Cataloguing 10 million human gut microbial genes: Unparalleled accomplishment

Research on the gut microbiome (all of the bacteria in the digestive tract) has multiplied over the past several years, helped in great part by new sequencing technologies. The gut microbiome, which scientists have labelled a "new organ" that is composed of tens of trillions of bacteria -- ten times as many as the number of cells in the human body -- is directly linked to the immune system and brain. It is a major player in chronic illnesses such as obesity and Type 2 diabetes. However, research in the field depends on access to reference gene databases (or catalogues), which is particularly important when identifying the functions of microbial genes. Few and far between, existing catalogues were created using samples from a limited number of people and geographical origins.

INRA researchers, as part of the MetaHIT international consortium, put together a catalogue of microbial genes that regroups pre-existing catalogues (European, American and Chinese) and enhanced it with new sequences. Apart from being an unparalleled resource, the analyses done for the catalogue showed that it contains the broadest collection of microbial genes -- and by extension, their functions -- present in the global population. With ten million genes, this new catalogue presents the most impressive array of human intestinal bacteria in the world.

Most of the genes (around six million) are shared by just 1% of the population, making them quite rare. While there is substantial data today regarding the most common genes, future research will focus on determining the importance and role of these rare genes.

Thanks to this catalogue, the most clinically significant genes can be described, most notably those related to illnesses such as Type 2 diabetes, cirrhosis of the liver, cardiovascular diseases and some cancers. It will also provide a more complete picture of imbalances in the gut microbiome (dysbiosis), particularly those caused by medication.