Some people think of their bodies as a temple, others as a wonderland. Me, I think of mine as a petri dish. I am a long-term experiment on microbial community dynamics – with plenty of drama! Love stories, betrayal, war and peace. You name it; it’s going on in here somewhere.
We all think we’re special – and now science is corroborating that idea. My microbes are just as unique as I am. The bacterial community in my nasopharynx is vastly different from that of my gut, which is vastly different from that of my skin, which is vastly different from that of my mouth… and so on1. Furthermore, each of these microbial communities (called ‘microbiota’) is highly dissimilar to that of the person next to me. Although the current evidence suggests that human microbiota fall into three major types (termed ‘enterotypes’)2, the variation in exact microbial abundance and diversity among individuals is staggering; even identical twins harbor significantly different gut microbes than one another3!
I don’t always get along well with my microbiota. There are the odd days, like yesterday, where my microbial populations wreak havoc on my digestive system. Then others, where they cause me to break out in spots4. And still others, where they lend a helpful hand to intruding pathogens by conferring their acquired antibiotic resistances1. But most of the time, I am very happy with my pet microbes. They are constantly working away at alleviating my allergies5, protecting me from infection6, stabilizing my mood7, helping me repel or attract others, including pesky mosquitoes8, and allowing me to make the most of what I eat9 (even playing a key role in weight gain10).
I have never been particularly germ-conscious. As an evolutionary biologist, I know that a little immigration is good for the
body population, fueling the fire of natural selection with a bit more additive genetic variation. So I don’t clean my counters with bleach, and I do let my dog share my bed. There are occasional consequences (I refer again to my illness yesterday), but for the most part I have a fairly healthy immune system. My philosophy is thanks in part to George Carlin’s sermon (http://www.youtube.com/watch?v=-Y-yH_Qyipc), and thanks in part to my studies. But it is also common sense – we are the result of millions of years of evolution. If we were hypersensitive to every bacterium that landed on our kitchen counters, natural selection would have taken us out a long time ago.
I may be weird, but the fact that I am more microbe than me – 10 times more! – is my motivation for taking good care of myself. A sense of responsibility for the health and welfare of all of those microbial cells that are working with me every day to keep us going. They are why I eat right, exercise (occasionally), drink in moderation, and get enough sleep.
So the next time you are scrubbing away at your sinks or dosing yourself with anti-microbials, take a moment to think about all of those commensal bacteria working away to make you… well, you. (and, on that note, keep them to yourself!)
Some food for thought:
1Ecology drives gene exchange within human microbiota: http://www.nature.com/nature/journal/v480/n7376/full/nature10571.html
Smillie CS, Smith MB, Friedman J, Cordero OX, David LA, & Alm EJ (2011). Ecology drives a global network of gene exchange connecting the human microbiome. Nature, 480 (7376), 241-4 PMID: 22037308
2Our microbiota fall into three main categories (with lots of variation!): http://www.nature.com/nature/journal/v473/n7346/full/nature09944.html
3Microbiota of identical twins: http://www.pnas.org/content/107/16/7503.short
5A potential link between microbiome diversity and allergies: http://www.pnas.org/content/early/2012/05/01/1205624109.abstract
6It seems the microbes on our skin help warn us about pathogen attack: http://www.nature.com/news/the-skin-s-secret-surveillance-system-1.11075
7Mind-altering microorganisms: http://www.nature.com/nrn/journal/v13/n10/abs/nrn3346.html
8Human skin microbiota affects attractiveness to malaria mosquitoes: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0028991
9A nice review on the role of our gut microbes and their recent evolution: http://www.annualreviews.org/doi/pdf/10.1146/annurev-micro-090110-102830
10A core gut microbiome in obese and lean twins: http://www.nature.com/nature/journal/v457/n7228/abs/nature07540.html
And a great piece about our microbiome’s in the Economist: http://www.economist.com/node/21560523