Microbes R Us

14 06 2012

Well, they’ve finally done it. Researchers have mapped the microbes living on humans.

Seems like they wouldn’t be hard to find, since they’re all over and in the body, but they are little—hence the “micro” part. And there are trillions of them on each of us. But, they are accountable for only 1 to 3 percent of the body’s mass. So if you weigh 180 pounds, the microbes make up between 1.8 and 5.4 pounds. Imagine. Trillions of anything weighing just 1.8 pounds.

If you think about it too much, it’ll give you the willies. Tiny critters in your nose, on your eyelashes, on your mouth, on your skin, on your lips . . . you get the idea.

Humans do have mutually beneficial relationships with some of these microorganisms. The microbes in the gut are famous for being helpful. We give them a place to live and they give us the ability to digest certain foods and produce vitamins and anti-inflammatories.

Other microbes, called pathogens, can and do cause illness in some of us. Yet many healthy people carry pathogens that don’t cause disease. Go figure.

The National Institutes of Health organized a group of researchers to map out the “normal microbial makeup of healthy humans (in the Western population).” The results of this mapping will be a bumper crop of hypotheses followed by a flood of studies which will, it’s hoped, move infectious disease research considerably further down the road.

NIH shares a bit of what’s already come out of this mapping:

CLINICAL APPLICATIONS

As a part of HMP, NIH funded a number of studies to look for associations of the microbiome with diseases and several PLoS papers include medical results. For example, researchers at the Baylor College of Medicine in Houston compared changes in the vaginal microbiome of 24 pregnant women with 60 women who were not pregnant and found that the vaginal microbiome undergoes a dramatic shift in bacterial species in preparation for birth, principally characterized by decreased species diversity. A newborn is a 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.

Researchers at the Washington University School of Medicine in St. Louis examined the nasal microbiome of children with unexplained fevers, a common problem in children under 3 years of age. Nasal samples from the feverish children contained up to five-fold more viral DNA than children without fever, and the viral DNA was from a wider range of species. Previous studies show that viruses have ideal temperature ranges in which to reproduce. Fevers are part of the body’s defense against pathogenic viruses, so rapid tests for viral load may help children avoid inappropriate treatment with antibiotics that do not kill the viruses but may harm the child’s healthy microbiome.

These are among the earliest clinical studies using microbiome data to study its role in specific illnesses. NIH has funded many more medical studies using HMP data and techniques, including the role of the gut microbiome in Crohn’s disease, ulcerative colitis and esophageal cancer; skin microbiome in psoriasis, atopic dermatitis and immunodeficiency; urogenital microbiome in reproductive and sexual history and circumcision; and a number of childhood disorders, including pediatric abdominal pain, intestinal inflammation, and a severe condition in premature infants in which the intestine actually dies.

All good news, but the scope of the mass of microbes on and in me still gives me the willies.

By Trish Parnell

Image courtesy of NIH


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