They have us surrounded. Even inside the spaces we build for ourselves — like homes and offices — we are a tiny minority. Invisible bacteria, fungi, and viruses outnumber us by orders of magnitude.
We will always be outnumbered, but we may have a say in which microbes we’re surrounded by, according to a new study that’s one of the first to investigate how building design influences the microbial diversity of indoor spaces. “Design choices at the level of a whole building make a really big impact on the types of invisible organisms that you see in a room,” said microbial ecologist Jessica Green, an author of the new study. The work is part of an emerging body research suggesting that design decisions — from the architect’s blueprint to the choice of ventilation system to the materials picked by the interior designer — help shape the microbes in our midst.
In three recent studies, her team at the University of Oregon dissected the microbial diversity of a single building on campus called Lillis Hall, which houses professor’s offices and classrooms. In one study, they used a modified Shop-Vac to collect 155 dust samples throughout the building. Back in the lab, they extracted bacterial DNA and sequenced a gene called 16S. All bacteria have a copy of this gene, but its sequence differs from one type of bacteria to another, making it a useful ID marker. Classifying fungi and viruses is trickier, but Green hopes to tackle them in future studies.
Restrooms and classrooms, which are visited by many people throughout the day, tended to be dominated by bacteria commonly found on human skin, including Lactobacillus and Staphylococcus. Offices, especially those with windows, tended to have higher levels of soil-dwelling Methylobacterium. Mechanically ventilated offices, on the other hand, had more Deinococcus, which may be better suited to the hot dry air pumped out by the heating system in these rooms, Green says.
In addition to dust, Green and her team have also examined air samples and surfaces in Lillis Hall. In another recent study they found that rooms with a natural ventilation system that brings in outside air at night have microbial profiles more similar to outside air, compared to rooms with mechanical ventilation system that was turned off at night to save money. “What we found is if you have this really expensive mechanical ventilation system and you turn it off at night, you’re leaving this bag of microbes that people are immersed in when they come back in the morning,” Green said.
The interactions between building design, microbial diversity, and health might be stronger in other types of buildings — such as hospitals. Green is part of a consortium studying how microbial communities develop in two newly constructed hospitals, one in Chicago and one in Germany.
But she thinks those interactions will turn out to exist in other types of buildings too. She notes that scientists are only just beginning to discover how the microbiome, the collection of microbes that live inside our guts, can impact our health by interacting with everything from the immune system to the brain. And where do those microbes come from? ”We pick them up from the built environment,” Green said. For a species that spends nearly 90% of its time indoors, that’s something to think about.