Scientists have just announced the discovery of a new, incredible a common virus that lives inside human intestinal bacteria. He got the name “crAssphage” and at almost six times more common than all other bacterial viruses taken together. But how did we manage not to notice him so much time?
A photo from open sources
The reason we haven’t found crAssphage before is because that we didn’t know that we had to look for him. That’s what it is means.
While new sequencing technologies are becoming more and more fast and cheap, they still have one weakness: they good for discovering things we already know exist but they are poorly suited for the search for new organisms. When researchers study an organic sample, they get soup from DNA fragments of all living things related to this sample – bacteria, viruses and the person himself. Then these fragments need to be assembled in the sequence that we can to identify. If we find a genome-specific chain some bacteria – that means we found this bacterium in the sample.
The problem is that if we don’t know yet sequences of a virus unknown to us – we cannot detect using this technique. But in fact, the author of the new crAssphage research Bas Datil reports that they are almost unknown 75 percent of the DNA sequences in the samples they studied.
The Datila team was able to find a new virus by using a completely different approach based on a simple idea: fragments that time after time are found in the same sample, with a high degree of probability are parts of a single genome. They used the technique so called cross-assembly to identify one such group repeating sequences in samples taken from 12 people. Then they assembled these sequences into a single genome.
And they got exactly that: crAssphage virus, named after it cross-assembly technique, which led to his discovery. They found that crAssphage lives inside Bacteroides – a common group of bacteria that live in our intestines.
As a result of research, the team found crAssphage in 75% intestinal sequences of people in the USA, Europe, and South Korea. we until we know what exactly these phages do in our intestines, but they definitely play a role in our intestinal microbial ecosystem.
And finally, an interesting fact: scientists have calculated that in our the body is about 100 times more viral particles than actually human cells. So we still have a lot of work to do. find out what we really are.
DNA viruses
