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.