Skin microbiome basics
The skin is the largest organ in the human body. It plays a vital role as a barrier for the body and is also home to an ecosystem of a diverse milieu of microorganisms: bacteria, fungi and viruses.
The skin microbiome, otherwise known as microflora or microbiota, is simply all of the microorganisms present on the skin. Most of the microorganisms that colonize the skin are beneficial to human skin and health; this is known as commensalism, when an association between two organisms sees one species benefit while the other neither benefits or is harmed.
There are over 1,000 different bacterial species on our skin – some of the most common phyla of bacteria are actinobacteria, proteobacteria, firmicutes and bacteroidetes. The skin microbiome is constantly changing depending on location, environment, age, gender, and cosmetics or other products used – in fact, an individual’s skin microbiome composition may be as unique as their DNA.
While there is still a lot to discover about the skin microbiome, we do know the important role it plays in the health, wellbeing, and protection of the human body. Skin microorganisms provide essential protection against pathogens, support of our immune system, and impact skin health, beauty and personal care.
In fact, disturbances in the skin barrier (or stratum corneum) and the composition of the skin microbiome have also been linked to skin health, and the presence, or aggravation of, skin conditions such as eczema, rosacea, acne, allergies or even the skin’s ageing process1.
While both the oral and gut microbiome have benefited from intense research over the last decade, the skin microbiome is only now emerging as a focus area for many. In particular, we are awakening to the potential implications of furthering the understanding of the skin microbiome, and the role it can play in providing better, or even personalized, products for skin health and personal care.
The microbiome as a key to human health is here to stay, and the skin microbiome is a new frontier in this research.
For those of you who are less familiar with the skin microbiome, we have created the below glossary to help navigate a selection of key terms used throughout our content.
Microscopic organisms that are found all around us and even inside our bodies. Also known as microbes, microorganisms include a massive range of organisms such as bacteria, fungi and viruses.
The microorganisms in a particular environment (including the body or a part of the body). The human microbiota consists of the 10-100 trillion symbiotic microbial cells harboured by each person.
The collection of microbial genomes in an environment.
However, both microbiota and microbiome are often used interchangeable.
Another, but lesser used, term for the skin microbiome or skin microbiota.
Bacteria v. fungi v. viruses
The three domains of living microorganisms. These are:
- Bacteria are extremely diverse and in terms of number are by far the most successful organism on Earth. The benefits of bacteria are increasingly well known, such as bifidum (the probiotic commonly found in yoghurts) as well as the harmful effect of bacteria such as salmonella.
- Fungi are eukaryotes which means they have a defined nucleus and organelles. The cells are larger than prokaryotes such as bacteria. Fungal colonies can be visible to the human eye once they have achieved a certain level of growth, for example mould on bread.
- Viruses essentially consist of nucleic acid (DNA or RNA) and a protein coat. They cannot grow or reproduce apart from in a host living cell. Influenza and Hepatitis are well known examples of viruses.
A bacterium, fungus, virus, or other microorganism that can cause disease or illness to its host.
Living in a relationship in which one organism derives food or other benefits from another organism without hurting or helping it.
The epidermis is the outermost of the three layers that make up the skin. A mature epidermis is an effective barrier against dehydration from the loss of body water, poisoning from the absorption of noxious substances, and systemic infection from invading surface microorganisms2. The other two layers are the dermis and hypodermis.
An association of microorganisms in which microbial cells adhere to each other on a living or non-living surface3.
- Probiotic: a microorganism introduced into the body for its beneficial qualities
- Prebiotic: a non-digestible food ingredient that promotes the growth of beneficial microorganisms in the intestine
- Postbiotics: non-viable bacterial products or metabolic by-products from probiotic microorganisms that have biologic activity in the host4
Microbial diversity is defined as the variability among living organisms. The main key of microbial diversity on earth is due to evolution.
Term for a microbial imbalance on or inside the body.
The skin barrier has seven functions, including maintenance of water content and balance, reduction of the effects of ultraviolet (UV) light exposure and mitigation of the effects of oxidative stresses. Perhaps the most well-known is that of protection against the external environment and foreign substances or pathogens.
Actinobacteria are a phylum (group) of Gram-positive bacteria and can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to soil systems.
Proteobacteria are a major phylum of bacteria. Proteobacteria include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter and many other notable genera. Others are free-living and include many of the bacteria responsible for nitrogen fixation.
Firmicutes are a phylum of bacteria, most of which have a Gram-positive cell wall structure and some of which do not produce spores. Many Firmicutes produce endospores, which are resistant to desiccation and can survive extreme conditions.
The phylum of Bacteroidetes is composed of three large classes of Gram-negative, non-spore-forming, anaerobic or aerobic, and rod-shaped bacteria that are widely distributed in the environment, including in soil, sediments, and sea water, as well as in the guts and on the skin of animals.