Ultraviolet radiation, both UVA and UVB, influences the composition of the skin microbiome
J Invest Dermatol
Inhabiting each square centimeter of skin are approximately 1 million bacteria from hundreds of distinct species. Recent studies have begun to investigate the complex relationship between host and microorganisms leading to non-infectious pathologies such as acne, atopic dermatitis, and psoriasis. Though the skin is continuously exposed to external environmental stressors such as ultraviolet (UV) radiation, there have been no studies examining the effects of UV on the skin microbiome. To test our hypothesis that UV will alter the cutaneous microbiome, 22 participants were exposed to various doses of UVA (22-47 J/cm2) or UVB (100-350 mJ/cm2) and skin was swabbed before, immediately after, and 24h after UV exposure. DNA was isolated from the swabs and sequenced to identify the microbial composition for each sample. There was vast intra- and inter-subject variation in the skin microbiome at all time points, and phylum- and species-level differences were identified. Specifically, within the Proteobacteria phyla, an increase of the order Burkholderiales was observed after UV compared to pre-UV (59% vs 24%, p=0.0172). There was no clear difference in microbial composition between UVA- and UVB-irradiated skin; however, the sensitivity of various microbes to UV as well as their re-colonization potential following exposure differed. Taken together, the results demonstrate that UV radiation, both UVA and UVB, has profound qualitative and quantitative influences on the composition of the skin microbiome, which may affect skin diseases in which UV radiation is a factor, and may contribute to the efficacy of phototherapy and photochemotherapy.