Bacterias are one of the oldest and most abundant microscopic life forms on planet Earth, distributed throughout all possible habitats and even in the digestive tract of higher animals.
Bacterias are responsible for many of the processes of decomposition and therefore recycling of organic matter and energy, as well as in 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 cultivated in the laboratory and are used in different food processing processes, in reality a large percentage of the existing species are still not described.
Diseases caused by bacteria are numerous, both in man and in animals, and are combated with various strains of drugs called antibiotics.
Characteristics Of Bacterias
1. Biological classification
Although the word ‘bacteria’ was initially used to describe all microscopic organisms, before biological and medical studies allowed us to distinguish the different 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 the archaea (or archaebacteria) in the same kingdom called moneras, which is a name for prokaryotic beings (those who do not have their genetic material contained in a cell nucleus). But they present to these fundamental and distinctive biochemical differences.
The oldest known bacteria originated together with the archaea about 4,000 million years ago, constituting the first unicellular prokaryotic organisms. For thousands of years these will have been the dominant forms of life on the planet, but it is still unknown which of the two will have emerged first.
3. Distinctive features
Bacterias are unicellular organisms varied in form and behavior. There are pathogenic and harmless, free-living and parasitic bacteria that make photosynthesis and that feed on other cells, with or without organs to move around.
However, they are ten times smaller than eukaryotic cells (with a defined nucleus) and have a cell wall composed of peptidoglycan. They are microscopic beings (barely larger than viruses) simple, and a membrane similar to that of animal and plant cells.
4. Types of bacteria
According to its very varied form, it is possible to classify bacteria into three broad categories:
Cocos Those bacteria of spherical shape. At the same time, they are classified as:
They have the shape of two spherical grains attached.
They have the shape of four spherical grains attached.
They have the shape of spherical grains in chains.
They have the shape of spherical, cluster-shaped, irregular grains.
Bacillus Bacteria that have the shape of a rod.
- Helical shapes. Those bacteria with more or less spiral shape, in turn divided into three groups:
- Vibrio. Slightly curved, comma-shaped.
- Espirilo. They have a rigid helical shape.
- Spirochaete. They have a corkscrew shape.
Bacteria, according to their sources of energy, can be of two types:
- Autotrophs Those that generate their own energy, using carbon dioxide (CO2) either through processes of photosynthesis (phototrophs) or the use of nitrogen or sulfur (chemiotrophs).
- Heterotrophs They must be nourished from the consumption of organic matter, coming from other living beings, like bacteria that decompose the flesh of dead animals.
Many bacterias are capable of displacement, while others are immobile or fixed. Those that move, they do it by means of flagella of proteins that serve to impel them like tails, or by cellular contractions or, even, sliding on the surfaces.
7. Gram stain
There is another classification of bacteria according to whether or not they respond to Gram stain, which is a laboratory technique to color and identify them under the microscope. The bacteria that respond to the dye are called Grampositive and those that do not, Gramnegative.
This difference is important because it is explained through a different cellular structure between the two: while the positive ones retain the dye thanks to the junction between the cell membrane and the peptidoglycan cell wall, the negative ones do not allow it to enter the cell through a second lipid membrane outside the cell wall.
Bacterias reproduce asexually, through a cell division called mitosis, once one has reached the proper size. As a result, two identical bacteria are formed from a bacterium, which can be, in particularly rapid cases, every 9.8 minutes.
Another form of reproduction that they possess is the budding, process in which a bacterium produces a protuberance of its body and little by little it is turning it into a totally new, but identical individual.
Some bacterias have certain forms of sexual reproduction (two individuals contribute genetic material to form a single 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 different.
9. Human diseases
There are many human diseases of bacterial origin, some of them well known, such as syphilis, gonorrhea, pneumonia, cholera, diphtheria, tuberculosis, scarlet fever, leprosy or anthrax.
10. Bacterial flora
Contrary to what it would seem, not all the bacteria in our body produce 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) can these bacteria become a problem.