How microbes define, shape —
and might even heal us
As both a scientist and a human being, I am continually awestruck by discoveries about the power of the microbiome to define and shape us. But what excites me most is the very real prospect that, as we come to better understand and even influence the microbiome, it could have the power to heal us.We’re already starting to link our microbes to a wide spectrum of specific diseases, from the obvious — like infectious diseases and inflammatory bowel disease — to surprising ones such as multiple sclerosis, autism, and depression.
It’s worth noting that just because we know a microbe is involved in a specific disease, it doesn’t mean the answer — or the cure — is to eliminate that microbe. In fact, doing so might cause irreversible damage. It may turn out that targeting diet or inhibiting an enzyme (that’s a protein that speeds up a particular chemical reaction) might be more effective than attacking the microbes directly. And yet the reason there is so much excitement about the microbiome is the prospect of discovering entirely new mechanisms to treat conditions that have resisted existing therapies.
Susceptibility to essentially every kind of infection hinges greatly on genetics.But first, let’s ask: How is it we know that certain microbes are associated with particular diseases?
The easiest cases to make are those where one particular microbe has a significant impact on health, which essentially describes the last 150 years of infectious disease research. If you get exposed to a microbe such as Salmonella, or Giardia, or Mycobacterium tuberculosis (the bacterium that causes tuberculosis), you expect to get sick. And then, if you treat it with the right antibiotic (or other drug), you expect to get better.
But wait: Do you always get sick just because you’re exposed?
Actually, our risk of sickness depends on a combination of exposure, genetic makeup, and other factors. Some people are born with resistance to certain diseases. You’ve probably heard of Typhoid Mary, a New York cook in the early twentieth century who carried the bacteria that causes the disease typhoid fever. She infected family after family with her excellent cooking that was laced with a dose of her not-so-excellent microbes. But Mary was never sick. She was naturally immune to the fever she carried inside her. Where does such resistance come from? Well, it’s these questions that make mouse studies popular with researchers: besides the fact that we can more ethically give a mouse an infection, we can also manipulate the mouse’s genome. From these studies, we’ve learned that susceptibility to essentially every kind of infection hinges greatly on genetics. And mouse versions of Typhoid Mary are easy to create in the lab — not just for typhoid fever but also for a whole range of other infections. It’s proof that our genes influence which microbes make each of us sick.
We’re beginning to realize that there may be many more diseases where we’re all exposed to the same microbe, but it’s dangerous only to some of us. We still need more research to explain why.
But in the meantime, what follows is a roundup of the key diseases in which we now suspect that microbes may play a part.
http://ideas.ted.com/how-microbes-define-shape-and-might-even-heal-us/
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