Archaea Vs Bacteria- Definition, 15 Major Differences, Examples

Archaea Vs Bacteria Overview

Definition of Archaea

The early prokaryotes known as archaea constitute a different domain from bacteria and eukaryotes based on their unique traits.

  • The name “Archaea,” which refers to the old or archaic structure of these organisms, is derived from the Greek word “archaios.”
  • Typically, these species live in harsh conditions, including deep marine vents, salty waterways, hot springs, and even under petroleum deposits.
  • These thrive in low-oxygen settings and are mostly anaerobic. The majority of archaea must be identified using methods unrelated to culture, since they cannot be grown in labs.
  • These organisms may have traits in common with both bacteria and eukaryotes. They share certain genes, metabolic pathways, and enzymes with eukaryotes but have an embryonic membrane-less nucleus like bacteria.
  • These species do, however, also have certain distinctive traits. As opposed to the ester bond seen in bacteria and eukaryotes, the membrane lipids of archaea include fatty acids connected to glycerol molecules via ether bonds.
  • Archaea often have unique metabolic pathways and genes that promote their survival, since they frequently live in harsh settings.Halophilic archaea have a special set of genes that let them survive by limiting the amount of osmosis.
  • Archaea reproduce asexually by budding, fission, and fragmentation.There is no typical mitosis or meiosis to divide the cell.
  • The majority of archaea support several elements’ biogeochemical cycles, including those for carbon, nitrogen, and sulphur.
  • Many archaea are methanogens. Methane is produced as a by-product of anaerobic cellular respiration by many archaea.
  • These species don’t engage in oxygen-producing photosynthesis, although some of them (phototrophs) do utilise sunshine as a source of energy.

Bacteria Definition

Single-celled primordial creatures called bacteria come in a wide range of forms, sizes, structures, and even environments.

  • Bacteria are prokaryotes with a basic structure and a limited number of cell organelles. They also contain a membraneless nucleus.
  • The term “bacteria” refers to a class of creatures that may be found in a wide variety of environments, from the tops of mountains to within the bodies of other living things.
  • Some bacteria are useful for a variety of processes, including the manufacture of antibiotics, industrial usage, and biogeochemical cycles. Some, however, are harmful germs that cause minor to major illnesses.
  • Bacteria are the tiniest living things on the planet.A variety of staining methods are used to see these creatures under a microscope.
  • Based on staining methods, gramme-positive and gramme-negative bacteria are separated.
  • Almost all bacteria have a peptidoglycan-based cell wall that shields them from dangerous substances. A developing nucleus without a membrane that contains the genetic material and few ribosomes may be found in the cytoplasm.
  • Fatty acids are bonded to glycerol via ester linkages to form the membrane lipids of bacteria.
  • Transfer-messenger RNA is an additional unique RNA found in bacteria (tmRNA).
  • Bacteria have DNA as their genetic material, which is passed on via asexual reproduction to their progeny.
  • Although genetic material is transferred via numerous processes such as transformation, transduction, and conjugation, reproduction occurs by binary fission, budding, and fragmentation.

Key Differences (Archaea vs Bacteria)

Basis for Comparison Archaea Bacteria
Definition Archaea is a group of primitive prokaryotes that based on their distinct characteristics form a separate domain from bacteria and eukaryotes. Bacteria are single-celled primitive organisms that form a domain of organisms diverse in shape, size, structure, and even habitats.
Habitat Most archaea are extremophiles and are found in extreme environments like the deep sea, mountains, hot springs, salt brine, etc. Bacteria reside in different habitats ranging from soil, water to inside living, and non-living organisms.
Cell wall The archaeal cell wall is made up of pseudopeptidoglycan and lack D-aminoacids and N-acetylmuramic acid. The bacterial cell wall is made up of peptidoglycan consisting of N-acetylmuramic acid and D-amino acids.
Membrane lipid The fatty acids in membrane lipids of archaea are bound to glycerol by ether bonds. The fatty acids in membrane lipids of bacteria are bound to glycerol by ester bonds.
Glucose oxidation Archaea do not use glycolysis or Kreb’s cycle for glucose oxidation but follow metabolic pathways similar to these. Glycolysis and Kreb’s cycle are important metabolic pathways in bacteria for glucose oxidation.
Photosynthesis Archaea do not perform oxygen-generating photosynthesis but are phototrophs, that use sunlight as a source of energy. Many bacteria containing photosynthetic pigments can perform photosynthesis to prepare their own food.
Types Archaea are divided into different groups like Methanogens, Thermophiles, and Halophiles on the basis of their characteristics. Bacteria are divided as Gram-negative and Gram-positive based on their response to Gram staining.
Flagella Archaeal flagella, also termed archaella, are synthesized by adding subunits at the base. Bacterial flagella are hollow and are assembled by adding subunits moving from the central pore towards the tip of the flagella.
Reproduction Archaea reproduce by fission, budding, and fragmentation. Sporulation doesn’t occur in archaea. Some bacteria are capable of forming spores that help them survive extreme conditions for a particular period of time.
tRNA Thymine is absent in the t-RNA of archaea. Thymine is present in the t-RNA of bacteria.
tmRNA tmRNA (transfer messenger RNA) is found in archaea. tmRNA is found in bacteria.
Chromosomes Introns are present in the chromosomes of archaea. Introns are absent in the chromosomes of bacteria.
RNA polymerase RNA polymerase in archaea is complex with more than eight polypeptides. They might even have multiple RNA polymerases. Bacterial RNA polymerase is simple, with four polypeptides.
Pathogenicity Archaea are non-pathogenic. Bacteria might be pathogenic or non-pathogenic.
Examples Thermosphaera aggregans, Staphylothermus marinus, Sulfolobus tokodaii. Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Salmonella Typhi.

Examples of Archaea


  • Sulfolobus is a genus of thermophilic and acidophilic organisms that are a part of the Archaea domain.
  • They develop at a temperature of around 80 °C and a pH of 2–3. Volcanic springs are where you’ll primarily find them.
  • Due to their thermostability and ability to act at low pH, the proteins discovered in Sulfolobus are especially crucial in biotechnology.
  • The last electron acceptor used by these microbes during cellular respiration makes them unique as well.
  • As a result, these organisms’ autotrophic or heterotrophic modes of feeding rely on sulphur.
  • DNA replication was also studied using Sulfolobus as a model. During research on these species, several replication origin locations were found.
  • Sulfolobus tokodaii and Sulfolobus metallicus are two species that fall under this genus.


  • Methanogens are prokaryotes that are members of the Archaea domain and are so termed because they generate methane as a by-product of their metabolic processes.
  • These are mostly found in wetlands and in the gastrointestinal systems of different ruminants, including humans. Hot springs and deep-sea vents are home to several extremophile methanogens.
  • There are more than 50 species of methanogens that have been identified so far, and many of them use various metabolic processes to create methane.
  • In the presence of hydrogen, certain methanogens convert carbon dioxide into methane. Others, however, use anaerobic respiration to create methanol.
  • Methanogens are primarily utilised in the biocomposition method of treating wastewater, which is a quicker and more affordable method.
  • Methanosarcina bakeri, Methanosarcina acetivorans, and Methanococcus maripaludis are a few common species of methanogens.

Examples of Bacteria

Eccherichia coli (E. coli)

  • A model microbe employed in several scientific investigations is E. coli. Many of these organisms may be found in the lower intestines of humans and other warm-blooded animals, and they can be found in a variety of settings.
  • The majority of E. coli strains are not harmful, but a few may cause moderate to severe diarrhoea. Even certain microorganisms can make vitamin K and B-12.
  • Coli is a facultative anaerobe that is Gram-negative and thrives at ambient temperature.
  • It is useful for research investigations since it is rod-shaped and has a brief life cycle.
  • Coli has peritrichous flagella and is non-sporing.


  • A family of rod-shaped, Gram-positive, non-spore-forming bacteria known as Lactobacillus exists.
  • The word “Lactobacilli” refers to microorganisms that may create lactose as a by-product of the metabolism of glucose.
  • Most of these organisms can be found in milk and milk-derived products.
  • Commercial production of fermented milk and other vegetables uses a wide range of lactobacillus species.
  • Lactobacillus brevis, Lactobacillus casei, and Lactobacillus plantarum are a few of the species of this genus that are often employed.
  • Even live things’ bodies contain these creatures, including the human gut and vagina.

References and Sources

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  • 1% – https://en.wikipedia.org/wiki/Archaea
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  • <1% – https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/methanogens
  • <1% – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC125487/
  • <1% – https://www.justanswer.com/health/3grmk-culture-urine-routine-result-read-multiple-organisms-present-each.html
  • <1% – https://www.bartleby.com/essay/Bacteria-Are-The-Smallest-Living-Organisms-P33TR8TKRY3Q
  • <1% – https://ucmp.berkeley.edu/archaea/archaeamm.html
  • <1% – https://sciencing.com/archaea-structure-characteristics-domain-13717691.html
  • <1% – https://quizlet.com/187938139/archaea-flash-cards/
  • <1% – https://owlcation.com/stem/What-are-Chemosynthetic-Bacteria
  • <1% – https://onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.13361
  • <1% – https://medium.com/the-biochemists/why-are-gram-negative-bacteria-resistant-to-antibiotics-c732fe9afd06
  • <1% – https://en.wikipedia.org/wiki/Bacterial_conjugation
  • <1% – https://biodifferences.com/difference-between-archaea-and-bacteria.html
  • <1% – http://microbewiki.kenyon.edu/index.php/Sulfolobus
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