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Unknown bugs dominate the human microbiome

There’s been growing attention to the human microbiome – the collection of bacteria, viruses, and other microbes residing inside our bodies – and how a variety of diseases interact with it. For the most part, however, that attention has focused on particular regions of the body, notably the gastrointestinal tract, or specific microorganisms.

Turns out, biologists have only just begun to scratch the surface: 99 percent or more of the microbiome consists of organisms that, as far as the paper’s authors can tell, no one has even seen before, let alone categorized or named. Some of that stuff was pretty weird, Stephen Quake, PhD, a professor of bioengineering and applied physics told me for a press release:

We found the gamut... We found things that are related to things people have seen before, we found things that are divergent, and we found things that are completely novel.

To wit, the team found an entirely new kind of the highly diverse but poorly understood group of torque teno viruses:

Among the known torque teno viruses, one group infects humans and another infects animals, but many of the ones the researchers found didn’t fit in either group. 'We’ve now found a whole new class of human-infecting ones that are closer to the animal class than to the previously known human ones, so quite divergent on the evolutionary scale,' [Quake] said.

The new study grew out of the group’s earlier efforts to better understand and predict whether lung, heart, and bone marrow transplant patients’ immune systems would reject, or attack, a donated organ. In theory, changes in the microbiome in the blood could help doctors see rejection coming before the immune system did too much damage. But in analyzing blood samples from transplant patients and separate ones from pregnant women, the team, including lead author Mark Kowarsky, a graduate student in physics, realized that nearly all of the microbiome DNA they found wasn’t recorded in any database.

Previously: Investigating the human microbione: "We're only just beginning and there is so much more to explore" and The Good Gut: Discussing the stomach's world of disease-fighting microbes
Photo by M J Richardson

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