Our unique ‘microbial aura’ travels with us wherever we go

Every individual has a unique “microbial aura” that we spread constantly wherever we go, according to research published recently in the journal Science.

"Your bacterial community [is] a composite of all of the decisions and interactions you’ve ever made in your life. Unless you lived exactly the same life as me, you would not have the same microbiome. You are, in essence, microbially unique," explains Jack Gilbert, one of the authors of the new paper and director of the Home Microbiome Study at the Argonne National Laboratory.

If you were to move in to a new home, for example, the collection of bacteria that live on and around the surfaces of the home would become so transformed by your personal microbiome that it could be indentified as belonging to you based on just a sample of its bacteria.

This unique microbial signature could make the microbiome the next crime-solving technology, Gilbert says. As opposed to fingerprints, which provide what Gilbert calls "presence/absence" information — either the person was there or they weren’t — the microbiome is a living thing.

“Once you deposit it onto a surface, like a door handle or a light switch,” Gilbert says, “it will start to change — and it changes subtly over time. So you could say not just that [a] person was there, but you may be able to identify when they were last there.” This information might even help to identify who was the last person to interact with a dead body at a crime scene, and how long ago.

Your body is a "microbial ecosystem,” but it’s made up of other small ecosystems. “Your gut microbiome is quite different from the microbiome that is in your hand; your hand microbiome is quite different from the microbiome that lives in your nose or on your face; your mouth is different from your elbow, etc.,” Gilbert explains. “I could tell if your feet were interacting with the floor or your hands were interacting with the door knobs,” he continues. “It’s really helping us to identify the transmission routes by which bacteria get into our body.”

In fact, Gilbert says, just by physically interacting with another person you will share a certain proportion of each other’s microbiome — maybe five or 10 percent. “You’ll be more microbiologically similar to your partner than you will to anybody else that you come into contact with. But even if you just live in the same space as that person … just by sharing the same air and the same surfaces, you’re going to become slightly more microbiologically similar,” Gilbert says.

The more scientists learn about the microbiome, the more they understand how influential it is. “We like to think of the world as being compartmentalized, but everything is pretty much in a continuum. [Almost] all of life exists interconnected by the bacteria and the viruses that we constantly shed and pick up,” Gilbert says.

Gilbert’s most ambitious project is to build a microbial map of Chicago. In 2013, he started mapping the microbial signatures in the waterways, parks, buildings — and now even in the air. He is trying to determine how the microbial signature changes over time.

“The urban environment is our most rapidly growing ecosystem on the planet,” he says. “While all other ecosystems around the world might be wiped out by human activity, the urban ecosystem is growing very rapidly, and we have next to no idea about the bacterial communities that exist in it. That’s a knowledge gap we’re trying to fill.”

Prior to the last couple of hundred years, human beings lived most of their lives outdoors. Then we moved into a primarily indoor environment. Gilbert and others are trying to figure out how the homes and the bacteria that live in our homes, might be shaping our childrens’ microbiome.

“If we can manipulate it, maybe we can make our children healthier,” he says. “We could eradicate all kinds of diseases in that way. Maybe have an influence on autism, on schizophrenia, on depression and anxiety, as well as myriad other physiological conditions. We’re really on the cusp of trying to understand how those interactions work. It’s a very exciting time.”

This story is based on an interview that aired on PRI's Science Friday with Ira Flatow