Physiological characterization and molecular identification of some rare yeast species causing onychomycosis

Species distribution and antifungal susceptibility profiles of yeasts isolated from onychomycosis: a cross-sectional study with insights into emerging species

Candida onychomycosis is a common fungal infection affecting the nails, primarily caused by Candida (C.) species. Regarding the increasing trend of Candida onychomycosis and the antifungal resistant phenomenon in recent years, this study aims to evaluate the epidemiological characteristics of Candida onychomycosis, the distribution of emerging species, and the antifungal susceptibility profiles of isolates. Onychomycosis caused by yeast species was confirmed through direct examination and culture of nail scraping among all individuals suspected to have onychomycosis and referred to a medical mycology laboratory between June 2019 and March 2022. Species of yeast isolates were identified using the multiplex PCR and PCR-RFLP methods. The antifungal susceptibility of isolates to common antifungal agents and imidazole drugs was evaluated according to the M-27-A3 CLSI protocol. Among 101 yeast strains isolated from onychomycosis, Candida parapsilosis complex (50.49%) was the most common species, followed by C. albicans (20.79%) and C. tropicalis (10.89%). Rare species of yeasts such as C. guilliermondii and Saccharomyces cerevisiae were also identified by molecular methods. Results obtained from antifungal susceptibility testing showed significant differences in MIC values of isoconazole, fenticonazole, and sertaconazole among different species. Overall, a fluconazole-resistant rate of 3% was found among Candida species. Moreover, there was a statistically significant difference in MICs of fenticonazole and clotrimazole between the two most prevalent causative species, C. parapsilosis complex and C. albicans. Correct identification of the causative agents of onychomycosis and performing susceptibility testing could be helpful in choosing the most appropriate antifungal therapy.

Biodegradation of Tetracycline Antibiotics by the Yeast Strain Cutaneotrichosporon dermatis M503

In this study, the Cutaneotrichosporon dermatis strain M503 was isolated and could efficiently degrade tetracycline, doxycycline, and chlorotetracyline. The characteristics of tetracycline degradation were investigated under a broad range of cultural conditions. Response surface methodology (RSM) predicted that the highest degradation rate of tetracycline could be obtained under the following conditions: 39.69 °C, pH of 8.79, and inoculum dose of 4.0% (v/v, ~3.5 × 10⁶ cells/mL in the medium). In accordance with the five identified degradation products of tetracycline, two putative degradation pathways, which included the shedding of methyl and amino groups, were proposed. Moreover, the well diffusion method showed that the strain of M503 decreases the antibacterial potency of tetracycline, doxycycline, and chlorotetracycline. These findings proposed a putative mechanism of tetracycline degradation by a fungus strain and contributed to the estimation of the fate of tetracycline in the aquatic environment.

Draft Genome Assembly and Annotation for Cutaneotrichosporon dermatis NICC30027, an Oleaginous Yeast Capable of Simultaneous Glucose and Xylose Assimilation

The identification of oleaginous yeast species capable of simultaneously utilizing xylose and glucose as substrates to generate value-added biological products is an area of key economic interest. We have previously demonstrated that the Cutaneotrichosporon dermatis NICC30027 yeast strain is capable of simultaneously assimilating both xylose and glucose, resulting in considerable lipid accumulation. However, as no high-quality genome sequencing data or associated annotations for this strain are available at present, it remains challenging to study the metabolic mechanisms underlying this phenotype. Herein, we report a 39,305,439 bp draft genome assembly for C. dermatis NICC30027 comprised of 37 scaffolds, with 60.15% GC content. Within this genome, we identified 524 tRNAs, 142 sRNAs, 53 miRNAs, 28 snRNAs, and eight rRNA clusters. Moreover, repeat sequences totaling 1,032,129 bp in length were identified (2.63% of the genome), as were 14,238 unigenes that were 1,789.35 bp in length on average (64.82% of the genome). The NCBI non-redundant protein sequences (NR) database was employed to successfully annotate 11,795 of these unigenes, while 3,621 and 11,902 were annotated with the Swiss-Prot and TrEMBL databases, respectively. Unigenes were additionally subjected to pathway enrichment analyses using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Cluster of Orthologous Groups of proteins (COG), Clusters of orthologous groups for eukaryotic complete genomes (KOG), and Non-supervised Orthologous Groups (eggNOG) databases. Together, these results provide a foundation for future studies aimed at clarifying the mechanistic basis for the ability of C. dermatis NICC30027 to simultaneously utilize glucose and xylose to synthesize lipids.

Performance of Meyerozyma caribbica as a novel manganese peroxidase-producing yeast inhabiting wood-feeding termite gut symbionts for azo dye decolorization and detoxification

For hazardous toxic pollutants such as textile wastewater and azo dyes, microbial-based and peroxidase-assisted remediation represents a highly promising and environmentally friendly alternative. Under this scope, gut symbionts of the wood-feeding termites Coptotermes formosanus and Reticulitermes chinenesis were used for the screening of manganese peroxidase (MnP) producing yeasts intended for decolorization and detoxification of textile azo dyes, such as Acid Orange 7 (AO7). To this end, nine out of 38 yeast isolates exhibited high levels of extracellular MnP activity ranging from 23 to 27 U/mL. The isolate PPY-27, which had the highest MnP activity, was able to decolorize various azo dyes with an efficiency ranging from 87.2 to 98.8%. This isolate, which represents the molecularly identified species Meyerozyma caribbica, was successfully characterized in terms of morphological and physiological traits, as well as enzymatic activities. Almost complete decolorization was achieved by the MnP-producing M. caribbica strain SSA1654 after 6 h of incubation with 50 mg/L of the sulfonated azo dye AO7 at 28 °C with an agitation speed of 150 rpm. The maximum decolorization efficiency of AO7 reached 93.8% at 400 mg/L. The decolorization of AO7 was confirmed by Fourier transform infrared (FTIR) and UV-Vis spectral analysis. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used to identify AO7 decomposition intermediates. Based on UV-Vis spectra, FTIR, HPLC, and GC-MS analyses, a plausible AO7 biodegradation mechanism pathway was explored, showing azo bond (-N=N-) cleavage and toxic aromatic amines mineralization CO₂ and H₂O. Microtox® and phytotoxicity assays confirmed that the AO7 metabolites produced by the strain SSA1654 were almost non-toxic compared to the original sulfonated azo dye.

Gut Microbial Alterations in Diarrheal Baer's Pochards (Aythya baeri)

The structure and composition of gut microbiota correlate with the occurrence and development of host health and disease. Diarrhea can cause alterations in gut microbiota in animals, and the changes in the gut microbial structure and composition may affect the development of diarrhea. However, there is a scarcity of information on the effects of diarrhea on gut fungal composition and structure, particularly in Baer's pochard (Aythya baeri). The current study was performed for high-throughput sequencing of the fungal-specific internal transcribed spacer 1 (ITS-1) to detect the differences of gut mycobiota in healthy and diarrheal Baer's pochard. Results showed that the gut mycobiota not only decreased significantly in diversity but also in structure and composition. Statistical analysis between two groups revealed a significant decrease in the abundance of phylum Rozellomycota, Zoopagomycota, Mortierellomycota, and Kickxellomycota in diarrheal Baer's pochard. At the genus levels, fungal relative abundance changed significantly in 95 genera, with 56 fungal genera, such as Wickerhamomyces, Alternaria, Penicillium, Cystofilobasidium, and Filobasidium, increasing significantly in the gut of the diarrheal Baer's pochard. In conclusion, the current study revealed the discrepancy in the gut fungal diversity and community composition between the healthy and diarrheal Baer's pochard, laying the basis for elucidating the relationship between diarrhea and the gut mycobiota in Baer's pochard.