Eubacteria: Definitions, Examples, Scientific Classifications, Characteristics, Reproduction, Mode of Nutrition, and Structure

Eubacteria Overview

The domain Bacteria contains the Eubacteria, while the domain Archaebacteria contains the Archaebacteria. Eubacteria contain the basic features of a prokaryotic organism, but they may also create spores and can be dangerous (cause illness in people and animals). Eubacteria reproduce via binary fission or budding and frequently form enormous colonies capable of producing extracellular structures such as "biofilms" that defend the colony in novel ways.

What is Eubacteria?

They are also known as "true bacteria." Eubacteria are prokaryotic organisms (those without a membrane-bound nucleus), with unicellular and single-cellular DNA chromosomes. They have peptidoglycan in their cell wall and, if they are motile, flagella. It is one of the three domains in Woese's three-domain categorization scheme. They may be found in a wide range of habitats all around the world.  Except for archaebacteria, almost all bacteria come under this category. 

Examples of Fascinating Eubacteria

Nitrobacter and Nitrosomonas are bacteria that may use inorganic substances such as carbon dioxide and energy sources as carbon sources to make complex molecules that are reduced nitrogen compounds. Nitrosomonas can oxidize ammonium to nitrite, whereas Nitrobacter can oxidize nitrite to nitrates via the nitrification process. Nitrates, a byproduct of nitrification, are a transportable type of nitrogen that is extremely important in agriculture. Zoogloea species contribute to sewage treatment procedures such as the activated sludge system. These bacteria develop into a slimy, fluffy material that is necessary for the operation of such systems. Humans can consume Xanthomonas campestris. It has the ability to produce xanthan utilizing lactose. Because xanthan has a thickening effect, it is used to make salad dressing, dairy products, shampoos, cold creams, and cosmetics.

Scientific Classification of Eubacteria

The following table gives details about the scientific classification of eubacteria-

Evolution of Eubacteria

After analyzing the nucleotide sequences in each cell, three domains of life were hypothesized in the 1990s based on the fact that ribosomes varied in the three types of cells (Archaebacteria, Eubacteria, and Eukaryota). Despite being prokaryotes, Eubacteria and Archaebacteria were divided due to differences in the small rRNA component in both domains. Because archaebacteria dwell in harsh settings, they are regarded to be the first species to exist on Earth. Molecular theories support the idea that genes were transported horizontally across the three types of cells, influencing the evolution of life. Some bacteria have developed into mitochondria and chloroplasts via gene transfer, according to the Endosymbiotic hypothesis. To continue the evolutionary process, mitochondria and chloroplasts were genetically transported between domains.

Characteristics of Eubacteria

The following are some of the characteristics of eubacteria-

1. Eubacteria is also known as true bacteria. 
2. Peptidoglycans give Eubacteria their strong cell walls.
3. Some bacteria have pili, which are tiny appendages on the surface of the cell that aid in sexual reproduction. Pili also aids pathogen adhesion to their hosts.
4. They are classed as gram-positive or gram-negative depending on the kind of cell wall and the gram stain they use.
5. These are single-celled prokaryotic creatures.
6. These bacteria range in size from 0.2 to 50 micrometers.
7. The vast majority of Eubacteria are heterotrophic in nature. A few, however, are photosynthetic or chemosynthetic.
8. They use flagella to move around.

How does Eubacteria Reproduce?

After the copying of genetic material, the parent cell is normally divided into two daughter cells in a process known as binary fission. Some bacteria can generate spores in unfavorable situations such as nutritional deprivation, chemical exposure, or radiation. Although these spores cannot multiply, they are extremely resistant to poisons, radiation, heat, and dryness. Bacillus and Clostridium spore-forming bacteria are considered dangerous microorganisms, hence sterilization treatments must eradicate bacterial spores. When environmental circumstances improve, bacterial spores begin to vegetate and proliferate once more.

Mode of Nutrition in Eubacteria

The majority of eubacteria are heterotropic. Eubacteria are unable to synthesize food and must obtain it from other sources such as other plants, organic carbon sources, or animal materials. Heterotrophs break down dead matter or parasites found in a host. Some eubacteria are autotrophic. They produce food using either chemosynthetic or photosynthetic means. Cyanobacteria is the most common kind of eubacteria.

Biological Importance of Eubacteria

The globe is replete with many eubacterial species, and our bodies include several eubacterial species that are physiologically significant in our lives. Our bodies are only made up of the eubacteria habitats that make up our typical flora. Normal flora does not damage us and is healthy for our bodies. They guard our bodies against dangerous eubacteria, for example, while others can generate biologically vital compounds such as B vitamins and vitamin K. Several eubacteria species are utilized in the bulk manufacture of chewable or tablet vitamins because they are a cheap, safe, and non-toxic source of vitamins. Propionibacterium and Pseudomonas species, for example, create vitamin B12, whereas Acetobacter species use glucose to make ascorbic acid (vitamin C).

Types of Eubacteria

They are classified into four kinds based on their shape-

1. Coccus Bacteria: They are spherical in form. For example, Staphylococcus and Pneumococcus.
2. Bacillus: These bacteria are rod-shaped. Anthracis, B. megaterium, and B. thuringiensis are a few examples.
3. Vibrio: These bacteria have a comma form. V. cholera, V. parahaemolyticus, and V. vulnificus are a few examples.
4. Spirillum: Spirillum bacteria are spiral-shaped bacteria. Spirochaete, Treponema, Borrelia, and Leptospira are a few examples. 

They are categorized into two groups based on the stain they take during Christian Gram's gram staining-

1. Gram-Positive Bacteria: They pick up the gram stain but are not harmful. Staphylococcus, Streptococcus, and so forth.
2. Gram-Negative Bacteria: They are pathogenic and do not pick up the gram stain. For example, E. coli and Salmonella. 

Structure of Eubacteria

The following is a description of the structure of a eubacterial cell-

The cell wall, which is composed of peptidoglycan, is the cell's outermost layer. In addition, some bacteria have a capsule that is made up of carbohydrates and proteins. Many eubacteria contain flagella, which are cellular appendages that allow them to move in a circular motion. Flagella are made up of flagellin proteins that protrude from the cell wall. The flagella's base is anchored within the cell membrane. The cell membrane, which is composed of a bilayer of phospholipids, proteins, and carbohydrates, follows the cell wall. The plasma membrane is selectively permeable, which means that not all particles pass through it. Cytoplasm, which contains cellular contents, is enclosed by the cell membrane. Eubacteria do not have a fully formed nucleus or other membrane-bound organelles. The nucleoid is a bare and coiled structure seen in the cytoplasm that is termed DNA. Eubacteria also include extrachromosomal circular DNA termed plasmids, which enable antibiotic resistance as well as pathogenicity. Enzymes and proteins are present in the cytoplasm to carry out metabolic functions. Mesosomes are invaginations of the cell membrane that may be observed in the cytoplasm. These enzymes are photosynthetic and respiratory in nature.

Classification of Eubacteria 

There are two primary kinds of Eubacteria, which are as follows-

Cyanobacteria

They are also known as BGA (Blue Green Algae). Gram-negative bacteria are what they are. Cyanobacteria are the earliest species to demonstrate oxygenic photosynthesis. They have chlorophyll, just like higher plants. They are usually found in freshwater, however, a few are found in saltwater. They form symbiotic relationships with nearly all eukaryotic species. Anabaena, for example, is found in association with the coralloid roots of Cycas. Their bodily structures differ. They might be unicellular, filamentous, or colonial in nature. They may have trichomes. They do not, however, have flagella. Because they include nitrogenase-containing heterocysts, such as Nostoc, cyanobacteria aid in nitrogen fixation. They reproduce in an asexual manner. They lack true sexual reproduction.

Mycoplasma

They come in a variety of morphologies and are known as PPLO (Pleuropneumonia Like Organisms). Because they lack genuine cell walls, they are referred to as "bacteria with their coats off" and "plant kingdom jokers." With a size of roughly 0.02-0.2 microns, PPLO are the tiniest living organisms. They are facultative anaerobic organisms. They eat in a heterotrophic way and are often parasitic. Some of them are saprotrophs. They are both pathogenic to plants and animals. Mycoplasma is resistant to medications such as penicillin and bacitracin. They do not, however, have resistance to medicines like streptomycin, chloramphenicol, and tetracycline. Because of its tiny size, Mycoplasma can slip through bacteriological screens.

Difference between Archaebacteria and Eubacteria

The following table gives the difference between Archaebacteria and Eubacteria-

Points to Remember

1. Eubacteria, sometimes known as "true" bacteria, are single-celled prokaryotic microbes.
2. In Eubacteria, reproduction occurs by binary fission or budding.
3. Bacilli, Cocci, and Spirilla are the three primary forms of bacteria categorized based on their morphology.
4. Gram-positive, Gram-negative, and Miscellaneous Eubacteria are the most common classifications for Eubacteria.
5. Gram-negative bacteria are dangerous to humans, whereas Gram-positive bacteria are healthy.
6. Streptococcus pneumonia, Lactobacillus, proteobacteria, cyanobacteria, chlamydias, and spirochetes are all Eubacteria.