A short abstract of the doctoral research

The skin is one of the body’s largest organs and is constantly exposed to the external environment. It hosts a complex microbial ecosystem of bacteria, fungi, viruses, and micro-eukaryotes that supports the skin barrier, provides colonization resistance, and interacts with the immune system, but may also contribute to disease when homeostasis is disrupted. Over the past century, lifestyle changes associated with industrialization (e.g., altered hygiene, diet, pollution, and physical activity) have coincided with a rise in immune-mediated skin disorders such as acne, dandruff, rosacea, and psoriasis.

This doctoral dissertation investigates the skin microbiome and metabolome in sebaceous (oil-rich) skin regions affected by conditions such as psoriasis capitis and acne vulgaris. By integrating advanced sequencing and untargeted metabolomics, it compares inflamed and healthy sebaceous skin to identify microbial and metabolic biomarkers.

Sebaceous skin showing inflammation, ranging from mild erythema to severe acne, consistently exhibited reduced microbial diversity, altered community composition, increased sebum production, and enrichment of fatty acid esters and long-chain fatty acids. Using an artificial sebum model, the growth and biofilm-forming capacity of Malassezia species were further demonstrated under physiologically relevant conditions. These findings emphasize the role of microbial diversity in preserving skin homeostasis. Multi-omics and in vitro models provide opportunities to identify candidate biomarkers and to develop curative and preventive strategies that restore microbial homeostasis and improve skin health.