Ewwww!

The often cited statistic is this: only one in ten cells of the human body is human. What are the other nine? Microbial cells. Cells from really small mites and worms, but also cells from bacteria and single-celled eukaryotes. Huh? Euk, what?

Biologists like to give fancy names to not-so-fancy differences. Of all the cells in the world, they can be divided in to two types: those with a nucleus (eukaryote) and those without a nucleus (a prokaryote). We are eukaryotes made of many cells, and can be seen without a microscope. So we're macroscopic multicellular eukaryotes. But there are also really small eukaryotes that one would need a microscope to see. We call those microbial eukaryotes. These include a lot of fungi (which can become macroscopic when cells join forces to make fruiting structures like mushrooms) and scary things like plasmodium, the cause of malaria.

Prokaryotes are all single-celled organisms, which means that they exist as individual cells. Bacteria are prokaryotes, and so are a related group of organisms called the Archaea. But back to the human body.

Only one in ten cells is human? Why don't we look like a gimush of bacteria and other microbes? Well, human cells are about 10 times bigger than bacterial cells, so we only see the human composite. But if we had microscopic vision, we'd see a whole different picture.

This is precisely what a lot of scientists are doing right now, not with microscopes, but with DNA sequencers. They're taking samples of humans and sequencing DNA to identify and classify the bacteria and other microbes present, which collectively are referred to as the 'Human Microbiome'. We want to determine the microbiome for people with different diseases (Crohn's disease, IBS, obesity, etc.) and compare them to the microbiomes of people without these diseases. These comparisons might tell us how microbiomes differ in diseased individuals so that one day we may be able to treat them by altering the microbiome ecosystem. For example, we could provide them with a beneficial bacterial species that kills a harmful bacterial species.

How do you feel about swallowing bacteria to treat disease?