Comparative analysis of Malassezia furfur mitogenomes and the development of a mitochondria-based typing approach

Clinical data analysis of 86 patients with invasive infections caused by Malassezia furfur from a tertiary medical center and 37 studies

Objective

Malassezia furfur (M. furfur) is a lipophilic, conditionally pathogenic yeast that mainly causes skin infections, but the reports of related invasive infections are increasing. The aim of this study is to provide clinical data to assist physicians in the management of patients with invasive infections caused by M. furfur.

Methods

A case of pulmonary infection caused by M. furfur in a hematopoietic stem cell transplant patient for aplastic anemia was reported. In addition, the literature on invasive infection by M. furfur published in PubMed and Web of Science in English until 31 July 2022 was reviewed.

Results

Clinical data analysis of 86 patients (from 37 studies and our case) revealed that most of them were preterm (44.2%), followed by adults (31.4%). M. furfur fungemia occurred in 79.1% of the 86 patients, and 45 of them were clearly obtained from catheter blood. Other patients developed catheter-related infections, pneumonia, peripheral thromboembolism, endocarditis, meningitis, peritonitis and disseminated infections. Thirty-eight preterm infants had underlying diseases such as very low birth weight and/or multiple organ hypoplasia. The remaining patients had compromised immunity or severe gastrointestinal diseases. 97.7% of patients underwent invasive procedures and 80.2% received total parenteral nutrition (TPN). Fever, thrombocytopenia and leukocytosis accounted for 55.8%, 38.4% and 24.4% of patients with M. furfur invasive infections, respectively. 69.8% of the patients received antifungal therapy, mainly amphotericin B (AmB) or azoles. Of 84 patients with indwelling catheters, 58.3% underwent the removal of catheters. TPN were discontinued in 30 of 69 patients. The all-cause mortality of 86 patients was 27.9%.

Conclusions

M. furfur can cause a variety of invasive infections. These patients mostly occur in premature infants, low immunity and severe gastrointestinal diseases. Indwelling catheters and TPN infusion are major risk factors. AmB, l-AmB and azoles are the most commonly used agents, and simultaneous removal of the catheter and termination of TPN infusion are important for the treatment of M. furfur invasive infections.

Co-evolution of large inverted repeats and G-quadruplex DNA in fungal mitochondria may facilitate mitogenome stability: the case of Malassezia

Mitogenomes are essential due to their contribution to cell respiration. Recently they have also been implicated in fungal pathogenicity mechanisms. Members of the basidiomycetous yeast genus Malassezia are an important fungal component of the human skin microbiome, linked to various skin diseases, bloodstream infections, and they are increasingly implicated in gut diseases and certain cancers. In this study, the comparative analysis of Malassezia mitogenomes contributed to phylogenetic tree construction for all species. The mitogenomes presented significant size and gene order diversity which correlates to their phylogeny. Most importantly, they showed the inclusion of large inverted repeats (LIRs) and G-quadruplex (G4) DNA elements, rendering Malassezia mitogenomes a valuable test case for elucidating the evolutionary mechanisms responsible for this genome diversity. Both LIRs and G4s coexist and convergently evolved to provide genome stability through recombination. This mechanism is common in chloroplasts but, hitherto, rarely found in mitogenomes.

Malassezia: A Commensal, Pathogen, and Mutualist of Human and Animal Skin

Identified in the late nineteenth century as a single species residing on human skin, Malassezia is now recognized as a diverse genus comprising 18 species inhabiting not only skin but human gut, hospital environments, and even deep-sea sponges. All cultivated Malassezia species are lipid dependent, having lost genes for lipid synthesis and carbohydrate metabolism. The surging interest in Malassezia results from development of tools to improve sampling, culture, identification, and genetic engineering, which has led to findings implicating it in numerous skin diseases, Crohn disease, and pancreatic cancer. However, it has become clear that Malassezia plays a multifaceted role in human health, with mutualistic activity in atopic dermatitis and a preventive effect against other skin infections due to its potential to compete with skin pathogens such as Candida auris. Improved understanding of complex microbe-microbe and host-microbe interactions will be required to define Malassezia's role in human and animal health and disease so as to design targeted interventions.

Exploring Mitogenomes Diversity of Fusarium musae from Banana Fruits and Human Patients

Fusarium musae has recently been described as a cross-kingdom pathogen causing post-harvest disease in bananas and systemic and superficial infection in humans. The taxonomic identity of fungal cross-kingdom pathogens is essential for confirming the identification of the species on distant infected hosts. Understanding the level of variability within the species is essential to decipher the population homogeneity infecting human and plant hosts. In order to verify that F. musae strains isolated from fruits and patients are part of a common population and to estimate their overall diversity, we assembled, annotated and explored the diversity of the mitogenomes of 18 F. musae strains obtained from banana fruits and human patients. The mitogenomes showed a high level of similarity among strains with different hosts’ origins, with sizes ranging from 56,493 to 59,256 bp. All contained 27 tRNA genes and 14 protein-coding genes, rps3 protein, and small and large ribosomal subunits (rns and rnl). Variations in the number of endonucleases were detected. A comparison of mitochondrial endonucleases distribution with a diverse set of Fusarium mitogenomes allowed us to specifically discriminate F. musae from its sister species F. verticillioides and the other Fusarium species. Despite the diversity in F. musae mitochondria, strains from bananas and strains from human patients group together, indirectly confirming F. musae as a cross-kingdom pathogen.

Mitogenomics and mitochondrial gene phylogeny decipher the evolution of Saccharomycotina yeasts

Saccharomycotina yeasts belong to diverse clades within the kingdom of fungi and are important to human everyday life. This work investigates the evolutionary relationships among these yeasts from a mitochondrial (mt) genomic perspective. A comparative study of 155 yeast mt genomes representing all major phylogenetic lineages of Saccharomycotina was performed, including genome size and content variability, intron and intergenic regions’ diversity, genetic code alterations, and syntenic variation. Findings from this study suggest that mt genome size diversity is the result of a ceaseless random process, mainly based on genetic recombination and intron mobility. Gene order analysis revealed conserved syntenic units and many occurring rearrangements, which can be correlated with major evolutionary events as shown by the phylogenetic analysis of the concatenated mt protein matrix. For the first time, molecular dating indicated a slower mt genome divergence rate in the early stages of yeast evolution, in contrast with a faster rate in the late evolutionary stages, compared to their nuclear time divergence. Genetic code reassignments of mt genomes are a perpetual process happening in many different parallel evolutionary steps throughout the evolution of Saccharomycotina. Overall, this work shows that phylogenetic studies based on the mt genome of yeasts highlight major evolutionary events.

Multiple Hybridization Events Punctuate the Evolutionary Trajectory of Malassezia furfur

Malassezia species are important fungal skin commensals and are part of the normal microbiota of humans and other animals. However, under certain circumstances these fungi can also display a pathogenic behavior. For example, Malassezia furfur is a common commensal of human skin and yet is often responsible for skin disorders but also systemic infections. Comparative genomics analysis of M. furfur revealed that some isolates have a hybrid origin, similar to several other recently described hybrid fungal pathogens. Because hybrid species exhibit genomic plasticity that can impact phenotypes, we sought to elucidate the genomic evolution and phenotypic characteristics of M. furfur hybrids in comparison to their parental lineages. To this end, we performed a comparative genomics analysis between hybrid strains and their presumptive parental lineages and assessed phenotypic characteristics. Our results provide evidence that at least two distinct hybridization events occurred between the same parental lineages and that the parental strains may have originally been hybrids themselves. Analysis of the mating-type locus reveals that M. furfur has a pseudobipolar mating system and provides evidence that after sexual liaisons of mating compatible cells, hybridization involved cell-cell fusion leading to a diploid/aneuploid state. This study provides new insights into the evolutionary trajectory of M. furfur and contributes with valuable genomic resources for future pathogenicity studies. IMPORTANCEMalassezia furfur is a common commensal member of human/animal microbiota that is also associated with several pathogenic states. Recent studies report involvement of Malassezia species in Crohn's disease, a type of inflammatory bowel disease, pancreatic cancer progression, and exacerbation of cystic fibrosis. A recent genomics analysis of M. furfur revealed the existence of hybrid isolates and identified their putative parental lineages. In this study, we explored the genomic and phenotypic features of these hybrids in comparison to their putative parental lineages. Our results revealed the existence of a pseudobipolar mating system in this species and showed evidence for the occurrence of multiple hybridization events in the evolutionary trajectory of M. furfur. These findings significantly advance our understanding of the evolution of this commensal microbe and are relevant for future studies exploring the role of hybridization in the adaptation to new niches or environments, including the emergence of pathogenicity.

Mitochondrial Transcription of Entomopathogenic Fungi Reveals Evolutionary Aspects of Mitogenomes

Entomopathogenic fungi and more specifically genera Beauveria and Metarhizium have been exploited for the biological control of pests. Genome analyses are important to understand better their mode of action and thus, improve their efficacy against their hosts. Until now, the sequences of their mitochondrial genomes were studied, but not at the level of transcription. Except of yeasts and Neurospora crassa, whose mt gene transcription is well described, in all other Ascomycota, i.e., Pezizomycotina, related information is extremely scarce. In this work, mt transcription and key enzymes of this function were studied. RT-PCR experiments and Northern hybridizations reveal the transcriptional map of the mt genomes of B. bassiana and M. brunneum species. The mt genes are transcribed in six main transcripts and undergo post-transcriptional modifications to create single gene transcripts. Promoters were determined in both mt genomes with a comparative in silico analysis, including all known information from other fungal mt genomes. The promoter consensus sequence is 5'-ATAGTTATTAT-3' which is in accordance with the definition of the polycistronic transcripts determined with the experiments described above. Moreover, 5'-RACE experiments in the case of premature polycistronic transcript nad1-nad4-atp8-atp6 revealed the 5' end of the RNA transcript immediately after the in silico determined promoter, as also found in other fungal species. Since several conserved elements were retrieved from these analyses compared to the already known data from yeasts and N. crassa, the phylogenetic analyses of mt RNA polymerase (Rpo41) and its transcriptional factor (Mtf1) were performed in order to define their evolution. As expected, it was found that fungal Rpo41 originate from the respective polymerase of T7/T3 phages, while the ancestor of Mtf1 is of alpha-proteobacterial origin. Therefore, this study presents insights about the fidelity of the mt single-subunit phage-like RNA polymerase during transcription, since the correct identification of mt promoters from Rpo41 requires an ortholog to bacterial sigma factor, i.e., Mtf1. Thus, a previously proposed hypothesis of a phage infected alpha-proteobacterium as the endosymbiotic progenitor of mitochondrion is confirmed in this study and further upgraded by the co-evolution of the bacterial (Mtf1) and viral (Rpo41) originated components in one functional unit.