What is the Difference Between Archaea and Bacteria

The main difference between archaea and bacteria is that the cell walls of archaea are made up of pseudopeptidoglycan, whereas the cell walls of bacteria are made up of lipopolysaccharides or peptidoglycan.

Archaea and bacteria are two types of prokaryotic organisms. They do not contain nuclei. Also, they are single-celled organisms.

Key Areas Covered

1. What is Archaea
– Definition, Facts, Features
2. What is Bacteria
– Definition, Facts, Features
3. Similarities Between Archaea and Bacteria
– Outline of Common Features
4. Difference Between Archaea and Bacteria
– Comparison of Key Differences
5. FAQ – Archaea and Bacteria
– Answers to frequently asked questions

Key Terms  

Archaea, Bacteria

Difference Between Archaea and Bacteria - Comparison Summary

What is Archaea

Archaea is a domain of single-celled organisms that belong to the kingdom Prokaryota. They lack cell nuclei. The general size and shape of archaea are similar to that of bacteria. Some have flat and square cells, as in Haloquadratum walsbyi. Although the shape of the archaea cells is similar to that of bacteria, their genes and metabolic pathways are more identical to that of eukaryotes. For example, archaea transcription and translation enzymes are similar to eukaryotic enzymes. Another example of the unique metabolic pathways in archaea is the presence of ether lipids, such as archaeols, in the cell membrane.

Compare Archaea and Bacteria

Figure 1: Archaea in Water 

Furthermore, archaea use diverse energy sources ranging from sugars, ammonia, metal ions, and hydrogen to eukaryotes. Also, the salt-tolerant Haloarchaea uses sunlight as the energy source to fix carbon. Like bacteria, archaea are extremophiles living in hot springs and salt lakes. Also, they live in almost all habitats, including marshlands, soil, and oceans. Archaea in plankton are among the most abundant organisms on Earth.    

What is Bacteria

Bacteria are unicellular prokaryotes that are freely living biological cells of fewer micrometers long cells. Since bacteria are prokaryotes, they lack membrane-bound organelles such as nuclei, mitochondria, and chloroplasts. Generally, one of the main characteristic features of bacteria is the presence of a cell wall made up of peptidoglycans. Some bacteria contain an envelope surrounding the cell wall. Their genetic material occurs in the cytoplasm as a single circular DNA molecule. Another characteristic feature of bacteria is the presence of extrachromosomal DNA elements known as plasmids, which are important in recombinant DNA technology. Significantly, all of the biochemical reactions of the bacterial cell occur inside the cytosol.

Archaea vs Bacteria

Figure 2: Rod-Shaped Bacillus

Moreover, the four major shapes in which bacteria can exist are bacillus (rod shape), coccus (spherical shape), spirilla (spiral shape), and Vibrio (curved shape). In addition, there are two types of bacteria based on the structure of the cell wall. They are Gram-positive and Gram-negative bacteria. Bacteria produce several types of responses to gaseous oxygen. Based on the response, bacteria can be classified as aerobic bacteria, which tend to live in the presence of oxygen; anaerobic bacteria, which tend to live without oxygen; and facultative anaerobes, which can live in both environments.

Similarities Between Archaea and Bacteria

  • Archaea and bacteria are two types of prokaryotes.
  • They are single-celled organisms.
  • They do not contain nuclei or membrane-bound organelles.
  • They are very similar in size and shape.
  • Also, they contain enzymes for DNA replication and protein synthesis.
  • Their asexual reproduction occurs through binary fission, budding, or fragmentation.
  • Both can be extremophiles. 

Difference Between Archaea and Bacteria


Archaea refers to microorganisms similar to bacteria in size and simplicity of structure but radically different in molecular organization. Meanwhile, bacteria refer to a member of a large group of unicellular microorganisms with cell walls but lack organelles and an organized nucleus, including some that can cause disease.

Cell Wall

The cell wall of archaea is made up of pseudopeptidoglycan, while the cell wall of bacteria is made up of lipopolysaccharide or peptidoglycan.

Cell Membrane

Archaea contain ether lipids, including archaeols, in their cell membrane, while bacteria do not have ether lipids in their cell membrane.


Archaea undergo carbon fixation, while bacteria undergo nitrogen fixation.


Archaea does not produce endospores, while bacteria produce endospores.

Pathogens or Parasites

Archaea do not serve as pathogens or parasites, while bacteria can be pathogens that cause diseases. 

FAQ: Archaea and Bacteria

What are the major differences between bacteria and archaea?

There are major differences between archaea and bacteria. The cell wall of archaea does not contain peptidoglycans, while the bacteria’s cell wall contains peptidoglycans. Also, archaea show a closer evolutionary relationship to eukaryotes than to bacteria.  

What are the three types of archaea?

Methanogens, thermophiles, and halophiles are the three major types of archaea. Methanogens are anaerobic organisms that produce methane gas. 

Do archaea have DNA polymerase?

Archaea contains similar DNA polymerases to eukaryotic DNA polymerase. However, they have unique DNA polymerases with the fastest replication fork movement.  


In brief, archaea and bacteria are two types of prokaryotes that are single-celled organisms. They do not contain nuclei. The cell wall of archaea contains pseudopeptidoglycan. Also, their cell membrane contains ether lipids. Additionally, archaea undergo carbon fixation. In comparison, bacteria’s cell wall contains peptidoglycan or lipopolysaccharide. Also, they undergo nitrogen fixation. Apart from that, they produce endospores and become pathogens, causing diseases. Therefore, the main difference between archaea and bacteria is their cell wall and other characteristics.    

  1. Encyclopædia Britannica, inc. (2023d, December 28). Archaea. Encyclopædia Britannica.
  2. Bacteria. Genome.gov. (n.d.).
Image Courtesy:
  1. Morning-Glory Hotspring” By ZYjacklin – Own Work (Public Domain) via Commons Wikimedia
  2. Bacillus subtilis 2” By Dr Graham Beards – Own Work (CC BY SA 4.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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