We explain what bacteria are, how they are classified and the evolution of these organisms. In addition, its characteristics, reproduction and more.
Bacteria are one of the oldest and most abundant forms of microscopic life on planet Earth , distributed throughout all possible habitats and even in the digestive tracts of higher animals .
Bacteria are responsible for many of the decomposition processes and therefore recycling of organic matter and energy , as well as the fixation of atmospheric nitrogen . At the same time, some of them are capable of parasitizing living beings , both animals and plants, through what is known as infections.
Although many species of bacteria have been able to be cultivated in the laboratory and are used in different food-making processes, in reality a large percentage of the existing species remain undescribed .
Diseases caused by bacteria are numerous, both in humans and animals, and are fought with various strains of drugs called antibiotics .
Although the word 'bacteria' was initially used to describe all microscopic organisms , before biological and medical studies allowed us to distinguish the various types of microbes, today they are recognized as one of the six kingdoms of life according to the most recent classification.
In previous models they were located together with archaea (or archaebacteria ) in the same kingdom called moneras , which is a name for prokaryotic beings (those that do not have their genetic material contained in a cell nucleus ). But they present fundamental and distinctive biochemical differences towards these.
The oldest known bacteria originated together with archaea about 4 billion years ago , constituting the first prokaryotic unicellular organisms . For thousands of years these will have been the dominant life forms on the planet, but it is still unknown which of the two will have emerged first.
Bacteria are single-celled organisms varied in shape and behavior . There are pathogenic and harmless bacteria, free-living and parasitic, that photosynthesize and feed on other cells , with or without organs to move around.
However, most of them are ten times smaller than eukaryotic cells (with a defined nucleus) and have a cell wall composed of peptidoglycan. They are simple microscopic beings (barely bigger than viruses ), and a membrane similar to that of animal and plant cells .
According to their extremely varied shape, it is possible to classify bacteria into three broad categories:
Bacteria reproduce asexually , through a cell division called mitosis, once one has reached the right size. As a result, two new identical bacteria are formed, which can be, in particularly fast cases, every 9.8 minutes.
Another form of reproduction that they have is budding , a process in which a bacterium produces a protrusion of its body and little by little it turns it into a totally new, but identical individual.
Some bacteria have certain forms of sexual reproduction (two individuals contribute genetic material to form one, new and different from both), called bacterial conjugation. Two of them exchange genetic material and replicate to give rise to four new and genetically distinct ones.
There are very many human diseases of bacterial origin, some of them well known, such as syphilis, gonorrhea, pneumonia, cholera, diphtheria, tuberculosis, scarlet fever, leprosy or anthrax.
Contrary to what it might seem, not all bacteria in our body cause infections. Many of them are part of the bacterial flora in our intestines, helping us break down food and deal with nutrients. Only in cases of immunosuppression (weakness of the immune system ) these bacteria can become a problem.
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