According to a new paper published in the journal Cell, researchers have discovered 140,000 new virus species living in the human gut, over half of which have never been seen before.
Gut bacteria are intimately involved in health and disease in the human body. They affect metabolism, the immune system, and the nervous system. In some cases, they play a role in a wide range of illnesses and conditions, including malnutrition, heart disease, obesity, and multiple sclerosis.
Many of these are a type of virus called bacteriophages which play a massive role in regulating the number of bacterial cells in the human gut.
The number and diversity of the viruses the researchers have found are surprisingly high, and the results of the study have paved opportunities for new studies on understanding how viruses living in the gut affect human health.
The researchers have also analyzed the genomes of 2,898 distinct strains of isolated and cultured human gut bacteria.
"It's important to remember that not all viruses are harmful but represent an integral component of the gut ecosystem….These samples came mainly from healthy individuals who didn't share any specific diseases. It's fascinating to see how many unknown species live in our gut and to try and unravel the link between them and human health," said Dr Alexandre Alemeida, a postdoctoral fellow at EMBL-EBI and the Wellcome Sanger Institute.
Among the new viruses discovered, the most prevalent was a new group of viruses believed to have a common ancestor, which the authors referred to as the Gubaphage.
After crAssphage, which is a bacteriophage (the virus that infects bacteria) discovered in 2014 by computational analysis of human faecal metagenomes, Gubaphage was found to be the second most prevalent virus clade in the human gut.