The living environment in our intestines is even more complex than one might think, a study makes clear: it is not only teeming with bacteria, but also with the viruses that attack them. Using genetic analysis, researchers have identified thousands of new representatives of these so-called bacteriophages. The results now form the basis for a database on the intestinal flora viruses, which will be used to research their role in human health.
The intestinal habitat is moving more and more into the focus of science: The bacteria that colonize our digestive tract have proven to be masterminds of our health in recent years. The composition of this microbial community affects the immune system, metabolism and many other aspects of health. The characteristics of the intestinal flora of a person are determined by various factors. However, one thing has so far remained relatively little researched: the influence of pathogens in the intestinal bacteria. Because just as coronavirus and co infect us, certain viruses also target microbes. They are called bacteriophages – “bacteria eaters”.
Tiny things that attack dwarves
Like all viruses, they are “pirates of life”: They do not have their own metabolism, but use the life force of their host cells. Many bacteriophages have leg-like structures that allow them to attach to the surface of the bacteria. Then they smuggle the genetic material stored in a head part into the cells. As a result, they transform them into virus factories that produce new particles until they collapse. The released bacteriophages then set off on their journey to new victims. In this way, they can greatly affect the populations of bacteria and also contribute to the development of genetic changes. There are even approaches to use phages that specialize in certain bacteria in a targeted manner to combat infectious diseases.
It has been known for a long time that the harmless or “friendly” bacteria in the human intestine are also attacked by certain types of phages. “The extent of the viral diversity in the human gut has remained largely unclear,” writes the research team headed by the Wellcome Sanger Institute in Hinxton. This is why the scientists have now systematically explored the viral biodiversity with the help of metagenomics. This technique of comparative DNA analyzes made it possible to rummage through the genetic data of over 28,000 samples of human intestinal flora and almost 3000 genomes of bacterial isolates for the viral pathogens.
It’s teeming
As the scientists report, they identified a total of around 140,000 viral species found in the human intestine, more than half of which were still completely unknown. These also include viruses that apparently have a special common history of development. The scientists have now given this group the name “Gubaphagen”. They found that their representatives are the second most common viruses in the human intestine after the so-called crAssphages. It is now an open question what role the newly discovered Gubaphages play in the intestinal environment.
“It’s fascinating to see how many unknown species live in our gut and try to decipher the link between them and human health,” says co-author Alexandre Almeida of the Wellcome Sanger Institute. “It is important to emphasize that not all of these viruses are necessarily problematic, but rather represent an integral part of the intestinal ecosystem. This is also made clear by the fact that the samples mainly came from healthy people who do not have any specific diseases, ”says the scientist.
The researchers have now also used the information on the more than 140,000 bacteriophages as a basis for developing a new database for science: They are presenting the publicly accessible “Gut Phage Database”. The genomes they contain can now be used by scientists to research the significance of the “bacteria eater” for the microbes in us and thus for our health. “An important aspect of our work was therefore to ensure that the reconstructed viral genomes are of the highest quality,” says lead author Camarillo-Guerrero of the Wellcome Sanger Institute. His colleague Trevor Lawley concludes: “The new catalog on the viruses in the human gut comes at the right time to serve as a guide in future studies.”
Source: Wellcome Sanger Institute, professional article: Cell, doi: 10.1016 / j.cell.2021.01.029