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The most ancient recognised living form present on earth is Archaebacteria. They represent kingdom monera. Under the microscope, Archaebacteria are categorised as bacteria because of their structure, morphology and other characteristics representing bacteria. They are unique from prokaryotes yet show few common traits of eukaryotes. 

Table of Contents

  • What are Archaebacteria?
  • Characteristics of Archaebacteria
  • Types of Archaebacteria
  • Significance of Archaebacteria
  • Important Examples of Archaebacteria
  • Practice Questions
  • Frequently Asked Questions

What are Archaebacteria?

Archaebacteria is a primitive bacteria microorganism, having a single and lacks a cell nucleus. They prefer a harsh environment to live in. The most prevalent example is methanogen, which tends to be extremely salty and hot. Each archaebacterium can survive in severe conditions like volcanic vents and the depth of the oceans. Therefore are popularly referred to as extremophiles.


Picture: Archaebacteria

Source: geeks for geeks

Characteristics of Archaebacteria

Learn important characteristics of Archaebacteria from the following:

  • Just archaebacteria are capable of methanogenesis, which means they can grow in the shortage of oxygen levels, thus called obligatory or facultative anaerobes. 
  • Archaebacteria are supported and shaped by their rigid cell wall, protecting them from exploding in the hypotonic environment.
  • Archaebacteria are shielded from the effects of Lysosomes through their cell wall composed of Pseudomurein. A pathogenic bacteria’s cell wall is dissociated by the immune host system's production of the enzyme lysozyme.
  • The cell membrane is made up of lipids.
  • Membrane-bound organelles like nuclei, lysosomes, mitochondria, endoplasmic reticulum or chloroplasts are present in Archaebacteria.
  • Archaebacteria have a dense cytoplasm filled with necessary elements like nutrients and active metabolic substances.
  • They can be capable of resisting up to 200 atmospheric pressure.
  • Via binary fusion, Archaebacteria can reproduce asexually.
  • The discrepancy in their ribosomal RNA diverges them from both prokaryotes and eukaryotes
  • They can live in extremely acidic or alkaline aquatic environments.
  • Archaebacteria can survive significantly higher temperatures over boiling points.

Types of Archaebacteria

Based on the phylogenetic relationship, Archaebacteria can be categorised, and some are listed below:


They can be found in various habitats and tolerate extreme temperatures. They have specific proteins that enable them to withstand the heat of about 240 degrees Celsius. They can be found in hot springs and deep marine vents. For example, thermoacidophiles, hyperthermophiles and thermophiles.


Popularly known for being the oldest category of microorganism present on earth. Since they share games with Euyarchaeota and Crenarchaeota, they all descend from the same ancestors. For example, Hyperthermophiles.


The only type of microorganism that can live under extremely alkaline environments and produce methane. It includes halophiles and methanogens.


The category belongs to the genus Gonococcus. It is known as the obligate symbiont of Archaea.


A type of archaea which oxidises ammonia.

Significance of Archaebacteria

Archaebacteria hold importance in nature. They are:

  • Researchers have reevaluated the accepted notion of species just because of the Archaebacteria. There is gene flow across each member of the species, such as archaebacteria.
  • Archaebacteria are methanogens and thus can produce methanes.
  • Archaebacteria can dissociate organic matter while interacting with them and thus can be utilised in cooking and lighting due to methane release.

Important Examples of Archaebacteria

Learn some important examples of archaebacteria from the following:

Methanobrevibacter smithii

It is present in humans and produces methane, which aids in plant sugar breakdown and extracts energy from the consumed food. Some of them protect from colon cancer. Obesity and colon cancer are due to the presence of euryarchaeota bacteria in the human gut at high intensity.


They are found in sea vents called Loki’s castle. They are thermophilic in nature, having a unique genome. Some of their genes are involved in phagocytosis. Lokiarchaeota has some eukaryotic genes that help to control their shape. They are considered to be from the same ancestor as eukaryotes.

Practice Questions

Q1. Archaebacteria can live in a distinct range of environments, including harsh, thus called as

A. Thermophiles
B. Extremophilies
C. Acidophiles
D. Hypothermophiles

Ans. B. Extremophiles. - Due to their adaptation in distinct extreme environments, archaebacteria are also called extremophiles.

Q2. Archaebacteria can live in

A. Alkaline condition
B. Acidic condition
C. Cold condition
D. All of the above

Ans. D. All of the above - Archaebacteria can live in extremely harsh conditions like highly alkaline, acidic environments. Methanogens can live even in cold conditions.

Q3. Archaebacteria poses

A. Rigid cell wall
B. No cell wall
C. All of the above
D. None of the above

Ans. A. Rigid cell wall - Archaebacteria possess a rigid cell wall.

Frequently Asked Questions

Q1. Can I see archaebacteria with the naked eye?
Answer. No, you cannot see archaebacteria from the naked eye but can see under a microscope.

Q2. Can archaebacteria produce their food?
Answer. Yes. They can produce their food autotrophic. Some obtain their food from other organisms. They are called heterotrophic.

Q3. Are archaebacteria harmful for human beings?
Answer.  Archaebacteria are both beneficial and harmful in certain conditions for human beings. Mostly they possess benefits like reducing the pH of the skin etc.

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