Ikeuchi:

We are engaged in research regarding the impact on microorganisms that coexist with humans brought about by microorganisms and chemical substances found in natural air. The human body is said to be made up of approximately 40 trillion cells. Coexisting in areas that are in contact with the external environment (air) are many species of microorganisms, exceeding the number of human cells, including 100 trillion in the gastrointestinal tract, one trillion on the skin, as well as other places such as within the mouth and respiratory organs. Together, they form what is called the microbiome (MB) (see figure 1). This symbiotic relationship was built over the long evolutionary process of humans, and it can be said that humans and microorganisms are a single organism that have coexisted and evolved together over a countless number of years.

In recent years, there is less contact with nature due to rapid urbanization which has been disrupting this symbiotic relationship. It is suggested that this could be a possible cause of various illnesses, including allergic diseases such as asthma and atopic dermatitis. We think that taking in air that is rich in a variety of microorganisms has an important role in balancing the symbiotic relationship between humans and microorganisms, and are conducting research on the impact that air quality has on skin microbiome, which refers to the microorganisms coexisting on the skin.

Soga:

As the air contains extremely small quantities of microorganisms (see Part 2), we did not know how much the skin microbiome will change. Therefore, we pasted adhesive stickers on the skin using a fixed amount of pressure and analyzed the DNA of skin microbiomes that were adhered to the stickers, establishing a technique that can easily analyze the species and quantities of skin microbiomes with high accuracy. When we used this technique to compare the skin microbiomes of different individuals, we saw that there is significant variation in the species and quantities of skin microbiomes between individuals^{3, 4} (see top left of figure 2).
Next, we investigated the degree of change in skin microbiome after spending time in natural air. As a result, we discovered that, before and after spending time in a natural environment, every subject saw an increase in skin microbiome species and a change in its composition (see lower left of figure 2). In addition, we investigated how skin microbiome changes in daily life through long-term monitoring of daily skin microbiome and the subjects’ behavioral patterns. We found that the skin microbiome changes periodically with the environment that one spends time in, such as days working in the office, non-working days spent with family, and days of leisure surrounded by an abundance of nature. We also came to understand that the air quality of the places one spends time in is reflected in the changes of the skin microbiome, and that the air quality in natural environments, rich in a variety of microorganisms, induce even greater changes5 (see right side of figure 2).

Motoyama:

It is still not known how the skin microbiome needs to change in order for the skin to become genki, or healthy. Therefore, we cultivated pathogenic bacteria(Staphylococcus aureus) and resident bacteria(Staphylococcus epidermidis) on artificial skin, such as those used in skin transplants, and succeeded in creating an artificial symbiotic model of the skin and skin microbiome^{6, 7, 8, 9}. When we evaluated the impact that air quality has on skin microbiome using this symbiotic model, we found that certain species of plants generate air quality (plant chemosignal) that creates conditions in skin microbiome symbiosis that are advantageous to resident bacteria and have the effect of suppressing damage and inflammation to the skin caused by pathogenic bacteria (see figure 3).

In the future, we hope to create spaces that are not only pleasant to the eyes but also make the condition of the human skin genki, or healthy, by growing plants that are known—using the symbiotic model—to have beneficial effects on skin microbiome within Genki-kûkan™.

Ikeuchi:

We are also engaging in research about natural air quality and its impact on the human immune system. It will be interesting if we can create spaces that make us more resistant to colds over time. We are also trying to show, scientifically, effects such as relaxation, stress relief, and fatigue mitigation by investigating the changes in biologically active substances and physiological states of humans when spending time inside Genki-kûkan™. In addition, as we experience spaces that coexist with plants through the Genki-kûkan™ Research Project, there seems to be an improvement in interpersonal communication and ideas being generated more easily. We hope to introduce these research areas in the future when we have some results.