Mary Roach
Author, "Grunt: The Curious Science of Humans at War"

The Secret Life of Bacteria

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On a day-to-day life in the colon is probably pretty mundane, says science writer Mary Roach.

Mary Roach

Mary Roach grew up in a small house in Etna, New Hampshire. She graduated from Wesleyan in 1981, and then moved out to San Francisco. She spent a few years working as a freelance copy editor before landing a half-time PR job at the SF Zoo. During that time she wrote freelance articles for the local newspaper's Sunday magazine.

Though she mostly focuses on writing books, she writes the occasional magazine piece. These have run in Outside, National Geographic, New Scientist, Wired, and The New York Times Magazine, as well as many others. A 1995 article of herse called "How to Win at Germ Warfare" was a National Magazine Award Finalist, and in 1996, her article on earthquake-proof bamboo houses took the Engineering Journalism Award in the general interest magazine category. Mary Roach also reviews books for The New York Times.

Her first book, Stiff, was an offshoot of a column she wrote for Her other books include Spook: Science Tackles the Afterlife, Bonk: The Curious Coupling of Science and Sex, Packing for Mars: The Curious Science of Life in the Void, and Grunt: The Curious Science of Humans at War.



Mary Roach: A day in the life of the bacteria in your gut.  They are on a different schedule from you because you’re eating and it’s taking a certain amount of time for the bacteria to make their way.  The bacteria are all in the large intestine which is the end of the line.  Well, the rectum is the end of the line.  But this is a place where your body’s kind of done with everything. You’ve absorbed – in the small intestine you’ve absorbed all the nutrients that you can that your body’s going to use.  And the stuff that they don’t want it’s the kind of stuff that you throw into the compost.  The large intestine – that’s the composter.  That’s where the bacteria live and they can use it.  And they’re like, “Oh, I’ll take that.”

So all your bacteria are down there and in your colon and they’re waiting for you to be done with what you’re gonna do with it.  And then it’s passed along so it’s a certain amount of, you know, it’s like five hours before you’re sort of – it’s making its way.  And coincidentally – that’s the peak in flatulence is about five hours after a meal when the bacteria are kind of doing their thing.  Because flatulence is gas produced by bacteria breaking down – it’s usually sugars of some kind with lentils and beans being the most famous contributors.

Anyway, so they are happily doing their thing.  So they’re on a lag from your schedule so whenever you’re eating then you sort of wait a while and then they’re eating.  And I don’t know exactly what else they do with their lives in there.  I don’t know how they pass the time in between.  I don’t know how much fighting is going on.  I think it seems to be like a lot of gang tribe warfare going on because, you know, when you hear about a fecal bacteria this is – if you were a gut bacteria and suddenly here comes this whole – it’s this, you know, population – giant population of foreigners.  You know, it’s like some crazy immigration situation where they’re duking it out and the strongest ones win.  So that’s a whole global warfare scene going on.

On a day-to-day life in the colon is probably pretty mundane.  It’s very centered around food, a little bit of, you know, reproduction.  Yeah, it’s a simple life I think.  Pleasant.  Probably pleasant.  The weather is great.  It’s very uniform.  It’s kind of like – kind of like the Bahamas in there.  It’s very – minus the tropical breezes I guess.  Oh no, a little bit of the breezes.

Directed / Produced by Jonathan Fowler and Elizabeth Rodd