Sunday, April 29, 2012

Who's the host?

With Passover behind us, I can better reflect on a thought I had during the seder.  One of the rituals that I have always found fascinating is the hand washing (u’rchatz) before eating the karpas. While the ritual is meant to wash away “impurities,” I view this ancient custom as a great precedent for modern hygienic practices. Maybe we Jews were ahead of the curve! In fact, this practice may have singlehandedly helped the Jews suffer fewer deaths than other ethnic groups when the Bubonic Plague ravaged Europe in 14th century. Five points for humanity, no points for germs, right?  Well, not so fast.

You don’t really think that the occasional Purell gets rid of 99.99% of the germs in your body, do you? It may sanitize your hands - which frequently contact transient germs - but what most mysophobes fail to accept is that our bodies serve as choice dwellings for microbes.  Thirty-seven degrees? Check. Nutrients? Check. We humans are ideal incubators, aren’t we?! You see, while a human body comprises about a trillion cells, it also happily hosts TEN trillion bacteria. Those germs account for 2 - 5 pounds of our weight. (I knew it wasn't just the Passover cookies!) An average person has 30,000 human genes and 3,000,000 bacterial genes, which, if you think about it hard enough, means that each one of us is only 10% human, and 90% germs. The gut flora alone includes a few fungi, a handful of protists, and 500 different species of bacteria that comprise the majority population of our microbiota. In essence, our intestine is like a hotel with very different guests!
How do we co-exist with these microbes? Before you go rushing to the bathtub to scrub your skin raw, you must know that these bacteria help keep us alive.  Bacteria get a lot of bad press for all the disease they cause, but they also serve to protect our skin from the environment, assist in food digestion, produce vitamins, and train our immune systems. We really do have an amazing interaction with these critters. And I hate to break it to you, but we’re pretty much at their mercy. Fortunately, what works for us is the intricate balance between tolerance and immunological response.
Mimicking our society, an individual bacterium can’t cause much impact. However, when they form a critical mass, interesting things begin to happen. Kind of like a minyan. What's more? They're miniature yentas! Indeed, I think it's time to stop thinking of these critters as asocial individuals, when in fact, they love to talk.
Speaking of talks, one of the great talks that stuck to me in my research years was a presentation on quorum sensing by Dr. Bonnie Bassler from Princeton. It made me feel big and vulnerable as she went on to explain how bacteria talk.  With "quorum sensing," each bacterium releases a signaling molecule to be counted in the roll call, letting the group know that they can proceed with undertaking an activity. As in society, each voice counts. So an individual pathogen may not be harmful, but it can turn deadly with peer pressure.  When bacteria sense that they are in a large enough group – a quorum – they can mobilize to attack the host, triggering the onset of disease. 
If you find this germ-talk fascinating, then prepare thyself: bacteria are bilingual! One type of compound lets them communicate with their species while another let them have chat with other species. After all, in order to work together in communities, they need to get to know their neighbors too. In keeping with a societal model, they fight with each other, eavesdrop, and cheat so that one guy's molecule doesn't get delivered to his pals. It may not be a pretty picture, but then again, it is a great way for checks and balances.
Can you imagine if all the bacteria spoke only one language? I think even the five lions of Voltron uniting wouldn't stand a chance. It also reminds me of the Tower of Babel story in Genesis.  According to midrash, the hubristic humans built the tower as an act of defiance to G-d. But as easily as the tower was built (at least in my mind), the humans flitted away, confused, when G-d confounded their speech. To me, this story emphasizes not only the importance of diverse languages, but also of diverse ideas. However, if there's anything our little bacterial guests teach us, it's that one voice can make a difference in putting the community to action. But the main take home message for me is this: some musings on religious rituals are best left unshared over the holiday meal.

*Published in Etz Hayim's Chronicles, May 2012 issue

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