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The coronavirus pandemic has made the world obsessed with viruses like nothing has happened, but new evidence reveals that humans never even notice the vast extent of viral existence – even when it’s within us.
A new database project compiled by scientists has identified more than 140,000 viral species that live in the human gut – a giant catalog that is all the more astonishing given that more than half of these viruses were previously unknown to science .
If tens of thousands of newly discovered viruses seem like an alarming development, that’s understandable. But we shouldn’t misinterpret what these viruses inside us actually represent, the researchers say.
“It is important to remember that not all viruses are harmful, but that they are an integral part of the intestinal ecosystem,” explains biochemist Alexandre Almeida of the Institute for Bioinformatics of the European Molecular Biology Laboratory (EMBL- EBI) and the Wellcome Sanger Institute.
“These samples were mainly from healthy individuals who did not share any specific disease.”
The new virus catalog – called the Gut Phage Database (GPD) – was respected by analyzing more than 28,000 individual metagenomes – publicly available DNA sequencing records of gut microbiome samples collected in 28 countries – as well as nearly 2,900 reference genomes of cultured intestinal bacteria.
The results revealed 142,809 viral species that reside in the human gut, constituting a specific type of virus known as a bacteriophage, which infects bacteria, in addition to single-celled organisms called archaea.
In the mysterious environment of the gut microbiome – inhabited by a diverse mix of microscopic organisms, encompassing both bacteria and viruses – bacteriophages are believed to play an important role, regulating both bacteria and the health of the human gut. himself.
“Bacteriophages… profoundly influence microbial communities by functioning as horizontal gene transfer vectors, encoding beneficial ancillary functions for host bacterial species and promoting dynamic coevolutionary interactions,” the researchers write in their new paper.
For a long time, our knowledge of this phenomenon has been blocked by limitations in our understanding of bacteriophage species.
In recent years, new advances in metagenomic analyzes have dramatically broadened our awareness of the viral variety we are examining here – and perhaps no more than the Gut Phage Database, which the researchers describe as “massive expansion. of the diversity of human intestinal bacteriophages. “.
“To our knowledge, this set represents the most comprehensive and comprehensive collection of human intestinal phage genomes to date,” write the study authors.
“Having a comprehensive database of high-quality phage genomes opens the door to a multitude of analyzes of the human gut virome at significantly improved resolution, allowing the association of specific viral clades with distinct microbiome phenotypes. “
Already, the database is updating what we know about viral behavior.
Research shows that more than a third (36%) of the viral clusters identified are not limited to infecting a single species of bacteria, which means that they can create gene flow networks across phylogenetically distinct bacterial species.
In addition, the researchers found 280 viral clusters spread around the world, including a newly identified clade called Gubaphage, which appears to be the second most common viral clade in the human gut, after what is known as the crAssphage group. .
Given some similarities between the two, the researchers initially thought that Gubaphage might belong to a proposed family of crAssphage-like viruses, before determining that the clades were, in fact, distinct.
There is still so much to learn, and not just about the Gubaphage – but more multitudes of viruses than we have ever dreamed of. However, thanks to research efforts like this, the discoveries of tomorrow are closer and new information will come more quickly.
“Bacteriophage research is experiencing a renaissance,” says microbiologist Trevor Lawley of the Wellcome Sanger Institute.
“This high-quality, large-scale catalog of human intestinal viruses comes at the right time to serve as a template to guide ecological and evolutionary analysis in future virome studies.
The results are reported in Cell.
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