Microbiome: The trillions of bacteria, viruses and fungi that call our bodies home represent a new frontier in health and medicine

In the words of science writer Robert T. Gonzalez, “When astronomers talk about the number of planets in the Milky Way Galaxy, they talk in terms of hundreds of billions. When microbiologists talk about the human microbiome — the bacteria, viruses and fungi living in and on our bodies – they talk in terms of hundreds of trillions.

To put that comparison into perspective:

  • One billion is a thousand millions.
  • One billion seconds is about 31.5 years.
  • One billion pennies stacked on top of each other would make a tower nearly 870 miles high.
  • One trillion is a million millions.
  • One trillion seconds is over 31,000 years.
  • One trillion pennies stacked on top of each other would make a tower about 870,000 miles high, the same distance traveled by going to the moon, back to earth and then to the moon again.

Through the National Institutes of Health Human Microbiome Project and other research, we are on the cusp of unlocking the mystery surrounding these trillions of microorganisms – collectively the microbiome – that share space with our bodies.

Microbes inhabit nearly every part of our body – on the skin, in the gut and up the nose. Sometimes they make us sick; more often, they work in harmony with our bodies and perform vital functions that keep us alive.

For example, in the gastrointestinal tract, microbes allow us to digest foods and absorb nutrients that otherwise would be lost. On our skin, bacteria feed on waxy secretions of skin cells, which they use to create a protective layer that bars harmful pathogens. It’s a delicate balance of good and bad, our own personal ecosystem.

In the Human Microbiome Project, 200 scientists at 80 institutions conducted intensive studies of 242 healthy U.S. volunteers. The screening process for the participants was rigorous, with participants being disqualified for something as seemingly minor as a dental cavity. That research is an important starting point for what could bring major changes in how we view and treat disease.

In a press release issued by the National Institutes of Health, James M. Anderson, M.D., Ph.D., director of the NIH Division of Program Coordination, Planning and Strategic Initiatives, summed it up by saying, “We have defined the boundaries of normal microbial variation in humans. We now have a very good idea of what is normal for a healthy Western population and are beginning to learn how changes in the microbiome correlate with physiology and disease.”

For nearly a century, doctors have waged war against bacteria through the use of antibiotics. The problem with antibiotics, however, is that they kill both good and bad bacteria. It’s like spraying weed killer in a garden. You eradicate weeds, but at what cost to the healthy plants you want to keep? Researchers are now seeking ways to introduce good bacteria in the fight against sickness, with positive results.

A good example is the use of fecal transplants to treat Clostridium difficile (C. difficile) infection, where stool from a healthy donor is delivered like a suppository to an infected patient. As its name implies, C. difficile is a stubborn bacterial infection caused when other flora in the gut have been wiped out through use of broad-spectrum antibiotics.

In a June 2013 interview for Medscape, Dr. Scott Peterson of the Infectious and Inflammatory Disease Center at Sanford-Burnham Medical Research Institute relayed the story of a woman who had a serious C. difficile infection and was close to death.

“Because she was in such a critical state, her clinician decided to try something radical, which was a fecal microbiome transplantation,” Dr. Peterson stated. “He took the fecal microbiome from her husband and implanted it into her colon. Remarkably, whereas antibiotic treatment completely failed in this particular patient, the microbiome transplantation allowed the woman to recover within days to a state of health.

“She was literally near death and within 48 hours was showing a remarkable improvement in her state, just as a result of this microbiome transplant.”

A growing number of doctors are using fecal transplants to treat C. difficile infection. In 2013, researchers at the University of Alberta reviewed 124 fecal transplants and concluded that the procedure is safe and effective, with 83 percent of patients experiencing immediate improvement as their internal ecosystems were restored. Research is underway to determine if the transplants are effective in treating other conditions, such as Crohn’s disease, irritable bowel syndrome and irritable bowel disease.

There is also interesting research on the link between gut microbes and obesity and diabetes. Researchers at the Academic Medical Center in Amsterdam are conducting a trial to see if fecal transplants can be an effective treatment for obesity. Among the 45 obese, male participants, some are getting transplants of their own stool, while others are getting transplants from lean donors. Those who received transplants from lean donors are metabolizing sugar differently than those who didn’t. So far, however, there is no evidence that the transplants are resulting in weight loss.

Other research indicates that alterations in the gut microbiome can influence behavioral responses, including learning, memory and stress response, and may have a connection to pro-inflammatory immune responses in the central nervous system that underlie diseases such as multiple sclerosis.

There is much yet to learn, but it appears that we are moving toward a time when we will approach some medical problems from a microbiome point of view.