Is it true that there are more bacteria in the human body than cells of the body itself?

That bacteria are useful and harmful, regularly report and Media, And advertising. It also often sounds that there is more bacteria in our body than cells of the body itself. We decided to check if it was true.

On our planet There is not less than 5 x 10³⁰ bacteria, their biomass exceeds the total biomass of all animals and plants. Bacteria are organisms of various forms (round, stick -shaped) to several micrometers in length. They are one of the first forms of life on Earth and are common in all habitats.

The first studies on the ratio of cells of the human body and bacteria that are inhabiting in it, Spent Microbiologist Thomas Laki in 1972. According to his calculations, only in the gastrointestinal tract of a person lives about 100 trillion of bacteria, while the human body, as a scientist calculated, is made up of 10 trillion of his own cells, which made up a ratio of 10: 1 in favor of bacteria. For a long time, this ratio was finally considered true, but with the advent of more accurate calculation methods, some scientists questioned this study into question.

A team of microbiologists from the Weizmann Institute of Science in Rekhovot (Israel) under the leadership of Ron Milo used magnetic resonance imaging to calculate the number of cells of the human body. Their CalculationsConsidering the different tissue density, showed that on average an adult consists of 30 trillion cells, most of which - 25 trillion - falls on a lot of red blood cells. In second place are platelets - approximately 1 trillion. And only 3 trillion are tissues of the body itself (bones, leather, internal organs, etc.). Thus, as a result of the first stage of the study, the outcome of bacteria has not become so significant - only 3: 1.

In the second stage, the experimenters questioned the conclusions of Thomas Lucky on the number of bacteria, Markingthat he hoped the population of the gastrointestinal tract on the analysis of the sample from the colon, while in the small bacteria much less. The data adjusted by them began to look less dramatic: 1.3 bacteria account for 1 cell of the body itself. The most densely populated place was still the large intestine: about 100 trillion of microorganisms per liter (with an average volume of 0.4 l) lives in it. The saliva contains 100 billion, and on each square centimeter of the skin - another 10 million. In defense of Thomas Lucky Laki, it should be noted that in 1972 there was no now generally accepted trinemic system of Karl Vozes and bacteria Combined With archeas in a common group of prokaryotes. While Ron Milo was already counting only representatives of the kingdom of bacteria.

It is worth noting that the cute ratio dedicated to Ron is not constant. With each act of defecation Displayed Such a number of bacteria that for some time the body cells get a numerical advantage.

It is also important to mention that in his work, Ron cute took into account only bacteria, while in the human body Live Also archeas, mushrooms, viruses and other types of microorganisms. If you add to the study, for example, viruses, which are even more than bacteria, then the numerical superiority of the microbioma will increase again. The second significant factor is that the middle model of a person protrudes A man weighing 70 kg, and if you calculate the ratio for a woman who has a blood volume (and, therefore, the amount of red blood cells) is less, then the proportion will move by about a third in favor of bacteria. 

Thus, the bacteria in the human body most often really more than its own cells. For the standard ratio Accepted 1.3: 1, however, scientists use more and more advanced calculation methods, therefore, perhaps this figure is not final. In particular, one of the largest projects in this area, American "Human microbia", works on the clarification of the classification and the number of various microorganisms in our body and is asked by the issues of interacting with their human body.

Most of the truth

What do our verdicts mean?

Read on the topic:

1. Dmitry Alekseev "Microbes of the intestines and health"
2. "Bacteria had to be reinvented with oxygen three times"
3. Elizabeth Bonch-Osmolovskaya "How archeas differ from bacteria"