Biodiversity hypothesisBiodiversity hypothesis

March 28, 2022

Genki-kûkan™ Research Initiative (Part 3)
Effects of natural air quality on humans

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  • SDG ICON. Goal 3: Good health and well-being
  • SDG ICON. Goal 9: Industry, innovation, infrastructure
  • SDG ICON. Goal 17: Partnerships for the goals

The Toyota Motor Corporation Frontier Research Center and the Toyota Central R&D Labs. (TCRDL) are working jointly on a Genki-kûkan™ Research Initiative to develop spaces that can improve the mental and physical well-being of people1, 2. In Part 2, we introduced air quality, a key aspect of the Genki-kûkan™ Research Project. In Part 3, we spoke to members of the project, Akinori Ikeuchi, Naoki Soga, and Yumi Motoyama, who are engaged in research on the effects of natural air quality on humans.

Team member of Genki-kûkan™research “Effect of air quality to human”

Interview participants (from left)
Naoki Soga
(Human microbiome research team leader)
Akinori Ikeuchi*
(Project Manager, Genki-kûkan™ Research Project)
Yumi Motoyama*
(Human microbiome research team member)
*On temporary assignment from TCRDL.

― What kind of research are you conducting regarding the effects on humans?


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.

  • Species and amonts of commensal bacteria with human
    Figure 1. Species and quantity of microorganisms (normal bacterial flora) that coexist with humans

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.

Skin microbiome

It is said that there are 103 to 105 of skin microbiomes living on 1 cm2 of skin, maintaining the skin surface at weak acidity to prevent infection by pathogens. Research in recent years has shown that the skin microbiome has a close relationship with the condition of the skin, such as abnormal propagation of harmful bacteria like Staphylococcus aureus on the skins of patients with atopic dermatitis.

― Does skin microbiome change with air quality?


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 individuals3, 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).

  • Visualization of skin microbiomes and impact of air quality,  showing sampling method, diversity and dairy variance of skin MB.
    Figure 2. Visualization of skin microbiomes and impact of air quality

― What kind of air quality has positive effects on humans?


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 microbiome6, 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).

  • Research on mechanism of skin microbiome using artificial skin model, showing localization of skin MB on human skin and influence of chemo-signal of plant to symbiotic model of skin.
    Figure 3. Research on mechanism of skin microbiome using artificial skin model

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™.

― What other types of effects on humans are you researching?


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.

  • Various effects of Space symbiotically with plants to human, such as communication, creativity, fatigue, immune system, microbiome, etc..

Message from Associate Professor Saeko Nakajima, Faculty of Medicine, Kyoto University (research partner)

Saeko Nakajima, Department of Dermatology, Kyoto University Graduate School of Medicine

The skin is an organ that forms a barrier between the body and the external environment. The skin microbiome, which exists on top of the skin, is always in contact with the air. However, there has been almost no research conducted on how air quality affects skin microbiome. We are conducting research together with Toyota Motor Corporation on the kind of impact that air quality has on skin microbiome. In the future, I hope to investigate the kind of air quality that has beneficial effects on skin microbiome and the specific substances that bring about those effects, so please keep an eye out for the results of our research.

Profile: Specially Appointed Associate Professor, Department of Drug Discovery for Inflammatory Skin Diseases (concurrently with Department of Dermatology), Graduate School of Medicine, Kyoto University Professor Nakajima graduated from Osaka Medical College (present Osaka Medical and Pharmaceutical University) in 2003 and took on her current position in May 2021. She specializes in atopic dermatitis, drug eruption, and skin microbiome.


Genki-kûkan™ Research Initiative (Part 1), Reproducing slices of nature in the laboratory, Frontier Research Center, Toyota Motor Corporation.
Genki-kûkan™ Research Initiative (Part 2), Air quality research that opens up a new world, Frontier Research Center, Toyota Motor Corporation.
日本ゲノム微生物学会(2021)、池内暁紀「大気と皮膚のマイクロバイオーム研究 その1 ~空気質研究の全体概要~」
日本ゲノム微生物学会(2021)、名倉理沙「大気と皮膚のマイクロバイオーム研究 その2 ~屋内・屋外空間における大気マイクロバイオームの比較~」
日本ゲノム微生物学会(2021)、曽我直樹「大気と皮膚のマイクロバイオーム研究 その4 ~大気MBが皮膚MB に及ぼす影響~」
日本ゲノム微生物学会(2021)、幸田勝典「大気と皮膚のマイクロバイオーム研究 その5 ~皮膚MBの影響評価法の構築~」
Naoki Soga, “An in vitro mixed Infection model with commensal and pathogenic Staphylococci for the exploration of interspecific interactions and their Impacts on skin physiology”, 2021, Cell Bio Virtual 2021
K. Kohda, X. Li, N. Soga, R. Nagura, T. Duema, S. Nakajima, I. Nakagawa, M. Ito and A. Ikeuchi “An in vitro mixed infection model with commensal and pathogenic Staphylococci for the exploration of interspecific interactions and their impacts on skin physiology” 2021, Front. Cell. Infect. Microbiol., 11, 712360

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