We don’t see them, but we are surrounded by them. There are all kinds of them and, although very small in size, they go a long way in making our world what it is today.
Eubacteria are microorganisms found in most ecosystems on Earth and can range from functions beneficial to our species to harmful, causing us disease and organic damage.
Then we are going to dive into the field of eubacteria, also called true bacteria, and we will find out how they reproduce, what forms they can take and group together.
What are eubacteria?
Eubacteria are unicellular prokaryotic organisms. These microorganisms are known as real bacteria or simply as bacteria and their domain is one of the three domains of life proposed according to the current evolutionary model., with Eukarya and Archaea.
Until relatively recently, the term “bacteria” was used interchangeably to refer to any prokaryotic and unicellular organism, but over time this domain has been divided into that of eubacteria (Eubacteria) and archaebacteria (Archaebacteria). , later renamed to bacteria and archaea (Archaea)
In the case of prokaryotic organisms (without a cell nucleus), these organisms are relatively simple, having its genetic material dispersed throughout the cell matrix. But despite their simplicity, they are also among the most abundant living organisms in nature and are found in virtually every ecosystem on the planet. They live in any environment: earth, water, air and also on biotic and abiotic surfaces.
Over 5,000 different species of true bacteria have been described, which is why many biologists and bacteriologists believe that eubacteria are among the most common organisms in nature. There are all kinds of them, which are also found in pathogenic species, that is, they cause disease in other living things., although most eubacteria are harmless and even beneficial for the rest of their lives.
Characteristics of eubacteria
As we mentioned, true eubacteria or bacteria are very simple, single-celled, prokaryotic organisms. One of its main features is the absence of a membranous nucleus where its DNA is closed., or any other membrane cytosolic organelle. Added to this, we can highlight other very interesting characteristics of eubacteria.
The first is that in addition to being prokaryotes, they have a cell membrane formed from a lipid bilayer, as in eukaryotic or nucleus cells. In the case of eubacteria, this lipid bilayer contains a watery interior, known as the cytosol, where the genetic material of the cell is located and, among them, also cellular proteins such as ribosomes to be able to translate proteins.
Eubacteria are covered with a protective wall made of a polymer called peptidoglycan. This polymer is composed of repeated residues of N-acetyl-glucosamine carbohydrate and N-acetylmuramic acid, linked by β-1,4 bonds. In some cases, bacteria have filamentous protein structures on their surface that allow them to move around called cilia (if they are short and numerous) or flagella (if they are long and sparse).
The genetic material of prokaryotic cells is found in a specialized region of the cytosol known as the nucleoid. because, although not being a well-defined nucleus, it fulfills more or less the same functions. Eubacteria have all of their genetic material collected on a single circular chromosome. Additionally, in the cytosol we can also find other extrachromosomal DNA fragments, called plasmids, which can be shared with other bacteria by a structure called pilus and usually carry useful metabolic information.
In many cases, eubacteria are surrounded by a gelatinous capsule or matrix known as glycocalyx.. It is a component rich in carbohydrates that protrude from the membrane and cell wall, which provide some resistance to adverse environmental conditions, pathogens and antibiotics.
Some eubacteria can transform into endospores in case they are faced with extreme environmental situations. They are structures of resistance that help them tolerate factors such as extreme temperatures, too acidic or too basic pH levels, excessive radiation… In fact, it is thanks to their ability to become endospores that they can survive in almost any part of the planet. , to any type of surface and feeding on anything.
Size and shape
Bacteria are tiny in size but this they can oscillate between 0.2 and 50 microns approximately, although the average size is between 1 and 3 µm. Its shape varies considerably from species to species, the most common being the following three.
Coconuts are spherical or ovoid cells, which are usually found individually or arranged in space, depending on the plane in which they were divided as they can sometimes stay together even after they have been separated. They can be found in pairs, chains or in many groups depending on the species.
2. Rods or bacilli
Canes or bacilli are solitary or attached cells. Due to the similar shape to that of a stick, these alveoli resemble those of a sausage or a chorizo in case they are in a group.
Spirals they are spiral-shaped bacteria as the name suggests, generally flexible.
Types of bacteria
Currently, the most accepted classification for the domain of bacteria consists of the following 5 sections.
Proteobacteria they form one of the most widespread, abundant and diverse groups among microorganisms. To this section belong many bacteria having a pathogenic power for man and other species of the animal kingdom, being in this group the genera Salmonella, Helicobacter, Escherichia, Neisseria, Vibrio …
One of the main characteristics of proteobacteria is that they cannot be stained by the Gram method, which is why they are known as Gram-negative bacteria. These microorganisms are divided into the following groups:
Spirochetes are spiral-shaped bacteria up to great length, up to 500 µm long. Many are free microorganisms found in fresh or salt water, bodies of water rich in organic matter. Some are pathogenic to mammals, such as Leptospira bacteria.
Chlamydia bacteria they are usually intracellular parasites and this cut consists of only one class (Chlamydia). At the same time, this group is divided into two orders called Chlamydiales, with 4 families; and Parachlamydiales, with 6.
Cyanobacteria were once known as blue-green algae, or rather cyan in color as the name suggests. They are photoautotrophic, free or endosymbiont bacteria.
5. Gram-positive bacteria
We finally have the case of Gram-positive bacteria, whose name means they can be stained by the Gram stain method, invented by Danish bacteriologist Hans Christian Gram (1853-1938). In this cut we find:
- Firmicutes: bacteria that produce endospores. It is used for industrial purposes.
- Actinobacteria: used for the bioremediation of contaminated water and soil.
- Mycoplasma: includes pathogenic bacteria residing in mucous membranes and epithelia.
Nutrition of eubacteria
In the area of bacteria, we can find both heterotrophic and autotrophic organisms. Heterotrophic bacteria are those that need to feed on external sources, as in the animal kingdom, while autotrophs are able to produce their own food from inorganic compounds, just as plants do.
Most heterotrophic bacteria are saprophytes, which means that they feed on dead or decaying organic matter. In other cases, we find parasitic bacteria, that is, they live inside or outside of another organism, causing some kind of harm. There is also the case of symbiotic bacteria which establish a relationship of mutual support with another organism., giving him benefits while receiving food in return.
In the case of autotrophic eubacteria, photosynthetic or chemosynthetic bacteria can be found, which may or may not depend on the presence of oxygen. In the case of photosynthesis, they produce organic substances by photosynthesis using the energy given to them by the rays of the sun. and operate different types of photosynthetic pigments, such as chlorophyll. In the case of chemosynthetic bacteria, they use inorganic compounds such as ammonium, molecular hydrogen, iron or sulfur to produce their organic molecules.
Usually, true bacteria reproduce by binary fission, a mechanism of asexual reproduction unique to prokaryotes and other single-celled organisms. As the name suggests, in this process two identical cells are formed from the fission of a progenitor or stem cell. Binary fission is a very fast reproductive mechanism, although the time varies among species of bacteria, with some dividing in less than 20 minutes and others in several hours.
The process begins with the duplication of genetic material, i.e. the bacterial chromosome of circular shape. The progenitor cell then begins to increase in size and moments later the chromosome creates a copy of itself, migrating one to one pole of the cell and the other to the other. At this point, the cell has grown to almost double its original size.
Within the bacteria, a series of proteins begin to be activated, which are responsible for forming a dividing ring between the two daughter cells., located more or less in the middle of the stem cell. In the region where this division ring has formed, a new transverse cell wall begins to be synthesized, which ends up separating the two chromosomes located at each pole of the cell and which causes the separation of the two identical daughter cells.
Depending on the orientation in which the duplicated chromosomes are distributed, we are talking about different types of binary fission (longitudinal, transverse or irregular) but in all cases the same events that we have mentioned occur.
The importance of these microorganisms
Real bacteria allow the world to be as it is today, in addition to they can be used for economic purposes. For example, these microorganisms participate in the cycle of nutrients such as phosphorus, sulfur, carbon and nitrogen, breaking down organic matter producing these nutrients as a residue of their action. In the case of photosynthetic bacteria, they use solar energy to synthesize organic compounds and release oxygen into the atmosphere, just like plants do.
We have bacteria inside of us, but they are good. Some species act as symbionts in the gastrointestinal system of many animals, including humans and many ruminant herbivores, involved in digestion. Among these we can highlight Lactobacillus acidophilus and Streptococcus thermophilus.
In the field of biomedical research, bacteria are often used as model organisms for the study of various phenomena on life and are also exploited to produce various biotechnological compounds useful to mankind. Without the bacteria, it would not be possible to have foods like cheese or yogurt, or drugs like insulin, obtained from a transgenic strain of Escherichia coli.
- Chen, Hongliang and Wen, Yating and Li, Zhongyu. (2019). Chlamydia clear victory: the subversion of the host’s innate immunity. Frontiers in microbiology. 10. 10.3389 / fmicb.2019.01412.
- Schaechter, M. (2009). Encyclopedia of Microbiology. Academic Press.
- Stop Puig, Raquel. (December 16, 2020). Eubacteria: characteristics, nutrition, reproduction, classification. Lifeder. Retrieved from https://www.lifeder.com/eubacterias/.
- Taussig, LM and Landau, LI (2008). Pediatric Respiratory Medicine eBook. Elsevier Health Sciences.