Talaromyces marneffei Genomic, Transcriptomic, Proteomic and Metabolomic Studies Reveal Mechanisms for Environmental Adaptations and Virulence

Mucor germinans, a novel dimorphic species resembling Paracoccidioides in a clinical sample: questions on ecological strategy

Dimorphism is known among the etiologic agents of endemic mycoses as well as in filamentous Mucorales. Under appropriate thermal conditions, mononuclear yeast forms alternate with multi-nucleate hyphae. Here, we describe a dimorphic mucoralean fungus obtained from the sputum of a patient with Burkitt lymphoma and ongoing graft-versus-host reactions. The fungus is described as Mucor germinans sp. nov. Laboratory studies were performed to simulate temperature-dependent dimorphism, with two environmental strains Mucor circinelloides and Mucor kunryangriensis as controls. Both strains could be induced to form multinucleate arthrospores and subsequent yeast-like cells in vitro. Multilateral yeast cells emerge in all three Mucor species at elevated temperatures. This morphological transformation appears to occur at body temperature since the yeast-like cells were observed in the lungs of our immunocompromised patient. The microscopic appearance of the yeast-like cells in the clinical samples is easily confused with that of Paracoccidioides. The ecological role of yeast forms in Mucorales is discussed.IMPORTANCEMucormycosis is a devastating disease with high morbidity and mortality in susceptible patients. Accurate diagnosis is required for timely clinical management since antifungal susceptibility differs between species. Irregular hyphal elements are usually taken as the hallmark of mucormycosis, but here, we show that some species may also produce yeast-like cells, potentially being mistaken for Candida or Paracoccidioides. We demonstrate that the dimorphic transition is common in Mucor species and can be driven by many factors. The multi-nucleate yeast-like cells provide an effective parameter to distinguish mucoralean infections from similar yeast-like species in clinical samples.

New Polyene Macrolide Compounds from Mangrove-Derived Strain Streptomyces hiroshimensis GXIMD 06359: Isolation, Antifungal Activity, and Mechanism against Talaromyces marneffei

Mangrove-derived actinomycetes represent a rich source of novel bioactive natural products in drug discovery. In this study, four new polyene macrolide antibiotics antifungalmycin B-E (1-4), along with seven known analogs (5-11), were isolated from the fermentation broth of the mangrove strain Streptomyces hiroshimensis GXIMD 06359. All compounds from this strain were purified using semi-preparative HPLC and Sephadex LH-20 gel filtration while following an antifungal activity-guided fractionation. Their structures were elucidated through spectroscopic techniques including UV, HR-ESI-MS, and NMR. These compounds exhibited broad-spectrum antifungal activity against Talaromyces marneffei with minimum inhibitory concentration (MIC) values being in the range of 2-128 μg/mL except compound 2. This is the first report of polyene derivatives produced by S. hiroshimensis as bioactive compounds against T. marneffei. In vitro studies showed that compound 1 exerted a significantly stronger antifungal activity against T. marneffei than other new compounds, and the antifungal mechanism of compound 1 may be related to the disrupted cell membrane, which causes mitochondrial dysfunction, resulting in leakage of intracellular biological components, and subsequently, cell death. Taken together, this study provides a basis for compound 1 preventing and controlling talaromycosis.

Differential innate immune responses of human macrophages and bronchial epithelial cells against Talaromyces marneffei

Talaromyces marneffei is a thermally dimorphic fungal pathogen endemic in Southeast Asia. As inhalation of airborne conidia is believed as the major infection route, airway epithelial cells followed by pulmonary macrophages are the first cell types which the fungus encounters inside the host. In this study, we established an in vitro infection model based on human peripheral blood-derived macrophages (hPBDMs) cultured with the supplementation of autologous plasma. Using this model, we determined the transcriptomic changes of hPBDMs in response to T. marneffei infection by quantitative real-time reverse-transcription polymerase chain reaction as well as high-throughput RNA sequencing. Results showed that T. marneffei infection could activate hPBDMs to the M1-like phenotype and trigger a potent induction of chemokine and pro-inflammatory cytokine production as well as the expression of other immunoregulatory genes. In contrast to hPBDMs, there was no detectable innate cytokine response against T. marneffei in human bronchial epithelial cells (hBECs). Using a green fluorescent protein-tagged T. marneffei strain and confocal microscopy, internalization of the fungus by hBECs was confirmed. Live cell imaging further demonstrated that the infected cells exhibited normal cellular physiology, especially that the process of cell division could be observed. Moreover, T. marneffei also survived better inside hBECs than hPBDMs. Our results illustrated a potential role of hBECs to serve as reservoir cells for T. marneffei to evade immunosurveillance by phagocytes, from which the fungus reactivates when the host immunity is weakened and causes infection. Such immunoevasion and reactivation may also help explain the long incubation period observed for talaromycosis, in particular the travel-related cases. IMPORTANCE Talaromyces marneffei is an important fungal pathogen especially in Southeast Asia. To understand the innate immune response to talaromycosis, a suitable infection model is needed. Here, we established an in vitro T. marneffei infection model using human peripheral blood-derived macrophages (hPBDMs). We then examined the transcriptomic changes of hPBDMs in response to T. marneffei infection with this model. We found that contact with T. marneffei could activate hPBDMs to the M1-like phenotype and induced mRNA expressions of five cytokines and eight immunoregulatory genes. Contrary to hPBDMs, such immunoresponse was not elicited in human bronchial epithelial cells (hBECs), despite normal physiology observed in infected cells. We also found that infected hBECs did not eliminate T. marneffei as efficiently as hPBDMs. Our observation suggested that hBECs may potentially serve as reservoir cells for T. marneffei to evade immunosurveillance. When the host immunity deteriorates later, then the fungus reactivates and causes infection.

An Overlooked and Underrated Endemic Mycosis-Talaromycosis and the Pathogenic Fungus Talaromyces marneffei

Talaromycosis is an invasive mycosis endemic in tropical and subtropical Asia and is caused by the pathogenic fungus Talaromyces marneffei. Approximately 17,300 cases of T. marneffei infection are diagnosed annually, and the reported mortality rate is extremely high (~1/3). Despite the devastating impact of talaromycosis on immunocompromised individuals, particularly HIV-positive persons, and the increase in reported occurrences in HIV-uninfected persons, diagnostic and therapeutic approaches for talaromycosis have received far too little attention worldwide. In 2021, scientists living in countries where talaromycosis is endemic raised a global demand for it to be recognized as a neglected tropical disease. Therefore, T. marneffei and the infectious disease induced by this fungus must be treated with concern. T. marneffei is a thermally dimorphic saprophytic fungus with a complicated mycological growth process that may produce various cell types in its life cycle, including conidia, hyphae, and yeast, all of which are associated with its pathogenicity. However, understanding of the pathogenic mechanism of T. marneffei has been limited until recently. To achieve a holistic view of T. marneffei and talaromycosis, the current knowledge about talaromycosis and research breakthroughs regarding T. marneffei growth biology are discussed in this review, along with the interaction of the fungus with environmental stimuli and the host immune response to fungal infection. Importantly, the future research directions required for understanding this serious infection and its causative pathogenic fungus are also emphasized to identify solutions that will alleviate the suffering of susceptible individuals worldwide.

Key thermally dimorphic fungal pathogens: shaping host immunity

Exposure to fungal pathogens from the environment is inevitable and with the number of at-risk populations increasing, the prevalence of invasive fungal infection is on the rise. An interesting group of fungal organisms known as thermally dimorphic fungi predominantly infects immunocompromised individuals. These potential pathogens are intriguing in that they survive in the environment in one form, mycelial phase, but when entering the host, they are triggered by the change in temperature to switch to a new pathogenic form. Considering the growing prevalence of infection and the need for improved diagnostic and treatment approaches, studies identifying key components of fungal recognition and the innate immune response to these pathogens will significantly contribute to our understanding of disease progression. This review focuses on key endemic dimorphic fungal pathogens that significantly contribute to disease, including Histoplasma, Coccidioides and Talaromyces species. We briefly describe their prevalence, route of infection and clinical presentation. Importantly, we have reviewed the major fungal cell wall components of these dimorphic fungi, the host pattern recognition receptors responsible for recognition and important innate immune responses supporting adaptive immunity and fungal clearance or the failure thereof.

Study of Dimorphism Transition Mechanism of Tremella fuciformis Based on Comparative Proteomics

Tremella fuciformis is a dimorphic fungus that can undertake a reversible transition between yeast-like conidia and hyphal forms. The transformation mechanism and proteomic differences between these two forms have not been reported. Therefore, in this study, we attempted to explore the differential protein profiles of dikaryotic yeast-like conidia from fruiting bodies and mycelia (FBMds) and dikaryotic mycelia (DM) by synthetically applying high-resolution MS1-based quantitative data-independent acquisition (HRMS1-DIA) full proteomics and parallel reaction monitoring (PRM) targeted proteomics. The results showed that a total of 5687 proteins were quantified, and 2220 of them (39.01%) showed more than a two-fold change in expression. The functional analysis of the differentially expressed proteins (DEPs) confirmed that the DEPs were mainly located in the membrane and nucleus. The FBMds tended to express proteins involved in biosynthesis, metabolism, DNA replication and transcription, and DNA damage repair. At the same time, DM exhibited an increased expression of proteins involved in signal transduction mechanisms such as the mitogen-activated protein kinase (MAPK) signaling pathway and the Ras signaling pathway. Further, phosphorylation analysis confirmed the importance of the MAPK signaling pathway in T. fuciformis dimorphism, and comparative metabolism analysis demonstrated the metabolic difference between FBMds and DM. The information obtained in the present study will provide new insights into the difference between FBMds and DM and lay a foundation for further research on the dimorphism formation mechanism of T. fuciformis.

HIV-negative case of Talaromyces marneffei pulmonary infection with a TSC2 mutation

Talaromyces marneffei is a rare dimorphic pathogenic fungus that can induce severe infections in human immunodeficiency virus (HIV)-infected patients. However, such infections have also been reported in non-HIV hosts. This current case report describes a very rare case of a T. marneffei pulmonary infection in an HIV-negative patient with a mutation in the tuberous sclerosis complex subunit 2 (TSC2) gene. A 24-year-old male patient presented with cough and expectoration for 6 months. Computed tomography showed multiple ground-glass opacities and cystic and cavitated lesions in both lungs. Next generation sequencing (NGS) of the bronchoalveolar lavage fluid was performed to confirm T. marneffei pulmonary infection. The results were further verified using bronchoscopy specimen cultures. This was an HIV-negative patient without a travel history to endemic zones and his blood exon sequencing results showed a mutation in the TSC2 gene. To date, he has recovered well with voriconazole therapy. In summary, patients with TSC2 mutations that induce bronchopulmonary dysplasia may be potential hosts for T. marneffei. Early and timely diagnosis is important for improving prognosis. NGS plays a critical role in the diagnosis of T. marneffei pulmonary infection.

Proteomic analysis on the regulation of DOPA-melanin synthesis in Talaromyces marneffei

BACKGROUND

Yeast form of T.marneffei can produce DOPA-melanin which perform an important role in the pathogen surviving in macrophage. So far, the proteomic associated with melanin synthesis remain unclearly in T.marneffei.

METHODS

The whole yeast cell proteins were extracted from T.marneffei cultured with or without l-DOPA. Using two-dimensional gel electrophoresis combined with MALDI-TOF mass spectrometry, distinguished proteins were identified between T.marneffei cultured with or without l-DOPA. Furthermore, geldanamycin were used to assess the inhibition effect on T.marneffei melanin production in vitro.

RESULTS

16 distinguished proteins were identified in DOPA-melanized yeast cells, as well as 15 triple-up-expressed proteins and 7 triple-down-expressed proteins in comparison with non DOPA-melanized yeast cells. Of note, proteins differentially expressed proteins were predominantly heat shock proteins. HSP90/60/70 genes expressions increased significantly demonstrated by q-RT-PCR, which was consistent with the proteomics changes. GO analysis showed that the majority of differentially expressed proteins including HSPs(especially HSP90) were found enriched in stress response, cellular process, protein folding, stimuli response and biological process. KEGG pathway analysis showed that proteins were enriched predominantly in phagosome. HSP90 inhibitor(Geldanamycin) inhibited the brown-black pigment production of T.marneffei yeast grown on brain heart infusion agar, as well as the inhibition effect was observed by transmission electron microscope.

CONCLUSIONS

The results demonstrates that HSP90 palys an essential role in T.marneffei DOPA-melanin synthesis pathway.

Screening of Phosphate-Solubilizing Fungi From Air and Soil in Yunnan, China: Four Novel Species in Aspergillus, Gongronella, Penicillium, and Talaromyces

Phosphate-solubilizing fungi (PSF) play an important role in increasing the bioavailability of phosphorus in soils for plants. Thirteen fungal strains, one collected from air and 12 from soil, were screened and described here in detail. These fungal strains were tested for their ability to solubilize tricalcium phosphate (TCP) on both solid and liquid Pikovskaya (PVK) media in vitro. The airborne fungal strain KUMCC 18-0196 (Aspergillus hydei sp. nov.) showed the most significant phosphate solubilizing activity on a solid PVK medium with the solubilization index (SI) (2.58 ± 0.04 cm) and the highest solubilized phosphates (1523.33 ± 47.87 μg/mL) on a liquid PVK medium. To the best of our knowledge, A. hydei sp. nov. is the first phosphate-solubilizing fungus reported from air. We also provide the identification especially for Aspergillus, Penicillium and Talaromyces, generally reported as PSF. It is important to not only screen for PSF but also identify species properly so that researchers have a clearer taxonomic picture for identifying potential taxa for future plant growth-promoting applications. Herein, A. hydei (section Nigri), Gongronella hydei, Penicillium soli (section Lanata-Divaricata) and Talaromyces yunnanensis (section Talaromyces) are fully described and introduced as new to science. These four new species are identified based on both morphological characteristics and multigene phylogenetic analyses, including the genealogical concordance phylogenetic species recognition method where necessary. Penicillium austrosinense is considered to be a synonym of P. guaibinense.

Genomic and Postgenomic Diversity of Fungal Plant Biomass Degradation Approaches

Plant biomass degradation by fungi is a widely studied and applied field of science, due to its relevance for the global carbon cycle and many biotechnological applications. Before the genome era, many of the in-depth studies focused on a relatively small number of species, whereas now, many species can be addressed in detail, revealing the large variety in the approach used by fungi to degrade plant biomass. This variation is found at many levels and includes genomic adaptation to the preferred biomass component, but also different approaches to degrade this component by diverse sets of activities encoded in the genome. Even larger differences have been observed using transcriptome and proteome studies, even between closely related species, suggesting a high level of adaptation in individual species. A better understanding of the drivers of this diversity could be highly valuable in developing more efficient biotechnology approaches for the enzymatic conversion of plant biomass.

Diagnostic laboratory immunology for talaromycosis (penicilliosis): review from the bench-top techniques to the point-of-care testing

The pathogenic fungus Talaromyces (formerly Penicillium) marneffei is a thermally dimorphic fungus that can cause disseminated infection in patients with secondary immunodeficiency syndrome, in particular in the setting of advanced HIV infection. The areas of highest incidence are in Southeast Asia, Southern China, and Indian subcontinents. Talaromycosis (formerly penicilliosis) is identified as an AIDS-defining illness, and it has recently been recognized in non-HIV-associated patients with impaired cellular-mediated immunity. Microbiological culture is the gold standard method for the diagnosis of T. marneffei infection and usually requires up to 2-4 weeks for detectable growth to occur, which may result in a delay of appropriate treatment. Immunodiagnosis has become an alternative method for confirming talaromycosis. This article reviews various immunological tests for the diagnosis of talaromycosis, including a proposed novel rapid point-of-care assay using a new T. marneffei yeast phase-specific monoclonal antibody.

Proteomic analysis of serum proteins from HIV/AIDS patients with Talaromyces marneffei infection by TMT labeling-based quantitative proteomics

BACKGROUND

Talaromyces marneffei (TM) is an emerging pathogenic fungus that can cause a fatal systemic mycosis in patients infected with human immunodeficiency virus (HIV). Although global awareness regarding HIV/TM coinfection is increasing little is known about the mechanism that mediates the rapid progression to HIV/AIDS disease in coinfected individuals. The aim of this study was to analyze the serum proteome of HIV/TM coinfected patients and to identify the associated protein biomarkers for TM in patients with HIV/AIDS.

METHODS

We systematically used multiplexed isobaric tandem mass tag labeling combined with liquid chromatography mass spectrometry (LC-MS/MS) to screen for differentially expressed proteins in the serum samples from HIV/TM-coinfected patients.

RESULTS

Of a total data set that included 1099 identified proteins, approximately 86% of the identified proteins were quantified. Among them, 123 proteins were at least 1.5-fold up-or downregulated in the serum between HIV/TM-coinfected and HIV-mono-infected patients. Furthermore, our results indicate that two selected proteins (IL1RL1 and THBS1) are potential biomarkers for distinguishing HIV/TM-coinfected patients.

CONCLUSIONS

This is the first report to provide a global proteomic profile of serum samples from HIV/TM-coinfected patients. Our data provide insights into the proteins that are involved as host response factors during infection. These data shed new light on the molecular mechanisms that are dysregulated and contribute to the pathogenesis of HIV/TM coinfection. IL1RL1 and THBS1 are promising diagnostic markers for HIV/TM-coinfected patients although further large-scale studies are needed. Thus, quantitative proteomic analysis revealed molecular differences between the HIV/TM-coinfected and HIV-mono-infected individuals, and might provide fundamental information for further detailed investigations.

Taxonomy and evolution of Aspergillus, Penicillium and Talaromyces in the omics era - Past, present and future

Aspergillus, Penicillium and Talaromyces are diverse, phenotypically polythetic genera encompassing species important to the environment, economy, biotechnology and medicine, causing significant social impacts. Taxonomic studies on these fungi are essential since they could provide invaluable information on their evolutionary relationships and define criteria for species recognition. With the advancement of various biological, biochemical and computational technologies, different approaches have been adopted for the taxonomy of Aspergillus, Penicillium and Talaromyces; for example, from traditional morphotyping, phenotyping to chemotyping (e.g. lipotyping, proteotypingand metabolotyping) and then mitogenotyping and/or phylotyping. Since different taxonomic approaches focus on different sets of characters of the organisms, various classification and identification schemes would result. In view of this, the consolidated species concept, which takes into account different types of characters, is recently accepted for taxonomic purposes and, together with the lately implemented 'One Fungus - One Name' policy, is expected to bring a more stable taxonomy for Aspergillus, Penicillium and Talaromyces, which could facilitate their evolutionary studies. The most significant taxonomic change for the three genera was the transfer of Penicillium subgenus Biverticillium to Talaromyces (e.g. the medically important thermally dimorphic 'P. marneffei' endemic in Southeast Asia is now named T. marneffei), leaving both Penicillium and Talaromyces as monophyletic genera. Several distantly related Aspergillus-like fungi were also segregated from Aspergillus, making this genus, containing members of both sexual and asexual morphs, monophyletic as well. In the current omics era, application of various state-of-the-art omics technologies is likely to provide comprehensive information on the evolution of Aspergillus, Penicillium and Talaromyces and a stable taxonomy will hopefully be achieved.