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    Bacterial You: The Environment Within

    Field Notices


    Luther College Chips
    September 18, 2008

    You’re outnumbered!

    The body cells with your DNA in their nuclei are outnumbered, that is, by the bacteria that make your body their home.

    Your cells are outnumbered, in fact, by a factor of ten or even twenty to one!

    Before you run for the Purell, let me warn you that you would have to drink it to make a significant dent in these numbers. The bacterial metropolis of “you” is deep inside your gut.

    And before you think seriously about executing the final solution on those inner bacteria of yours, also consider this; those tiny organisms are mostly there because you need them as much as they need you.

    I first learned about the bacterial number balance from reading Lynn Margulis, a biologist who has made it her life work to puzzle out the way single-celled organisms without a nucleus manage to make a living in a harsh, competitive world where cooperation is often an advantage.

    Margulis’ answer is called “endosymbiotic theory.” The idea, now widely accepted, is that very simple organisms, like bacteria, evolved to live cooperatively with other organisms, often inside one another.

    Hence the bacteria in your digestive system. They love the warm, moist, protected little world you make for them, complete with the steady balanced diet you send their way.

    But endosymbiotic theory takes this all a step further. It says that the multi-celled complex organism that is you also evolved to rely on the single-celled organisms that early on inhabited your ancestors.

    In breaking down food so they can digest it, those bacteria made the mac and cheese in your last orange meal in the caf more fully useable, more completely nutritious, for you as well.

    According to retired Luther biology professor Roger Knutson, bacteria are “ubiquitous,” outside you as well as inside you. The blend of bacteria living on your skin is unique: a kind of signature. According to Knudson it gives you the smell you and others recognize as your own.

    Those idiosyncratic bacteria of yours also eat up the material on your skin that might attract less friendly organisms—including the dreaded species that have earned bacteria the nickname “germs.”

    In his book Furtive Fauna, Knutson says of your more typical bacterial residents: “Do what you can to keep the ones you have and possibly even cheer them on a bit. You and they have been living together successfully for decades.”

    Our working relationship with resident aliens goes back further than decades. Margulis points to the mitochondria that power our cells to show how deep endosymbiosis goes.

    Your mitochondria have DNA more like bacteria than like your own. They are resident aliens that, in trade for a comfy home in each of your cells, provide the chemical energy every ounce of you needs. These organelles are not only a fixture of your cellular makeup; they are an absolutely essential element in each of those cells. Neither cell nor mitochondrion could survive without the other.

    I take a lesson from the way we are put together. Our life, in its basic fabric, is made up of working relationships. Plants, animals, fungi, protists, bacteria, and archaea have each evolved as part of a complexly woven web of existence that makes each of us a regular walking biome of species.

    I take a cue for my attitude towards the rich diversity of that web from Knutson’s words. Keep it going. Cheer it on.

    So as for being beaten in the internal numbers race, I say, “three cheers” for the trillions of those winning little bacteria humming away inside me.



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