So we are not 100% human,
and that’s a good thing.
Living in and on our bodies are trillions of microorganisms
or microbes for short –
(Laughter)
these include bacteria, viruses, yeast.
And these microscopic organisms collaborate;
they form ecosystems that are very much a part of who we are.
Until recently, the functions of these communities were largely unexplored,
but we’re learning that they are critical for our health
and for our well-being.
You see, traditionally, the study of microbes had been focused
on the role of pathogens,
those bad actors that can cause disease by acting alone.
About a decade ago now,
I joined a consortium of research scientists across the United States
in an effort to take the first census of microorganisms
that live in and on the different parts of our bodies.
The National Institutes of Health sponsored this Human Microbiome Project,
and that jump-started this field of research.
The time was right for this program.
Dramatic reduction in cost in DNA sequencing made it possible
for us to study the genes of the microbes that live in and on us.
And I’ll just get technical for a minute here:
the microbes, their genes and their other products,
together, that’s the human microbiome.
So when we set out on this new research,
some of us thought that there might be a core group of microorganisms
shared between all people.
We were wrong.
But we did learn that each person has a unique microbiome,
and there’s not just one way to be healthy.
However, there are commonalities among the microbial communities
at the different body sites:
so the mouth, the gut, the skin, and in women, the vagina.
That is particularly true when we look at what the microbes are doing,
when we look at their functions.
And so, the microbial communities that live in my mouth
are more similar to the microbial communities that live in your mouths
than to those that live on my forearm, for example.
So, microbiome science is relatively new.
It will take us many more years to fully understand
the role of these microbial communities.
And while we know that there’s not just one way to be healthy,
it’s now clear that imbalances in microbial communities
are associated with a number of different diseases, disorders,
and other adverse health outcomes.
So, for example, an imbalance in the gut microbiome,
that’s associated with inflammatory bowel disease;
an imbalance in the vaginal microbiome
is a risk factor for complications in pregnancy;
and an altered microbiome is also linked
with obesity and other immune-related diseases.
So we’re learning how these organisms impact our health.
In essence, the microbial communities that live on us
constitute an overlooked organ.
One that we hadn’t previously realized existed or acknowledged,
but one that is critical for many aspects of our health.
So this begs the question:
Can we cultivate a microbiome for health?
And I think the answer is yes
although we are just beginning to understand how we might do so.
So, one way we might do that is realize
that our lifestyle impacts our microbes too.
There are several studies that have shown that a change in diet
has a dramatic impact on the microbial communities that live in our gut.
Antibiotic treatment can also impact the microbiome.
So as a society we must address indiscriminate use of antibiotics.
Antibiotics can be good.
They can save lives, [treating illnesses] caused by bacteria that cause infections;
however, their mechanisms are not precise,
and they can also kill the beneficial organisms,
and strip the normal flora.
So it’s something we need to be careful of and use these only when needed.
In some extreme examples, antibiotic use can lead to proliferation
of an organism called Clostridium difficile in the gut.
Now, that’s a serious intestinal infection.
And when standard treatment fails, it’s actually been demonstrated
that a fecal microbiota transplant can be effective.
So, that is what you think it is.
This is not your standard organ transplant.
(Laughter)
I won’t go into the details of how this is conducted,
but stool from a healthy donor is collected,
and that’s used to repopulate the gut of the patient.
Bacterial species that have been suppressed or killed off are replaced,
and gut function is restored.
And so while these examples are very exciting –
and I think that one demonstration here with the fecal microbiome transplant
is one of those examples –
I think we must also exercise caution
and not begin to modulate our microbial communities
before we fully understand their functions
and the potential risks of doing so.
So, we’ve established that the microbiome is part of us,
and that we may even have some degree of control over it,
and I think that offers a very new perspective
on the age-old question of nature vs. nurture:
the relative importance of our genetic makeup or innate qualities
compared to our experiences in shaping who we are as individuals.
If we are able to cultivate a microbiome for health,
we may actually, in fact, be able to change our very nature.
So where does it all start?
Where do we get our microbes?
Comparisons of the human microbiome with that of other primates
suggest that our microbiome has coevolved with us.
We’re still learning
how our microbial communities and the genes and the functions
are passed from one generation down to the next,
and how we maintain our human microbial gene pool.
One of my research directions as part of the Vaginal Microbiome Consortium
at Virginia Commonwealth University
is focused on that question,
beginning with understanding the role of the microbiome
in reproductive health and in pregnancy.
So, we used to think that infants were completely sterile when they were born;
now there’s some debate within the scientific community
about whether infants may be exposed to the microbiome in utero
as part of normal development.
However, what is clear is that some infants are exposed
to microbial infection, and that can have adverse consequences.
So in some of these cases, the infection is spread through the bloodstream,
and it crosses over the placental barrier.
So some of you may have heard
that pregnant women are often advised not to eat soft cheeses,
yeah?
That’s to prevent risk of listeriosis,
which is caused by a bacterium that can lead to loss of pregnancy.
Pregnant woman who contract the Zika virus,
whether that’s through an infected mosquito or through a sexual partner,
can pass that virus on to their fetus,
and that can have devastating consequences on development
as we’re seeing an increasing number of infants born with microcephaly,
a birth defect where a baby’s head is smaller than expected.
However, the most common route of infection, of intrauterine infection,
is ascending infection from organisms that originate in the vagina.
So, in studies based here in Richmond, Virginia,
more than 5,000 women have contributed samples and data
to our ongoing microbiome projects.
That has made it possible for us to generate the largest data sets
on the vaginal microbiome in the world.
Through these studies, we’ve learned that the vaginal microbiome
of pregnant women is different from that of non-pregnant women;
and other groups have seen this as well.
Specifically, pregnant women tend to have vaginal flora dominated by Lactobacilli.
So, these Lactobacilli are related to organisms that are found in yogurt.
And we think that their role now is to keep out
other potentially pathogenic organisms from ascending and infecting the uterus,
which can contribute to preterm birth.
One in ten infants in the United States is born preterm.
And while many premature babies do just fine,
preterm birth is still the leading cause of infant death.
So one of the things that you may find surprising
is that many of these vaginal organisms haven’t been characterized at all.
So one of the things that we’re doing in my lab downtown
is studying the genomes of these organisms to better understand their functions.
We have established that the vaginal microbiome is important
for preventing ascending infection
and for promoting healthy pregnancy.
At birth, the vaginal microbiome also seems to play a very important role
in seeding the microbiome of the infant.
There are several studies now that have demonstrated
that C-section babies compared to vaginally-born babies
have different microbiome composition, at least in the early months of life.
Similarly, there have been studies that have looked at mode of feeding.
And so breast milk contains microbes
and prebiotics, which act as food for microbes.
And so breastfeeding can actually help to shape an infant’s gut microbiome.
Antibiotics, particularly repeated courses of antibiotics,
can impair the microbiome establishment in early life.
And, we’re still learning exactly what this means;
that’s not something that’s completely clear.
However, there have been some recent studies that suggest
that an impairment in early microbiome establishment
may be linked with some risks for diseases later in life,
such as obesity or asthma.
More studies are definitely needed in this field
to better understand what these long-term risks may be.
So, we know that moms matter,
and transmission of the microbiome from mother to child at birth
is something that’s very important
for keeping our microbial gene pool, if you will.
However, I’ve only told you part of the story.
Microbes are also passed between people,
and these aren’t just the ones that cause disease.
Children acquire microbes playing with other children.
People who live in a household, they share microbes.
There is even a study suggesting we may share some microbes with our pets.
I think that these interactions may have a very important role
for us maintaining our human microbial gene pool.
And once we recognize that our microbes are part of us,
I think we’ll realize
that we’re more interconnected than we ever would have imagined.
(Applause)
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