The bacterium domain is one of the three domains identified in the tree of life and constitutes the most primitive form of life. Of all organisms, bacteria are the most abundant on the planet.
They can inhabit various ecosystems, from springs of water at 100 degrees Celsius to the poles, at temperatures below 15 degrees Celsius.
In 1977 Carl Woese, together with other scientists, determined this new classification based on characteristics such as the type of cell, the compounds that make up its membrane, and the structure of RNA.
Bacteria are prokaryotic organisms that lack a membrane-enclosed nucleus and organelles. For their displacement they use flagella or sliding flexion movements, while others remain immobile.
Bacteria are made up of a circular DNA molecule called a nucleoid, which is found in the cytoplasm.
These organisms fulfill various functions on the planet: they affect human health and industrial development.
Living beings are classified into three domains: eucarya, which are plants, animals, fungi, chromist (algae and plankton) and protists; archaea, which refers to microbes that live in extreme environments; and eubacteria or bacteria, which includes all other bacteria.
The bacterium domain includes all bacteria (eubacteria) and cyanobacteria (blue-green algae), which are the most common forms of this domain.
History
Microbiological knowledge has focused the interest of scientists since Charles Darwin described the tree of life, which includes the organisms in charge of giving life on the planet.
In the seventeenth century, the existence of bacteria and their possibility of contagion were discovered, but it was only until 1977 that Carl Woese identified the basic domains that contain life.
The classification of plants and animals was based on comparative anatomy and embryology, but it was very difficult to understand the function of bacteria due to their vast physiological diversity.
characteristics
The bacterium domain includes almost all microscopic unicellular beings. They have few associated proteins and do not have a nuclear membrane, mitochondria or plastids, typical of plants and fungi.
These prokaryotic cells are between 0.2 and 10 millimeters wide and are made up of a circular DNA molecule called a nucleoid, which is found in the cytoplasm. They use small organelles to move and have few associated proteins.
Bacteria are very important in nature since they are present in the natural cycles of nitrogen, carbon and phosphorus, among others. Bacteria can transform organic substances into inorganic ones, and vice versa.
This group of organisms is nourished by absorption, photosynthesis or chemosynthesis and its reproduction is asexual, by binary fission; that is to say, before reproduction occurs, the duplication or copying of that genetic material occurs, and thus cell division occurs. This division can also occur through buds.
The shape of bacteria is very varied, and often the same species adopts different morphological types. This phenomenon is known as pleomorphism. It is possible to find four types of bacteria: cocci, which are shaped like a sphere; bacilli, such as Escherischia coli; the spirilla, which are helical cells; and vibrios, which cause cholera.
Bacteria are found in all terrestrial and aquatic ecosystems and thrive in extreme environments. These environments include hot and acidic springs, radioactive waste, the depths of the sea or any area of the earth's crust.
Some types of bacteria are independent and others are parasitic: they feed on other organisms and a wide variety of things.
Types of bacteria
In general terms, bacteria can be classified into three types:
Aerobic
These bacteria need oxygen to grow and survive.
Anaerobic
They cannot tolerate oxygen.
Facultative anaerobes
They are bacteria that prefer to grow in the presence of oxygen, although they can really do without it.
Within the bacterium domain there are eleven orders:
- Eubacterial, spherical or bacillary, comprising almost all pathogenic bacteria and phototrophic forms
- Pseudomonales, an order divided into ten families, including the pseudomonae and the spirillacae
- Spirochetals (treponemes, leptospires)
- Actinomycetales (mycobacteria, actinomycetes)
- Rickettsiales
- Mycoplasmal
- Chlamydobacteria
- Hifomicrobiales
- Beggiatoales
- Cariofanales
- Myxobacterials
Features
Bacteria are very important for the recycling of various elements; many important steps in biogeochemical cycles depend on these. They are responsible for the decomposition of organic matter in its most basic forms so that it can return to the soil or air.
There are ten times more bacterial cells than human cells in the human body. Most are concentrated in the skin and digestive tract.
The function is to protect the body and also to create an environment conducive to the development of other physiological functions, but when the normal number of bacteria is disturbed, diseases occur.
The protection provided by the immune system allows many of these bacteria to be beneficial and harmless. However, some pathogenic bacteria can cause infectious diseases such as diphtheria, syphilis, cholera, typhus, scarlet fever, and leprosy.
There are two hundred species of bacteria that turn out to be pathogenic for humans, but the vast majority are indifferent or beneficial.
Bacteria are important in industrial processes such as the manufacture of chemicals and medicines, the treatment of wastewater, and in the production of foods such as cold cuts, vinegar, butter, yogurt, cheese, olives, pickles and onions.
Scientists around the world use different types of bacteria for medical purposes for the production of antibiotics, creating vaccines and treating various diseases.
In cosmetics, bacteria are essential for the production of anti-wrinkle creams, skin protectants and antioxidants.
References
- Pohlschröder, M., Prinz, WA, Hartmann, E., & Beckwith, J. (1997). Protein translocation in the three domains of life: variations on a theme. Cell, 91 (5), 563-566.
- Ciccarelli, FD, Doerks, T., Von Mering, C., Creevey, CJ, Snel, B., & Bork, P. (2006). Toward automatic reconstruction of a highly resolved tree of life. science, 311 (5765), 1283-1287.
- Beveridge, TJ (1994). Bacterial S-layers. Current Opinion in Structural Biology, 4 (2), 204-212.
- Marchionatto, JB (1948). Phytopathology Treaty. Bs As: Ediciones Librería del Colegio. pp: 45-47