While our blueprint of the gastrointestinal tract is more detailed than ever, one Western researcher understands we need to go on more than a ‘gut feeling’ to fully unlock its role in human health and disease.
In a recent international study, researchers identified 1,952 new bacterial species living in the human gut – that number almost triples existing knowledge of known species. It is a massive step forward in developing an important blueprint on the role gut bacteria play in the human body.
But the work is far from over – if it ever will be, explained Biochemistry professor Greg Gloor.
On the study, Gloor collaborated with researchers at EMBL’s European Bioinformatics Institute and the Wellcome Sanger Institute. The resulting paper, A new genomic blueprint of the human gut microbiota, was published in the February 2019 edition of Nature.
“It’s all about knowing their function,” Gloor said. “If we know what the functions of these bacterial species are, and how they interact with us, then we will be able to, at some point, say, ‘You have this set of bacterial function in your gut and what you’re missing is this one, and if you add that function back in, then maybe you’ll become less lactose intolerant or, maybe, you’ll be less susceptible to cardiovascular disease.’”
The gastrointestinal system – aka the gastrointestinal tract, digestive system, digestive tract or, simply, the gut – is a group of organs that includes everything that connects the mouth to the rectum. The gut serves many essential roles in sustaining and protecting the overall health and wellness of our bodies, starting with the intake and absorption of nutrients and water. This digestive process provides the building blocks the body needs to live, to function, and to stay healthy.
We have many bacteria in our body. In fact, we have about the same number of them as we do human cells, and the vast majority of those are in the colon. Most are good for us and produce metabolites that are useful. The ones found in our gut not only help you digest foods, they make products that impact many bodily systems and can be good for our physical and mental health.
Despite extensive studies, researchers are still working on identifying the individual microbial species that live in our guts and understanding what roles they play in human health.
“There are so many will still don’t even know about. It’s hard to count them because we don’t really know what a bacterial species is,” said Gloor, noting bacterial genomes are fluid and genes move from one species to another rather easily. “The sequences of the (new) genomes themselves are very different from sequences of genes anyone has seen to date. They are recognizably similar, but they’re not identical.”
For the study, Gloor developed a methodology allowing him to examine high-throughput sequencing data sets comparing the genes in the new bacteria found versus the genes in the bacteria already known.
“Most methodologies assume it’s an election – you count the values and the bacteria with the highest count wins. What high-throughput sequencing is, is a poll where you have a margin of error,” he said. “So in a count, one additional vote wins. In a poll, if two people are within the margin of error, you can’t say they’re different. We just extended that concept to the massively multivariate sets that are out there.”
Although researchers are closer to creating a comprehensive list of the commonly found microbes in the North American and European gut, there is a significant lack of data from other regions of the world.
“We’ve pretty much sequenced everything we can possibly sequence in North Americans and Europeans; we have a really good idea of which bacteria are there at the species level,” Gloor said.
“We have a much less complete description of what species are in African, South American and other underrepresented populations. Every time we sequence someone’s gut microbiote there we’re going to find something new.”
His estimates suggest that at lease another 4,000-5000 genomes in the human gut have yet to be discovered in South America, Africa and Asia.
“There is a lot that we still don’t know,” said Gloor.