Gut Microbiome 101: A Beginner's Guide

Microbes are everywhere, and almost no place is immune to their presence . Our bodies also carry an abundance of microbes that live on our skin and the mucous membranes of our hollow organs, such as the stomach and intestines, forming microbial communities that live in mutualistic symbiosis with humans . They are given different names depending on where they are located, so we have oral flora, lung flora, vaginal flora, skin flora, etc. , and we focus on the gut flora . The process of formation of the gut microbiota The gut microbiota plays a vital role in the normal functioning of the human body and is an integral part of all stages of the digestive process as it synthesizes nutrients, neutralizes toxins, and more . Gut flora is an essential element of our health, and without them, the body cannot function properly . However, babies are almost sterile at birth, and the fetus' digestive tract is bacteria-free . So how does the gut microbiota form? Microbes from outside enter the newborn's gut through childbirth, breastfeeding, and human contact . 　　The initial microbes enter the body through the air inhaled by the newborn . When they enter the body, they stay on the mucous membranes of the nasal cavity, from there they enter the throat and further into the body . 　　The other entrance is the mouth, where in addition to the air, a newborn's mouth is in contact with many things that have microbes, such as their own fingers, the mother's skin and bedding, and anything they might put in their mouths, and these microbes then migrate to the gut . 　　The main vehicle for microorganisms to enter the human body is food, which is loaded with various microorganisms . The first food for a newborn is breast milk . Breastfeeding babies are not only ingesting breast milk, but also the bacteria contained in breast milk . Once in the body, these bacteria make their way into the gut, where there are familiar Lactobacillus and Bifidobacterium, the main beneficial bacteria in the gut . 　　Breast milk is ideal for the development of the neonatal gut microbiota . Between the 1960s and 1970s, many infants were formula-fed, and the resulting lack of gut flora was the cause of many health problems . It is the recognition of the true root causes of these diseases that has led to a renewed emphasis on breastfeeding and recognition of its benefits . Sometimes breastfeeding may not be possible, and scientists have tried to apply these benefits to infant formula, adding live probiotics to make it closer to breast milk, but it is also difficult to fully achieve the level of breast milk . 　　Like all living things, microorganisms can only survive in an environment that provides favorable conditions for their growth, the temperature and humidity must be suitable, and the environment must provide the nutrients they need in sufficient quantities . 　　Some microbes die once they enter the digestive tract because the environment is too harsh; others simply pass through and are eventually excreted in the feces because the living conditions they need cannot be met in the digestive tract . However, some of the microbes that enter will find ideal living conditions with an adequate food supply, they will colonize the gut, and when they multiply, they will colonize the gut and develop their unique flora . 　　The increase in the number of microbes in the early gut is fairly rapid, and 48 hours after birth, infants' first stools are high in microbes, but not very diverse . After a week, the microbial diversity was higher, as was the total number . From this point on, this microbial composition remains stable throughout the period the infant continues to drink breast milk . 　　Once the baby is weaned and solid foods begin to replace breast milk, many new microbes enter the gut, and the composition of the gut flora changes dramatically . The new microbes that enter the digestive tract increase the number of species already present, and the abundance of new food provides them with nutrients and makes them easier to reproduce . Since then, their numbers have greatly increased . 　　The number of gut bacteria is very large 　　The number of microorganisms in the intestinal flora is extremely large, in the trillions . Early estimates put these microbes in 10 times the number of our own cells, but the latest research suggests that this number is smaller, but still far exceeds the number of our own cells . 　　If we gather all the gut microbes in one container, this container must be able to hold 1-2 liters, and all these microbes weigh about 1. 5-2 kilograms . 　　There are 500-1000 different bacteria in the gut microbiota, and a single bacterium may in turn comprise a large number of subgroups or serotypes . For example, E. coli includes many different serotypes, some of which produce toxins, but most are generally harmless . 　　Gut microbes are so tiny that they are invisible to the naked eye, only about a micron in size, or 0. 001 millimeters . If they were compared to a single hair, they could be a thousand times smaller than the thickness of a hair . One cubic millimeter can hold about 100 million microorganisms . 　　Propagation of gut microbes A 　　large number of microbes are excreted in feces every day, and it is estimated that all of these microorganisms together make up half of the weight of feces . In order to maintain the number of gut microbiota, these excreted microbes must be constantly replaced with new ones . This is easy to achieve for two reasons: 　　every time we eat, a large number of bacteria are reintroduced into the body through the food . 　　Bacteria multiply very quickly . 　　Bacteria have a unique reproduction method that allows their offspring to multiply rapidly, a "mother cell" divides into two new "daughter cells", each of which divides to produce two new daughter cells, and so on. . The number of offspring is not increased by one unit per generation, but doubled per generation, i. e. in multiples of 2, 4, 8, 16, 32, etc. Therefore, the rate of bacterial reproduction is very fast . Humans reproduce one generation every 20 years or so, while bacteria typically reproduce every 15-60 minutes, and with that in mind, bacteria multiply faster . 　　Are germs dangerous? 　　Bacteria have a bad reputation, people talk about bacteria discoloration, think they are all harmful . Indeed, they can infect us, make us sick or even die . So why does our body still provide a habitat for so many bacteria? In fact, there are billions of different types of bacteria on Earth, but only a few are pathogenic, and the vast majority are harmless or even beneficial . 　　In nature, it is bacteria that give life to inert minerals in the soil and enable plants to absorb these minerals, such as nitrogen, phosphorus and sulfur . Bacteria are also responsible for breaking down dead plants and animals, and their tissues contain a lot of reusable material . In order for them to be recycled, they need to be freed from the organic structures that hold them in place . Bacteria break down tissue into smaller particles, which are then reabsorbed into a new life cycle . 　　Gut bacteria play a very beneficial role in all aspects of our physical and psychological functions: they can synthesize vitamins and more from simple substances in the food we eat; they can also help break down our own insufficient digestion. or indigestible food particles, such as dietary fiber; finally, they are also able to destroy certain toxins, rendering them harmless . 　　They can be seen as invisible "workers" in our gut, bacterial "workers" who stick to their posts, perform their duties, and drive the normal operation of the gut factory . Our physical and mental health is closely related to how pleasant it is for our gut bacteria to work in a factory . The survival of plants and animals depends entirely on the microbial world . 　　The human body reaps huge benefits from the gut microbiota, which in turn is the beneficiary, as the gut provides them with nutrients and a warm and humid environment every day, which is essential for their survival . Such a relationship in which organisms of two different species both benefit from the presence of the other species is a "symbiotic relationship", such as the bacteria that live in the gut and us humans, and the bacteria that favor this relationship are "symbiotic bacteria", And the bacteria that adversely affect this relationship are "pathogens" . 　　Distribution of Intestinal Bacteria 　　Although the entire digestive tract is colonized by bacteria, the distribution and quantity of bacteria in different parts of the digestive tract are not identical . In the stomach, due to the extremely low pH, the level of bacteria is low, about 1000-10000 per milliliter of contents . The high acidity of gastric juice kills many of the bacteria that pass through it, but a certain number of bacteria survive and enter the gut . Once there, they began to multiply and their numbers increased dramatically . 　　Of course, the duodenum and jejunum, which are next to the stomach, contain relatively few types and numbers of bacteria due to their lower pH . From the duodenum to the ileum, with the distance from the stomach, the acidity becomes weaker and weaker, forming a pH gradient, and the number of bacteria also begins to increase with the gradient. When it reaches the colon, it forms the microorganism with the largest bacterial density in the world. Colonies, which can reach 100 billion to 1 trillion per milliliter of content . 　　The distribution of various types of microbes in the gut occurs naturally, based on the unique properties of each microbe . 　　Among the relatively few microbes in the stomach and proximal small intestine, there are some aerobic bacteria that need oxygen to survive because air in the stomach is easily carried to this area . Anaerobic bacteria do not need oxygen to survive, they will survive and multiply in more distal parts, so they are mostly anaerobic bacteria in the second half of the small intestine and colon . 　　In order to survive and grow in the gut, bacteria not only need to reach specific areas, but they must also be able to take root after reaching a specific spot, in other words, they need to attach to the gut wall . If the gut doesn't want to host certain bacteria, the gut lining releases lymphocytes that attack them and drive them away . Bacteria that cannot attach to the surface of the intestinal wall cannot be part of or contribute to the maintenance and growth of the intestinal flora, and they are excreted in the feces . Those bacteria that attach to the gut wall stay to renew and maintain the gut flora . 　　In order to find a place to inhabit, the bacteria must also find an available location . There is intense competition for territories that can provide them with living space, and countless bacteria are involved in the competition, and when bacteria in a given area are too numerous or they are already entrenched, new bacteria will not be able to find any place to settle . 　　In addition to the normal healthy flora, the gut can temporarily shelter certain pathogenic invaders, but they are not considered part of the gut flora . 　　According to this, a healthy gut flora can be divided into three components: 　　Dominant flora: they are attached to the intestinal wall and generally remain stable, comprising 99% of the microbial 　　subdominant flora: they are variable, or more Or less rooted in the gut, including 0. 9% of the microbes 　　Passing microbes: These microbes simply pass through the gut without attaching to the gut wall, making up 0. 1% of the total 　　gut microbiota is unique to each person 　　No A standard composition of gut flora that applies to all, each of us has our own unique gut flora, as unique as our fingerprints . We all have a small number of bacteria in common, but there are many different types of bacteria between individuals . The content of yeast and other fungi also varies from individual to individual . The composition of the gut microbiota differs not only in the type of microorganisms, but also in quantity . Some groups of microbes are more numerous than others because they find foods in the gut that better suit their needs . 　　In conclusion, our gut is home to a large number of bacteria, fungi and viruses, all of which make up our gut microbiome . Far from being a threat to our health, they are essential for the proper functioning of our bodies . Next, we will explain the function of the intestinal flora in detail, so stay tuned!   Disclaimer: This article only represents the author's personal opinion and has nothing to do with China Probiotics Network . Its originality and the text and content stated in the text have not been verified by this site, and this site does not make any guarantee or commitment to the authenticity, completeness and timeliness of this text and all or part of its content and text. Readers are only for reference and please Verify the relevant content yourself .   Copyright Notice 1. Some articles reproduced on this site are not original, and their copyright and responsibility belong to the original author . 2. All reprinted articles, links and pictures on this website are for the purpose of conveying more information, and the source and author are clearly indicated. Media or individuals who do not wish to be reprinted can contact us for infringing information that can provide sufficient evidence. , bio149 will be deleted within 12 hours after confirmation . 3. 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Microbes are everywhere, and almost no place is immune to their presence
.
Our bodies also carry an abundance of microbes that live on our skin and the mucous membranes of our hollow organs, such as the stomach and intestines, forming microbial communities that live in mutualistic symbiosis with humans
.
They are given different names depending on where they are located, so we have oral flora, lung flora, vaginal flora, skin flora, etc.
, and we focus on the gut flora
.


　　The process of formation of the gut microbiota The

　　gut microbiota plays a vital role in the normal functioning of the human body and is an integral part of all stages of the digestive process as it synthesizes nutrients, neutralizes toxins, and more
.
Gut flora is an essential element of our health, and without them, the body cannot function properly
.
However, babies are almost sterile at birth, and the fetus' digestive tract is bacteria-free
.
So how does the gut microbiota form? Microbes from outside enter the newborn's gut through childbirth, breastfeeding, and human contact
.


　　The initial microbes enter the body through the air inhaled by the newborn
.
When they enter the body, they stay on the mucous membranes of the nasal cavity, from there they enter the throat and further into the body
.


　　The other entrance is the mouth, where in addition to the air, a newborn's mouth is in contact with many things that have microbes, such as their own fingers, the mother's skin and bedding, and anything they might put in their mouths, and these microbes then migrate to the gut
.


　　The main vehicle for microorganisms to enter the human body is food, which is loaded with various microorganisms
.
The first food for a newborn is breast milk
.
Breastfeeding babies are not only ingesting breast milk, but also the bacteria contained in breast milk
.
Once in the body, these bacteria make their way into the gut, where there are familiar Lactobacillus and Bifidobacterium, the main beneficial bacteria in the gut
.


　　Breast milk is ideal for the development of the neonatal gut microbiota
.
Between the 1960s and 1970s, many infants were formula-fed, and the resulting lack of gut flora was the cause of many health problems
.
It is the recognition of the true root causes of these diseases that has led to a renewed emphasis on breastfeeding and recognition of its benefits
.
Sometimes breastfeeding may not be possible, and scientists have tried to apply these benefits to infant formula, adding live probiotics to make it closer to breast milk, but it is also difficult to fully achieve the level of breast milk
.


　　Like all living things, microorganisms can only survive in an environment that provides favorable conditions for their growth, the temperature and humidity must be suitable, and the environment must provide the nutrients they need in sufficient quantities
.


　　Some microbes die once they enter the digestive tract because the environment is too harsh; others simply pass through and are eventually excreted in the feces because the living conditions they need cannot be met in the digestive tract
.
However, some of the microbes that enter will find ideal living conditions with an adequate food supply, they will colonize the gut, and when they multiply, they will colonize the gut and develop their unique flora
.


　　The increase in the number of microbes in the early gut is fairly rapid, and 48 hours after birth, infants' first stools are high in microbes, but not very diverse
.
After a week, the microbial diversity was higher, as was the total number
.
From this point on, this microbial composition remains stable throughout the period the infant continues to drink breast milk
.


　　Once the baby is weaned and solid foods begin to replace breast milk, many new microbes enter the gut, and the composition of the gut flora changes dramatically
.
The new microbes that enter the digestive tract increase the number of species already present, and the abundance of new food provides them with nutrients and makes them easier to reproduce
.
Since then, their numbers have greatly increased
.


　　The number of gut bacteria is very large

　　The number of microorganisms in the intestinal flora is extremely large, in the trillions
.
Early estimates put these microbes in 10 times the number of our own cells, but the latest research suggests that this number is smaller, but still far exceeds the number of our own cells
.


　　If we gather all the gut microbes in one container, this container must be able to hold 1-2 liters, and all these microbes weigh about 1.
5-2 kilograms
.


　　There are 500-1000 different bacteria in the gut microbiota, and a single bacterium may in turn comprise a large number of subgroups or serotypes
.
For example, E.
coli includes many different serotypes, some of which produce toxins, but most are generally harmless
.


　　Gut microbes are so tiny that they are invisible to the naked eye, only about a micron in size, or 0.
001 millimeters
.
If they were compared to a single hair, they could be a thousand times smaller than the thickness of a hair
.
One cubic millimeter can hold about 100 million microorganisms
.


　　Propagation of gut microbes A

　　large number of microbes are excreted in feces every day, and it is estimated that all of these microorganisms together make up half of the weight of feces
.
In order to maintain the number of gut microbiota, these excreted microbes must be constantly replaced with new ones
.
This is easy to achieve for two reasons:

　　every time we eat, a large number of bacteria are reintroduced into the body through the food
.


　　Bacteria multiply very quickly
.


　　Bacteria have a unique reproduction method that allows their offspring to multiply rapidly, a "mother cell" divides into two new "daughter cells", each of which divides to produce two new daughter cells, and so on.

.
The number of offspring is not increased by one unit per generation, but doubled per generation, i.
e.
in multiples of 2, 4, 8, 16, 32,
etc.
Therefore, the rate of bacterial reproduction is very fast
.
Humans reproduce one generation every 20 years or so, while bacteria typically reproduce every 15-60 minutes, and with that in mind, bacteria multiply faster
.


　　Are germs dangerous?

　　Bacteria have a bad reputation, people talk about bacteria discoloration, think they are all harmful
.
Indeed, they can infect us, make us sick or even die
.
So why does our body still provide a habitat for so many bacteria? In fact, there are billions of different types of bacteria on Earth, but only a few are pathogenic, and the vast majority are harmless or even beneficial
.


　　In nature, it is bacteria that give life to inert minerals in the soil and enable plants to absorb these minerals, such as nitrogen, phosphorus and sulfur
.
Bacteria are also responsible for breaking down dead plants and animals, and their tissues contain a lot of reusable material
.
In order for them to be recycled, they need to be freed from the organic structures that hold them in place
.
Bacteria break down tissue into smaller particles, which are then reabsorbed into a new life cycle
.


　　Gut bacteria play a very beneficial role in all aspects of our physical and psychological functions: they can synthesize vitamins and more from simple substances in the food we eat; they can also help break down our own insufficient digestion.
or indigestible food particles, such as dietary fiber; finally, they are also able to destroy certain toxins, rendering them harmless
.


　　They can be seen as invisible "workers" in our gut, bacterial "workers" who stick to their posts, perform their duties, and drive the normal operation of the gut factory
.
Our physical and mental health is closely related to how pleasant it is for our gut bacteria to work in a factory
.
The survival of plants and animals depends entirely on the microbial world
.


　　The human body reaps huge benefits from the gut microbiota, which in turn is the beneficiary, as the gut provides them with nutrients and a warm and humid environment every day, which is essential for their survival
.
Such a relationship in which organisms of two different species both benefit from the presence of the other species is a "symbiotic relationship", such as the bacteria that live in the gut and us humans, and the bacteria that favor this relationship are "symbiotic bacteria", And the bacteria that adversely affect this relationship are "pathogens"
.


　　Distribution of Intestinal Bacteria

　　Although the entire digestive tract is colonized by bacteria, the distribution and quantity of bacteria in different parts of the digestive tract are not identical
.
In the stomach, due to the extremely low pH, the level of bacteria is low, about 1000-10000 per milliliter of contents
.
The high acidity of gastric juice kills many of the bacteria that pass through it, but a certain number of bacteria survive and enter the gut
.
Once there, they began to multiply and their numbers increased dramatically
.


　　Of course, the duodenum and jejunum, which are next to the stomach, contain relatively few types and numbers of bacteria due to their lower pH
.
From the duodenum to the ileum, with the distance from the stomach, the acidity becomes weaker and weaker, forming a pH gradient, and the number of bacteria also begins to increase with the gradient.
When it reaches the colon, it forms the microorganism with the largest bacterial density in the world.
Colonies, which can reach 100 billion to 1 trillion per milliliter of content
.


　　The distribution of various types of microbes in the gut occurs naturally, based on the unique properties of each microbe
.


　　Among the relatively few microbes in the stomach and proximal small intestine, there are some aerobic bacteria that need oxygen to survive because air in the stomach is easily carried to this area
.
Anaerobic bacteria do not need oxygen to survive, they will survive and multiply in more distal parts, so they are mostly anaerobic bacteria in the second half of the small intestine and colon
.


　　In order to survive and grow in the gut, bacteria not only need to reach specific areas, but they must also be able to take root after reaching a specific spot, in other words, they need to attach to the gut wall
.
If the gut doesn't want to host certain bacteria, the gut lining releases lymphocytes that attack them and drive them away
.
Bacteria that cannot attach to the surface of the intestinal wall cannot be part of or contribute to the maintenance and growth of the intestinal flora, and they are excreted in the feces
.
Those bacteria that attach to the gut wall stay to renew and maintain the gut flora
.


　　In order to find a place to inhabit, the bacteria must also find an available location
.
There is intense competition for territories that can provide them with living space, and countless bacteria are involved in the competition, and when bacteria in a given area are too numerous or they are already entrenched, new bacteria will not be able to find any place to settle
.


　　In addition to the normal healthy flora, the gut can temporarily shelter certain pathogenic invaders, but they are not considered part of the gut flora
.


　　According to this, a healthy gut flora can be divided into three components:

　　Dominant flora: they are attached to the intestinal wall and generally remain stable, comprising 99% of the microbial

　　subdominant flora: they are variable, or more Or less rooted in the gut, including 0.
9% of the microbes

　　Passing microbes: These microbes simply pass through the gut without attaching to the gut wall, making up 0.
1% of the total

　　gut microbiota is unique to each person

　　No A standard composition of gut flora that applies to all, each of us has our own unique gut flora, as unique as our fingerprints
.
We all have a small number of bacteria in common, but there are many different types of bacteria between individuals
.
The content of yeast and other fungi also varies from individual to individual
.
The composition of the gut microbiota differs not only in the type of microorganisms, but also in quantity
.
Some groups of microbes are more numerous than others because they find foods in the gut that better suit their needs
.


　　In conclusion, our gut is home to a large number of bacteria, fungi and viruses, all of which make up our gut microbiome
.
Far from being a threat to our health, they are essential for the proper functioning of our bodies
.
Next, we will explain the function of the intestinal flora in detail, so stay tuned!

---

Microbes are everywhere, and almost no place is immune to their presence
.
Our bodies also carry an abundance of microbes that live on our skin and the mucous membranes of our hollow organs, such as the stomach and intestines, forming microbial communities that live in mutualistic symbiosis with humans
.
They are given different names depending on where they are located, so we have oral flora, lung flora, vaginal flora, skin flora, etc.
, and we focus on the gut flora
.


　　The process of gut flora formation The

　　gut flora plays a vital role in the normal functioning of the human body and is an integral part of all stages of the digestive process as it synthesizes nutrients, neutralizes toxins, and more
.
Gut flora is an essential element of our health, and without them, the body cannot function properly
.
However, babies are almost sterile at birth, and the fetus' digestive tract is bacteria-free
.
So how does the gut microbiota form? Microbes from outside enter the newborn's gut through childbirth, breastfeeding, and human contact
.


　　The initial microbes enter the body through the air inhaled by the newborn
.
When they enter the body, they stay on the mucous membranes of the nasal cavity, from there they enter the throat and further into the body
.


　　The other entrance is the mouth, where in addition to the air, a newborn's mouth is in contact with many things that have microbes, such as their own fingers, the mother's skin and bedding, and anything they might put in their mouths, and these microbes then migrate to the gut
.


　　The main vehicle for microorganisms to enter the human body is food, which is loaded with various microorganisms
.
The first food for a newborn is breast milk
.
Breastfeeding babies are not only ingesting breast milk, but also the bacteria contained in breast milk
.
Once in the body, these bacteria make their way into the gut, where there are familiar Lactobacillus and Bifidobacterium, the main beneficial bacteria in the gut
.


　　Breast milk is ideal for the development of the neonatal gut microbiota
.
Between the 1960s and 1970s, many infants were formula-fed, and the resulting lack of gut flora was the cause of many health problems
.
It is the recognition of the true root causes of these diseases that has led to a renewed emphasis on breastfeeding and recognition of its benefits
.
Sometimes breastfeeding may not be possible, and scientists have tried to apply these benefits to infant formula, adding live probiotics to make it closer to breast milk, but it is also difficult to fully achieve the level of breast milk
.


　　Like all living things, microorganisms can only survive in an environment that provides favorable conditions for their growth, the temperature and humidity must be suitable, and the environment must provide the nutrients they need in sufficient quantities
.


　　Some microbes die once they enter the digestive tract because the environment is too harsh; others simply pass through and are eventually excreted in the feces because the living conditions they need cannot be met in the digestive tract
.
However, some of the microbes that enter will find ideal living conditions with an adequate food supply, they will colonize the gut, and when they multiply, they will colonize the gut and develop their unique flora
.


　　The increase in the number of microbes in the early gut is fairly rapid, and 48 hours after birth, infants' first stools are high in microbes, but not very diverse
.
After a week, the microbial diversity was higher, as was the total number
.
From this point on, this microbial composition remains stable throughout the period the infant continues to drink breast milk
.


　　Once the baby is weaned and solid foods begin to replace breast milk, many new microbes enter the gut, and the composition of the gut flora changes dramatically
.
The new microbes that enter the digestive tract increase the number of species already present, and the abundance of new food provides them with nutrients and makes them easier to reproduce
.
Since then, their numbers have greatly increased
.


　　The number of gut bacteria is very large

　　The number of microorganisms in the intestinal flora is extremely large, in the trillions
.
Early estimates put these microbes in 10 times the number of our own cells, but the latest research suggests that this number is smaller, but still far exceeds the number of our own cells
.


　　If we gather all the gut microbes in one container, this container must be able to hold 1-2 liters, and all these microbes weigh about 1.
5-2 kilograms
.


　　There are 500-1000 different bacteria in the gut microbiota, and a single bacterium may in turn comprise a large number of subgroups or serotypes
.
For example, E.
coli includes many different serotypes, some of which produce toxins, but most are generally harmless
.


　　Gut microbes are so tiny that they are invisible to the naked eye, only about a micron in size, or 0.
001 millimeters
.
If they were compared to a single hair, they could be a thousand times smaller than the thickness of a hair
.
One cubic millimeter can hold about 100 million microorganisms
.


　　Propagation of gut microbes A

　　large number of microbes are excreted in feces every day, and it is estimated that all of these microorganisms together make up half of the weight of feces
.
In order to maintain the number of gut microbiota, these excreted microbes must be constantly replaced with new ones
.
This is easy to achieve for two reasons:

　　every time we eat, a large number of bacteria are reintroduced into the body through the food
.


　　Bacteria multiply very quickly
.


　　Bacteria have a unique reproduction method that allows their offspring to multiply rapidly, a "mother cell" divides into two new "daughter cells", each of which divides to produce two new daughter cells, and so on.

.
The number of offspring is not increased by one unit per generation, but doubled per generation, i.
e.
in multiples of 2, 4, 8, 16, 32,
etc.
Therefore, the rate of bacterial reproduction is very fast
.
Humans reproduce one generation every 20 years or so, while bacteria typically reproduce every 15-60 minutes, and with that in mind, bacteria multiply faster
.


　　Are germs dangerous?

　　Bacteria have a bad reputation, people talk about bacteria discoloration, think they are all harmful
.
Indeed, they can infect us, make us sick or even die
.
So why does our body still provide a habitat for so many bacteria? In fact, there are billions of different types of bacteria on Earth, but only a few are pathogenic, and the vast majority are harmless or even beneficial
.


　　In nature, it is bacteria that give life to inert minerals in the soil and enable plants to absorb these minerals, such as nitrogen, phosphorus and sulfur
.
Bacteria are also responsible for breaking down dead plants and animals, and their tissues contain a lot of reusable material
.
In order for them to be recycled, they need to be freed from the organic structures that hold them in place
.
Bacteria break down tissue into smaller particles, which are then reabsorbed into a new life cycle
.


　　Gut bacteria play a very beneficial role in all aspects of our physical and psychological functions: they can synthesize vitamins and more from simple substances in the food we eat; they can also help break down our own insufficient digestion.
or indigestible food particles, such as dietary fiber; finally, they are also able to destroy certain toxins, rendering them harmless
.


　　They can be seen as invisible "workers" in our gut, bacterial "workers" who stick to their posts, perform their duties, and drive the normal operation of the gut factory
.
Our physical and mental health is closely related to how pleasant it is for our gut bacteria to work in a factory
.
The survival of plants and animals depends entirely on the microbial world
.


　　The human body reaps huge benefits from the gut microbiota, which in turn is the beneficiary, as the gut provides them with nutrients and a warm and humid environment every day, which is essential for their survival
.
Such a relationship in which organisms of two different species both benefit from the presence of the other species is a "symbiotic relationship", such as the bacteria that live in the gut and us humans, and the bacteria that favor this relationship are "symbiotic bacteria", And the bacteria that adversely affect this relationship are "pathogens"
.


　　Distribution of Intestinal Bacteria

　　Although the entire digestive tract is colonized by bacteria, the distribution and quantity of bacteria in different parts of the digestive tract are not identical
.
In the stomach, due to the extremely low pH, the level of bacteria is low, about 1000-10000 per milliliter of contents
.
The high acidity of gastric juice kills many of the bacteria that pass through it, but a certain number of bacteria survive and enter the gut
.
Once there, they began to multiply and their numbers increased dramatically
.


　　Of course, the duodenum and jejunum, which are next to the stomach, contain relatively few types and numbers of bacteria due to their lower pH
.
From the duodenum to the ileum, with the distance from the stomach, the acidity becomes weaker and weaker, forming a pH gradient, and the number of bacteria also begins to increase with the gradient.
When it reaches the colon, it forms the microorganism with the largest bacterial density in the world.
Colonies, which can reach 100 billion to 1 trillion per milliliter of content
.


　　The distribution of various types of microbes in the gut occurs naturally, based on the unique properties of each microbe
.


　　Among the relatively few microbes in the stomach and proximal small intestine, there are some aerobic bacteria that need oxygen to survive because air in the stomach is easily carried to this area
.
Anaerobic bacteria do not need oxygen to survive, they will survive and multiply in more distal parts, so they are mostly anaerobic bacteria in the second half of the small intestine and colon
.


　　In order to survive and grow in the gut, bacteria not only need to reach specific areas, but they must also be able to take root after reaching a specific spot, in other words, they need to attach to the gut wall
.
If the gut doesn't want to host certain bacteria, the gut lining releases lymphocytes that attack them and drive them away
.
Bacteria that cannot attach to the surface of the intestinal wall cannot be part of or contribute to the maintenance and growth of the intestinal flora, and they are excreted in the feces
.
Those bacteria that attach to the gut wall stay to renew and maintain the gut flora
.


　　In order to find a place to inhabit, the bacteria must also find an available location
.
There is intense competition for territories that can provide them with living space, and countless bacteria are involved in the competition, and when bacteria in a given area are too numerous or they are already entrenched, new bacteria will not be able to find any place to settle
.


　　In addition to the normal healthy flora, the gut can temporarily shelter certain pathogenic invaders, but they are not considered part of the gut flora
.


　　According to this, a healthy gut flora can be divided into three components:

　　Dominant flora: they are attached to the intestinal wall and generally remain stable, comprising 99% of the microbial

　　subdominant flora: they are variable, or more Or less rooted in the gut, including 0.
9% of the microbes

　　Passing microbes: These microbes simply pass through the gut without attaching to the gut wall, making up 0.
1% of the total

　　gut microbiota is unique to each person

　　No A standard composition of gut flora that applies to all, each of us has our own unique gut flora, as unique as our fingerprints
.
We all have a small number of bacteria in common, but there are many different types of bacteria between individuals
.
The content of yeast and other fungi also varies from individual to individual
.
The composition of the gut microbiota differs not only in the type of microorganisms, but also in quantity
.
Some groups of microbes are more numerous than others because they find foods in the gut that better suit their needs
.


　　In conclusion, our gut is home to a large number of bacteria, fungi and viruses, all of which make up our gut microbiome
.
Far from being a threat to our health, they are essential for the proper functioning of our bodies
.
Next, we will explain the function of the intestinal flora in detail, so stay tuned!

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