IN-24-C040 - Impact of Indoor Environmental Factors on Similarity of Eukaryotic and Bacterial Communities in Japanese Residences

In modern societies, a significant portion of human life is spent indoors, where the environmental conditions are crucial for health. Contemporary residential designs, characterized by enhanced thermal insulation and airtightness, offer improved thermal comfort. Modern housing design, characterized by improved insulation and air tightness, aims to improve thermal comfort and reduce fungal proliferation and infection risks. However, emerging research indicates that fostering microbiome diversity, rather than stringent microbial control, may augment health benefits. This study delves into the interplay between indoor environmental factors—temperature and humidity—and microbiome structure in modern and traditional houses in Japan. Our investigation spanned 16 residences, encompassing diverse thermal performances. Indoor and outdoor air temperatures and humidity were measured, and their aerosol samples were collected. Additionally, aerosol samples from these living spaces and outdoors were collected. They were processed in the laboratory and subjected to bioinformatics analysis using the SILVA database (ver. 138). Bioaerosol eukaryotic and bacterial microbial communities were compared, respectively, and the clustering of eukaryotes showed high similarity between outdoor and indoor air. In addition, clusters were formed by season and sampling area. The similarity of eukaryotic communities between indoor air and outdoor air was higher in homes with higher ventilation rates. Bacterial communities, unlike eukaryotic communities, had less similarity between indoor air and outdoor air. For indoor air, clusters were formed by the presence or absence of air conditioning. Therefore, it was clear that the use of heating and cooling equipment, ventilation rates, or the indoor temperature and humidity environment formed by them affected the indoor microbial community.