To admit, at first I decided that authors can not be trusted, no one person can adhere to absolutely opposite points of view. But it turned out that it could, if it were Mechnikov. This extremely contradictory nature, having written the book "Etudes of Optimism", tried to minimize itself as a minimum twice. So, despite the fact that Mechnikov argued that bacteria are the main reason for the brevity of our lives, he believed that the use of curdled milk containing a large number of live cultures can prolong life. Very many were inspired by his example. In fermented milk there were bacteria, including the Bulgarian bacillus, they produced lactic acid, killing harmful microbes, which shorten our life. People, of course, used to eat fermented products, but now they started to do it for the sake of bacteria!