People Are Human-Bacteria Hybrid

Here’s a slap on the side of the head!

Most of the cells in your body are not your own, nor are they even human. They are bacterial. From the invisible strands of fungi waiting to sprout between our toes, to the kilogram of bacterial matter in our guts, we are best viewed as walking “superorganisms,” highly complex conglomerations of human, fungal, bacterial and viral cells.

That’s the view of scientists at Imperial College London who published a paper in Nature Biotechnology Oct. 6 describing how these microbes interact with the body. Understanding the workings of the superorganism, they say, is crucial to the development of personalized medicine and health care in the future because individuals can have very different responses to drugs, depending on their microbial fauna.

The scientists concentrated on bacteria. More than 500 different species of bacteria exist in our bodies, making up more than 100 trillion cells. Because our bodies are made of only some several trillion human cells, we are somewhat outnumbered by the aliens. It follows that most of the genes in our bodies are from bacteria, too.

“We have known for some time that many diseases are influenced by a variety of factors, including both genetics and environment, but the concept of this superorganism could have a huge impact on our understanding of disease processes,” said Jeremy Nicholson, a professor of biological chemistry at Imperial College and leader of the study. He believes the approach could apply to research on insulin-resistance, heart disease, some cancers and perhaps even some neurological diseases.

“The human genome provides only scant information. The discovery of how microbes in the gut can influence the body’s responses to disease means that we now need more research into this area,” said Nicholson. “Understanding these interactions will extend human biology and medicine well beyond the human genome and help elucidate novel types of gene-environment interactions, with this knowledge ultimately leading to new approaches to the treatment of disease.”

Nicholson’s colleague, professor Ian Wilson from Astra Zeneca, believes the “human super-organism” concept “could have a huge impact on how we develop drugs, as individuals can have very different responses to drug metabolism and toxicity.”

Having waded through a fair amount of molecular and cellular biology recently, it has seemed reasonable to me to look at humans—and other complex organisms—as colonies rather than simply one entity. We are made up of trillions of cells with their own lives organized into matrioshka-like hierarchies of systems. But the super-organism is a new view. Hmm…