It’s real, and it’s magnificent.

by Jeffrey Perkel, Ph.D., technology editor 

Ladies, can we talk about the vaginal ecosystem for a moment?

First, an admission: I’m a guy. I could happily have lived my entire life without reading the phrase “vaginal ecosystem.” But I digress.

As it turns out, the vaginal ecosystem is a thing, and people study it. Why? Because it’s really important.

A growing body of research shows that the human body’s normal microbial complement – aka, its “microbiome” or ecosystem – is an integral part of what it means to be human. (One of my undergraduate microbiology professors, noting that there are, like, 10 bacterial cells for every human cell in a normal human adult, used to say he was a “microbial bus.” But, again, I digress.) The human microbiome helps protect us from infection, enables us to break down and absorb nutrients, tweaks metabolism, and so on. Probiotics? That’s just bacteria. (PS: That’s something you might want to think about the next time you stock up on antimicrobial soaps and creams.) Recognizing the importance of the symbiosis between human and microbe, the US National Institutes of Health have allocated some $140 million to fund the Human Microbiome Project, a preliminary effort to catalog our microbial fauna.

In the vagina, bacteria are important, too. For one thing, the class of bacteria called lactobacilli produce the lactic acid that makes the vagina acidic and thus, relatively inhospitable to other microbial baddies. It is in the vagina that baby has a first encounter with bacteria. The developing fetus’ immediate environment is sterile. But during birth, passage through the birth canal exposes the child to bacteria, as do all subsequent activities – you know, breathing, breastfeeding, crawling on the floor…

Research suggests these microbial communities may also play a significant role in preterm birth, and on February 11, the US National Institute of Nursing Research (NINR), part of the National Institutes of Health, announced it was allocating some $2 million to explore that link. (Here’s a news article on the announcement.)

The request for applications, entitled “The Influence of the Microbiome on Preterm Labor and Delivery,” explains, “Although there are multiple contributors, evidence suggests that bacterial colonization of the normally sterile intra-uterine environment may be responsible for as many as 40% of preterm births.” Bacterial vaginosis, for instance, which is basically a shift in the vaginal microbiome, “affects approximately 15% of women of reproductive age and is a known risk factor for preterm labor and delivery in addition to late miscarriages.”

Of course, preterm labor is a serious public health issue. “Preterm birth … is the leading cause of neonatal mortality worldwide,” the funding announcement says. “Preterm infants are at increased risk of life-long disability, poor health, and early death compared with infants born later in pregnancy.” Nearly one in eight children were born prematurely in the US in 2009 (12.18%). Beyond the emotional toll on families, preterm birth also imposes a serious financial cost. “A report by the Institute of Medicine estimated that the annual societal economic burden associated with preterm birth in the U.S. was at least $26 billion in 2005, or approximately $51,600 per infant born preterm, not including the cost of medical care beyond early childhood or caretaker costs.”

Clearly, then, mapping the vaginal ecosystem is worth doing, as is probing how changes in that ecosystem impact pregancy and genital health. (Applications are due by 5:00 PM local time May 9, if you’re interested.) The funding announcement offers a few suggestions for possible study topics, including analysis of the “types, location, and influence of bacteria found in women who experience preterm labor and delivery;” “biomarkers that reflect changes in the woman’s microbiome and can be used as indicators of risk for preterm labor and delivery;” and “interventions that shift the woman’s microbiome toward more protective states in order to reduce the risk for preterm labor and delivery.”

But just how does one go about mapping the vaginal ecosystem anyway? In a word, metagenomics. In the research lab, scientists mostly study domesticated microbes like E. coli, which are nice enough to grow on agar plates. But the vast majority of bacteria in the world, including most of the human microbiome, don’t do that. Scientists have no idea how to make them grow in the lab, and thus, how to manipulate their behavior. In the past, this presented a serious problem, because it’s hard to study something you can’t grow.

Enter metagenomics, also called “community genomics.” Though there are several approaches to metagenomics, all have one thing in common: They use DNA sequencing techniques to do what laboratory culture plates cannot — tease apart the countless different microbes in a raw bacterial sample. Basically, instead of culturing organisms to see what they do, metagenomics looks for genetic signatures to break the sample down into its component parts. The result is a kind of microbial census of the sample: who, what, and how many. Such information is vital because it’s impossible to measure the microbiome’s impact, and how that changes as the population changes, without first knowing what a normal microbiome looks like and what it does.

Researchers have studied the metagenomics of such environments as an ”acid mine drainage system,” the world’s oceans, and the human gut. In June 2012, researchers funded by the Human Microbiome Project published a study that for the first time took such a census of the microbiome of the human vagina and measured how it changes during pregnancy.

The team collected samples from three locations within the vagina of 24 pregnant women at different times during pregnancy, as well as from 60 non-pregnant women. They then sequenced a specific gene (the 16S ribosomal RNA gene) from all the bacteria in each sample and used those data to take the roll, so to speak, of the microbes they found. The data indicated that (big surprise) a woman’s vaginal microbiome changes as pregnancy progresses and differs from that of non-pregnant women. Specifically, both the number and kinds of bacteria present seem to decrease over time during pregnancy.

According to a press release announcing those findings, “the vaginal microbiome undergoes a dramatic shift in bacterial species in preparation for birth, principally characterized by decreased species diversity.” It goes on to say, “A newborn is a bacterial sponge” – bacterial sponge?! – “as it populates its own microbiome after leaving the sterile womb; passage through the birth canal gives the baby its first dose of microbes, so it may not be surprising that the vaginal microbiome evolved to make it a healthy passage.”

Now, thanks to the Human Microbiome Project and, yes, metagenomic analyses of the vaginal ecosystem, researchers are finally beginning to get a handle on how that evolution takes place, and its impact on human health. And that’s no joke.