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The human skin houses millions of microorganisms. Over a surface of 1-2 square meters, it is packed with several environmental niches. Skin microorganisms have long been recognized as having a mechanistic role in skin physiology, training and regulating the skin’s immune system, affecting the pH of the skin’s surface through lipid metabolism, and giving resistance to pathogen colonization. Moreover, it has recently been demonstrated that the skin microbiome can control the development, maintenance, and operation of the epidermal barrier. In contrast, a variety of behavioral and host-specific factors, such as the significant physiologic changes brought on by skin aging, influence the composition of the skin’s microbiome.
Skin microbiome diversity increases with age
Previous studies have proposed that the skin microbiome changes significantly over time, particularly as humans age. Skin aging is marked by changes in tissue structure, such as epidermal thinning, flattening of the epidermis-dermis interface, and collagen and elastin loss. Following tissue changes, biophysical measures such as skin capacitance or evaluations of the quality and quantity of collagen, as well as clinical parameters like wrinkles, sagging, or color abnormalities, are altered. The high-resolution alterations in the skin’s microbiota are thought to be related to the skin’s aging-related biophysical changes as well as being a biomarker of aging.
A recent study was carried out to analyze the skin microbiome’s species, strains, and gene content distribution in older vs. younger adults using shotgun metagenomic sequencing. The following host attributes were also collected; Body mass index(BMI) and biophysical parameters like skin capacitance (SC), dermis water content (DWC), and collage diffusion coefficient (CDC). The analysis was restricted to just the facial skin microbiome of healthy caucasian women in order to decrease data dimensionality and account for confounding factors of the skin microbiome composition, 26 younger and 25 older women were recruited for the study. In line with findings from prior research on Caucasians and other ethnic groups, it was discovered that skin microbiome diversity increased with age at the species level. Also, it was found that genetically similar strains belonging to the same species could behave differently in relation to skin aging. Collagen quality and quantity (as determined by the CDC) were considerably reduced with skin aging due to its gradual degradation. It was discovered through high-resolution characterization of the skin microbiome that the biophysical characteristics of the skin habitat were related to both community structuring and strain population structuring. The CDC was most impressively able to statistically explain numerous age-related trends found in the microbiome.
The composition and functional potential of the skin microbiome, as well as the number of bacterial strains detected in nosocomial infections and the prevalence of antibiotic-resistance genes, are related to biophysical properties, particularly the collagen diffusion coefficient. With these properties, scientists can better study the microbes causing infections and they can also understand the genetic composition of antibiotic-resistant bacteria.
Utilizing the resolution offered by shotgun metagenomics, the relationships between microbial species, strains, and gene content on the skin and its biophysical characteristics as it ages were investigated. Results demonstrate significant correlations between skin biophysical characteristics and aging-related changes in the skin microbiota and generate testable hypotheses for the underlying mechanisms.