A collaborative research group led by Professor Masahira Hattori of Waseda University and Dr. Kana Takayasu of the University of Tokyo (others such as Keio University) has a circadian rhythm in human saliva flora. Was revealed for the first time in the world.
Many organisms, including humans, have a biological clock with a cycle of about 24 hours, which regulates circadian rhythm (circadian rhythm), which is a diurnal variation of various physiological functions during the day and night, and maintains homeostasis throughout the body. Working for (maintaining health).This time, the collaborative research group discovered that the circadian rhythm, which was considered to be a phenomenon in living cells and organs, also exists in the bacterial flora in human saliva.The bacterial flora (saliva flora) is a population of about 700 species and 1,000 billion bacteria in human saliva.
The collaborative research group collected saliva flora of healthy adults (6 men and women) every XNUMX hours for XNUMX consecutive days, and analyzed the changes in the type and composition of the bacteria in detail by a method called metagenomic analysis.
As a result, the amount of saliva bacteria (68-90%) of more than half fluctuates (increases / decreases) in a cycle of about 24 hours, and the larger the amount of bacteria, the clearer the circadian rhythm. It was found that the daily increase / decrease pattern was different.Also, circadian rhythms were observed only in the oral salivary flora and not in vitro.Furthermore, aerobic bacteria change from day to night, and anaerobic bacteria change from early morning to noon.It was found that the number of bacteria tends to be higher at night than at noon.
This achievement will be useful for assessing stress and health status, developing diagnostic methods for body clock disorders that are said to increase the risk of developing lifestyle-related diseases such as obesity / diabetes and cancer, and improving health. It is expected to be applied to the improvement of lifestyle.
Paper information:[DNA Research] Circadian oscillations of microbial and functional composition in the human salivary microbiome (English)