### Microorganisms Reflecting Dryness and Barrier Function In the dataset, the following microorganisms are notable for their reflection of dryness and barrier function impairments: 1. **Staphylococcus epidermidis**: Often present on healthy skin, it can decrease in abundance with increased dryness, leading to impaired barrier function and susceptibility to pathogenic bacteria. 2. **Cutibacterium acnes**: Normally abundant in sebaceous (oily) areas, its presence can diminish in dry conditions. 3. **Corynebacterium species**: These bacteria can increase with dryness and barrier function impairment. 4. **Acinetobacter**: Can proliferate in compromised skin conditions, including dry skin. ### Variation with Age The skin microbiome composition changes with age, affecting the abundance of these microorganisms: 1. **Young Skin**: - Higher diversity and abundance of **Cutibacterium acnes** due to more active sebaceous glands. - **Staphylococcus epidermidis** is well-regulated, maintaining a healthy skin barrier. 2. **Aging Skin**: - **Staphylococcus epidermidis** and **Cutibacterium acnes** decrease in abundance due to reduced sebum production and increased dryness. - **Corynebacterium** and **Acinetobacter** species may increase due to impaired barrier function and higher TEWL (Trans-Epidermal Water Loss), leading to increased susceptibility to colonization by harmful bacteria . The dataset indicates that age-related changes in skin conditions, such as increased dryness and impaired barrier function, significantly influence the skin microbiome's composition and diversity, making aging skin more susceptible to harmful bacteria due to reduced levels of protective microorganisms like **Staphylococcus epidermidis** and **Cutibacterium acnes**.