Eubacteria – Definition, Structure, Characterisitcs, Types, Examples

What is Eubacteria?

  • Eubacteria, commonly referred to as “true bacteria,” are single-celled prokaryotic organisms ubiquitously distributed across diverse habitats globally. These organisms are distinct from archaebacteria and collectively form one of the three primary domains of life, specifically the Bacteria domain.
  • Prokaryotic organisms are primarily bifurcated into two categories: Eubacteria and Archaebacteria. The former belongs to the Bacteria domain, while the latter is categorized under the Archaebacteria domain. Characteristically, eubacteria exhibit typical prokaryotic features.
  • Notably, they possess the capability to produce spores and can manifest as pathogenic entities, leading to diseases in both humans and animals. Reproductive mechanisms in eubacteria include binary fission and budding. These organisms can also establish expansive colonies, giving rise to extracellular structures termed “biofilms,” which confer protection to the colony in specialized manners.
  • The classification of all extant organisms is streamlined into three primary domains: Eukaryota, Eubacteria, and Archaea. The Eubacteria domain encompasses true bacteria, making it one of the most extensive domains with a vast array of organisms.
  • When addressing the cellular architecture of eubacteria, it is imperative to note that they, along with archaebacteria, are prokaryotic in nature. In contrast, the Eukarya domain is exclusively eukaryotic, housing both unicellular and multicellular entities, including protists, plants, algae, and animals.
  • A salient feature of prokaryotic eubacteria is the presence of cell walls predominantly composed of peptidoglycan. However, it’s worth noting that not all bacterial species possess cell walls. Irrespective of this, all eubacteria are equipped with a cell membrane, which is an assembly of glycerol and fatty acids linked via ester bonds.
  • Microscopically, eubacteria are minute entities that necessitate staining techniques for visualization and morphological assessment. Gram staining, a pivotal microbiological procedure, classifies bacteria into gram-positive and gram-negative based on their cell wall composition and staining properties.
  • Gram-positive bacteria exhibit a thick, multilayered peptidoglycan cell wall, enriched with lipoteichoic acid. This acid plays a dual role: facilitating bacterial growth and safeguarding the cell wall from potential lysis. Furthermore, lipoteichoic acid imparts antigenic specificity, aiding in the classification of gram-positive bacteria.
  • Conversely, gram-negative bacteria possess a thinner cell wall with a singular peptidoglycan layer, devoid of lipoteichoic acid. This absence renders them incapable of retaining the gram stain. Their cell wall’s fragile nature makes them prone to mechanical disruptions.
  • However, the outer membrane of gram-negative bacteria is laden with negatively charged entities like lipopolysaccharides, phospholipids, and lipoproteins. This unique composition not only allows them to elude the host’s immune system but also offers resistance against various external threats, including certain antibiotics.
  • In summation, eubacteria, integral to the Bacteria domain, are prokaryotic microorganisms with diverse characteristics, playing pivotal roles in various ecological and pathological contexts. Their cellular architecture and staining properties offer insights into their classification and functional attributes.

Definition of Eubacteria

Eubacteria, also known as true bacteria, are prokaryotic microorganisms that belong to the domain Bacteria. They are single-celled organisms lacking a nucleus, with DNA organized in a single circular chromosome. Eubacteria can be gram-negative or gram-positive and have economic, agricultural, and medical significance. Examples include E. coli, Lactobacilli, and Azospirillum.

Characteristics of Eubacteria

Eubacteria, often referred to as “true bacteria,” are prokaryotic microorganisms that exhibit a myriad of distinct characteristics. These organisms are primarily unicellular, although certain species can form filamentous colonies or aggregate into surface biofilms. Herein, we delineate the salient features of eubacteria:

  1. Cellular Structure: Eubacteria are prokaryotic, meaning they lack a membrane-bound nucleus. Their cellular composition includes lipids, carbohydrates, proteins, and nucleic acids. The size of these organisms typically ranges from 0.2 to over 5 micrometers.
  2. Cell Wall Composition: The cell wall of eubacteria is predominantly composed of peptidoglycan, arranged in a cross-linked chain pattern. This peptidoglycan imparts rigidity to the cell wall. Based on the peptidoglycan content and their response to the Gram stain, eubacteria are categorized into gram-positive and gram-negative groups. Gram-positive bacteria retain the Gram stain and are often beneficial to human health, while gram-negative bacteria do not retain the stain and can be pathogenic.
  3. Locomotion: Many eubacteria possess flagella, which are whip-like structures that facilitate movement.
  4. Reproduction: Eubacteria primarily reproduce asexually through binary fission. Some species also exhibit budding as a mode of reproduction. Additionally, certain eubacteria have pili, which are slender appendages on the cell surface. These structures not only aid in sexual reproduction but also play a pivotal role in enabling pathogens to adhere to their hosts.
  5. Genetic Material: Eubacteria typically possess a single, circular chromosome. However, variations exist, with some species like Vibrio cholerae having two chromosomes. Others might have linear chromosomes. Notably, eubacteria lack introns in their genetic makeup.
  6. Cellular Organelles: Eubacteria house 70S-type ribosomes, which are intricate assemblies of RNA and protein responsible for protein synthesis through the process of translation.
  7. Metabolism: These organisms undergo both glycolysis and the Krebs cycle for energy production. While the majority of eubacteria are heterotrophic, deriving their nutrition from organic sources, some are capable of photosynthesis or chemosynthesis.
  8. Morphology: Eubacteria exhibit diverse morphologies, ranging from cocci (spherical) and bacilli (rod-shaped) to more intricate forms like vibrio, filament, and spirochetes.
  9. Survival Mechanisms: In adverse environmental conditions, certain eubacteria can produce spores, allowing them to remain dormant and resilient. Some of these spore-forming bacteria can be pathogenic and cause diseases in hosts.
  10. Cytosol Composition: The plasma membrane of eubacteria encloses the cytosol, a gel-like substance primarily composed of water, dissolved nutrients, DNA, and cytoskeletal elements.

In conclusion, eubacteria, as the name “true bacteria” suggests, are quintessential prokaryotic organisms with a plethora of characteristics that enable them to thrive in diverse environments. Their significance ranges from ecological roles to implications in human health, both beneficial and detrimental. Examples of eubacteria include Rhizobium, which forms symbiotic relationships with leguminous plants, and Clostridium, some species of which can be pathogenic to humans.

Structure of Eubacteria

Structure of Eubacteria
Structure of Eubacteria

The eubacterial cell, representative of the “true bacteria,” is a marvel of biological architecture, exhibiting a complex yet well-organized structural framework. This article elucidates the intricate structural components of eubacteria and their respective functions.

  1. Capsule: Encasing certain eubacterial cells is a capsule primarily composed of polysaccharides or polypeptides. This structure confers multiple advantages to the bacterium. In pathogenic bacteria, for instance, the capsule offers protection against phagocytosis, as observed in pneumococcus. Additionally, the capsule serves as a repository for waste disposal and food storage.
  2. Cell Wall: Situated beneath the capsule, the cell wall is predominantly composed of peptidoglycan. This rigid structure imparts a definitive shape to the bacterial cell. One of its primary roles is to safeguard the cell against drastic osmotic pressure variations.
  3. Flagella: These are elongated appendages primarily composed of flagellin molecules. Flagella bestow motility upon bacteria, propelling them through fluid mediums in a wave-like motion. The number and positioning of flagella can vary across bacterial species, with some possessing a singular flagellum, while others may have multiple distributed across the cell surface.
  4. Pilli or Fimbriae: These are short, hair-like projections that extend beyond the cell wall, originating from the cell membrane. Composed of proteins like pilin or fibrillin, fimbriae play a pivotal role in bacterial attachment to host surfaces and are instrumental during the process of conjugation.
  5. Plasma Membrane: This semi-permeable lipid bilayer membrane, primarily constituted of lipids and proteins, demarcates the cell’s internal environment from the external milieu. It facilitates the selective transport of ions, molecules, nutrients, and water across the membrane, ensuring cellular homeostasis.
  6. Ribosome: Eubacteria house 70S ribosomes within their cytoplasm. These molecular machines are integral to the protein synthesis process, translating the genetic information encoded in mRNA into functional proteins.
  7. Nucleoid: This region, devoid of a membrane, houses the bacterial DNA, typically in the form of a singular, circular chromosome. The nucleoid is the genetic epicenter of the bacterial cell, directing its various cellular activities.
  8. Mesosome: These are specialized structures, often manifesting as tubules or vesicles. Mesosomes augment the surface area for efficient transport processes. They also serve as attachment sites for certain peptides, regulate autolytic enzyme activity, and assist in septum formation during bacterial cell division.

In summation, the eubacterial cell is a paradigm of structural and functional sophistication. Each component, from the protective capsule to the genetic nucleoid, plays a distinct role, ensuring the survival and propagation of these prokaryotic entities in diverse environments.

Types of Eubacteria 

Eubacteria, commonly referred to as “true bacteria,” exhibit a diverse array of types based on various classification criteria. This article elucidates the primary categories of eubacteria based on their staining properties, cellular morphology, and specific characteristics.

Gram-Positive Bacteria Cell Wall Structure
Gram-Positive Bacteria Cell Wall Structure
Gram Negative Bacteria Cell Wall Structure
Gram Negative Bacteria Cell Wall Structure
  1. Based on Gram Staining:
    • Gram-Positive Bacteria: These bacteria possess a thick cell wall, predominantly composed of peptidoglycan (approximately 80%). Upon undergoing Gram staining, they retain a blue, violet, or purple hue. Their cell walls have a low lipid content, rendering them susceptible to lysozyme and certain antibiotics. Intracellular structures called mesosomes are present in these bacteria. Notable examples include Azotobacter and Mycobacterium.
    • Gram-Negative Bacteria: These bacteria have a comparatively thinner cell wall with a lower peptidoglycan content (around 20%). They do not retain the blue stain but instead take up the pink or red color of safranin. Their elevated lipid content provides resistance against lysozyme and some antibiotics. Typically, mesosomes are absent in these bacteria. Examples encompass Salmonella and E. coli.
  2. Cyanobacteria:
    • A distinct subgroup within eubacteria, cyanobacteria are prokaryotic cells characterized by their ability to perform oxygenic photosynthesis. Their cell wall is a composite of murein, cellulose, hemicellulose, and pectin. Notably, they lack flagella. Some cyanobacteria feature specialized cells called heterocysts. Reproductive structures and motile reproductive bodies are absent in cyanobacteria.
  3. Based on Morphology and Arrangement:
    • Coccus: These are spherical, oval, or rounded bacteria. Their arrangement can further classify them:
      • Monococcus: Single, isolated cells. Example: Micrococcus.
      • Diplococcus: Paired cells. Example: Pneumonia-causing bacteria.
      • Tetracoccus: Group of four cells.
      • Streptococcus: Chain-like arrangement.
      • Staphylococcus: Clustered arrangement, resembling grape bunches.
    • Bacillus: These are rod-shaped or elongated bacteria. Short rods, which might sometimes resemble cocci, are termed coccobacilli. Their arrangement can be:
      • Monobacillus: Single, isolated cells. Example: Lactobacillus.
      • Diplobacillus: Paired cells.
      • Streptobacillus: Chain-like arrangement.
    • Helical Bacteria: These bacteria have a coiled or twisted morphology. They can be:
      • Spirochete: Spiral-shaped.
      • Vibrio: Comma-shaped, with Vibrio cholera being a representative example.

In summary, eubacteria are a vast and diverse group of prokaryotic organisms. Their classification based on staining properties and morphology provides insights into their structural and functional attributes, enabling a better understanding of their roles in various ecological and pathological contexts.

Classification of Eubacteria

Eubacteria, representing the domain of “true bacteria,” encompass a vast array of species, each with distinct characteristics. Their classification into various phyla is based on specific morphological, physiological, and genetic attributes. This article delves into the primary phyla of eubacteria and their defining features.

  1. Proteobacteria: This phylum predominantly consists of gram-negative bacteria. Originating from photosynthetic ancestors, proteobacteria are further categorized into five classes:
    • Alphaproteobacteria
    • Betaproteobacteria
    • Gammaproteobacteria
    • Deltaproteobacteria
    • Epsilonproteobacteria
  2. Cyanobacteria: Recognized by their blue-green pigmentation, cyanobacteria are photosynthetic, akin to plants and algae. Their ability to fix atmospheric nitrogen makes them agriculturally significant, enriching soil fertility.
  3. Chlorobi: This phylum houses the green sulfur bacteria, which are photosynthetic in nature. During photosynthesis, Chlorobi reduces carbon dioxide using organic compounds, such as carbohydrates and acids. Their morphological diversity is evident in their rod, spiral, cocci, or budding forms.
  4. Chloroflexi: Members of this phylum, often referred to as green nonsulfur bacteria, are capable of photosynthesis. For instance, the genus Chloroflexi exemplifies this capability.
  5. Chlamydiae: These are pathogenic, gram-negative cocci with a distinctive developmental cycle. Transmission between humans occurs via direct contact or airborne respiratory routes.
  6. Planctomycetes: These gram-negative, budding bacteria exhibit a unique combination of features. While their DNA aligns closely with bacteria, their cell wall composition mirrors that of archaea. Intriguingly, certain Planctomycetes possess organelles reminiscent of eukaryotic structures.
  7. Bacteroidetes: These anaerobic bacteria predominantly colonize the human oral cavity and intestinal tract. Found in fecal matter, they can potentially cause infections following surgical procedures or puncture injuries.
  8. Fusobacteria: Characterized as anaerobic entities, fusobacteria can adopt pleomorphic or spindle-shaped cellular forms.
  9. Spirochaetes: These bacteria exhibit a coiled morphology, reminiscent of metal springs. Their motility is facilitated by flagella, which operate using axial filaments. Commonly found in the human oral cavity, certain spirochaetes are known to be pathogenic.

In conclusion, the eubacterial domain is a mosaic of diverse phyla, each contributing uniquely to the ecological and pathological landscapes. Their classification offers insights into their evolutionary lineage, ecological roles, and potential implications in human health.

Evolution of Eubacteria 

Eubacteria, commonly known as “true bacteria,” have a rich evolutionary history that traces back to the earliest life forms on Earth. Their evolutionary journey provides insights into the development and diversification of life on our planet. This article delves into the evolutionary trajectory of eubacteria and the theories that underpin their origin and diversification.

  1. Prokaryotic Classification: The most primitive bacteria, along with blue-green algae or cyanobacteria, are categorized as prokaryotic cells. These cells are characterized by the absence of a nuclear membrane, resulting in the direct exposure of their hereditary material (DNA) to the cytoplasm. Additionally, they lack introns, segments of DNA that do not code for proteins.
  2. Phylogenetic Evolution: The progenote, an ancestral hypothetical organism, is believed to have given rise to three distinct cell types over evolutionary time: Archaebacteria, Eubacteria, and Eukaryotes. This diversification marked significant milestones in the evolutionary timeline of life.
  3. Molecular Theories and Horizontal Gene Transfer: Molecular studies have posited that horizontal gene transfer, the direct transfer of genes between organisms outside of traditional reproduction, played a pivotal role in the evolution of life. Such transfers between the three primary cell types influenced their evolutionary trajectories, leading to the diverse array of organisms we observe today.
  4. Endosymbiotic Theory: A cornerstone in understanding eukaryotic cell evolution, the endosymbiotic theory posits that organelles like mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral eukaryotic cells. Over time, a symbiotic relationship developed, with the engulfed bacteria evolving into the aforementioned organelles. This theory underscores the significance of gene transmission in the evolutionary processes, particularly in the context of eubacteria.
  5. Diversity of Eubacteria: Eubacteria encompass a wide array of groups, each with distinct characteristics and ecological roles. This includes:
    • Cyanobacteria: Often referred to as blue-green algae, these bacteria are photosynthetic and have played a crucial role in shaping Earth’s atmosphere.
    • Chloroxybacteria, Paracoccus, Non-sulphur bacteria, Sulfur bacteria: These groups include various photosynthetic bacteria that utilize different pathways for energy capture.
    • Green Filamentous Bacteria and Green Sulfur Bacteria: These bacteria are characterized by their unique morphologies and metabolic pathways.
    • Spirochetes: Spiral-shaped bacteria that include some pathogenic species.
    • Desulphovibrio: Bacteria known for their role in sulfur cycling.

In summation, the evolution of eubacteria is a testament to the dynamic and intricate processes that have shaped life on Earth. From the simplest prokaryotic forms to the diverse array of eubacterial groups today, their journey offers profound insights into the mechanisms and events that have driven biological diversification over billions of years.

Reproduction in Eubacteria

Eubacteria, often referred to as “true bacteria,” employ a variety of reproductive strategies to ensure their survival and propagation. Their reproductive mechanisms are tailored to adapt to diverse environmental conditions, ensuring their persistence across various habitats. This article elucidates the primary modes of reproduction in eubacteria and the underlying processes.

  1. Asexual Reproduction:
    • Binary Fission: This is the predominant mode of reproduction in eubacteria. In this process, a single bacterial cell undergoes replication of its genetic material, followed by cellular division, resulting in two genetically identical daughter cells. Binary fission is a rapid and efficient method, allowing bacterial populations to grow exponentially under favorable conditions.
    • Budding: Some eubacteria reproduce via budding, wherein a small outgrowth, or bud, forms on the parent cell. This bud gradually enlarges and eventually detaches, becoming a separate entity.
  2. Spore Formation: Certain eubacteria possess the ability to form spores, especially under adverse environmental conditions such as nutrient scarcity, extreme temperatures, or exposure to harmful chemicals and radiation. These spores are metabolically dormant and are characterized by their resilience to harsh conditions, including resistance to heat, desiccation, and toxins. While spores are non-reproductive in their dormant state, they can revert to their vegetative form and resume reproduction once favorable conditions are restored.
  3. Genetic Exchange Mechanisms: While true sexual reproduction is absent in eubacteria, they have evolved mechanisms to exchange genetic material, introducing genetic variability within populations. These processes include:
    • Conjugation: This involves the direct transfer of genetic material between two bacterial cells through a structure called the pilus. One bacterium transfers a portion of its DNA to another, leading to genetic recombination.
    • Transformation: In this process, a bacterial cell takes up free DNA fragments from its surroundings, integrating this foreign DNA into its own genome.
    • Transduction: This involves the transfer of genetic material between bacterial cells mediated by viruses, specifically bacteriophages. The virus inadvertently packages bacterial DNA from one cell and introduces it into another during its infection cycle.

In conclusion, eubacteria exhibit a diverse array of reproductive strategies, ranging from simple asexual division to complex genetic exchange mechanisms. These strategies not only ensure their survival and proliferation but also introduce genetic diversity, enabling them to adapt and thrive in ever-changing environments.

Mode of nutrition of Eubacteria

Eubacteria, commonly known as “true bacteria,” exhibit a diverse range of nutritional modes, enabling them to inhabit a variety of ecological niches. Their nutritional strategies are tailored to the specific environments they occupy, allowing them to efficiently harness available resources. This article delves into the primary modes of nutrition observed in eubacteria.

  1. Heterotrophic Nutrition:
    • Most eubacteria fall under the category of heterotrophs. These organisms rely on external organic sources for their nutritional requirements. They do not possess the capability to synthesize their own food and, instead, derive nutrients from external organic matter.
    • Decomposers: Many heterotrophic eubacteria function as decomposers, breaking down dead organic material. This decomposition process is vital for recycling nutrients within ecosystems.
    • Parasitic Eubacteria: Some heterotrophic eubacteria adopt a parasitic lifestyle, residing within a host organism and deriving nutrients at the host’s expense. Such parasitic interactions can often lead to diseases in the host.
  2. Autotrophic Nutrition:
    • A subset of eubacteria are autotrophs, meaning they can synthesize their own food using inorganic substances.
    • Photosynthetic Autotrophs: These bacteria harness light energy to convert carbon dioxide and water into glucose, a process akin to photosynthesis in plants. Cyanobacteria, often referred to as blue-green algae, are prime examples of photosynthetic eubacteria. They contain pigments that capture light energy, enabling them to produce organic compounds while releasing oxygen into the atmosphere.
    • Chemosynthetic Autotrophs: Chemosynthetic eubacteria derive energy from chemical reactions involving inorganic substances. Instead of relying on light energy, these bacteria oxidize inorganic compounds, such as sulfur or nitrogen, to generate energy for synthesizing organic molecules.

In summary, eubacteria exhibit a spectrum of nutritional modes, ranging from heterotrophic decomposers and parasites to autotrophic photosynthesizers and chemosynthesizers. This nutritional versatility has enabled eubacteria to colonize a myriad of habitats, from nutrient-rich soils to extreme environments devoid of organic matter. Their diverse nutritional strategies underscore their adaptability and pivotal role in various ecological processes.

Importance of Eubacteria

Eubacteria, often referred to as “true bacteria,” play a pivotal role in various ecological, industrial, and health-related processes. Their ubiquity and metabolic diversity make them indispensable to life on Earth. This article elucidates the multifaceted importance of eubacteria in different spheres of life.

  1. Ecological Significance:
    • Soil Fertility: Eubacteria are instrumental in enhancing soil fertility. They participate in processes like nitrification, nitrogen fixation, and ammonification, converting atmospheric nitrogen into forms accessible to plants.
    • Decomposition: Eubacteria are primary decomposers in ecosystems, breaking down dead organic matter into essential nutrients, thereby recycling them back into the environment.
    • Petroleum Degradation: Certain eubacteria have the capability to degrade petroleum hydrocarbons, aiding in the bioremediation of oil spills and polluted sites.
  2. Industrial Applications:
    • Vitamin Synthesis: Eubacteria like Propionibacterium and Pseudomonas spp. are harnessed for the production of vitamins, such as vitamin B12. Their ability to produce vitamins in a cost-effective manner has revolutionized the supplement industry.
    • Dairy Industry: Lactobacillus, a type of eubacteria, is integral to the dairy industry, facilitating the fermentation process in products like yogurt and cheese.
    • Pharmaceuticals: Eubacteria, especially strains of Streptomyces, are invaluable to the pharmaceutical industry. They produce a plethora of antibiotics, offering therapeutic solutions to various bacterial infections.
  3. Biological Control:
    • Some eubacteria are employed as biopesticides, aiding in the control of insect pests, thereby reducing the reliance on chemical pesticides.
  4. Human Health:
    • Normal Flora: The human body is host to a myriad of eubacterial species, collectively termed the “normal flora.” These bacteria are not only harmless but also confer several benefits. They fortify the body’s defenses against pathogenic bacteria and synthesize essential nutrients, including vitamins B and K.
    • Protection Against Pathogens: The normal flora competes with potential pathogens for resources and space, often inhibiting their growth and preventing infections.
  5. Environmental Balance: Eubacteria play a crucial role in maintaining ecological balance. By decomposing organic matter, they ensure the continuous cycling of nutrients, supporting the sustenance of various life forms.

In essence, eubacteria are integral to the intricate web of life. Their roles span from ecological sustenance to industrial applications and health benefits. Understanding their significance underscores the need to study and conserve these microscopic powerhouses, ensuring their continued contribution to our planet’s well-being.

Examples of Eubacteria

Eubacteria, often referred to as “true bacteria,” encompass a vast array of species that play diverse roles in various ecosystems. While some are pathogenic, causing diseases in humans and other organisms, many others are beneficial, aiding in processes essential for life. This article highlights a selection of eubacterial species, elucidating their characteristics and significance.

  1. Escherichia coli (E. coli):
    • Classification: Belongs to the Proteobacteria phylum.
    • Morphology: Rod-shaped and Gram-negative, characterized by an additional membrane surrounding its cell wall.
    • Habitat: Commonly resides in the intestines of warm-blooded animals, including humans.
    • Significance: While most strains are benign and might even be beneficial to their hosts, certain strains can be pathogenic, causing food poisoning and other gastrointestinal ailments.
  2. Streptococcus pneumoniae (S. pneumoniae):
    • Classification: Part of the Firmicutes phylum.
    • Morphology: Spherical in shape and Gram-positive.
    • Habitat: Typically found in the respiratory tract, nasal cavity, and sinuses of healthy individuals.
    • Significance: While often harmless, it can become pathogenic, especially in immunocompromised individuals, leading to diseases like pneumonia, meningitis, bronchitis, and sepsis.
  3. Nitrobacter and Nitrosomonas:
    • Role in Nitrification: These bacteria play a crucial role in the nitrogen cycle. Nitrosomonas oxidizes ammonium to nitrite, while Nitrobacter further oxidizes nitrite to nitrate.
    • Significance: The nitrification process, resulting in the production of nitrates, is vital for agriculture. Nitrates serve as a primary nitrogen source for plants, promoting their growth.

It’s imperative to understand that the vast majority of eubacteria are not harmful. In fact, they are indispensable for various ecological processes, industrial applications, and even human health. For instance, many eubacteria are involved in nutrient cycling, waste decomposition, and the production of essential compounds. In the medical field, certain eubacteria are harnessed for the synthesis of antibiotics, while in agriculture, they aid in soil fertility and plant growth. The diverse roles of eubacteria underscore their significance in maintaining the balance and health of our planet’s ecosystems.

Difference between Eubacteria and Archaebacteria

Eubacteria and Archaebacteria are both prokaryotic organisms, meaning they lack a defined nucleus. However, they differ significantly in their structural, genetic, and environmental characteristics. This article elucidates the primary distinctions between these two bacterial domains.

1. Cellular Composition and Structure:

  • Cell Wall:
    • Eubacteria: The cell wall is primarily composed of peptidoglycan or murein, which consists of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
    • Archaebacteria: The cell wall lacks peptidoglycan. Instead, it is made up of pseudomurein, which comprises N-acetyltalosaminuronic acid (NAT) and N-acetylglucosamine (NAG).
  • Cell Membrane:
    • Eubacteria: Their cell membranes have phospholipids arranged in a bilayer with unbranched fatty acid chains.
    • Archaebacteria: Their cell membranes consist of phospholipids in a monolayer formation with branched isoprenoid chains.

2. Genetic Characteristics:

  • RNA Polymerase:
    • Eubacteria: Possess a simpler RNA polymerase.
    • Archaebacteria: Have a more complex RNA polymerase, akin to eukaryotes.
  • Introns:
    • Eubacteria: Typically lack introns in their genes.
    • Archaebacteria: Possess introns in some of their genes.

3. Metabolic Pathways:

  • Eubacteria: Primarily derive energy through glycolysis and the Krebs cycle.
  • Archaebacteria: Generally do not utilize glycolysis or the Krebs cycle for energy production.

4. Environmental Adaptations:

  • Eubacteria: These are versatile organisms found in diverse environments, from soil to the human gut.
  • Archaebacteria: These are extremophiles, often thriving in harsh environments like hot springs, acidic lakes, or salt flats.

5. Representative Examples:

  • Eubacteria: Some common examples include Bacillus, Mycobacterium, Clostridium, and Pseudomonas.
  • Archaebacteria: Examples encompass Pyrobaculum, Ferroplasma, Lokiarchaeum, and Thermoproteus.

In conclusion, while Eubacteria and Archaebacteria both fall under the category of prokaryotes, they exhibit distinct differences in their cellular structures, genetic makeup, metabolic pathways, and environmental adaptations. Understanding these differences is crucial for microbiologists and researchers, as it provides insights into the evolutionary history of life on Earth and the adaptability of organisms to diverse ecological niches.

Cell Wall CompositionPrimarily composed of peptidoglycan (NAG and NAM).Lacks peptidoglycan; made up of pseudomurein (NAT and NAG).
Cell Membrane StructurePhospholipids arranged in a bilayer with unbranched fatty acid chains.Phospholipids in a monolayer with branched isoprenoid chains.
RNA Polymerase ComplexitySimpler RNA polymerase.Complex RNA polymerase, similar to eukaryotes.
Presence of IntronsTypically lack introns.Possess introns in some genes.
Metabolic PathwaysDerive energy through glycolysis and the Krebs cycle.Do not utilize glycolysis or the Krebs cycle.
Environmental AdaptationsFound in diverse environments (soil, human gut, etc.).Thrive in extreme environments (hot springs, acidic lakes, salt flats, etc.).
Representative ExamplesBacillus, Mycobacterium, Clostridium, Pseudomonas.Pyrobaculum, Ferroplasma, Lokiarchaeum, Thermoproteus.
This table succinctly captures the primary distinctions between Eubacteria and Archaebacteria, providing a clear comparative overview of their characteristics.


Which of the following is NOT a characteristic of Eubacteria?
a) Single-celled organisms
b) Prokaryotic cells
c) Presence of a nuclear membrane
d) Can reproduce by binary fission

Which type of Eubacteria is known to perform photosynthesis similar to plants?
a) Spirochetes
b) Cyanobacteria
c) Clostridium
d) E. coli

The cell wall of Eubacteria is primarily made up of:
a) Cellulose
b) Chitin
c) Peptidoglycan
d) Lipids

Which of the following processes is a common mode of asexual reproduction in Eubacteria?
a) Meiosis
b) Binary fission
c) Mitosis
d) Budding

Which of the following is a Gram-positive bacterium?
a) E. coli
b) Bacillus
c) Salmonella
d) Vibrio

Which structure in Eubacteria aids in locomotion?
a) Pili
b) Ribosomes
c) Flagella
d) Mesosome

Eubacteria that can survive and thrive in extreme conditions are termed as:
a) Extremophiles
b) Mesophiles
c) Thermophiles
d) Psychrophiles

Which of the following Eubacteria is known to fix atmospheric nitrogen?
a) Lactobacillus
b) Rhizobium
c) Streptococcus
d) Staphylococcus

Which structure in Eubacteria is responsible for the transfer of genetic material during conjugation?
a) Flagella
b) Ribosomes
c) Pili
d) Mesosome

Which of the following is NOT a shape of Eubacteria?
a) Coccus
b) Bacillus
c) Spirogyra
d) Spirillum


What are eubacteria?

Eubacteria, also known as true bacteria, are a large group of prokaryotic microorganisms that are found in various habitats on Earth.

How do eubacteria differ from archaebacteria?

Eubacteria and archaebacteria are both types of prokaryotes, but they have distinct evolutionary lineages and differ in their genetic makeup, cell wall composition, and metabolic characteristics.

Are eubacteria harmful?

While some eubacteria can cause diseases in humans, animals, and plants, the majority of eubacteria are harmless or even beneficial. Only a small fraction of eubacteria are pathogenic.

What are the main modes of reproduction in eubacteria?

Eubacteria primarily reproduce through asexual methods such as binary fission, budding, and spore formation. They can also transfer genetic material through processes like conjugation, transformation, and transduction.

How do eubacteria obtain nutrition?

Eubacteria exhibit diverse nutritional strategies. Most eubacteria are heterotrophic and obtain their food by consuming organic carbon sources or by decomposing dead material. However, some eubacteria are autotrophic and can synthesize their own food through chemosynthesis or photosynthesis.

What are some examples of beneficial eubacteria?

Beneficial eubacteria include those involved in nitrogen fixation, soil fertility enhancement, sewage treatment, vitamin synthesis, antibiotic production, and probiotic functions in the human body.

Can eubacteria survive in extreme environments?

While eubacteria are generally adaptable to a wide range of habitats, certain species have the ability to survive in extreme conditions such as high temperatures, acidic or alkaline environments, high salinity, and even deep-sea hydrothermal vents.

How do eubacteria contribute to the environment?

Eubacteria play a crucial role in nutrient cycling, decomposition of organic matter, and maintaining ecological balance. They help in the breakdown of dead organisms and recycling of nutrients back into the ecosystem.

Can eubacteria be used in industrial applications?

Yes, eubacteria have numerous industrial applications. They are utilized in the production of antibiotics, enzymes, biofuels, and various other valuable compounds. They also play a role in food production, such as in the fermentation process for yogurt and cheese.

What is the importance of studying eubacteria?

Studying eubacteria is essential for understanding microbial ecology, human health, disease prevention, biotechnology, and environmental sustainability. It helps in developing new treatments, improving agricultural practices, and harnessing the potential of bacteria for various beneficial applications.

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