We know that buildings can make us sick. Take, for example, cases of lead poisoning, mold exposure, or the aptly named Sick Building Syndrome. But can they also make us healthier? Scientists are trying to answer that very question, starting with detailed studies of the microbes that populate our homes and offices. The end goal? Using this information to design structures constructed with bodies in mind.
This is a big shift in how we’ve previously conceptualized microbial life. We’ve long treated bacteria as the enemy. But it turns out that few of the germs we’re constantly trying to kill with hand sanitizer actually cause disease—and the more bacteria we have on the whole, the better. In fact, our habit of ultrasterilization appears to be hurting us. A number of recent studies have lent credence to the so-called “hygiene hypothesis,” which attributes the uptick in autoimmune and allergic diseases, including eczema and asthma, to a lack of early childhood exposure to germs.
So how do we get that healthy exposure to bacterial flora when we spend more than 90 percent of our time indoors? That’s the focus of an emerging field, so new that it doesn’t even have a proper name yet. Today, scientists studying the microbiology of the built environment are changing the way we think about bacteria and working toward ways to harness their potential for good. Here we’ll use the term “bio-inspired” to refer to design that incorporates biological processes or systems.
The emergence of ecosystem surveys
Before buildings can be designed with microbial life in mind, scientists have to get a handle on exactly what they’re dealing with in a given environment. The study of indoor microbiology isn’t new, says UC Davis biologist Jonathan Eisen, but it is moving faster than ever thanks to recent advances in DNA sequencing technology.
In the past, characterizing the microbes in a particular space required expensive, labor-intensive culturing, which was fairly limited in scientific value. But these days scientists can easily extract DNA from swabs and ship the genetic material to a sequencing facility, which sends back a complete list of all the organisms in the sample.
“If you wanted to grow up 50 million cultures of cells, that would take a warehouse,” says Eisen. “And we can now do that in seven hours for $1,000 with a machine the size of a microwave.”
Researchers have used this technology to inventory microbes in hospitals, wine- and cheese-making facilities, plumbing systems, subways in Hong Kong, Boston, and New York City—and that’s just counting projects in the last few years. With grants coming out of the Alfred P. Sloan Foundation’s Microbiology of the Built Environment program, there’s plenty more where that came from.
Together, these studies help to establish baselines of microbial life in the various indoor worlds we inhabit, which can tell us a lot about how we live and whether we could be living healthier.
Man-made microbial worlds
Indoor microbiomes demand a unique program of study because they’re fundamentally different from ones found in nature—and because we spend so much time in them. We control the growth of indoor bacteria in countless ways, from ventilation and plumbing to sterilization and foot traffic, and we leave bacterial signatures wherever we go. As a result, these indoor ecosystems end up looking a lot like us: human-associated bacteria are more than twice as plentiful in indoor air compared with outdoor air, meaning that when you’re inside, you’re breathing in a lot of your own germs. (That’s not necessarily as gross as it sounds—it’s still unclear what effect this kind of germ recycling has on our health.)
Do building materials affect how bacteria behave? That’s what Jack Gilbert, an environmental microbiologist at the University of Chicago, is investigating. He examines the metabolism of specific microbes under different indoor conditions. He’ll spray bacteria onto a variety of materials, such as steel, wood, and copper, looking for changes in their growth and proliferation, and he’ll adjust certain environmental variables, such as temperature and humidity—things humans like to control.
“Our aim is to see how those kinds of building operation parameters alter the growth and the activity of these microbial worlds,” Gilbert says.
These studies will inform the architecture of future offices, hotels, hospitals, and homes, in ways as complicated as installing bio-inspired filtration systems or as simple as opening windows.
Imagining “bio-inspired” design
As evidence continues to mount against ultrasterilization, scientists are looking for alternatives that nurture, rather than eradicate, microbial communities.
One way is through “bio-active” surfaces, permeable nanostructures with “good” bacteria stitched inside. Built into walls, chairs, carpets, and other indoor fixtures, these living surfaces would continuously secrete beneficial microbes into the indoor environment. In laboratory tests with mice and rats, these bio-active structures have been found to reduce the likelihood of allergic reactions and asthma attacks. “Instead of building new buildings per se, we could just refurbish all the existing buildings in Manhattan or downtown Chicago with bio-active walls or bio-active carpets,” Gilbert says.
Another (admittedly more fanciful) option would be to disperse bacteria through air conditioning. Microbes could be pumped into a space in spore or microdroplet form—invisible but inhalable. Lab studies have shown that certain beneficial bacterial genera (Blautia, Coprococcus, and Roseburia), when added to an environment, seem to reduce the likelihood that a mouse will have a food allergy.
But the risks with this method are considerable, since it’s difficult to know how bacteria will grow and interact once they’re dispersed. It’s possible that a bug could, under certain conditions, cause a disease outbreak, notes Gilbert.
“If we keep [bacteria] … inside walls, they’re much more stable and much less likely to potentially go rogue, versus putting them in little water droplets and dispersing them through the air, when they’re biologically active,” he says.
It might be simpler, Gilbert suggests, to ask everyone to buy more houseplants.
In any case, it will be some time before we see such aggressive attempts to alter the indoor microbiome, simply because there’s still so much we don’t know about microbial impacts on human health.
“It’s going to be incredibly hard to make proactive decisions and judgments [about whole building design] at least for the time being,” says Eisen. “We need a lot more data, and we don’t have any case studies to bash around yet, really, in building ecology.”
But he suspects that bio-inspired design might come soon for, say, a chain of hospitals that all have the same design. Then, he says, they can compare “basically the same building in 20 different sites.”
This type of design is already being implemented on a small scale. One of Gilbert’s research partners, the global architecture firm Skidmore, Owings & Merrill (SOM), is trying it out in a 9-1-1 call center in New York. Public Safety Answering Center II, currently under construction in the Bronx, will feature “bio walls” made up of plants that filter the air. Microbes in the plants’ roots filter out volatile organic compounds (VOCs), formaldehyde, and other toxins, while also generating oxygen for breathing.
It’s only a small step away from what we typically think of as “green” design, suggesting that future bio-inspired experimentation will take place under this umbrella of sustainability. Microbial ecology could become just another design consideration for architects, as well as an integral part of traditional conversations about form and function.
Ideally, buildings of the future will be living, breathing ecosystems, constantly replenished with good bacteria to support human immune systems, while keeping out the (very few) bad bacteria that can hurt us. And while we’re still a long way from that, Gilbert says, the study of indoor microbiology is moving us closer to “living in harmony with the environment, rather than trying to isolate ourselves from it.”
CORRECTION: A previous version of this story contained incorrect images and captions for SOM’s PSAC II and AMPS. They have been replaced in this post.