There are metropolises of microorganisms in every nook and cranny of your body, and scientists just conducted the largest study on them yet.
In a paper announcing the first results of an extension of the Human Microbiome Project, published (paywall) Sept. 20 in the journal Nature, researchers looked at over 2,000 microbial genomes from 265 people. They found that the microbiome is more expansive than they had previously understood, with thousands of discrete communities that carry out specific tasks in the body.
The “microbiome” technically means all the genes of the microbes living in our bodies. The term, however, is often used to refer to the collection of these tiny organisms in general. Researchers didn’t really begin to study these buggers until 2007, with the launch of the first Human Microbiome Project, which took a handful of samples from about 300 people and wrapped up in 2013. That initial project to hundreds of published papers, and contributed to the now widely accepted idea that some kinds of bacteria—predominantly those in the lower intestine—contribute to all sorts of aspects of our health, including the way we get nutrients from food and protect ourselves from disease.
This new study furthers the previous work. Researchers took samples from 128 women and 137 additional men, from a number of different sites, including under the tongue, the top of the mouth, cheeks, ears, noses, colons, and the women’s vaginas. They then used DNA sequencing technologies to come up with better pictures of the clusters of bacteria that live in each area.
New and improved sequencing techniques allowed the researchers to find 54 new species of bacteria that live in our bodies, as well as several types of viruses and fungi. They found the most concrete evidence yet that certain microbial groupings do specific jobs for the body: Groups of microbes in the mouth, for example, help break down sugars and nitrates, while other groups start synthesizing vitamin B. Other microbial groups from the mouth all the way through the gut can start breaking down short-chain fatty acids, typically found in high-fiber foods like fruits and vegetables.
The researchers re-sampled participants after a month or year at each area and found that microbes in the mouth tend to vary a lot, presumably because they get the most contact with the outside world through eating and breathing. Conversely, microbes in the vagina tended to stay the same over time, yet compared to samples from other parts of the body, vaginal microbiomes had the largest differences from (female) participant to participant.
There’s lots more work that can be done on these communities of microbes. Getting more and more information about the microbiome is like adding more and more details to a map of human health. By filling in the gaps in our understanding of how microbial communities affect parts of our health—like how they help us make vitamins, for example—we could eventually use this map as a basis for developing treatments for various conditions in the future.