Why the building microbiome matters

The microbiome is the assemblage of microbes that live on us, and in us. And not just us, the environment around us has its own microbiome. This is essential for everyone's good health. Phoebe Mankiewicz Ledins from Yale University, and Elizabeth Hénaff from New York University are interested in discovering how we can engineer the grown buildings of the future, to grow the right kinds of microbial colonisers...

Elizabeth - Well, the diversity of a microbiome is going to be related to the diversity of the ecosystem that it's part of. So a diverse ecosystem like a forest, for example, that has a bunch of different plant species and animal species and insect species inhabiting that forest, is also going to have a bunch of different types of microorganisms that are related to all of those visible organisms that we might be able to identify in that environment. And so in a built environment, we don't have as diverse of an ecosystem. We see more buildings than we see trees. And so because the kind of large scale ecosystem that we might be able to identify just looking around us is less diverse, then also the microorganisms are also less diverse. So the purpose of this work was kind of guided by this question about how can we make a building actually feel like a forest?

Chris - Phoebe, how are you going about this? What's the best way to tackle this, to work out what is there to start with, but then also work out how different interventions we can bring to bear will actually result in or translate into a change in the microbiome of the environment we inhabit?

Phoebe - So I think there's two parts to your question. One, how do we even look at microbiomes indoors? And that's a very particular question. And the second is how might we change the microbiome indoors? So how are we collecting and studying the microbiome indoors? We used swab collection. So that way we can say what kinds of DNA are on my desk? Where did that DNA come from? Could it be this microbe or that microbe? And what might those microbes be doing in the space? Could they be breaking down air pollutants, for example? And so the second part of your question of how do we change the microbiome within a space. In this paper, what we did was we designed these living machines that we often call green walls. And these have been around since the 1960s with NASA researchers. But the question is, if we pull air through plants and all of the microorganisms that live on plants, on their leaves and in their root system, can those machines improve indoor air quality? The microbiome question is, will the microorganisms in the root systems actually metabolise pollutants? And secondary to that, will the microorganisms in the root systems diversify the space in the environment that you put them in? So if it's on your desk, maybe it'll diversify your desk. And could that improve our own microbiome diversity and our own health long term?

Chris - And do they, Phoebe?

Phoebe - The short answer is they could. What we found was the three different growth media that we tried out in these living machines all have very diverse microbiomes.

So they probably could benefit our health long term if we could inoculate the space around us. And they all have very different metabolic profiles. So what our research shows is that the different growth media are probably going to be good at different things. And so that's really interesting moving forward, because if you know something about the space, maybe your office has a 3D printer in it and you really want to metabolise this particular set of compounds. Maybe there's a growth media that will support microorganisms that would be really good at metabolising that pollutant particularly.

Chris - Are there then two aspects to this in the sense that we could build things from the get go and do that with this in mind, making the ideal microbiome thrive there. But actually most of human endeavour has been building stuff hitherto. Therefore we are handed an enormous legacy. And it's got its microbial microbiomic problems. And this is presumably they're more a problem of retrofitting rather than de novo design.

Phoebe - Absolutely. Yeah. So when people think of the question, can you grow a building, which was what was posed by research directions, many might assume that this is what they mean is structural. And so the classic example of a structural grown architecture are the living bridges in Bangladesh, which are beautiful living architecture made of ficus trees. But of course, that takes quite a long time. And as you said, all of our buildings are already built right now. We are building new ones, but is there something we can do with what we already have? And so that's a big part of the question that we were asking is, could we grow beneficial plants and microbes in a way within indoor spaces that already exist that could change the air quality and the microbiome of our offices or living spaces that could improve our health long term? And the short answer is yes. And secondary to that is these living green walls, these living machines, many of them already exist as well. And so are there retrofits we could do to them that would make them work better over time as we gather new information about microbiomes and how they work?

Chris - How long then, and this is to both of you, and maybe we'll start with Elizabeth, before developers are submitting a planning application, the planners are saying, right, where is your impact assessment for the microbiome of the building you seek to construct? Are we there yet? Or is that coming?

Elizabeth - We're not there yet, but I think it's certainly coming. I'm really excited to be able to hopefully see that happen in my lifetime as a scientist. There's a couple of hurdles to implementing microbial metrics in building code. And namely, we don't really have a good predictive structure to understand what the resident microbiome would be of a building given how it's built. So given the materials that are being used, the ventilation system that's being implemented, but as a field, we're accumulating a lot of information to be able to build that kind of predictive model. So understanding, for example, for different types of building materials, what is the resident microbiome that would be able to settle on that building material and thrive there? And so we don't have quite yet like a Rhino plugin. Rhino is the software that architects use to model buildings and to model all sorts of other factors that are important for building structures. But I think that that's not too far away. And once we are able to do that kind of predictive modelling, then we can start to think about how these metrics would be incorporated into code.

Phoebe - On top of that, we also don't yet know how a particular microbiome might impact human health outcomes long-term. There are very few studies, although there are now studies. When I first started my PhD, there weren't any causal studies on this in humans. And now there are where we can change the microbiome of a place and then have measurable impacts to human health. So it's two things. One is how will the way we build our buildings impact the microbiome of that building in that place? And the second is how would the microbiome of that building in that place influence human health of the humans that are inhabiting those spaces? Those are two different questions and they're both being researched, but you need both of them to be able to then have policy to say you need to have these kinds of buildings in order to improve human health in cities.