Cutaneous microbiome studies in the times of affordable sequencing

Background: Skin is our first line of defense against pathogenic microorganisms and the intimate contact between the epidermis and microbes has been well known. Purposes: Microbes that cause infection are associated with inflammatory dermatoses and exacerbate wound healing. It is therefore of vital importance to understand the intricacies of skin-microbiota interactions. However, until recently our knowledge and understanding was limited by being unable to deal with uncultivatable microorganisms, which constitute a large majority. Basic procedures: Recent advances in DNA sequencing methodologies, analysis tools and affordability led to major breakthroughs in defining the cutaneous microbiome. Main findings: We now know that four phyla, Actinobacteria, Firmicytes, Proteobacteria and Bacteroidetes, constitute preponderance of skin bacteria, while Malassezia dominates the fungal microbiome. We know that there are some 300 different bacteria inhabiting our skin. We also know that there is remarkable interpersonal variation, that the microbiota change over time, that different body sites harbor specific microbial arrays and that microbiota characteristically change in skin diseases. Principal conclusions: The recent advances led to appreciation that microbes are, for the most part, our allies, useful and protective, and that with increased understanding we will be able to harness our cutaneous friends to maintain and promote our health. (C) 2014 Published by Elsevier Ireland Ltd on behalf of Japanese Society for Investigative Dermatology.