Human skin is a complex ecosystem characterized by dynamic interactions between the host, environment and other microbial species. Driven by NGS studies, our knowledge about skin microbiome composition is increasing and shows its importance in numerous mechanisms such as host’s protection, immunity training or disorders such as atopic dermatitis. However, the molecular dynamics between host and microbiome explaining influence of the latter on host physiology remain largely unknown. Capabilities of modern mass spectrometry-based proteomics are still underexploited but are a powerful tool for identify and quantify proteins and functional pathway contributing of interplay between skin-microbiome and host.
3 female and 3 male subjects are used for this study. Proteins were extracted and digested, labeled, combined and pre-fractionated. Each fraction was analyzed individually by mass spectrometry. These results were analyzed by PD 2.1 using 2 iterative steps in aim to reduce database and decrease the false discovery rate.
This optimized analysis workflow allowed for identification and quantification of more than 2500 human proteins and 975 microbial proteins. Taxonomic attribution shows large colonization of forehead by actinobacteria. Proteins were categorized according to their known functions as defined by COG annotations. The levels of beta oxidation pathways enzymes were different in-between the gender groups. These differences show interplay between bacteria and their host, as in female group, synthesis of lipids is upregulated in bacteria and in response, host upregulated lipid degradation. 
Microbial associated skin mechanisms are major questions to solve for health care consumers and dermatological patients. Obtaining a higher knowledge on different interplay between host and their microbial community is essential to improve next generation care products and patient treatment. As a result, this proof of concept study shows that modern proteomics is already a powerful tool to answer fundamental and applied research issues, and may help elucidating disorder etiologies as well as assessing leads for treating these.

Skin Metaproteomics: Understanding function of our microbial part.