August 4, 2012

One Hundred Trillion

 Hand sanitizers are everywhere now. "Antimicrobial" is the most desired adjective on a label, right up there with "organic." By some estimates, there are over 700 antimicrobial infused products, found in everything from dishwashing liquid and sponges to socks and underwear. Damn, I feel safer already. True, some of the major active ingredients bear a disturbing resemblance to the active ingredient in Agent Orange, but hey, what's that compared to being germ-free?

Germ-free. The Holy Grail of modern living. Japanese men and women walking around with breathing masks will soon be supplanted in their race to the top of the risk-free world by anxious mothers wiping the grocery cart handle with a disposable antimicrobial wipe thoughtfully provided by the grocery store at the entryway.

Now, the first rule of any military strategy is to know the enemy. Just how many of these little suckers are we talking about? One hundred trillion. You heard me. That's the number of bacteria, fungi and other microbe's cells in a typical human body. That would be each and every one of us. They outnumber human cells by 10 to 1. Only ten percent of us is ... well, us. That otherness adds up to a few pounds of our body weight. And that's nothing compared to the genetic match-ups. The human genome contains about 23,000 genes. Stack that up against the 8 million non-human genes that comprise the totality of the genetic mass of microbes. Makes you wonder who's in charge. Or as Pogo once famously observed, "We have met the enemy, and it is us."

This otherness we have inside us is collectively known as the human microbiome. It exists mostly in our mouth, our nose, our skin, our gut, and our uro-genital tracts. The exact composition of each individual's microbiome is unique, more unique than DNA. (Identical twins may have identical DNA, but their microbiomes will be very different.)

So what exactly are they doing with us ... or to us? Like everything else ... some good, some bad ... but the good way outweighs the bad. Most of them live in our gut, and we all know what happens if they act up. That has given our collective microbiomes a lot of bad press, leading in no small measure to the increasing popularity of sanitizing products.

Without getting in too far over my head on this, the take-away message I get is that we humans co-evolved with our microorganisms and presently exist in a symbiotic--mutually beneficial--relationship with them. We wouldn't be who and what we are without them. The more we learn about them, the deeper we see our connectedness. Lactobacillus johnsonii produces enzymes that digest milk. It normally lives in our gut, but it is also found in the birth canals of pregnant women, leading to speculation that infants are coated with it during birth. This may prepare the infant to digest breast milk. During breastfeeding, babies are exposed to as many as 600 species of bacteria and assorted sugars that jump start the beneficial bacteria needed for proper digestion.

Taking the idea of co-evolution a step further, some scientists have come up with something called the hologenome theory of evolution. Earlier I mentioned that the collective genome of the microorganisms far outnumbers the human genome. If you take the human genome and combine it with the genomes of the symbiotic microorganisms, you get a hologenome. This hologenome can react more rapidly to changing environmental circumstances than the human genome can on its own, giving the total organism much greater adaptive capability.

Does all this mean that we should stop using hand sanitizers? I have no clue, although there are valid concerns that the widespread use of antimicrobials has led to the increased presence of highly resistant strains of bacteria; less resistant forms are wiped out, clearing the field for those that aren't affected. And the greatest usage of these antimicrobial agents is by the food industry, where fears have long been expressed about the dangers of increasing drug-resistant microorganisms. The World Health Organization (WHO) considers antimicrobials to be "among the most misused of all medicines" and cautions against "the indisciminate use of antimicrobials in patients unlikely to derive any benefit."

My own sense is that we probably are spending too much money on products that have only limited effectiveness, hardly a novel occurrence in our consumer culture. The surge in antimicrobial products is driven by our natural desire to shield ourselves and our loved ones from risk of any kind. But that isn't how it always was.

Growing up in the 50s, risk was more tolerated than it is today. As kids, we were allowed to explore the world around us. If that sometimes led to accidents or injuries or minor infections ... well, live and learn, as they used to say. What time couldn't heal, penicillin could. Not so much today. All of which makes me wonder how kids brought up in today's hyper-cocooned environment--where they are always in touch via Twitter or Facebook or texting--would deal with truly hard times. Let's hope they never have to find out.

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