Associate Professor TASHIRO Yukihiro and his research group have isolated bacteria from human scalp hair (hair bacteria) and discovered their unique carbon-utilizing properties.

2024.09.04 Life & Health

Hair bacteria metabolize not only sebum and sweat but also hair care products as nutrition and settle on hair. Expectations for hair cosmetics development

POINT

Recently, it has been reported that indigenous bacteria _(*1) exist on the surface of human scalp hair (hair bacteria), but the source of nutrients used by the bacteria to live on the hair was unknown due to the dry and nutrient-poor environment of hair.
We were the first in the world to isolate bacteria from hair, and by comparing type strain_(*2) and isolates, we identified that some isolated strains from hair prefer lipids and have ability to capitalize on carbon sources contained in sebum and hair care products, unlike type strains.
Hair bacteria have been reported to affect the regulation of gene expression related to cellular anti-aging and life extension through contact with human epidermal cells inside hair follicles. To date, type strains have been used for evaluation, but using hair isolates in this study is expected to provide a clearer picture of the relationship between hair bacteria and humans.

SUMMARY

Elucidating the symbiotic relationship between the human body and microorganisms is one of the most essential factors in unraveling the mechanisms of biological activities. Recently, DNA-based analytical methods have revealed commensal bacteria on the surface of human hair (hair bacteria), and elucidated their bacterial flora and their inhabitation mode. On the other hand, information on the source of nutrient is limited, and it has been suggested that the supply of sebum and sweat from the scalp would be important for the residence of hair bacteria. However, quantitative evaluation of their carbon-nutrient capacities is still unclear because it requires the use of isolated bacteria.
A research group with Graduate School of Agriculture, Kyushu University, Associate Professor TASHIRO Yukihiro, Assistant Professor OSHIRO Mugihito, Professor Emeritus SAKAI Kenji, Postdoctoral Researcher YAMADA Azusa, Graduate Students NISHI Yuri and NOGUCHI Mei, along with Assistant Professor WATANABE Kota from Faculty of Applied Biosciences, Tokyo University of Agriculture, has established a bacterial isolation method from hair and obtained 63 species from 27 genera under 24 culture conditions. Some of the hair bacteria showed enhanced growth under anoxic and lipid-added conditions. In addition, it was shown for the first time in detail that some hair bacteria have the ability to utilize glucose from sweat, glycerol from sebum, and mannitol from a wide range of hair care products. In particular, the dominant hair isolates Cutibacterium acnes subsp. defendens and C. acnes subsp. acnes can capitalize on mannitol, which is not utilized by the type strains, suggesting that they may have acquired advantageous utilization in the hair environment.
This research found evidence of nutrient supply from the host to hair bacteria. Furthermore, the acquired isolates obtained can used to analyze of the effects on human hair follicles to elucidate the relationship between hair bacteria and humans, and are expected to be used in the development of hair cosmetics that take into account the bacterial flora in the future.
The results of this research were published online in the Japanese English-language Journal of Bioscience and Bioengineering on July 21, 2024.

Comment from the researcher

Although hair is not a directly vital part of the human body, it plays an important role in promoting personal impressions and communication with others. While research in the field of hair is of great interest to many people, hair and microbiology research is an emerging field with many unanswered questions. Just as the development of lactic acid bacteria in gut has popularized the general public's concern for the intestinal environment, we would like to further develop our research so that more people will pay attention the hair microorganisms when caring for their hair through hair bacteria research.

GLOSSARY

(*1) indigenous bacteria
Among the microorganisms present in the human body, this term refers to bacteria that are stable and common to all people throughout the year and do not exhibit significant virulence..

(*2) type strain
It is the bacterial strain that was used as the basis for describing the species as a new species, and refers to a pure-cultured viable strain.

Paper Information

Publication: Journal of Bioscience and Bioengineering
Title: Isolated hair bacteria reveal different isolation possibilities under various conditions
Authors: Azusa Yamada, Yuri Nishi, Mei Noguchi, Kota Watanabe, Mugihito Oshiro, Kenji Sakai and Yukihiro Tashiro
DOI: 10.1016/j.jbiosc.2024.06.003

Research-related inquiries

TASHIRO Yukihiro, Associate Professor

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