Occupants and surface types drive microbial dynamics in controlled indoor environmentsHou, Jianjian (Avtor) Nakajima, Makiko (Avtor) Nishiuchi, Yukiko (Avtor) Ogura, Daisuke (Avtor) Teramoto, Atsushi (Avtor) Kuratomi, China (Avtor) Iwamoto, Yoko (Avtor) Okamura, Yoshiko (Avtor) Moriguchi, Kazuki (Avtor) Dovjak, Mateja (Avtor) Takayama, Kento (Avtor) Tsugami, Yusaku (Avtor) Fujiyoshi, So (Avtor) Maruyama, Fumito (Avtor) built environmentindoor microbiomeeukaryoteoccupancyaquaponicsseasonsurface moisturehumidityhuman healthBackground Indoor microbial communities play a critical role in infuencing indoor environmental quality and human health and are shaped by occupant activity, surface characteristics, and environmental conditions. While previous studies have examined these factors individually, systematic evaluations of their combined interactions, particularly involving Heating, Ventilation, and Air Conditioning (HVAC) and drainage systems, remain limited. This controlled, long-term (1.5-year) investigation assessed how human occupancy, surface moisture (dry vs. wet), aquaponics (soilless plant-aquarium systems), and environmental parameters (humidity, ventilation, and seasonal variations) infuence bacterial and eukaryotic dynamics in tightly sealed residential units. Results Continuous air-conditioner operation without fresh-air intake led to elevated CO₂ levels during occupancy and pronounced seasonal humidity fuctuations, emphasizing the need for improved ventilation and adaptive humidity control in compact urban residences. Amplicon sequencing revealed higher microbial diversity on dry surfaces (aerosols, air-conditioner flter dust, and foor dust) than on wet surfaces (waste drains and showerheads). Wet environments supported bioflm-associated taxa adapted to moist conditions (e.g., Methylobacterium, Vermamoeba). Human occupancy signifcantly enriched air-conditioner flter dust with opportunistic bacteria (e.g., Finegoldia and Streptococcus), underscoring occupant-driven microbial accumulation via recirculated air. Additionally, the smallscale aquaponic system had minimal measurable infuence on microbial composition at the room scale, suggesting limited aerosolization or dispersal under typical usage conditions. Indoor relative humidity was signifcantly correlated with microbial diversity in air systems, notably enhancing moisture-adapted taxa such as Sphingomonas during humid seasons. Seasonal variations markedly infuenced eukaryotic communities (e.g., pollen infux).20252025-09-11 14:04:32Članek v reviji172849sl