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Critical Reviews in Microbiology Nov 2022While fungi are widely occupying nature, many species are responsible for devastating mycosis in humans. Such niche diversity explains how quick fungal adaptation is... (Review)
Review
While fungi are widely occupying nature, many species are responsible for devastating mycosis in humans. Such niche diversity explains how quick fungal adaptation is necessary to endow the capacity of withstanding fluctuating environments and to cope with host-imposed conditions. Among all the molecular mechanisms evolved by fungi, the most studied one is the activation of the phosphorelay signalling pathways, of which the high osmolarity glycerol (HOG) pathway constitutes one of the key molecular apparatus underpinning fungal adaptation and virulence. In this review, we summarize the seminal knowledge of the HOG pathway with its more recent developments. We specifically described the HOG-mediated stress adaptation, with a particular focus on osmotic and oxidative stress, and point out some lags in our understanding of its involvement in the virulence of pathogenic species including, the medically important fungi , , and , compared to the model yeast . Finally, we also highlighted some possible applications of the HOG pathway modifications to improve the fungal-based production of natural products in the industry.
Topics: Humans; Glycerol; Fungal Proteins; Osmotic Pressure; Aspergillus fumigatus; Osmolar Concentration; Saccharomyces cerevisiae; Biological Products
PubMed: 34893006
DOI: 10.1080/1040841X.2021.2011834 -
Microbiology Spectrum Jun 2023The opportunistic fungal pathogen Aspergillus fumigatus utilizes two high-affinity iron uptake mechanisms, termed reductive iron assimilation (RIA) and...
The opportunistic fungal pathogen Aspergillus fumigatus utilizes two high-affinity iron uptake mechanisms, termed reductive iron assimilation (RIA) and siderophore-mediated iron acquisition (SIA). The latter has been shown to be crucial for virulence of this fungus and is a target for development of novel strategies for diagnosis and treatment of fungal infections. So far, research on SIA in this mold focused mainly on the hyphal stage, revealing the importance of extracellular fusarinine-type siderophores in iron acquisition as well as of the siderophore ferricrocin in intracellular iron handling. The current study aimed to characterize iron acquisition during germination. High expression of genes involved in biosynthesis and uptake of ferricrocin in conidia and during germination, independent of iron availability, suggested a role of ferricrocin in iron acquisition during germination. In agreement, (i) bioassays indicated secretion of ferricrocin during growth on solid media during both iron sufficiency and limitation, (ii) ferricrocin was identified in the supernatant of conidia germinating in liquid media during both iron sufficiency and limitation, (iii) in contrast to mutants lacking all siderophores, mutants synthesizing ferricrocin but lacking fusarinine-type siderophores were able to grow under iron limitation in the absence of RIA, and (iv) genetic inactivation of the ferricrocin transporter Sit1 decreased germination in the absence of RIA. Taken together, this study revealed that ferricrocin has not only an intracellular role but also functions as an extracellular siderophore to support iron acquisition. The iron availability-independent ferricrocin secretion and uptake during early germination indicate developmental, rather than iron regulation. Aspergillus fumigatus is one of the most common airborne fungal pathogens for humans. Low-molecular-mass iron chelators, termed siderophores, have been shown to play a central role in iron homeostasis and, consequently, virulence of this mold. Previous studies demonstrated the crucial role of secreted fusarinine-type siderophores, such as triacetylfusarinine C, in iron acquisition, as well as of the ferrichrome-type siderophore ferricrocin in intracellular iron storage and transport. Here, we demonstrate that ferricrocin is also secreted to mediate iron acquisition during germination together with reductive iron assimilation. During early germination, ferricrocin secretion and uptake were not repressed by iron availability, indicating developmental regulation of this iron acquisition system in this growth phase.
Topics: Humans; Siderophores; Ferrichrome; Aspergillus fumigatus; Iron
PubMed: 37199664
DOI: 10.1128/spectrum.00496-23 -
PLoS Genetics Jan 2022Aspergillus fumigatus causes a range of human and animal diseases collectively known as aspergillosis. A. fumigatus possesses and expresses a range of genetic... (Comparative Study)
Comparative Study
Aspergillus fumigatus causes a range of human and animal diseases collectively known as aspergillosis. A. fumigatus possesses and expresses a range of genetic determinants of virulence, which facilitate colonisation and disease progression, including the secretion of mycotoxins. Gliotoxin (GT) is the best studied A. fumigatus mycotoxin with a wide range of known toxic effects that impair human immune cell function. GT is also highly toxic to A. fumigatus and this fungus has evolved self-protection mechanisms that include (i) the GT efflux pump GliA, (ii) the GT neutralising enzyme GliT, and (iii) the negative regulation of GT biosynthesis by the bis-thiomethyltransferase GtmA. The transcription factor (TF) RglT is the main regulator of GliT and this GT protection mechanism also occurs in the non-GT producing fungus A. nidulans. However, the A. nidulans genome does not encode GtmA and GliA. This work aimed at analysing the transcriptional response to exogenous GT in A. fumigatus and A. nidulans, two distantly related Aspergillus species, and to identify additional components required for GT protection. RNA-sequencing shows a highly different transcriptional response to exogenous GT with the RglT-dependent regulon also significantly differing between A. fumigatus and A. nidulans. However, we were able to observe homologs whose expression pattern was similar in both species (43 RglT-independent and 11 RglT-dependent). Based on this approach, we identified a novel RglT-dependent methyltranferase, MtrA, involved in GT protection. Taking into consideration the occurrence of RglT-independent modulated genes, we screened an A. fumigatus deletion library of 484 transcription factors (TFs) for sensitivity to GT and identified 15 TFs important for GT self-protection. Of these, the TF KojR, which is essential for kojic acid biosynthesis in Aspergillus oryzae, was also essential for virulence and GT biosynthesis in A. fumigatus, and for GT protection in A. fumigatus, A. nidulans, and A. oryzae. KojR regulates rglT, gliT, gliJ expression and sulfur metabolism in Aspergillus species. Together, this study identified conserved components required for GT protection in Aspergillus species.
Topics: Aspergillus; Aspergillus fumigatus; Aspergillus nidulans; Aspergillus oryzae; Fungal Proteins; Gene Expression Profiling; Gene Expression Regulation, Fungal; Gliotoxin; Methyltransferases; RNA-Seq; Transcription Factors
PubMed: 35041649
DOI: 10.1371/journal.pgen.1009965 -
Fungal Biology 2023The fungal cell is surrounded by a thick cell wall which obviously play an essential role in the protection of the fungus against external aggressive environments. In... (Review)
Review
The fungal cell is surrounded by a thick cell wall which obviously play an essential role in the protection of the fungus against external aggressive environments. In spite of 50 years of studies, the cell wall remains poorly known and especially its constant modifications during growth as well as environmental changes is not well appreciated. This review focus on the cell wall changes seen between different fungal stages and cell populations with a specific view to explain the resistance to stresses.
Topics: Aspergillus fumigatus; Fungal Proteins; Virulence; Cell Wall
PubMed: 37495316
DOI: 10.1016/j.funbio.2023.05.001 -
The Journal of Antimicrobial... Jul 2019Fungicide exposure in the environment has driven the emergence of azole-resistant Aspergillus fumigatus worldwide. A screening test allows identification of resistant...
BACKGROUND
Fungicide exposure in the environment has driven the emergence of azole-resistant Aspergillus fumigatus worldwide. A screening test allows identification of resistant isolates.
OBJECTIVES
We screened clinical samples for azole-resistant Aspergillus through azole-containing agar plates and identified mutations in the cyp51A gene of A. fumigatus.
METHODS
Aspergillus isolates from clinical samples collected in a tertiary care centre from 2014 to 2017 were screened for azole resistance. Samples were subcultured in azole-containing agar plates. Isolates with a positive screening test were subject to DNA extraction, DNA amplification and sequencing of the cyp51A gene (coding and promoter regions). Clinical data were obtained from medical records.
RESULTS
We screened 43 Aspergillus isolates from 39 patients for azole resistance. Three isolates from three patients grew on azole-containing agar plates: two A. fumigatus and one Aspergillus flavus. PCR analysis and cyp51A sequencing identified the TR34/L98H mutation in both A. fumigatus isolates. The prevalence of cyp51A mutations among A. fumigatus was 8.3% (2/24). Both patients with TR34/L98H mutants were azole naive and presented with invasive aspergillosis; one had multiple myeloma and the other was a liver retransplant recipient. They suffered progressive disease and failed voriconazole therapy.
CONCLUSIONS
To the best of our knowledge, this is the first report of azole-resistant A. fumigatus with the TR34/L98H mutation in two azole-naive patients with refractory invasive aspergillosis in Mexico.
Topics: Antifungal Agents; Aspergillosis; Aspergillus fumigatus; Azoles; Cytochrome P-450 Enzyme System; Drug Resistance, Fungal; Fungal Proteins; Humans; Mexico; Mutation; Public Health Surveillance
PubMed: 31220262
DOI: 10.1093/jac/dkz121 -
Biochimica Et Biophysica Acta.... Jan 2021To maintain iron homeostasis, fungi have to balance iron acquisition, storage, and utilization to ensure sufficient supply and to avoid toxic excess of this essential... (Review)
Review
To maintain iron homeostasis, fungi have to balance iron acquisition, storage, and utilization to ensure sufficient supply and to avoid toxic excess of this essential trace element. As pathogens usually encounter iron limitation in the host niche, this metal plays a particular role during virulence. Siderophores are iron-chelators synthesized by most, but not all fungal species to sequester iron extra- and intracellularly. In recent years, the facultative human pathogen Aspergillus fumigatus has become a model for fungal iron homeostasis of siderophore-producing fungal species. This article summarizes the knowledge on fungal iron homeostasis and its links to virulence with a focus on A. fumigatus. It covers mechanisms for iron acquisition, storage, and detoxification, as well as the modes of transcriptional iron regulation and iron sensing in A. fumigatus in comparison to other fungal species. Moreover, potential translational applications of the peculiarities of fungal iron metabolism for treatment and diagnosis of fungal infections is addressed.
Topics: Aspergillus fumigatus; Chelating Agents; Fungal Proteins; Gene Expression Regulation, Fungal; Homeostasis; Humans; Iron; Repressor Proteins; Siderophores; Virulence
PubMed: 33045305
DOI: 10.1016/j.bbamcr.2020.118885 -
Future Microbiology Mar 2020Allergic bronchopulmonary aspergillosis (ABPA) is a complex pulmonary disorder caused by dysregulated immune responses against . The disorder usually complicates the... (Review)
Review
Allergic bronchopulmonary aspergillosis (ABPA) is a complex pulmonary disorder caused by dysregulated immune responses against . The disorder usually complicates the course of patients with asthma and cystic fibrosis. Patients with ABPA most often present with asthma that is poorly controlled despite inhaled corticosteroids and long-acting β2 agonists. The treatment of ABPA is complicated due to the occurrence of recurrent exacerbations and spontaneous remissions. The drugs used for treating ABPA include systemic glucocorticoids, antifungal agents and biologics, each with its own benefits and drawbacks. In this review, we illustrate the treatment pathway for ABPA in different situations, using a case-based approach. In each case, we present the options for treatment based on the available evidence from recent clinical trials.
Topics: Animals; Antifungal Agents; Aspergillosis, Allergic Bronchopulmonary; Aspergillus fumigatus; Humans
PubMed: 32286102
DOI: 10.2217/fmb-2019-0276 -
Current Protocols in Microbiology Sep 2019Aspergillus fumigatus is a human pathogen and the principal etiologic agent of invasive and chronic aspergillosis leading to several hundreds of thousands of deaths...
Aspergillus fumigatus is a human pathogen and the principal etiologic agent of invasive and chronic aspergillosis leading to several hundreds of thousands of deaths every year. Very few antifungals are available to treat infections caused by A. fumigatus, and resistance is developing to those we have. Our understanding of the molecular mechanisms that drive pathogenicity and drug resistance have been hampered by the lack of large mutant collections, which limits our ability to perform functional genomics analysis. Here we present a high-throughput gene knockout method that combines a highly reproducible fusion PCR method to enable generation of gene replacement cassettes with a multiwell format transformation procedure. This process can be used to generate 96 null mutants within 5 days by a single person at a cost of less than £18 ($24) per mutant and is being employed in our laboratory to generate a barcoded genome-wide knockout library in A. fumigatus. © 2019 The Authors.
Topics: Aspergillus fumigatus; DNA Primers; Gene Knockout Techniques; Polymerase Chain Reaction; Transformation, Genetic
PubMed: 31518064
DOI: 10.1002/cpmc.88 -
Journal de Mycologie Medicale May 2023Infections caused by azole-resistant Aspergillus are a rising public health threat with high mortality rates, high treatment costs and limited available antifungals,...
BACKGROUND
Infections caused by azole-resistant Aspergillus are a rising public health threat with high mortality rates, high treatment costs and limited available antifungals, indicating an urgent need for new antifungals or strategies. Our aim was to investigate antifungal and antibiofilm activities of auranofin, an FDA-approved anti-antirheumatic drug.
METHODS
Fungal susceptibility testing for auranofin was carried out by the broth-based microdilution methods. Cell viability treated by auranofin was tested by resazurin dye testing. The synergistic effect of auranofin and antifungal drugs was evaluated using checkboard assay. The inhibitory of biofilms were measured by crystal violet staining. Gene expression level analysis and enzyme activity was investigated with qRT-PCR analysis and DTNB assay. The key amino acid residues in the binding of auranofin with A. fumigatus thioredoxin reductase (AfTrxR) were indicated by structural analyses, site-directed mutagenesis, and microscale thermophoresis (MST) assays.
RESULTS
Auranofin has fungicidal activity and in vitro antifungal spectrum including Aspergillus flavus, Aspergillus fumigatus, Aspergillus terreus, Aspergillus niger, even itraconazole (ITC)-resistant A. fumigatus. Additionally, it has antibiofilm activities against ITC-resistant A. fumigatus by reducing the expression level of SomA and MedA. Moreover, we discovered a synergistic effect of auranofin and ITC or amphotericin B against ITC-resistant A. fumigatus. Auranofin downregulated the gene transcription of AfTrxR, and strongly inhibited the enzyme activity of AfTrxR through interacting with residues C145 and C148.
CONCLUSIONS
Auranofin has fungicidal and antibiofilm activities in Aspergillus spp. and is also a potentiator of ITC or amphotericin B in vitro.
Topics: Antifungal Agents; Itraconazole; Aspergillus fumigatus; Amphotericin B; Auranofin; Voriconazole; Triazoles; Microbial Sensitivity Tests
PubMed: 37037064
DOI: 10.1016/j.mycmed.2023.101381 -
MBio Feb 2022Fungal infections are associated with high mortality rates in humans. The risk of fungal diseases creates the urgent need to broaden the knowledge base regarding their...
Fungal infections are associated with high mortality rates in humans. The risk of fungal diseases creates the urgent need to broaden the knowledge base regarding their pathophysiology. In this sense, the role of extracellular vesicles (EVs) has been described to convey biological information and participate in the fungus-host interaction process. We hypothesized that fungal EVs work as an additional element in the communication routes regulating fungal responses in intraspecies interaction systems. In this respect, the aim of this study was to address the gene regulation profiles prompted by fungal EVs in intraspecies recipient cells. Our data demonstrated the intraspecies uptake of EVs in pathogenic fungi, such as Candida albicans, Aspergillus fumigatus, and Paracoccidioides brasiliensis, and the effects triggered by EVs in fungal cells. In C. albicans, we evaluated the involvement of EVs in the yeast-to-hypha transition, while in and A. fumigatus the function of EVs as stress transducers was investigated. and A. fumigatus were exposed to an inhibitor of glycosylation or UV light, respectively. The results demonstrated the role of EVs in regulating the expression of target genes and triggering phenotypic changes. The EVs treatment induced cellular proliferation and boosted the yeast to hyphal transition in C. albicans, while they enhanced stress responsiveness in A. fumigatus and , establishing a role for EVs in fungal intraspecies communication. Thus, EVs regulate fungal behavior, acting as potent message effectors, and understanding their effects and mechanism(s) of action could be exploited in antifungal therapies. Here, we report a study about extracellular vesicles (EVs) as communication mediators in fungi. Our results demonstrated the role of EVs from Candida albicans, Aspergillus fumigatus, and Paracoccidioides brasiliensis regulating the expression of target genes and phenotypic features. We asked whether fungal EVs play a role as message effectors. We show that fungal EVs are involved in fungal interaction systems as potent message effectors, and understanding their effects and mechanisms of action could be exploited in antifungal therapies.
Topics: Humans; Antifungal Agents; Mycoses; Aspergillus fumigatus; Candida albicans; Extracellular Vesicles; Cell Communication
PubMed: 35012355
DOI: 10.1128/mbio.03272-21