It is no secret that there are many bacteria in the human body, on the surface of the skin, in the respiratory tract and in the intestines. If the human body is compared to mainstream society, then these bacteria are triads. Most of them have no name, no hukou, no preparation, and they are parasitic in some places in the human body. They rely on "stealing" for a living. Running out is awkward.
The above is the traditional understanding of human parasitic bacteria. But when scientists began to study them seriously, they found that the real situation was much more complicated. First of all, the number of human parasitic bacteria is staggering. It is estimated that the number of bacteria in the human body is 10 times the total number of human cells, that is, each human cell must supply 10 bacteria! Imagine if the number of gangs in a country is 10 times more than that of ordinary people, then you can't simply call them a triad. They must have participated in all aspects of the country's social life, and may even have taken over the government secretly. As ordinary people, we must know what the underworld has done.
Second, scientists have found that most human parasitic bacteria are not artificially cultured. Anyone familiar with microbiological research methods knows that if a kind of bacteria can't be artificially cultured, there is no way to expand it, and there is no way to clone it. Therefore, it is difficult to conduct research. This is why humans know about the situation of this bacterial triad. Very few main reasons.
Advances in gene sequencing technology have solved this problem. With the new technology, scientists can determine the order of all the gene fragments of interest in the sample without cultivating the bacteria, and use this as a basis to determine the type and characteristics of the bacteria contained in the sample. In 2012, Dr. Jeffrey Gordon, a geneticist at the University of Washington in the United States, and a team he led used the new technology to study the distribution and evolution of human intestinal bacteria.
The researchers extended their horizons to the entire planet, from an Amazonian tribe in Venezuela in South America, an indigenous tribe in Malawi in Africa, and several large cities in the United States, who found 531 healthy volunteers and obtained their stool samples. These people are of different ages and living conditions vary widely. The researchers extracted all the DNA from the sample and measured the gene sequence of the 16S ribosomal RNA contained in it using a new gene sequencing method. This 16SRNA is a nucleic acid molecule that must be used in protein synthesis. It is found in all bacteria. The 16SRNA sequence between different bacteria is slightly different and can be used to identify the type of bacteria.
Studies have shown that although the living environment of these three places is very different, the process of environmental microbes invading the human body is very similar. Simply put, newborns have no bacteria in the intestines at birth, and hundreds of bacteria begin to settle in the intestines within the first 6 months of life. Since then, the number has increased, and the number and distribution pattern of intestinal flora at the age of 3 years. It is not much different from adults.
The distribution of gut flora in a person's infancy and adulthood varies greatly, but this change seems to be in order to meet the needs of the human body as if the bacteria obey the human command. For example, folic acid is a vitamin that can be synthesized from both food and intestinal bacteria. Infants have a single food composition and can only rely on bacteria, so the bacteria in the intestines of the baby contain more folate synthase. Adults have abundant food sources and do not have to rely on bacterial synthesis. Therefore, adult intestinal bacteria contain more bacteria than use folic acid, and the content of folate synthase is lower. In contrast, vitamin B12 can only be synthesized by bacteria and cannot be obtained from food, and the body's demand for B12 increases with age, so the amount of B12 synthase in the intestine also increases with age.
Another interesting finding is that the gut microbiota in Americans is lower than in the other two countries, although Americans are sure to eat more species than the latter. Researchers speculate that this may be due to better sanitation in the United States or a large use of antibiotics. As for the impact of this diversity difference on health, further research is needed.