The pathogenic fungus Trichosporon asahii causes severe mycoses in immunocompromised hosts, such as neutropenic patients. In Cryptococcus neoformans, the unfolded protein response (UPR) sensor Ire1 induces hxl1 mRNA splicing and contributes to stress responses and virulence. The function of Ire1-triggered hxl1 mRNA splicing in stress tolerance and virulence of T. asahii, however, remains unclear. Here, we demonstrated that ire1- and hxl1 gene-deficient T. asahii mutants are sensitive to dithiothreitol (DTT), an inducer of endoplasmic reticulum stress, and exhibit reduced virulence in a silkworm infection model. DTT treatment induced hxl1 mRNA splicing in the wild-type strain, whereas ire1 gene-deficient mutants did not undergo hxl1 mRNA splicing. The ire1 gene-deficient mutants were more sensitive than the parent strain to DTT, H2O2, Congo red, and SDS, and showed reduced virulence in silkworms. Similarly, hxl1 gene-deficient mutants exhibited increased sensitivity to these stressors and reduced virulence. Both the ire1 gene-deficient and hxl1 gene-deficient mutants showed decreased expression of reactive oxygen species-detoxifying related genes CAT2, SOD1, and SOD2, compared with the parent strain. Together, these findings suggest that Ire1-triggered hxl1 mRNA splicing contributes to stress resistance and virulence in T. asahii.

Fungal populations and species can be characterised using DNA sequences from specific genomic regions or entire genomes. However, recognising taxa above the species level still relies primarily on phenotypic characters, particularly morphology, which are often limited in many fungal groups. We examined whether gene presence/absence information could be used for taxonomic characterisation. Using 259 genomes, including 71 newly sequenced ones, we generated a presence/absence matrix of orthologous groups (OGs). Cluster analysis using the Yule coefficient revealed that, in Ascomycota, the presence/absence patterns of OGs were likely associated with evolutionary processes down to the subphylum level. Conversely, in Basidiomycota, these patterns did not necessarily correspond to subphylum classifications, although the reason for this discrepancy remains unclear. Principal component analysis showed that each subphylum could be distinguished by its axes in both Ascomycota and Basidiomycota. We then identified characteristically present and absent OGs (98 for Ascomycota, 108 for Basidiomycota, and 321 across both subphyla). Gene Ontology analysis revealed statistically significant functional differences between Ascomycota and Basidiomycota: genes related to RNA polymerase II, nucleosome assembly (including the Rpd3L complex), and fungal-type cell wall organisation were enriched in Ascomycota, whereas the membrane and ubiquitin ligase complex were enriched in Basidiomycota. At the subphylum level, several OGs were identified as potential taxonomic markers, such as those associated with methylation (Pezizomycotina), mitochondria (Saccharomycotina), signal transduction (Agaricomycotina), and cell wall synthesis (Pucciniomycotina). Overall, presence/absence ortholog analysis provides a promising approach for characterising taxa based on genomic traits and may contribute to advancing fungal taxonomy above the species level.

Trichosporon asahii is a pleomorphic basidiomycetous yeast that causes deep-seated mycoses in immunocompromised individuals. T. asahii exhibits three morphological types: hyphae, yeasts, and arthroconidia. Hyphal formation is related to virulence and is accelerated by the addition of magnesium. However, the effects of magnesium on gene expression have not been elucidated. In this study, we aimed to investigate whether gene expression is affected by magnesium. RNA sequencing and genetic analyses revealed that magnesium addition increased the expression of genes related to arthroconidia formation in T. asahii. We identified 11 magnesium-enhanced expression (mee) genes, whose expressions increased more than 5-fold. Deletion of mee4, mee5, mee6, and mee11 decreased arthroconidia formation. Furthermore, increased mee6 expression depended on mee4 and mee5, which lie downstream of the TOR pathway, and increased mee11 expression depended on mee4. In addition, mee11 inhibited the expression of other mee genes, and mee6 inhibited the expression of mee4. Overall, we identified a gene expression network related to arthroconidia formation in T. asahii, providing insights into the transition from hypha to arthroconidia and enhancing our understanding of fungal pathogenesis.IMPORTANCEMagnesium induces cell elongation and changes in organelle distribution in T. asahii. In this study, RNA sequencing revealed that magnesium influenced gene expression. Among the genes whose expressions increased more than five-fold following magnesium addition, we identified arthroconidia-related genes whose deletions inhibited arthroconidia formation. Thus, an increase in magnesium cations promotes both hyphal formation and arthroconidia formation in T. asahii. This is the first study to elucidate genes related to arthroconidia formation.

Six novel meroterpenoids, dispanoic acids A-C (1-3), 2'-hydroxydaurichromanic acid (4), albatrellutin A (5), and dispanolactone (6), along with four known meroterpenoids, grifolin (7), grifolic acid (8), grifolin methyl ether (9), and grifolic acid methyl ether (10), were obtained by bioactivity-guided isolation from the n-hexane, CHCl3 and MeOH extracts of the fruiting body of Albatrellus dispansus. The structures of 1-6 were elucidated from NMR and MS spectroscopic data. Although 5 was determined to have the same structure as albatrellutin, its 1H and 13C NMR data were inconsistent with published data. Therefore, we synthesized albatrellutin (reported original structure) and a positional isomer of albatrellutin (revised structure). The published NMR data for albatrellutin and the synthesized positional isomer of albatrellutin were in good agreement. Thus, we corrected the structure of albatrellutin to the positional isomer and renamed it albatrellutin A. Compound 5, which has the structure originally reported as albatrelutin, was named neoalbatrellutin. Isolated compounds (1-10) were evaluated for their inhibitory activity against Candida albicans budded-to-hyphal-form transition (BHT). A new compound 3 showed potent inhibitory activity against BHT and biofilm formation by C. albicans and also downregulated expression of the hyphal wall protein 1 (HWP1).

Trichosporon asahii is a dimorphic fungus that causes severe invasive fungal infections, particularly in patients with neutropenia. Depending on nutrient availability, T. asahii exists in yeast, hyphae, or arthroconidia forms. Atg1, a serine/threonine kinase, involves in stress responses and virulence in several fungi. The role of Atg1 in regulating morphology, stress resistance, or virulence in T. asahii, however, remains poorly understood. Here, we generated three atg1 gene-deficient T. asahii mutants and investigated their phenotypic characteristics to reveal the role of Atg1 in T. asahii. The atg1 gene-deficient mutants exhibited no growth defects under high-temperature or various chemical stress conditions, including antifungal drugs. The mutants exhibited an increased proportion of hyphal cells when cultured in Sabouraud dextrose broth (SB), a medium commonly used for fungi. On the other hand, no morphologic differences were observed between the parent strain and the atg1 gene-deficient mutants under a nitrogen-limited condition. The virulence of these atg1 gene-deficient mutants was maintained in a silkworm infection model. Furthermore, all three generated atg1 gene-deficient mutants exhibited consistent phenotypes. Our findings suggest that while Atg1 does not play a major role in stress tolerance or virulence in T. asahii under the tested conditions, it plays a role in regulating its dimorphic morphologic changes.

Kodamaea ohmeri (formerly Pichia ohmeri) is a rare yeast-like fungus usually isolated from environmental sources such as insects and fruits, and human infections are uncommon. Since the first report in 1998, however, cases of bloodstream infection have been increasingly described, mainly in Asia. We report a case of K. ohmeri fungaemia associated with a peripherally inserted central catheter (PICC). A man in his sixties with diabetes mellitus developed fever during hospitalisation while the PICC was in place. Yeast-like fungi were detected in blood cultures and identified as K. ohmeri by MALDI-TOF mass spectrometry. Antifungal susceptibility testing showed susceptibility to micafungin and other echinocandins, and reduced susceptibility to fluconazole. Removal of the PICC and administration of micafungin led to resolution of clinical symptoms and negative blood cultures. A review of 52 published cases revealed a mortality rate of 30.8%, with about half associated with catheter use. As K. ohmeri is capable of biofilm formation, removal of the infection source appears crucial for favourable outcomes. This case represents successful treatment of a fluconazole low-susceptibility K. ohmeri fungaemia with micafungin, suggesting that this drug may be an effective therapeutic option.

Yeasts show few distinct morphological characteristics. The two basic forms of yeast, unicellular yeast and multicellular hyphal form, exhibit dimorphism. In a recent study on Trichosporon asahii, a dimorphic basidiomycetous yeast that causes trichosporonosis, the addition of magnesium induced hyphal formation and changes in organelle distribution. A detailed observation of organelle distribution revealed that the responses to magnesium addition varied widely among Trichosporonales yeasts. In this review, we show that differences in organelle phenotypes upon magnesium addition possibly contribute to the practical identification and classification of Trichosporonales yeasts.

Cutibacterium acnes, a major skin commensal bacterium, induces inflammatory cytokine production in keratinocytes through Toll-like receptor 2 (TLR2) signaling and contributes to acne vulgaris pathogenesis. Although glucocorticoids, e.g., dexamethasone (Dex), exert anti-inflammatory effects in related treatments, prolonged glucocorticoid exposure paradoxically induces acneiform eruptions, a phenomenon referred to as steroid-induced acne. Moreover, how commensal fungi influence bacterial-driven inflammatory signaling under glucocorticoid treatment remains unclear. In this study, we investigated how the lipophilic skin yeast Malassezia restricta affects C. acnes-induced TLR2 expression under Dex treatment using normal human epidermal keratinocytes. We discovered that M. restricta selectively suppressed Dex-enhanced C. acnes-induced TLR2 expression both at the transcriptional level and cell surface. Mechanistically, M. restricta enhanced p38 MAPK phosphorylation and inhibited NF-κB p65 nuclear translocation, indicating context-dependent glucocorticoid-primed TLR2 signaling modulation rather than simple inhibition. These results demonstrate that M. restricta modulates bacterial-induced inflammatory responsiveness in keratinocytes under glucocorticoid exposure and highlight the importance of fungal–bacterial interactions in shaping host immune signaling in steroid-treated skin. Our study provides new insight into the mechanistic basis of steroid-induced acne and the polymicrobial regulation of cutaneous innate immunity.

Trichosporon asahii is a dimorphic pathogenic fungus that causes catheter-related bloodstream infection in immunocompromised patients with neutropenia. Biofilm formation by T. asahii on the surfaces of medical devices such as catheters is influenced by various host environmental factors. Calcineurin, a protein phosphatase composed of the catalytic subunit Cna1 and the regulatory subunit Cnb1, regulates multiple stress responses and virulence of T. asahii. The role of calcineurin in biofilm formation under host-derived conditions, however, remains unclear. Here, we demonstrated that calcineurin is essential for biofilm formation in vivo by T. asahii. While the cna1 gene- and the cnb1 gene-deficient mutants formed biofilms comparable to those of the parent strain in vitro, it produced significantly less biofilm than the parent strain in the in vivo silkworm infection model. Similarly, tacrolimus, a calcineurin inhibitor, did not inhibit biofilm formation by T. asahii in vitro but markedly suppressed biofilm formation in vivo. Together, these findings suggest that calcineurin plays a crucial role in biofilm formation by T. asahii under host environmental conditions.

The pathogenic fungus Trichosporon asahii causes severe invasive fungal infections in immunocompromised patients with neutropenia. In Cryptococcus neoformans, calcineurin-responsive zinc finger 1 (Crz1) functions as a transcription factor downstream of the calcineurin signaling pathway and regulates the expression of genes involved in stress resistance and virulence. In T. asahii, Cna1 and Cnb1, which are key components of the calcineurin pathway, contribute to various stress responses and virulence. The role of Crz1 in stress tolerance and virulence in T. asahii, however, has remained unclear. Here, we demonstrate that a crz1 gene-deficient T. asahii mutant exhibited increased sensitivity to cell wall and endoplasmic reticulum stress. The crz1 gene-deficient mutant was sensitive to Congo red and tunicamycin but not to dithiothreitol or sodium dodecyl sulfate. Moreover, the virulence of the crz1 gene-deficient mutant in the silkworm infection model was reduced. These phenotypes of the crz1 gene-deficient mutant were restored by reintroducing the crz1 gene, confirming the association between Crz1 and these phenotypes. The half-maximal lethal dose of the cnb1 gene-deficient T. asahii mutant was higher than that of the crz1 gene-deficient mutant. These results suggest that Crz1 mediates the stress responses and virulence of T. asahii. The involvement of Crz1 in the virulence of T. asahii is small, however, compared with that of the calcineurin.

Abstract Fungal infections are rising globally, affecting nearly a quarter of the world's population. Driven by growing immunocompromised populations, the overuse of broad-spectrum antibiotics, and the emergence of multidrug-resistant fungi, conventional antifungal agents now face significant challenges in terms of efficacy, toxicity, and resistance. This review highlights emerging antifungal strategies, focusing on drug repurposing and nanomaterial-based approaches, in response to the growing challenge of fungal infections. Drug repurposing has revealed that numerous non-antifungal agents exhibited intrinsic antifungal activity or exerted strong synergistic effects combined with conventional antifungal drugs, thereby expanding the the therapeutic pipeline without requiring de novo drug discovery. Meanwhile, advanced polymeric and metallic nanomaterials offer key benefits, such as enhanced drug solubility, targeted delivery, improved biofilm penetration, multimodal fungicidal mechanisms, reduced host toxicity, and a lower propensity to induce resistance. Although most current studiesremain preclinical, the convergent advances in drug repurposing and nano-enabled antifungal technologies establish a promising route toward safer, more effective, and resistance-refractory therapies, underscoring the need for continued interdisciplinary innovation to accelerate clinical translation.

Introduction. Biofilms are a primary form of device-associated infections and typically exhibit high tolerance to antimicrobial agents. In biofilms formed by multiple microbial species, microorganisms may show even greater tolerance, complicating treatment. There is evidence that meropenem (MEPM) tolerance in Escherichia coli is increased in dual-species biofilms with Candida albicans, and effective treatments have not been established.Hypothesis/Gap Statement. If the presence of viable C. albicans increases the MEPM tolerance of E. coli in mature biofilms, then the killing of C. albicans will attenuate the MEPM tolerance of E. coli.Aim. We evaluated the effectiveness of various antifungal combination treatments against dual-species biofilms of E. coli and C. albicans in vitro and in vivo.Methodology. The reduction in the number of viable cells in dual-species mature biofilms formed by E. coli and C. albicans was evaluated after treatment with a combination of antifungal drugs (fluconazole, amphotericin B and micafungin) and MEPM. In addition, the in vivo effects of combination therapy were assessed using a silkworm biofilm infection model.Results. The combination of amphotericin B and MEPM reduced the viable cell counts of both E. coli and C. albicans within dual-species biofilms. In contrast, the combination of fluconazole and MEPM did not reduce the viable cell count of either species, whereas the combination of micafungin and MEPM reduced C. albicans only. The reduction in viable C. albicans counts by micafungin was less than that by amphotericin B, suggesting that micafungin did not affect the tolerance of E. coli. The combination of amphotericin B and MEPM also reduced the viable cell counts of both E. coli and C. albicans in the in vivo model.Conclusion. These findings suggest that the combination of amphotericin B and antibacterial agents is a potential treatment option to reduce the C. albicans-induced bacterial tolerance for catheter-related infections involving C. albicans co-infection.

The 8th Congress of the Asia-Pacific Society for Medical Mycology (APSMM 2024) was successfully held in conjunction with the 68th Annual Meeting of the Japanese Society for Medical Mycology (JSMM 2024), at the Kyoto International Conference Center in Japan, from November 6-9, 2024, under the aegis of Congress President Professor Takashi Sugita, Meiji Pharmaceutical University. The congress was attended by 610 medical mycologists from 19 countries and regions, including the Asia-Pacific region and representatives of the International Society for Human and Animal Mycology (ISHAM). It provided a platform to discuss the latest basic research, diagnosis, and treatments in medical mycology and to explore the future of the field.

The skin of patients with atopic dermatitis (AD) is in a state of dysbiosis, having a microbiome of reduced diversity dominated by exacerbators such as Staphylococcus aureus and by fungal taxa such as Malassezia. As the symptoms of AD improve, microbial diversity increases and the level of colonization by exacerbators decreases. The level of skin colonization is correlated with scores on AD evaluation indices, thus the goal of AD treatment is to improve dysbiosis. Although Malassezia species exacerbate AD, they also secrete proteases that inhibit the formation of biofilm by Staphylococcus aureus at non-lesional sites. Therefore, species in this genus may be either beneficial or harmful depending on the host environment. Androgenetic alopecia (AGA) develops when the growth phase of the hair cycle shortens, leading to an increase in the proportion of resting hair follicles. The scalp sebum of individuals with AGA has a higher triglyceride content than those without AGA, leading to greater colonization by Malassezia, which use triglycerides as nutrients. Furthermore, the scalp of AGA individuals (?) is in a state of dysbiosis, and Cutibacterium is replaced by Corynebacterium. This can lead to lipophilic bacterium-induced inflammation, which contributes to the progression of hair loss. This review focuses on two aspects of dermatitis linked to dysbiosis. First, we assess the changes in skin microbiome and cross-domain (bacteria versus fungi) microbial interactions in AD; then we consider the mechanism by which an altered scalp-sebum composition leads to the development of AGA.

We describe a novel Malassezia species named Malassezia polysorbatinonusus, isolated from a Japanese patient with seborrheic dermatitis. The internal transcribed spacer (ITS) region of the isolate (LSEM 4845T) were only 94.7

ABSTRACT In dimorphic yeasts, hyphal growth is primarily associated with infection and mycosis progression, with Trichosporon asahii causing deep-seated mycosis and summer-type hypersensitivity pneumonitis. Magnesium accelerates hyphal growth in T. asahii, leading to multi-septation, vacuolar expansion, and decreased lipid droplet size. However, the commonality of these phenotypes has not been studied in Trichosporonales yeasts. Therefore, to explore whether similar magnesium-induced phenotypes occur across Trichosporonales yeasts, we examined hyphal growth, multi-septation, vacuolar extension, and lipid droplet size and number in 30 species. Cell length increased with magnesium treatment in 13 yeasts: 5 Trichosporon (T. asahii, Trichosporon aquatile, Trichosporon asteroides, Trichosporon coremiiforme, and Trichosporon ovoides), three Apiotrichum (Apiotrichum brassicae, Apiotrichum montevideense, and Apiotrichum veenhuisii), three Cutaneotrichosporon (Cutaneotrichosporon cavernicola, Cutaneotrichosporon cutaneum, and Cutaneotrichosporon dermatis), Pascua guehoae, and Takashimella koratensis. C. dermatis also underwent pseudo-hyphal growth. Multi-septation increased in seven dimorphic yeasts, including five Trichosporon spp., Trichosporon faecale, and C. dermatis. The vacuolar area was significantly extended in T. asahii, T. aquatile, T. ovoides, and C. dermatis. Lipid droplet size increased only in Trichosporon inkin; however, it decreased in T. asahii, T. coremiiforme, and T. faecale. Additionally, lipid droplet number was preferentially altered in Apiotrichum and Cutaneotrichosporon. These results suggested that magnesium-induced multi-septation and vacuolar area expansion phenotypically distinguish Trichosporon hyphae from Apiotrichum and Cutaneotrichosporon hyphae and distinguish C. dermatis pseudo-hyphae from Cutaneotrichosporon spp. Moreover, differences in lipid droplet size can discriminate species within Trichosporon. Our results suggest that phenotypic alteration via magnesium treatment can contribute to the characterization of Trichosporonales yeasts. These findings provide insights into fungal pathogenesis and may support new treatment strategies.IMPORTANCEMagnesium sulfate considerably affects hyphal growth and cellular organization in Trichosporon asahii. To examine the commonality of this phenotype in Trichosporonales, we treated 30 Trichosporonales yeasts with magnesium sulfate and observed genus-level phenotypic alterations. Using cell length measurement, lipid droplet staining, septum staining, and vacuole staining, considerable hyphal diversity was observed among Trichosporonales. Notably, differences in the multi-septation phenotype and vacuolar size distinguished Trichosporon hyphae from Apiotrichum and Cutaneotrichosporon hyphae and distinguished Cutaneotrichosporon dermatis from other Cutaneotrichosporon spp. Moreover, differences in lipid droplet phenotype divided Trichosporon hyphae into two groups. Our study revealed the relationship between hyphal morphology and phylogenetic systematics in Trichosporonales.

Six yeast strains, representing a novel anamorphic species of the genus Rhodotorula, were investigated in this study. Among them, three strains, SU21, SU16 and SU14, were obtained from three different fruiting bodies of wild mushrooms in Thailand. One strain (ISM36-1) was isolated from soil in Japan, and two strains were isolated from soil (14Y315) and leaf litter (Y15Kr055) collected in Indonesia. Analysis of the sequences of the D1/D2 domain of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions showed that the six strains were identical or differed by only one nt substitution in both the D1/D2 domain of the LSU rRNA gene and the ITS regions. Rhodotorula paludigena CBS 6566T was the most closely related species but with 23-24 nt substitutions in the D1/D2 domain of the LSU rRNA gene and 38-39 nt substitutions in the ITS regions. Phylogenetic analysis based on the concatenated sequences of the ITS regions and D1/D2 domain showed that these strains represent a single species of the Rhodotorula clade that is distinct from other recognized species of the genus. Based on the phylogenetic analysis and phenotypic characteristics, these six strains were assigned to a novel species of the genus Rhodotorula, although sexual reproduction was not observed. The name, Rhodotorula tropicalis sp. nov., is proposed to accommodate the six strains. The holotype is TBRC 14874T and the ex-type culture is PYCC 8913 (=SU21). The MycoBank number of the novel species is MB 856795.

Trichosporon asahii is a pathogenic fungus that causes severe deep-seated fungal infections in neutropenic patients. Ku70, a key component of the non-homologous end-joining (NHEJ) pathway involved in the repair of DNA double-strand breaks, influences gene-targeting efficiency in T. asahii MPU129 strain using electroporation, a gene transfer method. Although phenotypic traits such as morphology and biofilm formation vary among T. asahii strains, the impact of different gene transfer methods on gene-targeting efficiency remains poorly characterized. In this study, we compared the gene-targeting efficiency of Agrobacterium tumefaciens-mediated transformation (ATMT) and electroporation. In T. asahii JCM2466 (CBS2479), a strain with high hyphal-forming ability, the ku70 gene-deficient mutant exhibited a higher gene-targeting efficiency via ATMT than the wild-type strain when generating a cnb1 gene-deficient mutant. The cnb1 gene encodes the β-subunit of calcineurin. In contrast, in the ku70 gene-deficient background of T. asahii JCM2466, cnb1-deficient mutants could not be generated by electroporation. The gene-targeting efficiencies of ATMT and electroporation in the ku70 gene-deficient mutant of T. asahii JCM2466 were 18% and 0%, respectively. The cnb1 gene-deficient mutants exhibited sensitivity to high temperature and several stress-inducing compounds. These results suggest that ATMT is a suitable gene transfer method for generating gene-deficient mutants in the ku70-deficient T. asahii JCM2466 background. Therefore, the choice of gene transfer method should be carefully tailored to the genetic background and phenotypic characteristics of each T. asahii strain.