Exploring the Complexities of Skin Microbiome: Bacteria, Fungi, and Their Impact on Skin Health

The human skin is a fascinating ecosystem that hosts a diverse array of microorganisms, including bacteria, fungi, viruses, and other microbes. These microorganisms vary in their distribution across the skin and can have both positive and negative effects on our skin health.

Aerobic bacteria are predominantly found on the surface layer of the skin, while anaerobic bacteria reside in the hair follicles and sebaceous glands. Common bacterial species include S. epidermidis, S. aureus, Micrococcus, and Cutibacterium acnes. Additionally, fungi such as Malassezia, Candida, and Trichophyton can also be present.

The distribution of these indigenous skin bacteria is influenced by factors such as UV exposure, pH, temperature, moisture, and sebum content. Different areas of the skin harbor distinct microorganisms. For example, seborrheic areas like the forehead and back contain Cutibacterium bacteria, while dry areas like the forearms and buttocks have diverse bacterial populations.

These skin-associated bacteria can be categorized as favorable, hazardous, or opportunistic. Favorable bacteria like S. epidermidis contribute to skin health by moisturizing the skin, enhancing the barrier function, and preventing the growth of harmful bacteria like S. aureus. On the other hand, hazardous bacteria such as S. aureus can cause various skin infections and thrive in alkaline environments. Opportunistic bacteria like C. acnes play a role in acne formation and their abundance can determine whether they are beneficial or harmful.

Maintaining a balance among these microorganisms is crucial for healthy skin. When the equilibrium is disrupted, skin and systemic diseases may occur. Researchers have been exploring the potential of selectively targeting specific bacteria to develop treatments for skin diseases. Moreover, the breakdown products and metabolites produced by indigenous bacteria have shown promising health-related functionalities. Short-chain fatty acids and glycerol, for instance, contribute to maintaining pH levels, moisturizing the skin, and exhibiting antibacterial activity.

Understanding the complexities of the skin microbiome and its impact on skin health opens new avenues for developing targeted skincare products and treatments that can harness the beneficial properties of indigenous bacteria while addressing imbalances and promoting overall skin well-being.

Full text

Human skin contains approximately 102–107 cells/cm2 and hosts around 1000 species of microorganisms including bacteria, fungi, viruses, and other microorganisms. These microorganisms differ in their distribution on the skin. Aerobic bacteria are primarily found on the surface, while anaerobic bacteria reside in hair follicles and sebaceous glands. Some commonly found bacteria include S. epidermidis, S. aureus, Micrococcus, and Cutibacterium acnes. Fungi like Malassezia, Candida, and Trichophyton are also present on the skin.

The microbial composition of the skin varies depending on factors such as UV exposure, pH, temperature, moisture, sebum content, and topography. Different areas of the skin harbor distinct microorganisms. For instance, seborrheic areas like the forehead and back contain Cutibacterium bacteria, while dry areas such as forearms and buttocks have Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes. Moist areas like the axillae, groin, navel, and soles contain Staphylococcus and Corynebacterium bacteria.

Skin-associated bacteria can be classified into favorable, hazardous, and opportunistic bacteria. Favorable bacteria like S. epidermidis contribute to skin health by moisturizing the skin, enhancing barrier function, and preventing the growth of harmful bacteria like S. aureus. Hazardous bacteria like S. aureus can cause various skin infections and thrive in an alkaline environment. Opportunistic bacteria like C. acnes play a role in acne formation and can be beneficial or harmful depending on their abundance.

Indigenous skin bacteria serve as a barrier against pathogens, but when the balance is disrupted, it can lead to skin and systemic diseases. Researchers have developed cosmetics that selectively target specific bacteria to assist in treating skin diseases. The breakdown products and metabolites produced by indigenous bacteria, such as short-chain fatty acids and glycerol, have been found to have health-related functionalities. For example, propionic acid maintains an acidic pH in hair follicles, limiting the growth of S. aureus. Glycerol retains moisture and strengthens the skin's barrier function. SCFAs exhibit antibacterial activity, and lactate and free fatty acids have various effects on the skin.

In conclusion, indigenous skin bacteria play a vital role in maintaining skin health, and their metabolites have potential health benefits. Understanding their distribution and functionalities can help develop targeted treatments and skincare products.

Link to further study https://www.mdpi.com/2311-5637/8/12/703