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It is true that bacteria can cause many diseases, that they were the culprits of huge epidemics devastating entire human populations, but this is only a small part of their “activity” on Earth. Bacteria in human life do not only contribute to infections, diseases and death.
These microscopic organisms have found a way to populate our bodies as they inhabit the most inaccessible corners of the Earth and not be in opposition to us. Moreover, attempts to eliminate them are unlikely to end well and result in serious health problems.
The presence of bacteria
Microorganisms, especially bacteria, are ubiquitous. They can be found literally everywhere, starting from places where everyone expects them, such as puddles, soil or decaying organic matter, and ending with completely unexpected places, such as hot springs or almost boiling waters near the mouths of submarine volcanoes. It turns out that these small organisms can probably even survive a flight into space, because traces of them have been found inside objects returning or falling to Earth in the form of meteorites. The estimated number of bacterial cells on Earth is 5 × 1030 cells, which makes up a huge proportion of all biomass (all living matter) in the world. Bacteria cannot be seen with the naked eye, so it may seem that they do not exist, that they are just the invention of scientists and doctors, but if they suddenly ran out of them, agriculture, the food industry would collapse, there would be masses of dead bodies on the ground, and finally there would be no oxygen, because the plants that produce it they would not have food in the form of mineral salts derived from dead organic matter decomposed by microorganisms. The multitude of environments in which bacteria can live and the multitude of activities they carry out are the result of an extremely high degree of flexibility and adaptability.
Microbes in the human body
The human body is protected against the invasion of pathogenic microorganisms due to the fact that it has an immune (immune) system. Its task is to recognize and destroy microorganisms that have entered the human body. An apparent paradox arises here: if our body is equipped with a protection against infection, how can bacteria colonize it with impunity? The key to solving this puzzle is the division of the human body into two types of sectors, the first of which must absolutely remain sterile (the so-called physiologically sterile), and the second is exposed to microorganisms and usually it does not bring negative effects, and is even desirable. Areas classified as free of microorganisms, generally speaking, are those that do not have a natural direct connection with the external environment or due to high sensitivity must be specially protected, e.g. the circulatory system, lower respiratory tract, paranasal sinuses, body cavities such as the space lined with the peritoneum or the peritoneal system. nervous. The sites colonized by bacteria (the so-called commensal bacteria or bacterial physiological flora) are the skin surface, the upper respiratory tract with the oral cavity and the entire digestive tract, and the genital tract in women together with the urethra.
The presence of microbes in these places in the human body is not accidental and benefits both sides. Bacteria gain the possibility of reproduction and access to a food source, while humans are protected against the multiplication of pathogenic microorganisms, because commensal bacteria do not allow competition in the form of pathogens and compete with them for a place to live.
Human physiological flora
In general, the human body is estimated to be composed of 100 trillion cells, while the number of bacteria inhabiting it is 10 times higher. The abundance of microorganisms that make up the human physiological flora varies and depends on their location. The smallest species and quantity diversity is found in the skin, then more bacteria can be found in the vagina, and in the digestive tract this amount is huge, especially in its final part, i.e. in the large intestine (colon). The skin contains aerobic (oxygen-tolerant) bacteria, mainly of the Staphylococcus epidermidis species and, to a smaller number, of other staphylococcal species. They prevent the spread of, for example, skin infections caused by fungi. In the vagina of women, there are both aerobic bacteria, such as small amounts of streptococci from the genera Streptococcus and Enterococcus, and relatively anaerobic and anaerobic bacteria: Lactobacillus and Bifidobacterium. Lactobacilli of the genus Lactobacillus constitute the basis of a normal vaginal flora and allow the maintenance of physiological acidity in the range of pH = 3,6-4,5. In the case of reduction or complete elimination of Lactobacillus from the vagina as a result of, for example, antibiotic therapy or improper hygiene, the pH may rise, which results in the rapid multiplication of pathogenic bacteria and symptoms of vaginitis. It is not uncommon to develop vaginal mycosis, the so-called vaginal candidiasis.
Bacterial flora of the digestive tract
The most abundant and best known is the physiological flora of the human digestive tract. Thanks to her scientific research, we have obtained information about the significant influence of these microorganisms on the functioning of the entire body and its health. The commensal flora of the gastrointestinal tract plays an important role in the process of digestion and assimilation of nutrients and has a protective effect against the invasion of pathogenic microorganisms by creating the so-called resistance to colonization and influencing the immune system of the human body. The number of bacterial cells inhabiting the human gastrointestinal tract increases both qualitatively and quantitatively, from the stomach to the colon. There are very few bacteria in the stomach due to the high acidity of gastric juice (pH ~ 1,5). These are mainly species that got in with the food and stay there for a very short period of time. In the duodenum and the jejunum (the first part of the small intestine), the amount of bacteria increases and amounts to approx. 103 – 104 bacteria / ml – these are mainly representatives of the genera Streptococcus and Lactobacillus. In the small intestine (the end of the small intestine), the number of bacteria is 107-108 cfu / ml and species diversity increases. In the entire large intestine, the bacterial population is around 1014, or 100 trillion – in one milliliter of intestinal content there are approx. 1011 cells / ml. The bacterial flora of the colon consists mainly of anaerobic bacteria (Clostridium, Eubacterium, Bacteroides; Bifidobacterium) and, in smaller numbers, representatives of aerobic and relatively anaerobic bacteria (Enterobacteriaceae; Streptococcus; Staphylococcus; Lactobacillus). So far, genetic analysis has identified over 400 species of bacteria found in the large intestine. Numerous scientific studies show that the bacterial flora of the gastrointestinal tract plays a very important role in maintaining the physiological balance of the body. It is very interesting to observe that the correct species composition of bacteria in the large intestine allows the child’s organism to produce the correct response of the immune system to infections. Excessive sterilization of food given to toddlers and bringing them up in a sterile clean environment does not allow the proper colonization of their digestive tracts by the desired bacteria. This may cause a pathological reaction to allergens in the future, leading to the development of allergies or even asthma.
Bacteria are our allies
Bacteria should not be underestimated and their significant role in the functioning of not only the world as a global ecosystem (a system of interrelationships between all living organisms), but also in our own organisms, which, after all, are small ecosystems inhabited by microscopic tenants. Let us not be afraid of them and do not prepare to evict them. Just as interfering with nature and eliminating individual species of plants and animals or even their entire populations from certain areas results in disturbance of the ecological balance and entails a chain of adverse events, interference with the physiological bacterial flora of the organism may lead to health problems such as infections or allergies. . Bacteria are allies, not only malevolent invaders waiting for our health and life.
Text: Tomasz Gosiewski, MD, PhD