Eubacteria: What They Are, Characteristics And Types
We don’t see them, but we are surrounded by them. They come in all forms and, although very small in size, they contribute enormously to making our world as it is today.
Eubacteria are microorganisms present in most ecosystems on Earth and that can have functions ranging from beneficial to our species to being harmful, causing diseases and organic damage.
Next Let’s delve into the domain of eubacteria also known as true bacteria, and we are going to discover how they reproduce, what shapes they can take and what groups there are.
Eubacteria are single-celled prokaryotic organisms. These microorganisms are known as true bacteria or simply as bacteria and their domain is one of the three domains of life proposed according to the current evolutionary model along with the Eukarya and the Archaea.
Until relatively recently, the term “bacteria” was used interchangeably to refer to any prokaryotic and unicellular organism, but over time this domain was divided into eubacteria (Eubacteria) and archaebacteria (Archaebacteria), later being renamed as bacteria and archaea (Archaea)
As they are prokaryotic organisms (without a cell nucleus), these organisms are relatively simple, having its genetic material spread throughout the cellular matrix. But despite their simplicity, they are also one of the most abundant living organisms in nature, found in practically any ecosystem on the planet. They live in any medium: soil, water, air and also on biotic and abiotic surfaces.
More than 5,000 different species of true bacteria have been described, which is why many scientists, biologists and bacteriologists, consider that eubacteria are the most common organisms in nature. There are all kinds of them, and there are also pathogenic species, that is, those that cause diseases in other living beings although most eubacteria are harmless and even beneficial for the rest of life.
Characteristics of eubacteria
As we have mentioned, eubacteria or true bacteria are very simple, unicellular and prokaryotic organisms. One of its main characteristics is the lack of a membranous nucleus in which its DNA is enclosed, or any other membranous cytosolic organelle. Added to this, we can highlight other very interesting characteristics of eubacteria.
The first is that, apart from being prokaryotes, they have a cell membrane formed by a double lipid layer, just as happens in eukaryotic cells or cells with a nucleus. In the case of eubacteria, This lipid bilayer encloses a watery interior, known as cytosol, where the genetic material of the cell is found and, among them, also cellular proteins such as, for example, ribosomes to be able to translate proteins.
Eubacteria are covered by a protective wall, which is made up of a polymer called peptidoglycan. This polymer is composed of repeated residues of the carbohydrate N-acetyl-glucosamine and N-acetylmuramic acid, linked by β-1,4 bonds. In some cases, bacteria have filament-shaped protein structures on their surface that allow them to move, known as cilia (if they are short and many) or flagella (if they are long and few).
The genetic material of prokaryotic cells is located in a specialized region of the cytosol known as the nucleoid since, despite not being a well-defined nucleus, it performs more or less the same functions. Eubacteria have all their genetic material collected in a single circular chromosome. Added to this, in the cytosol we can also find other extrachromosomal DNA fragments, called plasmids, which can be shared with other bacteria through a structure called pilus and, generally, carry useful metabolic information.
In many cases, eubacteria are surrounded by a gelatinous capsule or matrix known as a glycocalyx It is a component rich in carbohydrates that protrude from the membrane and cell wall, which provide a certain resistance to adverse environmental conditions, pathogens and antibiotics.
Some eubacteria can transform into endospores if they face extreme environmental situations. These are resistance structures that help them tolerate factors such as extreme temperatures, pH levels that are too acidic or too basic, excessive radiation… In fact, it is thanks to their ability to become endospores that they can survive almost anywhere on the planet, in any type of surface and feeding on anything.
Size and shape
Bacteria have tiny sizes but They can range between approximately 0.2 and 50 microns, although the average size is between 1 and 3 µm Its shape varies greatly from species to species, the following three being the most common.
1. Coconuts
Cocci are spherical or ovoid cells, which are usually found individually or spatially ordered, depending on the plane in which they have been divided since sometimes they can remain united even after having been divided. They can be found in pairs, chains or large groups depending on the species.
2. Canes or bacilli
Rods or bacilli are solitary or united cells. Given their rod-like shape, these cells resemble those of a sausage or a chorizo if you are in a group.
3. Spirits
The spirits 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 phyla.
1. Proteobacteria
The proteobacteria They make up one of the most widespread, abundant and diverse groups among microorganisms Many bacteria with pathogenic capacity for humans and other species of the animal kingdom belong to this phylum, including the genera Salmonella, Helicobacter, Escherichia, Neisseria, Vibrio…
One of the characteristics that make Proteobacteria stand out is that they cannot be stained using the Gram method, which is why they are known as Gram-negative bacteria. These microorganisms are divided into the following groups:
2. Spirochaetae
The spirochetes are spiral-shaped bacteria that can be very long, up to 500 µm long Many of them are free-living microorganisms present in fresh or salt water, bodies of water rich in organic matter. Some of them are pathogenic for mammals, such as the Leptospira bacteria.
3. Chlamydiae
Chlamydial bacteria They are generally intracellular parasites and this phylum is only composed of a single class (Chlamydia) In turn, this group is divided into two orders known as Chlamydiales, with 4 families; and Parachlamydiales, with 6.
4. Cyanobacteria
Cyanobacteria were once known as blue-green algae, or rather cyan in color as their name suggests. They are photoautotrophic, free-living bacteria or endosymbionts
5. Gram positive bacteria
Finally we have the case of Gram-positive bacteria, whose name means that they can be stained by the Gram stain method, invented by the Danish bacteriologist Hans Christian Gram (1853-1938). Within this phylum we find:
Nutrition of eubacteria
Within the domain of bacteria we can find both heterotrophic and autotrophic organisms. Heterotrophic bacteria are those that need to obtain their food from external sources as happens in the animal kingdom, while autotrophs are capable of producing their own food from inorganic compounds, just like plants do.
Most heterotrophic bacteria are saprophytic, meaning they feed on dead or decaying organic matter. In other cases we find parasitic bacteria, that is, they live inside or outside another organism, causing some type of detriment. We also find the case of symbiotic bacteria which establish a relationship of mutual support with another organism giving them some benefit while they receive food in return.
In the case of autotrophic eubacteria we can find photosynthetic or chemosynthetic, which may or may not depend on the presence of oxygen. In the case of photosynthesis, these produce organic substances through photosynthesis using the energy given by the sun’s rays and making different types of photosynthetic pigments work, 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.
Reproduction
Generally, true bacteria reproduce by binary fission, an asexual reproduction mechanism typical of prokaryotes and other unicellular organisms. As its name suggests, in this process two identical cells are formed from the fission of a progenitor or mother cell. Binary fission is a very fast reproduction mechanism, although the time varies depending on the species of bacteria, with some that divide in less than 20 minutes and others that take several hours.
The process begins with the duplication of the genetic material, that is, the circular-shaped bacterial chromosome Immediately afterwards, the progenitor cell begins to increase in size and, moments later, the chromosome creates a copy of itself, one migrating towards one pole of the cell and the other towards the other. At this point, the cell has reached almost double its original size.
Inside the bacteria, a series of proteins begin to activate, which are responsible for forming a division ring of the two daughter cells, located more or less in the middle of the mother cell. In the region where this dividing 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 causes the separation of the two identical daughter cells to occur.
Depending on the orientation in which the duplicated chromosomes are distributed, we speak of different types of binary fission (longitudinal, transversal or irregular), but in all of them the same events that we have mentioned occur.
The importance of these microorganisms
True bacteria make the world as it is today possible, in addition to can be used for economic benefit For example, these microorganisms participate in the cycling of nutrients such as phosphorus, sulfur, carbon and nitrogen, decomposing organic matter, producing these nutrients as the 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 us, but they are good. Some species act as symbionts in the gastrointestinal system of many animals, including humans and many ruminant herbivores, participating in digestion. Within these we can highlight the Lactobacillus acidophilus and the 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 different biotechnological compounds useful for humanity. Without bacteria it would not be possible to have foods such as cheese or yogurt, nor medicines such as insulin, obtained through a transgenic strain of the Escherichia coli.
