03 Air + Microbes Column  

 Architectural design drives the biogeography of indoor bacterial communities  

Buildings are complex ecosystems comprised of microorganisms interacting with each other and their environment, as well as the humans who spend most of their lives indoors. This study measured microbiological, architectural, and environmental features of 155 rooms throughout a multi-use educational building to assess whether architectural function, form, and organization predicted variation in the built environment microbiome. We found that indoor bacterial communities were extremely diverse but uneven, being dominated by members of phyla Proteobacteria, Firmicutes, and Deinococci. 

Architectural design characteristics related to space type, building arrangement, human use and movement, and ventilation source had a large influence on the structure of bacterial communities. Restrooms contained bacterial communities that were highly distinct from all other rooms, and spaces with high human occupant diversity and a high degree of connectedness to other spaces via ventilation or human movement contained a distinct set of bacterial taxa when compared to spaces with low occupant diversity and low connectedness. Within offices, the source of ventilation air had the greatest effect on bacterial community structure. The impact of design decisions in structuring the indoor microbiome offers the possibility to use ecological knowledge to shape our buildings in a way that will select for an indoor microbiome that promotes our health and well-being. (Kembel et al., 2014) 

 Urban greenness influences airborne bacterial community composition 

Urban green space provides health benefits for city dwellers, and new evidence suggests that microorganisms associated with soil and vegetation could play a role. While airborne microorganisms are ubiquitous in urban areas, the influence of nearby vegetation on composition of airborne microbial communities remains poorly understood. We examined airborne microbial communities in highly vegetated (parks) versus non-vegetated (parking lots) urban environments. Bacterial community composition in parks was significantly different from parking lots, although alpha diversity was similar. 

Direct gradient analysis showed that the proportion of vegetated area within a 50 m radius of the sampling station explained 15% of the variation in bacterial community composition. Individual parks were characterized by unique bacterial signatures, whereas parking lot communities tended to be similar to each other with higher relative abundance of family Acetobacteraceae, members of which are also commonly found in acidic mine drainages. This work sets a foundation for understanding how urban vegetation may impact microbial communities, with potential implications for designing equitable green neighborhoods and open space systems to foster human health. (Mhuireach et al., 2016) 

 Design and operation of built environments to reduce viral risks and improve human and planetary health 

The Covid-19 pandemic changed the way in which we operate and use buildings, one of the primary settings for the transmission of the SARS-CoV-2 virus. Due to the immediate risks posed by Covid-19, energy use for building operation was increased to refresh indoor air through filtration or outside air exchange. However, creating built environments that simultaneously promote the health of individuals, ecosystems and planet must balance multiple objectives. The Institute for Health in the Built Environment and Biology and the Built Environment Center at the University of Oregon have been conducting human-subject chamber and simulation studies that seek to develop parametric risk platforms and air detection strategies for improved viral awareness in buildings. This early detection could trigger mitigation strategies, such as increased air exchange or filtration, without continuously applying high energy intensive activities. However, the researchers are also developing risk-based simulation approaches to apply early in design that integrate valuable low-tech solutions, such as improved window operation, natural ventilation, relative humidity control within the 40%-60% range, and beneficial spatial arrangement for microbial control. (Horve et al., 2022, Parhizkar et al., 2022, Dietz, et al., 2020) 

Indoor air communities closely tracked outdoor air communities, but human-associated bacterial genera were more than twice as abundant in indoor air compared with outdoor air. Ventilation had a demonstrable effect on indoor airborne bacterial communities, as changes in outdoor air bacterial composition were detected indoors following a time lag dependent on ventilation strategy (mechanical cooling vs. passive night-flush). Our results suggest that both occupancy patterns and ventilation strategies are important for understanding airborne microbial community dynamics in the built environment. (Meadow et al., 2015, Kembel et al., 2012)