Buildings are complex ecosystems that house trillions of diverse microorganisms interacting with each other, with humans, and with their environment. In developed countries humans spend more than 90% of their lives indoors, and the indoor environment is potentially a major source of microbes colonizing humans. Elucidating the mechanisms that shape the built environment microbiome - the collection of microorganisms associated with buildings - is critical for understanding the relationship between building design and human health, and such an understanding could influence the development of sustainable and green design concepts. To obtain an integrated view of the built environment microbiome, we surveyed airborne bacteria across space, time and environments in a health care facility.
We found that the structure and composition of airborne bacterial communities significantly differs between indoor and outdoor environments, and that building attributes, specifically the source of ventilation air, airflow rates, relative humidity, and temperature, strongly influence the diversity of indoor bacterial communities. Furthermore, we observed that the abundance of potentially pathogenic bacteria was higher in indoor environments that had low airflow rates, that were ventilated mechanically, and that were relatively warm and dry. These building attributes are strongly influenced by architectural design, suggesting that design can be used to manage indoor microbial communities to improve human health and wellbeing. These results also suggest that sustainable design concepts (such as natural ventilation) could result in healthier indoor environments that also consume less energy.