Microscopic living organisms, the smallest on the planet, the most numerous inhabitants of the Earth - bacteria. These creatures are, at least, amazing, interesting science since then, with the invention of the multiple magnification of objects (microscope), they were finally noticed by mankind. Prior to this, the evolution of bacteria took place in humans, one might say, “under the very nose”, but no one paid due attention to them. And completely in vain!
Antiquity
They are the most ancient inhabitants of our planet. The long-standing habitat of bacteria is Earth. Bacteria appeared here as the first of living organisms, according to some scientists, about three and a half billion years ago (for comparison: the Earth’s age is about four billion). That is, roughly speaking, the age of bacteria is comparable with the age of the nature around us. By the way, the well-known history of mankind has only a few tens of thousands of years. Here we are "young" in comparison with these microorganisms.
The smallest and most numerous
Bacteria are also the smallest of all known wildlife. The fact is that the cells of almost all living organisms are approximately the same size. But not bacterial cells. The average bacterial cell is about ten times smaller than the average cell, for example, of a person. Due to such tinyness, they are also the most numerous inhabitants. It is known that in the lump of soil where bacteria live, there can be as many inhabitants as, for example, people in all countries of Europe.
Endurance
Nature, creating bacteria, has invested in them a huge margin of safety, significantly exceeding the endurance of other representatives of the fauna. Since the time of "deep antiquity" on Earth there have been many disasters, and bacteria have learned to tolerate them. To this day, the habitat of bacteria is so diverse that it causes deep interest of microbiologists. Microorganisms can sometimes be found in places where certainly no other creature can live.
Where bacteria can live
For example, in boiling geysers, where the water temperature can reach almost a hundred degrees above zero. Or - in underground oil lakes, as well as in unsuitable acid lakes, where any fish or other animal would immediately dissolve - this is where bacteria can live.
Scientists suggest that some types of bacteria can even exist in space! By the way, one of the versions of the world's population of living beings, the theory of the origin of life on the planet, is based on these data.
Disputes
In order to tolerate such adverse conditions, some bacteria form spores. We can say that this is a special, sleeping, resting form. Before forming a spore, the bacterium begins to dry out, removing fluid from itself. It decreases in size, remaining inside its shell, being covered additionally by another shell - a protective character. In this form, a microorganism can exist for a very, very long time, thus, as it were, “waiting for” difficult times. Then, depending on the environment in which the bacteria live - favorable or not - they can resume their life activity in full. This unique ability to survive in adverse conditions is being carefully studied by microbiologists.
Ubiquitous
To the question "where do bacteria live?" You can answer very simply: "Almost everywhere!" Namely: around us and in us, in the atmosphere, in soil, in water. And every person daily comes into contact with the myriads of these creatures, without noticing it. Among them there are pathogenic and opportunistic bacteria. There are also completely safe for the human body.
On the ground
In the soil where bacteria live, they contain the largest number. There are nutrients necessary for life, and the optimal amount of water, there is no direct sunlight. Most of these bacteria are saprophytes. They participate in the processes of formation of the fertile part of the soil (humus). However, pathogens are also present here: causative agents of tetanus, botulism, gas gangrene and other diseases. Then they can get into air and water, further infecting a person with these diseases.
So, the causative agent of tetanus, a fairly large stick, enters the body from the soil with various skin lesions and multiplies under anaerobic (without oxygen) conditions.
In water
Another place where bacteria can live is in the aquatic environment. They get here when they are washed away from the soil, and runoff falls into water bodies. For this reason, by the way, in artesian water there are much fewer bacteria than in the subsoil. And ordinary water from a lake or river can become an environment where pathogenic bacteria live, a place for the spread of many dangerous diseases: typhoid fever, cholera, dysentery and some others. So, for example, dysentery is caused by bacteria from Shigella species and is accompanied by severe intoxication of the body, gastrointestinal tract lesions.
In the atmosphere
In the air, where bacteria can live, there are not so many of them as in the soil. The atmosphere is an intermediate stage in the migration of microorganisms, therefore it cannot serve - due to lack of nutrients and insufficient humidity - as a permanent habitat for bacteria. Bacteria enter the air with dust, microscopic droplets of water, but then - they eventually settle on the soil. However, in densely populated places - large megacities, for example - the number of microorganisms contained in the air can be large, especially in the summer. And the air itself can serve as an environment where pathogenic bacteria, all kinds of infections live. Some of them: diphtheria, whooping cough. As well as tuberculosis caused by Koch's wand.
On man
On the skin of a person is a great many microorganisms. But they are unevenly distributed throughout the plane. Bacteria have “favorite” places, but there are sites resembling deserted deserts. Moreover, according to scientists, most microorganisms that live on the skin of people are not harmful. On the contrary, they perform a kind of protective function for a person from microbes that are considered dangerous. It has been scientifically proven that excessive sterility and cleanliness are not so good (of course, no one has yet canceled the simple rules of hygiene ). Least of all bacteria is in a person behind the auricles. The main amount is on the forearms (there are up to 45 species). Many bacteria live on the mucous membranes, the so-called wet areas, where they feel very comfortable. In dry (palms, buttocks) - the conditions of existence are not quite suitable for microorganisms.
Inside us
According to microbiologists, about three kilograms of bacteria live in the human intestines ! And in quantitative terms - this is a huge army, which can not be ignored. However, bacteria are smart neighbors. The bulk of those living in the human body (as well as other mammals) are useful and maintain a peaceful neighborhood with the "owners". Some help digestion. Others - perform protective functions: as a result of their actions, pathogens are immediately destroyed when they try to enter the defense territory. 99% of the population are bifidobacteria and bacteroids. And enterococci, E. coli (which is conditionally pathogenic), lactobacilli - from about 1 to 10%. Under adverse conditions, they can cause various diseases, but in the body of a healthy person they perform useful functions. Various mushrooms and staphylococci, which can also be pathogenic, also live there. But basically in the digestive tract there is a certain bacteriological balance, as if conceived by nature, maintaining human health at the proper level. And pathogenic microorganisms with a sufficiently high immunity cannot penetrate and cause harm.