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1.
Molecular epidemiology, antifungal susceptibility, and ERG11 gene mutation of Candida species isolated from vulvovaginal candidiasis: Comparison between recurrent and non-recurrent infections.
Esfahani, A, Omran, AN, Salehi, Z, Shams-Ghahfarokhi, M, Ghane, M, Eybpoosh, S, Razzaghi-Abyaneh, M
Microbial pathogenesis. 2022;:105696
Abstract
Vulvovaginal candidiasis (VVC) is a prevalent infection of the genitourinary tract affecting millions of women worldwide. In the present study, the importance of virulence factors, ERG11 gene mutations, ERG11 gene expression, and plasma membrane ergosterol content for fluconazole resistance in Candida species was investigated in 200 women suspected of vulvovaginitis. Isolated Candida species were identified using the ITS-restriction fragment length polymorphism (ITS-RFLP) technique. Antifungal susceptibility testing was performed according to the CLSI document. ERG11 gene expression was analyzed using real-time PCR. ERG11 gene mutation analysis was performed using sequencing methods, and the ergosterol content of the cell membrane was determined in fluconazole-resistant isolates. Furthermore, the production of phospholipase and proteinase enzymes was evaluated in recurrent and non-recurrent infections. VVC was diagnosed in 101 (50.5%) of the 200 clinical cases, of which 21 (20.8%) were confirmed as RVVC. Candida albicans was the most prevalent species, followed by C. glabrata, C. tropicalis, C. krusei, C. parapsilosis, and C. guilliermondii. Ketoconazole and fluconazole were the most effective drugs against C. albicans among five tested antifungals with MIC ranges between 0.06 and 16 μg/mL and 0.25-64 μg/mL. Substitutions of A114S, Y257H, T123I and A114V were detected in fluconazole-resistant C. albicans. The ergosterol content of the fungal cell membrane and the mean levels of ERG11 gene expression transcript were higher in fluconazole-resistant C. albicans isolates obtained from RVVC than in those obtained from VVC cases. Phospholipase and proteinase were produced in different amounts in all Candida species isolated from VVC and RVVC cases. In this review, our results demonstrated that several molecular mechanisms, including ERG11 gene expression, changes in the cell membrane ergosterol content, and mutations in ERG11 gene alone or simultaneously involved in fluconazole resistance of C. albicans species and the recurrence of VVC.
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2.
Exploiting Structural Modelling Tools to Explore Host-Translocated Effector Proteins.
Amoozadeh, S, Johnston, J, Meisrimler, CN
International journal of molecular sciences. 2021;(23)
Abstract
Oomycete and fungal interactions with plants can be neutral, symbiotic or pathogenic with different impact on plant health and fitness. Both fungi and oomycetes can generate so-called effector proteins in order to successfully colonize the host plant. These proteins modify stress pathways, developmental processes and the innate immune system to the microbes' benefit, with a very different outcome for the plant. Investigating the biological and functional roles of effectors during plant-microbe interactions are accessible through bioinformatics and experimental approaches. The next generation protein modeling software RoseTTafold and AlphaFold2 have made significant progress in defining the 3D-structure of proteins by utilizing novel machine-learning algorithms using amino acid sequences as their only input. As these two methods rely on super computers, Google Colabfold alternatives have received significant attention, making the approaches more accessible to users. Here, we focus on current structural biology, sequence motif and domain knowledge of effector proteins from filamentous microbes and discuss the broader use of novel modelling strategies, namely AlphaFold2 and RoseTTafold, in the field of effector biology. Finally, we compare the original programs and their Colab versions to assess current strengths, ease of access, limitations and future applications.
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3.
Skin Commensal Fungus Malassezia and Its Lipases.
Park, M, Park, S, Jung, WH
Journal of microbiology and biotechnology. 2021;(5):637-644
Abstract
Malassezia is the most abundant genus in the fungal microflora found on human skin, and it is associated with various skin diseases. Among the 18 different species of Malassezia that have been identified to date, M. restricta and M. globosa are the most predominant fungal species found on human skin. Several studies have suggested a possible link between Malassezia and skin disorders. However, our knowledge on the physiology and pathogenesis of Malassezia in human body is still limited. Malassezia is unable to synthesize fatty acids; hence, it uptakes external fatty acids as a nutrient source for survival, a characteristic compensated by the secretion of lipases and degradation of sebum to produce and uptake external fatty acids. Although it has been reported that the activity of secreted lipases may contribute to pathogenesis of Malassezia, majority of the data were indirect evidences; therefore, enzymes' role in the pathogenesis of Malassezia infections is still largely unknown. This review focuses on the recent advances on Malassezia in the context of an emerging interest for lipases and summarizes the existing knowledge on Malassezia, diseases associated with the fungus, and the role of the reported lipases in its physiology and pathogenesis.
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4.
General hospital outbreak of invasive candidiasis due to azole-resistant Candida parapsilosis associated with an Erg11 Y132F mutation.
Corzo-Leon, DE, Peacock, M, Rodriguez-Zulueta, P, Salazar-Tamayo, GJ, MacCallum, DM
Medical mycology. 2021;(7):664-671
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Abstract
An increasing number of outbreaks due to resistant non-albicans Candida species have been reported worldwide. Between 2014 and 2016, Candida isolates causing invasive candidiasis were recovered in a Mexican hospital. Isolates were identified to species level and antifungal susceptibility was determined. In the time period studied, 74 invasive candidiasis cases were identified, with 38% (28/74) caused by Candida parapsilosis, out of which 54% (15/28) were fluconazole resistant. The ERG11 gene was sequenced for 12 recoverable fluconazole-resistant C. parapsilosis isolates and SNPs identified. The 12 isolates had one common silent point mutation in ERG11 (T591C) and seven isolates had an additional (A395T) mutation, which corresponded to Y132F. Four of the isolates carrying this mutation were closely related within the same cluster by microsatellite typing. This is the first report of an invasive candidiasis outbreak in Mexico due to azole-resistant C. parapsilosis associated with the Y132F substitution.
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5.
DyP-Type Peroxidases: Recent Advances and Perspectives.
Sugano, Y, Yoshida, T
International journal of molecular sciences. 2021;(11)
Abstract
In this review, we chart the major milestones in the research progress on the DyP-type peroxidase family over the past decade. Though mainly distributed among bacteria and fungi, this family actually exhibits more widespread diversity. Advanced tertiary structural analyses have revealed common and different features among members of this family. Notably, the catalytic cycle for the peroxidase activity of DyP-type peroxidases appears to be different from that of other ubiquitous heme peroxidases. DyP-type peroxidases have also been reported to possess activities in addition to peroxidase function, including hydrolase or oxidase activity. They also show various cellular distributions, functioning not only inside cells but also outside of cells. Some are also cargo proteins of encapsulin. Unique, noteworthy functions include a key role in life-cycle switching in Streptomyces and the operation of an iron transport system in Staphylococcus aureus, Bacillus subtilis and Escherichia coli. We also present several probable physiological roles of DyP-type peroxidases that reflect the widespread distribution and function of these enzymes. Lignin degradation is the most common function attributed to DyP-type peroxidases, but their activity is not high compared with that of standard lignin-degrading enzymes. From an environmental standpoint, degradation of natural antifungal anthraquinone compounds is a specific focus of DyP-type peroxidase research. Considered in its totality, the DyP-type peroxidase family offers a rich source of diverse and attractive materials for research scientists.
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Quantifying biomolecular hydrophobicity: Single molecule force spectroscopy of class II hydrophobins.
Paananen, A, Weich, S, Szilvay, GR, Leitner, M, Tappura, K, Ebner, A
The Journal of biological chemistry. 2021;:100728
Abstract
Hydrophobins are surface-active proteins produced by filamentous fungi. The amphiphilic structure of hydrophobins is very compact, containing a distinct hydrophobic patch on one side of the molecule, locked by four intramolecular disulfide bridges. Hydrophobins form dimers and multimers in solution to shield these hydrophobic patches from water exposure. Multimer formation in solution is dynamic, and hydrophobin monomers can be exchanged between multimers. Unlike class I hydrophobins, class II hydrophobins assemble into highly ordered films at the air-water interface. In order to increase our understanding of the strength and nature of the interaction between hydrophobins, we used atomic force microscopy for single molecule force spectroscopy to explore the molecular interaction forces between class II hydrophobins from Trichoderma reesei under different environmental conditions. A genetically engineered hydrophobin variant, NCys-HFBI, enabled covalent attachment of proteins to the apex of the atomic force microscopy cantilever tip and sample surfaces in controlled orientation with sufficient freedom of movement to measure molecular forces between hydrophobic patches. The measured rupture force between two assembled hydrophobins was ∼31 pN, at a loading rate of 500 pN/s. The results indicated stronger interaction between hydrophobins and hydrophobic surfaces than between two assembling hydrophobin molecules. Furthermore, this interaction was stable under different environmental conditions, which demonstrates the dominance of hydrophobicity in hydrophobin-hydrophobin interactions. This is the first time that interaction forces between hydrophobin molecules, and also between naturally occurring hydrophobic surfaces, have been measured directly at a single-molecule level.
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7.
Coordinated regulation of iron metabolism in Cryptococcus neoformans by GATA and CCAAT transcription factors: connections with virulence.
Jung, WH, Sánchez-León, E, Kronstad, JW
Current genetics. 2021;(4):583-593
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Abstract
Iron acquisition is critical for pathogenic fungi to adapt to and survive within the host environment. However, to same extent, the fungi must also avoid the detrimental effects caused by excess iron. The importance of iron has been demonstrated for the physiology and virulence of major fungal pathogens of humans including Aspergillus fumigatus, Candida albicans, and Cryptococcus neoformans. In particular, numerous studies have revealed that aspects of iron acquisition, metabolism, and homeostasis in the fungal pathogens are tightly controlled by conserved transcriptional regulators including a GATA-type iron transcription factor and the CCAAT-binding complex (CBC)/HapX orthologous protein complex. However, the specific downstream regulatory networks are slightly different in each fungus. In addition, roles have been proposed or demonstrated for other factors including monothiol glutaredoxins, BolA-like proteins, and Fe-S cluster incorporation on the GATA-type iron transcription factor and the CBC/HapX orthologous protein complex, although limited information is available. Here we focus on recent work on C. neoformans in the context of an emerging framework for fungal regulation of iron acquisition, metabolism, and homeostasis. Our specific goal is to summarize recent findings on transcriptional networks governed by the iron regulators Cir1 and HapX in C. neoformans.
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Regulators of commensal and pathogenic life-styles of an opportunistic fungus-Candida albicans.
Rai, LS, Wijlick, LV, Bougnoux, ME, Bachellier-Bassi, S, d'Enfert, C
Yeast (Chichester, England). 2021;(4):243-250
Abstract
The yeast Candida albicans is primarily a commensal of humans that colonizes the mucosal surfaces of the gastrointestinal and genital tracts. Yet, C. albicans can under certain circumstances undergo a shift from commensalism to pathogenicity. This transition is governed by fungal factors such as morphological transitions, environmental cues for instance relationships with gut microbiota and the host immune system. C. albicans utilizes distinct sets of regulatory programs to colonize or infect its host and to evade the host defense systems. Moreover, an orchestrated iron acquisition mechanism operates to adapt to specific niches with variable iron availability. Studies on regulatory networks and morphogenesis of these two distinct modes of C. albicans growth, suggest that both yeast and hyphal forms exist in both growth patterns and the regulatory circuits are inter-connected. Here, we summarize current knowledge about C. albicans commensal-to-pathogen shift, its regulatory elements and their contribution to human disease.
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Investigating the cell and developmental biology of plant infection by the rice blast fungus Magnaporthe oryzae.
Eseola, AB, Ryder, LS, Osés-Ruiz, M, Findlay, K, Yan, X, Cruz-Mireles, N, Molinari, C, Garduño-Rosales, M, Talbot, NJ
Fungal genetics and biology : FG & B. 2021;:103562
Abstract
Magnaporthe oryzae is the causal agent of rice blast disease, the most widespread and serious disease of cultivated rice. Live cell imaging and quantitative 4D image analysis have provided new insight into the mechanisms by which the fungus infects host cells and spreads rapidly in plant tissue. In this video review article, we apply live cell imaging approaches to understanding the cell and developmental biology of rice blast disease. To gain entry to host plants, M. oryzae develops a specialised infection structure called an appressorium, a unicellular dome-shaped cell which generates enormous turgor, translated into mechanical force to rupture the leaf cuticle. Appressorium development is induced by perception of the hydrophobic leaf surface and nutrient deprivation. Cargo-independent autophagy in the three-celled conidium, controlled by cell cycle regulation, is essential for appressorium morphogenesis. Appressorium maturation involves turgor generation and melanin pigment deposition in the appressorial cell wall. Once a threshold of turgor has been reached, this triggers re-polarisation which requires regulated generation of reactive oxygen species, to facilitate septin GTPase-dependent cytoskeletal re-organisation and re-polarisation of the appressorium to form a narrow, rigid penetration peg. Infection of host tissue requires a further morphogenetic transition to a pseudohyphal-type of growth within colonised rice cells. At the same time the fungus secretes an arsenal of effector proteins to suppress plant immunity. Many effectors are secreted into host cells directly, which involves a specific secretory pathway and a specialised structure called the biotrophic interfacial complex. Cell-to-cell spread of the fungus then requires development of a specialised structure, the transpressorium, that is used to traverse pit field sites, allowing the fungus to maintain host cell membrane integrity as new living plant cells are invaded. Thereafter, the fungus rapidly moves through plant tissue and host cells begin to die, as the fungus switches to necrotrophic growth and disease symptoms develop. These morphogenetic transitions are reviewed in the context of live cell imaging studies.
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Fungal homologues of human Rac1 as emerging players in signal transduction and morphogenesis.
Hühn, J, Musielak, M, Schmitz, HP, Heinisch, JJ
International microbiology : the official journal of the Spanish Society for Microbiology. 2020;(1):43-53
Abstract
A wealth of data is accumulating on the physiological functions of human Rac1, a member of the Rho GTPase family of molecular switches and substrate of botulinum toxin, which was first identified as a regulator of cell motility through its effect on the actin cytoskeleton. Later on, it was found to be involved in different diseases like cancers, cardiac function, neuronal disorders, and apoptotic cell death. Despite the presence of Rac1 homologues in most fungi investigated so far, including Rho5 in the genetically tractable model yeast Saccharomyces cerevisiae, knowledge on their physiological functions is still scarce, let alone the details of the molecular mechanisms of their actions and interactions. Nevertheless, all functions proposed for human Rac1 seem to be conserved in one or the other fungus. This includes the regulation of MAPK cascades, polarized growth, and actin dynamics. Moreover, both the production and response to reactive oxygen species, as well as the reaction to nutrient availability, can be affected. We here summarize the studies performed on fungal Rac1 homologues, with a special focus on S. cerevisiae Rho5, which may be of use in drug development in medicine and agriculture.