Occupants and surface types drive microbial dynamics in controlled indoor environments.

Area of Science:

• Environmental microbiology
• Indoor air quality
• Human health

Background:

• Indoor microbial communities affect environmental quality and health.
• Previous studies analyzed factors individually, lacking combined interaction analysis.
• Limited research exists on Heating, Ventilation, and Air Conditioning (HVAC) and drainage systems' role.

Purpose of the Study:

• To assess the combined influence of human occupancy, surface moisture, aquaponics, and environmental parameters on indoor microbial dynamics.
• To investigate bacterial and eukaryotic communities in sealed residential units over 1.5 years.
• To understand microbial interactions within indoor environments.

Main Methods:

• Controlled, long-term investigation in sealed residential units.
• Assessment of human occupancy, dry vs. wet surfaces, aquaponics, humidity, ventilation, and seasonal variations.
• Amplicon sequencing for bacterial and eukaryotic analysis.

Main Results:

• Continuous air-conditioner use without fresh air increased CO₂ and humidity.
• Dry surfaces (filters, dust) showed higher microbial diversity than wet surfaces (drains, showerheads).
• Human occupancy enriched air-conditioner filters with opportunistic bacteria; aquaponics had minimal room-scale impact.

Conclusions:

• Human activity drives microbial accumulation in HVAC systems.
• Distinct microbial profiles exist for dry and wet indoor surfaces.
• Findings inform hygiene, HVAC maintenance, and building design for improved indoor microbial quality.