Knowledge Bank

Approximately 90% of our time spent is within the indoor environment where we are exposed to a diverse indoor microbiome. This indoor microbiome is influenced by a variety of factors, but especially ventilation, geographic location, and occupants. Occupancy can change both indoor bacterial and fungal communities in a home. Often, unoccupied homes (also known as “test houses”) are used to study processes that occur in indoor spaces. However, we need to better understand how well the indoor microbiome of an unoccupied test house might represent a standard occupied home, and therefore how well it might be used to study processes in the indoor environment. This study intends to evaluate the microbiome before and after ozone/smoke exposure in an unoccupied test home while comparing it to the composition of bacteria and fungi from undamaged, occupied homes across the continental United States. Smoke and ozone were injected into an unoccupied home located in Gaithersburg, Maryland, and dust was collected from the entire home before (n=2) and after (n=1) these perturbations. Homes across the United States (n=9) that were used for comparison were also vacuumed to retrieve dust. All dust samples were extracted, quantified with quantitative polymerase chain reaction (qPCR), and sequenced. From this experiment, the fungal concentrations of occupied home samples were significantly higher compared to the test home, and there were significant differences between Shannon diversity. Epicoccum was the most abundant genus for all test house samples and five of the nine occupied home samples, and there were variations among genera and ecological niches. Gram-negative bacteria dominated the test house samples, and overall were more diverse than the mycobiome. This study did not allow for us to assess viability. This suggests that occupancy and home use play a vital role in the indoor microbiome. Future directions may include increasing the number of dust samples from test homes, along with studying viability and function before and after smoke/ozone exposure.