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Archaea Vs Bacteria: Definition, 17+ Differences and Examples

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Definition of Archaea

Archaea is a group of early prokaryotes that form a unique domain from bacteria and eukaryotes based on their specific properties.

  • The term “Archaea” comes from the Greek word “archaios,” which means “primitive” or “old,” implying the organisms’ primordial structure.
  • Deep-sea vents, saline seas, hot springs, and even beneath petroleum deposits are common habitats for these organisms.
  • The majority of these organisms are anaerobic and thrive in low-oxygen settings. Because the majority of archaea cannot be cultivated in laboratories, they must be identified using culture-independent methods.
  • Both bacteria and eukaryotes may share some traits with organisms in this area. They have a developing membrane-less nucleus, similar to bacteria, although they share some genes, metabolic pathways, and enzymes with eukaryotes.
  • These organisms, on the other hand, exhibit certain distinct traits. In contrast to bacteria and eukaryotes, archaea’s membrane lipids comprise a fatty acid linked to a glycerol molecule by an ether bond rather than an ester bond.
  • Because archaea live in a variety of harsh conditions, they have unique metabolic pathways and genes to help them survive. Halophilic archaea have a unique combination of genes that let them survive by limiting the extent of osmosis.
  • Archaea reproduces asexually by budding, fission, and fragmentation. The normal division processes of mitosis and meiosis are absent.
  • The biogeochemical cycles for numerous elements like as carbon, nitrogen, and sulphur are aided by most archaea.
  • Many archaea are methanogens, meaning they create methane as a byproduct of anaerobic cellular respiration.
  • Even though these creatures do not produce oxygen through photosynthesis, some of them (phototrophs) use sunshine as a source of energy.

Definition of Archaea

Definition of Bacteria

Bacteria are single-celled primitive organisms with a wide range of shapes, sizes, structures, and even habitats.

  • Bacteria are prokaryotes with a membrane-free nucleus and few cell organelles, making their structure and function simple.
  • Bacteria is a domain that contains creatures that can be found in a wide range of environments, from high mountains to inside the bodies of other organisms.
  • Some bacteria are useful and aid in the manufacture of antibiotics, industrial use, and biogeochemical cycles, among other things. Some, on the other hand, are harmful microbes that cause mild to severe disorders.
  • Bacteria are the tiniest living organisms on the planet. They are minuscule. A variety of staining techniques are used to study these creatures under a microscope.
  • Bacteria are classified as Gram-positive or Gram-negative based on staining procedures.
  • Almost all bacteria have a peptidoglycan-based cell wall that protects them from hazardous substances. There are few ribosomes in the cytoplasm, and the genetic material is contained in a membrane-less incipient nucleus.
  • Bacterial membrane lipids are made up of fatty acids that are ester-bonded to glycerol.
  • Transfer-messenger RNA is a unique RNA found only in bacteria (tmRNA).
  • Bacteria have DNA as their genetic material, which is passed down to their children through asexual reproduction.
  • Binary fission, budding, and fragmentation are used in reproduction, however alternative techniques for transferring genetic elements are accessible, such as transformation, transduction, and conjugation.

Difference Between Archaea and Bacteria

(Archaea vs Bacteria)

Basis for Comparison Archaea Bacteria
Definition Archaea is a group of early prokaryotes that form a unique domain from bacteria and eukaryotes based on their specific properties.  Bacteria are single-celled primitive organisms with a wide range of shapes, sizes, structures, and even habitats.

The vast majority of archaea are extremophiles, living in harsh settings such as the deep sea, mountains, hot springs, salt brine, and so on.

Bacteria can be found in a variety of environments, including soil, water, and inside living and non-living things.
Cell wall

The pseudopeptidoglycan cell wall of archaea lacks D-aminoacids and N-acetylmuramic acid.

The peptidoglycan in the bacterial cell wall is made up of N-acetylmuramic acid and D-amino acids.

Membrane lipid

Ether bonds bind the fatty acids in archaea membrane lipids to glycerol.

Ester bonds bind the fatty acids in bacteria’s membrane lipids to glycerol.

Glucose oxidation

For glucose oxidation, Archaea do not use glycolysis or Kreb’s cycle, although they do follow metabolic pathways that are similar to these.

Glycolysis and Kreb’s cycle are key glucose oxidation metabolic processes in bacteria.
Photosynthesis Archaea are phototrophs, meaning they use sunlight as a source of energy rather than producing oxygen.  Many bacteria with photosynthetic pigments can produce their own food through photosynthesis.

On the basis of their features, Archaea are grouped into three groups: methanogens, thermophiles, and halophiles.

Gram-negative and Gram-positive bacteria are distinguished by their response to Gram staining.

Archaeal flagella, also known as archaella, is made by combining subunits at the base.

Bacterial flagella are hollow, and they are put together by adding subunits from the central pore to the tip.

Fission, budding, and fragmentation are all ways that Archaea proliferate. In archaea, spermation does not occur.

Some bacteria can produce spores, which enable them survive in harsh environments for a length of time.


Archaea’s t-RNA is devoid of thymine.

Thymine can be found in bacteria’s t-RNA.


Archaea have tmRNA (transfer messenger RNA).

tmRNA is a kind of RNA discovered in bacteria.


Introns can be found in archaea’s chromosomes.

Bacterial chromosomes are devoid of introns.

RNA polymerase Archaea’s RNA polymerase is made up of more than eight polypeptides. It’s possible that they have several RNA polymerases.

Bacterial RNA polymerase is a four-polypeptide enzyme.


Archaea are not harmful bacteria.

Bacteria can be pathogenic or non-pathogenic depending on their nature.


Sulfolobus tokodaii, Thermosphaera aggregans, Staphylothermus marinus

Salmonella Typhi, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus

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Examples of Archaea.

(a) Sulfolobus

  • Sulfolobus is a genus of organisms that belongs to the Archaea domain and is acidophilic as well as thermophilic.
  • They thrive in an environment with a pH of 2-3 and a temperature of around 80°C. The majority of these can be found in volcanic springs.
  • Sulfolobus proteins are very useful in biotechnology because they are thermostable and can work at low pH.
  • These microbes are also unique in that during cellular respiration, they utilise sulphur as the final electron acceptor.
  • As a result, for autotrophic or heterotrophic nutrition, these organisms rely on sulphur.
  • Sulfolobus has also been utilised as a model for DNA replication research. During research on these organisms, many replication origin locations were discovered.
  • Sulfolobus tokodaii and Sulfolobus metallicus are two species in this genus.

(b) Methanogens

  • Methanogens are prokaryotes in the Archaea domain that create methane as a byproduct of metabolic processes.
  • These are typically found in wetlands and in the gastrointestinal tracts of ruminants, including humans. Extremophilic methanogens can be discovered in hot springs and deep-sea vents.
  • So far, more than 50 species of methanogens have been identified, with many of them producing methane via various metabolic routes.
  • Methane is produced when methanogens reduce carbon dioxide in the presence of hydrogen. Others, on the other hand, make methanol by anaerobic respiration.
  • Methanogens are most commonly utilised in wastewater treatment using bio composition, which is a more cost-effective and speedier wastewater treatment method.
  • Methanosarcina bakeri, Methanosarcina acetivorans, and Methanococcus maripaludis are examples of common methanogens.

Examples of Bacteria

(a) Escherichia coli (E. coli)

  • E. coli is a model microbe that has been utilised in a variety of studies. These creatures can be found in a variety of habitats, including the lower intestines of humans and other warm-blooded animals.
  • The majority of E. coli strains are safe, but a few might cause mild to severe diarrhoea. Vitamin K and Vitamin B-12 are even produced by some bacteria.
  • E. coli is a Gram-negative, facultative anaerobe that thrives in the presence of oxygen at ambient temperature.
  • It’s rod-shaped and has a brief lifetime, making it perfect for study.
  • E. coli has peritrichous flagella and is non-sporing.

(b) Lactobacilli

  • Lactobacillus is a genus of Gram-positive, non-spore-forming microbes that are rod-shaped.
  • Lactobacilli is a name used to describe bacteria that can create lactose as a by-product of glucose metabolism.
  • Milk and milk derivatives are the most common sources of these microbes.
  • Lactobacillus strains are widely utilised in the commercial production of fermented milk and vegetables.
  • Lactobacillus brevis, Lactobacillus casei, and Lactobacillus plantarum are some of the most often utilised species in this genus.
  • These creatures can even be discovered inside live beings’ bodies, such as in the intestine and vagina of humans.




Archaea Vs Bacteria Citations 



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