Viruses centenarians | Science and life

Two years ago, we wrote that centenarians have a different intestinal microflora than younger people, and that due to the special microflora of centenarians, many secondary bile acids appear in the intestines, which inhibit the growth of pathogenic bacteria.

In a new article in Nature it is said that viruses in the intestines of centenarians also have peculiarities. These are bacteriophage viruses that parasitize bacteria. Obviously, there should be a lot of them in the intestines, since there are a lot of bacteria there. But until recently, it was extremely difficult to analyze the viral composition in the microflora. The presence of viruses, like bacteria, is best assessed by DNA from intestinal samples. However, one can imagine what a colossal amount of diverse DNA they contain. Reading this DNA, you get a huge number of sequences that need to be assigned to a particular family, genus or strain of microbes. With bacterial DNA, this is easier to do than with viral DNA – bacterial genomes are simply huge compared to viral ones. Viruses, on the other hand, have nothing but genes, and go and find them in a colossal amount of genetic information pulled out, for example, from a stool sample.

Employees Broad Institute Together with colleagues from Keio University and the University of Copenhagen, they used machine algorithms to search for viruses, which were trained by deep learning methods to search for viral genes in a wide variety of genetic sequences. Microflora DNA was taken from people of different ages, among which there was a group over 18 years old, a group over 60 years old and a group of centenarians, which included people over 100 years old. (Centenarians were found in Japan and Sardinia, which are famous for the fact that local residents there and there live exceptionally long.) Comparing their viruses, the researchers found, firstly, that centenarians have a more diverse viral microflora, that is, they live in their intestines more different types and strains of bacteriophages.

Secondly, in centenarians, more viruses live according to the so-called lytic cycle. A phage, having penetrated a bacterium, can integrate into its DNA and fall asleep in it for a while, or it can actively multiply and create viral particles, eventually killing the cell. Active reproduction of a phage with the killing of a bacterial cell is called a lytic cycle. And it turned out that in centenarians, viruses thus exterminate more bacteria. (By the way, phages in the intestinal microflora of children prefer to live in exactly the same way according to the lytic cycle.) It is possible that viruses thereby help get rid of dangerous and simply unpleasant microbes, which, although they do not cause obvious illness, still make the intestines and local bacteria worry. immune cells.

Finally, many long-lived viruses have genes related to the biochemical transformations of sulfate compounds. If a virus brings such a gene into a bacterium, it will be able to use it (in general, viruses often serve as a kind of postmen, carrying different genetic sequences from bacterium to bacterium). Thanks to the “sulfate” genes, the microflora of centenarians can more actively perform various reactions with sulfur-containing compounds. The products of such reactions are important for the intestinal mucosa, with them it becomes more durable and better protected from pathogenic microbes.

Of course, longevity is such a thing that you can’t get by with just the right bacteria and viruses, there’s a lot more to it. And for now, one should be careful about causal relationships here: we see that the microflora of centenarians has its own characteristics, but it may well be that the intestines of centenarians somehow become more hospitable to certain bacteria and viruses. But the right bacteria and viruses obviously contribute to the fact that a person is able to live for more than a century. Perhaps it will be possible to find a way to specifically change and maintain the composition of the bacterial-viral microflora so that it is similar to the microflora of centenarians, and this will serve to general improvement.