Archaebacteria – Primitive Microorganisms


Archaebacteria or Archaens though have a suffix bacteria added to it, it seems to have diverged from bacteria and more closely related to eukaryotes. This conclusion comes largely from the comparisons of genes that code ribosomal RNAs.

Despite knowing about the weird inhabitations of the archaeans there are certain key characteristics that make it more interesting. Their cell walls lack peptidoglycan (an important structure found in almost bacteria), the lipids in cell membranes of archaebacteria have distinctive ribosomal RNA (rRNA) sequences. With recent discovery, it is seen that it contains introns in its genetic material which is unlike bacteria.

So let’s delve into more interesting facts about archaebacteria.


Archaebacteria are basically classified into three major categories on the basis of their habitat and metabolic pathways.


Methanogens are chemoautotrophs since they derive energy from hydrogen gas to reduce carbon dioxide to methane. They are strict anaerobes , poisoned by even slight traces of oxygen. Methanogens are responsible for about releasing of two billions of methane gas into the atmosphere each year.

2. Extremophiles

They grow under the conditions which seems extreme to us.

Thermophiles(“Heat lovers”)

Thermophile archebacteria

These autotrophs thrive in temperatures ranging from 60 degrees to 80 degrees. Their metabolism is based on sulphur. It is quite interesting that some of the archaebacteria holds a place in the food chain around deep sea thermal vents. While others such as Sulpholobus inhabit the famous hot sulphur spring in Yellowstone National Park (USA) at 70 degrees to 75 degrees.

The recently described Pryolobus fumarii holds a current record of 106 degrees optimal temperature and 113 degrees maximum. It is so heat tolerant that even after 1 hour of autoclave( 121 degrees) it does not get killed

Halophiles (“ Salt Lovers”)

Halophile archaebacteria

These archaebacteria requires a salinity of 3%. They are often found in Great Salt Lake in Utah (USA), Mono Lake in California (USA) and the Dead Sea in Israel.

pH tolerant

Thrives in highly acidic medium around pH=0.7 and very basic of around pH=11.

Pressure tolerant

Some archaebacteria can thrive under 800 atmosphere.

3. Non-extreme Archaebacteria

Unlike the other archaebacteria these thrive in normal conditions as same as normal bacterias.


Earlier microbiologists have tried classifying prokaryotes in terms of their biochemistry and nutritional requirements. But this approach has pit falls. So Genome analysis has come to fore. This is a more powerful way to decode an organism. The complete DNA sequence of an organism defines the species with more perfect precision. Moreover this specification once determined is in a digital form – a string of letters – that can be fed directly into a computer and compared with corresponding information for any other living being. Because DNA is subjected to random changes over a long period of time we can find the difference between the two DNAs and have a quantitative indication of evolutionary distance between them.

1. Role of mutation and Natural Selection

Both in storage and in copying of genetic material random accidents and errors occurs which results in mutation. Now the mutation can be useful or destructive. Changes due to the second type- selective neutral changes-may be perpetuated or not. Through endless repetition of this cycle of trial and error-of mutation and natural selection organisms evolve.

2. Most bacteria and archae have 1000-4000 genes

Natural selection only favours those who have high fecundity rate. Moreover they have small size so they take up maximum nutrients and increase it’s reproductive rate.

  1. New genes are generated from pre-existing ones.
  2. Gene duplication
  3. Segment shuffling
  4. Horizontal or intercellular transfer


1.Waste water treatment

Archaea involved technology is essential for waste water treatment by integrating energy production and resource recovery into a process for producing clean water.


Archaea play a vital role in converting pollutants into eco-friendly materials.

3.Geochemical cycle

The present study related to exploration of coal mining area in Dhanbad has led to discovery of role of archaebacteria in geochemical cycle and coal-benefaction.


To overcome current limitations to understanding archaea, the combination of new cultivation strategies, high-resolution molecular technologies, more detailed biogeochemical approaches, traditional microbiological methods and bioinformatic tools are being used. New metabolic capabilities of these unveiled and widespread archaea are emerging.




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