Here’s a brainteaser: what do a Portuguese Man O’ War, a coral head, and you
have in common? …Turns out, you’re all superorganisms. Sounds pretty cool, right?
A superorganism is basically an organism made up of many smaller organisms. Think of it
like a city; all the people who live and work there have their own lives, but they rely
on each other for things like food, clothing, and other services. Together, they bring the
city to life. Now, let’s take a look at the Man O’ War. If we look closely, we see
tiny units called zooids. Just like the members of a city, these are each individual animals,
but they are specialized to work together as one large organism. The coral head is even
more complex. Scores of algae and bacteria live inside it. They provide the coral with
food through photosynthesis, along with essential nutrients that the coral could not obtain
on its own. And you are no different. Microbes living in your body play an essential role
in keeping you alive and well. Lactobacillus, Firmicutes, Candida, and HERV.
These are just a few of the bacteria, fungi, and viruses that call the human body their
home. We call this rich ecosystem of non-human cells microbiome. We get our initial
stock of microbes from our mothers in the birth canal, and the population grows over
time. There are so many microbes, in fact, that their cells outnumber human cells ten
to one. In an adult human, the microbiome may actually weigh up to five whole pounds.
Most important, however, is the staggering amount of genetic material contained within it. Our microbial genes,
outnumber our human genes by a factor of about 200. That means that over 99% of our biochemical functions—everything
that we break down, produce, convert, and recycle—occur by courtesy of our single-celled
friends. And that makes them really important. So important
that human breastmilk has co-evolved to nourish not only a baby’s developing body, but also
its microbes. Their unique molecular toolkits make enzymes, vitamins and compounds that fight
infection and disease. So it should come as no surprise that when the diversity of our
microbial ecosystem drops, we get sick.
We still have much to learn, but it’s clear now that our microbiome plays a fundamental role in human
health and disease. The Human Microbiome Project launched in 2007
to characterize the microbiome and assess its role in health and disease. Microbial communities
are harvested from their natural environments, like the nose, mouth, skin, or gut, and their
DNA is isolated and sequenced. This information can tell us what species are present, and
what functions they are performing. In the era of precision medicine, we can use this data
to formulate personalized therapies. For example, individuals with kidney stones may be given a probiotic of
Oxalobacter formigines, a gut bacterium that degrades mineral deposits.
Prebiotics, or compounds that selectively stimulate the growth of good microbes, may also become more widely used. Perhaps most exciting,
however, is the potential of endowing our microbial community with brand-new functions.
Using synthetic biology, scientists have already engineered viruses that degrade bacterial
blockades, E.coli that seek and destroy tumors, and microbes that silence the cholera toxin.
Introducing these functions into our own microbial ecosystems will present many challenges, but
the rewards are enticing. As we learn more about the human microbiome,
we will likely come to a greater appreciation of its role in our
health, development, and behavior. Our so-called “second genome” will become
a major factor in clinical medicine and biomedical research. So learn
to love your marvelous microbes. Take care of them, and they’ll
take care of you.