Consider this: The average person’s body contains about 100 trillion cells, but only maybe one in 10 is human.
This isn’t the latest Hollywood horror flick or some secret genetic engineering experiment run amok.
This, it turns out, is nature’s way: The human cells that form our skin, eyes, ears, brain and every other part of our bodies are far outnumbered by those from microbes, primarily bacteria but also viruses, fungi and a panoply of other microorganisms.
And a growing body of evidence indicates that the microbial ecosystems that populate our guts, mouths, noses and every other nook and cranny play crucial roles in keeping us healthy.
Moreover, researchers are becoming convinced that modern trends — diet, antibiotics, obsession with cleanliness, Caesarean delivery of babies — are disrupting this delicate balance, contributing to perplexing ailments including asthma, allergies, obesity, diabetes, autoimmune diseases, cancer and perhaps even autism.
“In terms of potential for human health, I would place it with stem cells as one of the two most promising areas of research at the moment,” said Rob Knight of the University of Colorado. “Everywhere we look, microbes seem to be involved.”
Equipped with super-fast new DNA decoders, scientists are accelerating the exploration of this realm at a molecular level, yielding provocative insights into how these microbial stowaways might wield far greater powers than previously appreciated in, paradoxically, making us human.
“The field has exploded,” said Jeffrey Gordon of Washington University, who pioneered the exploration of humanity’s microbial inhabitants, known as the “microbiome” or “microbiota.” “People have this sense of wonderment about looking at themselves as a compilation of microbial and human parts.”
Some equate these microbial inhabitants to a newly recognized organ. Acquired beginning at birth, this mass of fellow travelers might help steer normal development, molding immune systems and calibrating fundamental metabolic functions such as energy storage and consumption. There are tantalizing clues they might help shape brain development, influencing behavior.
Investigators are trying to identify which organisms might truly be beneficial “probiotics” that people could take to help their health. Others are finding substances that people might ingest to nurture the good bugs. Drugs might mimic the helpful compounds that these organisms produce.
Doctors have even begun microbiota “transplants” to treat a host of illnesses, including a sometimes-devastating gastrointestinal infection called C. difficile, digestive system ailments such as Crohn’s disease, colitis and irritable bowel disorder, and even in a handful of cases obesity and other afflictions, such as multiple sclerosis.
Advocates of the research urge caution, noting that most of the work so far has involved laboratory animals or small numbers of patients, many hypotheses remain far from proven and nothing has zero risk.
