Mycobiology最新文献

Komatsuna (Brassica rapa var. perviridis) is one of the most common leafy vegetables in Japan. In recent years, the frequent occurrence of abnormally high temperatures is becoming a threat for komatsuna as it is vulnerable to high temperature stress. In natural ecosystems, most plants coexist with endophytic fungi as a strategy to adapt to stressful environments. Among known symbiotic fungi, there are dark septate endophytes (DSEs), which are unique due to their prevalence under stressed environmental conditions. This study aimed to evaluate the use of DSEs to improve komatsuna growth using a greenhouse farming system, as a practice to improve sustainable agriculture. We examined the effect of inoculation with three DSE isolates: Phialocephala fortinii KS.F.6 (Pf), Exophiala pisciphila KS.F.3.4 (Ep) and Veronaeopsis simplex Y34 (Vs), on the growth of komatsuna under high temperature stress. The preliminary experiment showed that inoculation with isolates Ep and Vs reduced the heat injury index and increased the number of surviving plants under 35 °C heat stress. Furthermore, the greenhouse experiment showed that Ep and Vs increase the number of leaves, fresh weight, and dry weight of komatsuna. This is considered the first report of DSE symbiosis potential for komatsuna high-temperature-stress mitigation and growth performance induction.

This study investigates how shiro developmental stages, soil physicochemical properties, and seasonal variation shape fungal and bacterial communities associated with Tricholoma matsutake in a Pinus densiflora forest in Yeongju, South Korea. Seasonal soil samples from past, present, and future shiro zones were analyzed using ITS and 16S rRNA metabarcoding together with soil chemical measurements. Shiro-driven spatial heterogeneity, rather than seasonality, was the dominant factor structuring microbial communities. Fungal assemblages differed significantly among shiro stages, with exchangeable potassium (K⁺) emerging as the primary driver and a strong predictor of T. matsutake abundance. Elevated K⁺ in active shiro zones corresponded to reduced fungal diversity, suggesting competitive exclusion by dominant ectomycorrhizal taxa. In contrast, bacterial communities were shaped mainly by water-soluble iron (Fe), shifting from Acidobacteria-rich assemblages in past zones to Proteobacteria in active zones. The enrichment of siderophore-associated taxa suggests a potential role of Fe acquisition processes, broadly consistent with mechanisms proposed in the mycorrhiza helper bacteria hypothesis, though not directly tested here. Overall, T. matsutake development generates nutrient-specific biogeochemical gradients-K⁺ for fungi and Fe for bacteria-that reorganize soil microbial communities. These findings underscore tightly linked biotic-abiotic interactions in shiro ecology and highlight microbial and chemical features that may serve as indicators of shiro activity.

Fungal pathogens of the genus Pyrenophora pose significant threats to barley and wheat production worldwide. Pyrenophora tritici-repentis has long been recognized as the causal agent of yellow spot disease in wheat in Japan. However, preliminary molecular data have suggested the involvement of an additional Pyrenophora species. To clarify the species diversity and phylogenetic relationships of Pyrenophora species on Poaceae plants in Japan, a total of 13 isolates, obtained from symptomatic barley and wheat, along with 37 isolates from culture collections, were analyzed using a concatenated dataset of ITS, LSU, rpb2, and gapdh gene regions. The resultant tree revealed that all examined Japanese isolates previously labeled as Py. tritici-repentis were recognized as Py. trichostoma. Furthermore, these isolates shared a toxin-producing gene. Additionally, some Japanese isolates need to have their labels corrected. These findings indicate greater diversity of Pyrenophora than previously reported in Japan and highlight the need to revise the taxonomy of Pyrenophora species.

Flammulina velutipes is the most widely consumed edible mushroom in Korea, with a unique flavor and texture that support its popularity domestically and internationally. Korea produces approximately 26,000 tons of F. velutipes annually, accounting for 17% of its total mushroom production and generating export revenues of about 126 million USD. However, recent detection of Listeria monocytogenes in F. velutipes has led to product recalls and import restrictions in major markets, including the United States, thereby threatening export competitiveness. L. monocytogenes is a psychrotrophic foodborne pathogen capable of surviving and proliferating at low temperatures, causing severe diseases such as meningitis and sepsis in immunocompromised individuals, and miscarriage or fetal death in pregnant women. This study evaluated the antibacterial efficacy of peracetic acid (PAA) among several disinfectants for controlling Listeria contamination. Treatment with 80 ppm PAA once daily or once every two days effectively inhibited Listeria growth on F. velutipes surfaces without affecting mushroom fresh weight or marketability. Furthermore, PAA treatment suppressed not only Listeria but also other pathogenic microorganisms, suggesting improved overall microbial safety. PAA decomposes into water and oxygen, producing no harmful residues, and is approved for organic food production. Its ease of field application further enhances practicality. These findings indicate that PAA is an effective, eco-friendly method for controlling L. monocytogenes contamination in F. velutipes, and its implementation could strengthen the microbiological safety and export stability of Korean mushrooms in global markets.

Interest in algal endophytic fungi continues to grow as their ecological importance and potential applications in medicine, aquaculture, and environmental biotechnology become increasingly evident. This study used a culture-based approach to characterize the diversity and community structure of endophytic fungi associated with Sargassum thunbergii at five coastal sites on Jeju Island and to examine their relationships with marine environmental factors. Based on isolated and identified strains, we compared among-site community differences and links to environmental variables. In total, 235 isolates representing 94 species across 54 genera were obtained, with Ascomycota comprising 97.9% of all isolates. Community composition differed markedly by site, with high prevalence of several genera, including Didymella and Neocosmospora. α-diversity was higher at western sites (Gosan, Hyeopjae) and lower at northeastern sites (Gimnyeong, Onpyeong), and β-diversity analyses also separated communities among sites. Ordination and constrained analyses identified mean monthly water temperature and dissolved oxygen as the environmental factors most closely associated with community variation. Notably, Neocosmospora solani occurred at all sites, whereas many species were restricted to single locations. These findings are consistent with the idea that the physicochemical characteristics of Jeju's coastal waters may contribute to regional differences in S. thunbergii endophyte communities. This work provides a baseline for understanding alga-fungus interactions around Jeju and highlights the potential of endophyte diversity as a sensitive indicator of coastal environmental change.

A fungal isolate was obtained from ambrosia beetles (Xyleborus sp.) collected using beetle traps placed in an apple orchard in Gunwi-gun, Daegu, Republic of Korea. Cytochrome oxidase I (COI) gene sequencing confirmed that the beetles belonged to the genus Xyleborus. The fungal isolate, designated ARI-25-A12, was subjected to morphological and molecular identification and characterization. On malt extract agar (MEA), colonies exhibited a white, fur-like surface, and hyphae penetrated the medium along the margins. As the colony matured, the center became dull yellow, and after 20 days of incubation, the colony diameter reached 49.6-56.0 mm. Morphologically, conidiophores were hyaline, simple or occasionally branched, and conidia were hyaline, thin-walled, unicellular, and globose. Conidia produced yeast-like sprout cells through a budding-like process, and the average conidial size was 5.2 × 5.2 μm (n = 100). Molecular phylogenetic analyses based on ITS, LSU, SSU, and β-TUB gene sequences indicated that ARI-25-A12 is classified within the genus Raffaelea. Phylogenetic trees constructed from ITS sequences and a combined dataset of LSU, SSU, and β-TUB gene sequences consistently classified the isolate as a distinct lineage, clearly separated from previously reported Raffaelea species, with additional morphological differences supporting its distinct classification. Based on these results, ARI-25-A12 is described herein as Raffaelea xyleboricola sp. nov.

Pichia species are widely distributed across various ecosystems and have industrial significance, particularly in wine fermentation and bioproduct synthesis. During an investigation of yeast diversity in Korea, several previously unreported strains were isolated from environmental samples, including plants, insects, and air. Phylogenetic analyses based on the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) rRNA identified the strains as belonging to one novel species and three previously unrecorded species in Korea. The novel species exhibited distinct molecular, morphological, and physiological characteristics compared to its closest relatives, demonstrating the ability to assimilate acetic acid as the sole carbon source. It was proposed as Pichia acetica sp. nov. (holotype strain NIBRFGC000511223^T). In addition, we provided the detailed taxonomic descriptions of three previously unreported species in Korea, namely Pichia fermentans, P. garciniae, and P. kluyveri.

The order Polyporales is a diverse group of macrofungi, comprising approximately 2500 species worldwide. The majority of these species are wood-decaying saprotrophs that contribute to the carbon cycle by degrading lignin, cellulose, and hemicellulose. They also produce valuable enzymes with wide industrial applications. Despite their ecological and industrial importance, the diversity of Polyporales in Republic of Korea remains relatively understudied compared to the global scale. Mudeungsan, a representative National Park in southern region of Republic of Korea, has recently been recognized for its high biodiversity, supported by the studies of several new and unrecorded macrofungal species. To discover indigenous Polyporales species, we conducted surveys in Mudeungsan National Park from 2021 to 2023. Collected specimens were identified based on the morphological characteristics, molecular and phylogenetic analyses using the internal transcribed spacer and nuclear large subunit ribosomal DNA regions. Consequently, 12 specimens were identified as six unrecorded Polyporales in Republic of Korea: Efibula yunnanensis, Hyphoderma crystallinum, H. puerense, Mycoaciella efibulata, Skeletocutis lepida, and Steccherinum tenuissimum. This study provides morphological descriptions and phylogenetic trees to support the identification of six unrecorded species in Mudeungsan National Park.

The diminishing reserves of fossil fuels have spurred a global search for sustainable energy alternatives. Bioethanol, a renewable fuel derived from biomass, represents a promising alternative, particularly in tropical regions. Yeasts, key agents in ethanol fermentation, have attracted substantial attention for their ability to convert sugars into ethanol. However, the commonly used mesophilic yeast Saccharomyces cerevisiae is temperature-sensitive, limiting its effectiveness in tropical climates. Tropical countries such as Indonesia, Thailand, Vietnam, and Laos, harbor abundant non-conventional and thermotolerant yeast species. These yeasts offer multiple advantages, including reduced contamination risk, lower cooling requirements, and decreased production costs. Moreover, they can utilize complex substrates, such as sucrose, starch, xylose, and lignocellulose biomass, while tolerating high temperatures, ethanol stress, pH fluctuations, and various inhibitors. This review highlights the diversity, physiological traits, and dual industrial potential of thermotolerant and non-conventional yeasts isolated from tropical environments. These yeasts demonstrate robust substrate utilization (including pentoses), high-temperature tolerance, and resilience under stress, positioning them as promising candidates for second-generation bioethanol production as well as for producing value-added aroma compounds. Key species discussed include Ogataea polymorpha, Candida tropicalis, Kluyveromyces marxianus, Pichia kudriavzevii, Meyerozyma caribbica, Pichia stipitis, and Spathaspora passalidarum.

Helix-loop-helix (HLH) transcription factors are essential regulators of various cellular processes, including growth, differentiation, and development. In Aspergillus fumigatus, a major fungal pathogen, the HLH transcription factor encoded by the AfudrnA gene plays a critical role in the organism's asexual reproductive cycle. This study provides a comprehensive analysis of AfudrnA and its function in conidiation, a key asexual reproductive process. Through targeted deletion of AfudrnA, we observed a dramatic reduction in conidia production, leading to an aconidial phenotype, which suggests that AfudrnA is indispensable for conidiation in A. fumigatus. The deletion mutants, however, showed no significant changes in growth rate or sensitivity to antifungal agents, indicating that AfudrnA specifically influences conidiation rather than general growth or stress responses. To confirm the role of AfudrnA, we reintroduced the gene into the deletion mutants, which restored normal conidiation, further underscoring its essential role in the process. Moreover, expression analysis revealed that AfudrnA is highly expressed during the early stages of conidiation, with transcript levels peaking 6 h after induction of asexual development. Interestingly, the deletion of AfudrnA also led to a significant downregulation of brlA, a key regulator of conidiation, highlighting a potential regulatory interaction between these two factors. These findings elucidate the critical role of AfudrnA in the conidiation of A. fumigatus and contribute to our understanding of the molecular mechanisms governing asexual reproduction in filamentous fungi. This study not only enhances our knowledge of fungal biology but also provides potential targets for therapeutic intervention against fungal pathogens.