E pluribus me: I harbor hidden hordes
I thought I was a rugged individualist. Turns out, I’m not even an individual. And any ruggedness I may possess doesn’t arise from me.
While browsing around on science news websites a few days ago, I discovered that I harbor hidden hordes– a commonwealth of creatures that can determine my mood and thereby influence my behavior, and that have the power to support or destroy my health.
And it’s not just me. Look inward. You are not who you think you are. Seriously. Look down at the skin bag you call "me." Ninety percent of the cells in your body are alien; they are not even human. Ninety percent!
They are your microbes: bacteria, viruses, and fungi. But they’re mostly bacteria. Now, it’s true that a microbial cell is a lot smaller than a human cell. Still, the collection of not-you cells in your body amounts to something between two and five pounds of what you think of as you. These are teeny-tiny immigrants that have hitchhiked their way into your body.
You may douse yourself with antibacterial soap and swallow antibiotics, but you’ll never succeed in deporting those alien multitudes.
I don’t know about you, but this freaks me out. What I think of as me is actually a collection of organisms. I’m a community on two legs.
And, it turns out, there’s a lot of communication and cooperation going on among the various factions.
Thanks to its amazingly extensive surface area, the human gut is an especially robust population center for these microbes.
(In case you’re wondering just how much real estate these creatures have to spread out in, consider that your gut contains about 478 square yards of surface area. Shocking, isn’t it? Imagine a sidewalk that’s a yard wide, and extends for over a quarter mile. The lining of your labyrinthine gut could cover that whole sidewalk.)
The activity of your gut flora has a huge effect on your health, both physical and mental.
Among other things, these little beasts regulate your immune system, the digestion and absorption of food and medicine, and even produce ninety percent of the neurotransmitter serotonin. Serotonin is the stuff that regulates your mood, appetite, sleep, and memory.
And, when all is going well, the beneficial bugs crowd out the evil bugs that could kill you.
They are not simply sponging off you, they are also dependent upon each other.
One species may use the food you’re sending down, and break it up into waste products– metabolites that are then consumed by some other kind of creature that can’t consume your food, but is delighted to gobble up those metabolites.
Everything is humming along harmoniously when along comes an antibiotic, and maybe, while it’s killing the strep or whatever, it also kills a strain of bacteria that was happily consuming those waste products from the food-consuming bacteria.
That’s when you can get a buildup of metabolites that results in disease-causing inflammation or some other chain reaction that scientists are only beginning to understand.
Behold the new frontier in biology: the Human Microbiome Project. This is an ongoing, five-year project in which 200 scientists at 80 institutions are sequencing the genetic material of bacteria harvested from nearly 250 people.
In a paper published this past June in Nature, we learn that there are at least a thousand strains of bacteria in the gut of a single human being. And it appears that each of us supports a unique collection of bacteria.
From the moment of birth, microorganisms are slipping across our bodily borders with every breath and swallow we take. The food and drink we consume, along with any medications, encourage certain microbes to flourish while inhibiting others.
We acquire our first dose of microbes as we travel through the birth canal. Mothers also pass microbes to their babies through breast milk. Babies who are born via caesarian section or who are fed formula rather than breast milk will acquire different kinds of bacteria.
Whether or not these varying strains of bacteria account for variations in the future health of these babies is currently unknown.
But Dr. Natasha Campbell-McBride, the author of Gut and Psychology Syndrome, asserts that the wrong sort of gut flora can produce a variety of maladies, including autism, depression, and Crohn’s Disease. She claims to have successfully treated hundreds of patients by helping them repopulate their bodies with beneficial microbes.
As if it weren’t disturbing enough to learn that ninety percent of my body’s cells are not human, I also came across a TED talk online that’s giving me nightmares.
In this presentation, “How Bacteria ‘Talk,’” Princeton molecular biologist Bonnie Bassler reveals that, using a mechanism called quorum sensing, bacteria communicate with one another and "vote" on what their next move will be.
As an example, she tells of a Hawaiian squid that emerges from its hiding place in the sand after the sun goes down, in order to swim and hunt. The squid has two translucent pockets on the underside of its body that are filled with hitchhiking, bioluminescent bacteria.
Those bacteria can sense exactly how much moonlight is shining on the top of the squid’s body, and cast the same amount of light below the body, in order to cancel out any shadow cast by the squid. In this way, predators don’t see the squid, and it can hunt safely in the moonlight. The squid survives, and the bacteria survive. Win win.
Bassler says that the bacteria accomplish this synchrony by talking with “chemical words,” i.e., molecules that they produce. This is quorum sensing, and it’s how bacteria roll. Not just in Hawaiian squid, but in you and me.
Those chemical molecules are what she calls “votes.” The bacteria vote, the votes get counted somehow, and this leads to collective activity. And there are hundreds of known behaviors that they “vote” on and carry out.
One of the group activities they vote on is attacking your tissues and causing disease.
They wait. They grow. They count themselves. And when they sense a quorum, BAM, they strike, and you could be flat on your back with God-knows-what kind of malady.
But wait, it gets worse. They’re multilingual: they have molecules to communicate with other species of bacteria and they assign tasks. What grand maneuver might they be planning? You have no say in any of this.
So, do you suppose my bacteria can talk to your bacteria? Maybe that’s what attraction is all about: one bag of bacteria voting for proximity to another bag of bacteria, for some mutually beneficial purpose. Well, mutually beneficial for the bacteria.
(Are you thinking: "Hmm– that explains a lot?" Because that’s what I’m thinking.)
Walt Whitman had it right: “I am large, I contain multitudes.” Apparently, those inner immigrant multitudes have something in common with humans. They’ve learned how to harness their communal power: They vote.
Free Union resident Janis Jaquith has a visceral appreciation for the world around her.Read more on: bacteria