Nearly 2,000 previously unknown species of gut bacteria have been discovered by a team of international researchers using novel metagenomic data. The discovery greatly expands our knowledge of the microbial species living inside us, and establishes new computational methods to help reconstruct and identify undiscovered bacterial genomes.

Inside all of us there lies a vast population of trillions of microorganisms. Our gut in particular plays host to the largest microbial population and is home to potentially trillions of microbes. Although the vast majority of this bacteria consists of just 30 or 40 different species, it is still very much unknown exactly how many different kinds of bacteria live inside us.

Different estimates in bacterial species diversity range from 1,000 to 40,000, many of which are still yet to be identified. These undiscovered species may not survive well outside of the gut, or may be unique to geographical populations. This latest study set out to characterize undiscovered bacteria using new metagenomic analysis – a method that tracks potential unidentified genomic traces in human microbiome samples.

"Computational methods allow us to understand bacteria that we cannot yet culture in the lab," explains Rob Finn, one of the researchers working on the project. "Using metagenomics to reconstruct bacterial genomes is a bit like reconstructing hundreds of puzzles after mixing all the pieces together, without knowing what the final image is meant to look like, and after completely removing a few pieces from the mix just to make it that bit harder."

The research ultimately homed in on 1,952 unclassified metagenomic samples indicating previously unknown bacterial species. Almost half of these could not be classified to a known genus, meaning they may be entirely new families or genera. A great deal of the new data was also noted as coming from diverse geographical populations, suggesting future research needs to better study broader populations of people.

"We are seeing a lot of the same bacterial species crop up in the data from European and North American populations," says Finn. "However, the few South American and African datasets we had access to for this study revealed significant diversity not present in the former populations. This suggests that collecting data from underrepresented populations is essential if we want to achieve a truly comprehensive picture of the composition of the human gut."

Little is known about the newly discovered bacteria, and they are still yet to be cultured in laboratory conditions or properly classified. However, these new computational methods are undeniably allowing scientists to identify bacterial species that previously remained hidden from the usual analysis methods. Microbiome research may revolutionize medicine in the future but it is still certainly in a nascent stage, and the first step we need to complete is comprehensively identifying the diversity of bacteria that live inside us.

"Research such as this is helping us create a so-called blueprint of the human gut, which in the future could help us understand human health and disease better and could even guide diagnosis and treatment of gastrointestinal diseases," adds group leader on the project, Trevor Lawley.

The new researcher was published in the journal Nature.