The Transcriptome of Exophiala dermatitidis during Ex-vivo Skin Model Infection

Abstract

The black yeast Exophiala dermatitidis is a widespread polyextremophile and human pathogen, that is found in extreme natural habitats and man-made environments such as dishwashers. It can cause various diseases ranging from phaeohyphomycosis and systemic infections, with fatality rates reaching 40%. While the number of cases in immunocompromised patients are increasing, knowledge of the infections, virulence factors and host response is still scarce. In this study, for the first time, an artificial infection of an ex-vivo skin model with Exophiala dermatitidis was monitored microscopically and transcriptomically. Results show that Exophiala dermatitidis is able to actively grow and penetrate the skin. The analysis of the genomic and RNA-sequencing data delivers a rich and complex transcriptome where circular RNAs, fusion transcripts, long non-coding RNAs and antisense transcripts are found. Changes in transcription strongly affect pathways related to nutrients acquisition, energy metabolism, cell wall, morphological switch, and known virulence factors. The L-Tyrosine melanin pathway is specifically upregulated during infection. Moreover the production of secondary metabolites, especially alkaloids, is increased. Our study is the first that gives an insight into the complexity of the transcriptome of Exophiala dermatitidis during artificial skin infections and reveals new virulence factors.

Transcriptome Study of an Exophiala dermatitidis PKS1 Mutant on an ex Vivo Skin Model: Is Melanin Important for Infection?

“…The wild-type was able to grow on the full-thickness skin explants in our ex vivo skin wound model. After 7 days, the whole skin surface was covered by fungal biomass ( Figures 2A,B ) similar to previous results ( Poyntner et al, 2016 ). In contrast, the mutant strain partially covered the skin and adhered around the cut ( Figures 2C,D ).…”

“…Skin culture experiments were conducted as previously described ( Poyntner et al, 2016 ). Skin for the ex vivo skin wound model was obtained from a patient undergoing brachioplasty at Department of Plastic, Reconstructive and Aesthetic Surgery, Klinikum Bremen-Mitte, Germany.…”

“…Sequencing was performed using the Ion Torrent Proton and the HiQ sequencing kit (Life Technologies, Carlsbad, CA, United States). From the sequenced raw data, reads were mapped as described previously ( Poyntner et al, 2016 ). We removed reads originating from human sequences by mapping the total set of reads against the concatenated human (GRCh37) and E. dermatitidis genomes with STAR 2.4.1d ( Dobin et al, 2013 ).…”

“…A huge difference is observed in etiology and severity ( Sudhadham et al, 2008 ). Theories to explain these differences exist ( Matos et al, 2002 ; Poyntner et al, 2016 ) but detailed studies about the infection mechanisms are scarce. One of the proposed virulence factors is melanin ( Taborda et al, 2008 ), a negatively charged, hydrophobic macromolecule composed of oxidative polymerized phenolic or indolic monomers and often complexed with proteins and carbohydrates ( Butler and Day, 1998 ; Casadevall et al, 2000 ).…”

Synergistic Interactions in Microbial Biofilms Facilitate the Establishment of Opportunistic Pathogenic Fungi in Household Dishwashers

“…We have characterized the interactions within different bacterial species and how they impact each other during biofilm development, both under mono and mixed species cultures. Later, the ability of selected mixed bacterial consortia to incorporate the polyextremophile E. dermatitidis , ( Zalar et al, 2011 ; Poyntner et al, 2016 ) the prevalent fungal species in DW systems, was assessed. Fungi and bacteria play important roles in promoting the survival of their interacting partners ( Frey-Klett et al, 2011 ).…”