Excerpt from I Contain Multitudes by Ed Yong, plus links to reviews, author biography & more

10.
TOMORROW THE WORLD

The house I'm standing in is a Platonic vision of the all-American suburban idyll. Outside, there are white clapboards, a rocking chair on a porch, and kids riding around on bicycles. Inside, there's more space than Jack Gilbert and his wife Kat know what to do with. Like me, they're British, and are used to snugger spaces. They're also warm and good-humoured: Jack is a dervish of energy, while Kat is poised and grounded. One of their sons, Dylan, is watching cartoons. The other, Hayden, for reasons best known to him, is trying to punch me in the bum. I am protecting myself by backing up against the kitchen counter, and nursing a cup of tea. And as I do that, I'm also passively ejecting microbes all over the cup, the counter, and the rest of this beautifully furnished kitchen.

In fairness, so are the Gilberts. As we've seen, along with hyenas, elephants, and badgers, we humans release bacterial smells into the air around us. But we also release the bacteria themselves. All of us are constantly seeding the world with our microbes. Every time we touch an object, we leave a microbial imprint upon it. Every time we walk, talk, scratch, shuffle, or sneeze, we cast a personalised cloud of microbes into space. Every person aerosolises around 37 million bacteria per hour. This means that our microbiome isn't confined to our bodies. It perpetually reaches out into our environment. When I sat in Gilbert's car on the drive over here, I bled microbes all over his seat. Now that I'm reclining on his kitchen counter, I'm autographing it with my bacteria. I contain multitudes, yes, but only some of them; the rest, I extend into the world like a living aura.

To analyse these auras, the Gilberts recently swabbed their light switches, doorknobs, kitchen counters, bedroom floors, and their own hands, feet, and noses. They did this every day for six weeks. They also recruited and trained six other families, including singletons, couples, and families, to do the same. The results of this study – the Home Microbiome Project – showed that every home has a distinctive microbiome that largely comes from the people who live in it. Their hand bacteria coat the light switches and doorknobs. Their foot microbes cover the floors. Their skin bugs get on the kitchen surfaces. And all of this happens with astonishing speed. Three of the volunteers moved house over the course of the study and their new abodes quickly took on the microbial character of their old ones, even when, in one case, that old accommodation was a hotel room. Within 24 hours of moving into a new place we overwrite it with our own microbes, turning it into a reflection of ourselves. When people invite you to "make yourself at home", you and they really have no choice in the matter.

We also change the microbes of our housemates. Gilbert's team found that room-mates share more microbes than people who live apart, and couples are even more microbially similar. ("All that I am I give to you and all that I have I share with you," as the marriage vows go.) And if there's a dog around, these connections become super-charged. "Dogs bring in bacteria from the outside to the inside, and they increase the microbial traffic between people," says Gilbert. On the basis of his results, and on Susan Lynch's work showing that dog dust contains allergy-suppressing microbes, the Gilberts got a dog of their own. He's a ginger-and-white mix of golden retriever, collie, and Great Pyrenees, who answers to Captain Beau Diggley. "We saw the benefit in increasing the microbial diversity of the home, and we wanted to make sure that our kids had that capacity to train their immune systems," says Gilbert. "Hayden named him; where did the name come from, Hayden?" Hayden replies: "From my head."

Whether dog or human, all animals live in a world of microbes. And by moving through that world, we change the microbes in it. In travelling to Chicago to visit the Gilberts, I have left my skin microbes in their home, my hotel room, a few cafes, several taxis, and one aer- oplane seat. The good Captain Diggley is a fuzzy conduit that shuttles microbes from the soil and water of Naperville into the Gilbert residence. A Hawaiian bobtail squid, come the dawn, flushes its luminous Vibriofischeri partners into the surrounding water. Hyenas spray microbial graffiti onto stalks of grass. And all of us constantly welcome microbes onto and into our bodies, whether through inhalation or ingestion, touches or footfalls, injuries or bites. Our microbiomes have wide-reaching tendrils that root us in the wider world.

Excerpted from I Contain Multitudes by Ed Yong. Copyright © 2016 by Ed Yong. Excerpted by permission of Ecco. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.