Your body has 10x more bacterial cells than human ones

Carolyn Bohach, a microbiologist at the University of Idaho claims that our bodies contain 10 times more bacterial cells than human ones (bacterial cells are a lot smaller and thus occupy less volume). Human genome researchers believe that at least 40 of our genes are bacterial in origin. Let the compulsive washing begin!
All the bacteria living inside you would fill a half-gallon jug; there are 10 times more bacterial cells in your body than human cells, according to Carolyn Bohach, a microbiologist at the University of Idaho (U.I.), along with other estimates from scientific studies. (Despite their vast numbers, bacteria don't take up that much space because bacteria are far smaller than human cells.) Although that sounds pretty gross, it's actually a very good thing.

The infestation begins at birth: Babies ingest mouthfuls of bacteria during birthing and pick up plenty more from their mother's skin and milk–during breast-feeding, the mammary glands become colonized with bacteria. "Our interaction with our mother is the biggest burst of microbes that we get," says Gary Huffnagle, a microbiologist and internist at the University of Michigan at Ann Arbor. And that's just for starters: Throughout our lives, we consume bacteria in our food and water "and who knows where else," Huffnagle says.

Link (via 3 Quarks Daily)


  1. Most of the bacteria are on the inside not the outside of our bodies, and most of the bacteria are “friendly,” that is “not infectious.” Instead of trying to wash bacteria off (futile by the way), we should be encouraging a healthy ecosystem of good bacteria to live on our bodies in order to deprive the bad bacteria of resources and keep their population low.

    I predict that in the future we will be buying all sorts of products with beneficial bacteria, not just yogurt, but also armpit juice, kitchen cleanser, etc.

    Search for “competitive exclusion” bacteria.

  2. Since we likely evolved from bacteria in the first place I would think that all of our genes are bacterial in origin.

  3. We’re actually just highly-evolved hosts for the bacteria. The bacteria in humans has found the best host to spread itself around the globe, making it perhaps the most successful organism on this planet! Bacteria in other species must gaze on with envy.

  4. Um, “claims that”? This is well known. They also contain orders of magnitude more genes than the human genome, especially genes responsible for sugar metabolism. See e.g. recent paper in Science on the human microbiome.

  5. Which bacteria will protect my teeth instead of eat away at them, and which will make my underarms smell good instead of bad when I sweat?

  6. That there are only 10x more bacteria cells than human cells is a gross underestimate. (no pun intended).

    The population of bacterial cells is generally agreed to be 10^14. That’s 100000000000000x more bacteria cells than human cells. (Tannock, 1995)

    Also, the number of genes with bacterial origins is more like 223 (Relman, 2001)

    Microflora are awesome!

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