- State Key Laboratory of Mycology; Institute of Microbiology, Chinese Academy of Sciences; Beijing 100101 China
| | - Xuefen Ding
- State Key Laboratory of Mycology; Institute of Microbiology, Chinese Academy of Sciences; Beijing 100101 China
| | - Guanghua Huang
- State Key Laboratory of Mycology; Institute of Microbiology, Chinese Academy of Sciences; Beijing 100101 China
- College of life sciences, University of Chinese Academy of Sciences; Beijing 100049 China
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Zuza-Alves DL, Silva-Rocha WP, Chaves GM. An Update on Candida tropicalis Based on Basic and Clinical Approaches. Front Microbiol 2017; 8:1927. [PMID: 29081766 PMCID: PMC5645804 DOI: 10.3389/fmicb.2017.01927] [Citation(s) in RCA: 121] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 09/21/2017] [Indexed: 01/12/2023] Open
Abstract
Candida tropicalis has emerged as one of the most important Candida species. It has been widely considered the second most virulent Candida species, only preceded by C. albicans. Besides, this species has been recognized as a very strong biofilm producer, surpassing C. albicans in most of the studies. In addition, it produces a wide range of other virulence factors, including: adhesion to buccal epithelial and endothelial cells; the secretion of lytic enzymes, such as proteinases, phospholipases, and hemolysins, bud-to-hyphae transition (also called morphogenesis) and the phenomenon called phenotypic switching. This is a species very closely related to C. albicans and has been easily identified with both phenotypic and molecular methods. In addition, no cryptic sibling species were yet described in the literature, what is contradictory to some other medically important Candida species. C. tropicalis is a clinically relevant species and may be the second or third etiological agent of candidemia, specifically in Latin American countries and Asia. Antifungal resistance to the azoles, polyenes, and echinocandins has already been described. Apart from all these characteristics, C. tropicalis has been considered an osmotolerant microorganism and this ability to survive to high salt concentration may be important for fungal persistence in saline environments. This physiological characteristic makes this species suitable for use in biotechnology processes. Here we describe an update of C. tropicalis, focusing on all these previously mentioned subjects.
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Affiliation(s)
| | | | - Guilherme M. Chaves
- Laboratory of Medical and Molecular Mycology, Department of Clinical and Toxicological Analyses, Federal University of Rio Grande do Norte, Natal, Brazil
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Affiliation(s)
- Kenneth H. Wolfe
- School of Medicine, Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Geraldine Butler
- School of Biomolecular and Biomedical Science, Conway Institute, University College Dublin, Dublin 4, Ireland
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Abstract
This article provides an overview of sexual reproduction in the ascomycetes, a phylum of fungi that is named after the specialized sacs or "asci" that hold the sexual spores. They have therefore also been referred to as the Sac Fungi due to these characteristic structures that typically contain four to eight ascospores. Ascomycetes are morphologically diverse and include single-celled yeasts, filamentous fungi, and more complex cup fungi. The sexual cycles of many species, including those of the model yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the filamentous saprobes Neurospora crassa, Aspergillus nidulans, and Podospora anserina, have been examined in depth. In addition, sexual or parasexual cycles have been uncovered in important human pathogens such as Candida albicans and Aspergillus fumigatus, as well as in plant pathogens such as Fusarium graminearum and Cochliobolus heterostrophus. We summarize what is known about sexual fecundity in ascomycetes, examine how structural changes at the mating-type locus dictate sexual behavior, and discuss recent studies that reveal that pheromone signaling pathways can be repurposed to serve cellular roles unrelated to sex.
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