Scientists have identified over 140,000 species of virus living in the digestive system of humans, more than half of which they say have never been seen before, opening new doors for researches to deepen the understanding about how viruses living in the gut affect human health.

The researchers from the Wellcome Sanger Institute and EMBL’s European Bioinformatics Institute (EMBL-EBI) in a paper published on Thursday (February 18, 2021) in Cell analysed over 28,000 gut microbiome samples collected in different parts of the world. Using a DNA-sequencing method called metagenomics to explore and catalogue the biodiversity of the viral species found in 28,060 public human gut metagenomes and 2,898 bacterial isolate genomes cultured from the human gut, they found an astonishing number of virus types.

The human gut is an incredibly biodiverse environment. In addition to bacteria, hundreds of thousands of viruses called bacteriophages, which can infect bacteria, also live there.

It is known that imbalances in our gut microbiome can contribute to diseases and complex conditions such as Inflammatory Bowel Disease, allergies and obesity. But relatively little is known about the role of bacteria in the gut, and the bacteriophages that infect them, play in human health and disease.

Among the tens of thousands of viruses discovered by the researchers is a new highly prevalent group of viruses believed to have a common ancestor was identified, which the authors refer to as the Gubaphage. This was found to be the second most prevalent virus group in the human gut, after the crAssphage, which was discovered in 2014.

Both of these viruses seem to infect similar types of human gut bacteria, but the researchers say without further research it is difficult to know the exact functions of the newly discovered Gubaphage.

“It’s important to remember that not all viruses are harmful, but represent an integral component of the gut ecosystem,”Dr. Alexandre Almeida, Postdoctoral Fellow at EMBL-EBI and the Wellcome Sanger Institute, said.

Giving further insight, he said, “Most of the viruses we found have DNA as their genetic material, which is different from the pathogens most people know, such as SARS-CoV-2 or Zika, which are RNA viruses. Secondly, 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.”

Dr. Luis F. Camarillo-Guerrero, first author of the study from the Wellcome Sanger Institute, said a stringent quality control system combined with a machine learning approach was used to mitigate contamination and obtain highly complete viral genomes in the reconstruction of viral genomes.




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