Archaebacteria Kingdom
Archaebacteria kingdom is a group of single-celled organisms adapted to living under extreme conditions. Archaebacteria are almost as old as the Earth. They came into existence when the Earth was in its nascent stage and the conditions were extreme. Till date, these organisms live in conditions that mimic the extreme ones that were the norm, when the Earth was just beginning to take shape.
Kingdom Archaebacteria in a Nutshell
- Type of Organism: Unicellular
- Cell Structure: Prokaryotic
- Habitat: Extreme Environments
- Reproduction: Asexual (binary fission)
- How do I get energy: Autotrophs/Heterotrophs
Subgroups of Archaebacteria
They employ different chemical reactions to be able to survive in these harsh conditions. Thus, they are divided into 3 subgroups - methanogens, extreme halophines and thermoacidophiles. Let us learn more about the characteristics according to the sub-groups.
Methanogens
Metanogens are able to reduce CO2 into methane (CH4). They are obligately anaerobic and can die if exposed to oxygen. They produce marsh gas that can be observed as bubbles in stagnant water. They are also present in the gut of cattle and termites, since there is no oxygen there. Methanogens use carbon dioxide as an electron acceptor to oxidize hydrogen using co-enzymes like co-enzyme M and methanofuran. These co-enzymes are very unique to archaebacteria. These bacteria are rod shaped or spherical, and can be gram positive as well as negative.
Halophiles
Halophiles are bacteria that can survive in 10 times the concentration of salt present in sea. You can find halophilic archaebacteria in Great Salt Lake in Utah and the Dead Sea in Middle East. Halobacter uses photophosphorylation for metabolism. They use light activated ion pumps like bacteriorhodopsin and halorhodopsin for generation of ion gradients to pump out ions across the plasma membrane. The energy that is stored in the electrochemical gradients is converted to ATP by ATP synthase. They contain bacteriorhodopsin, a red or orange pigment.
Thermoacidophiles
The thermoacidophiles are organisms that can survive in extremely high temperatures and low pH. They can survive in 100° Celsius with a pH of 2. Most of these organisms are anaerobic in nature.
Methanogens
Metanogens are able to reduce CO2 into methane (CH4). They are obligately anaerobic and can die if exposed to oxygen. They produce marsh gas that can be observed as bubbles in stagnant water. They are also present in the gut of cattle and termites, since there is no oxygen there. Methanogens use carbon dioxide as an electron acceptor to oxidize hydrogen using co-enzymes like co-enzyme M and methanofuran. These co-enzymes are very unique to archaebacteria. These bacteria are rod shaped or spherical, and can be gram positive as well as negative.
Halophiles
Halophiles are bacteria that can survive in 10 times the concentration of salt present in sea. You can find halophilic archaebacteria in Great Salt Lake in Utah and the Dead Sea in Middle East. Halobacter uses photophosphorylation for metabolism. They use light activated ion pumps like bacteriorhodopsin and halorhodopsin for generation of ion gradients to pump out ions across the plasma membrane. The energy that is stored in the electrochemical gradients is converted to ATP by ATP synthase. They contain bacteriorhodopsin, a red or orange pigment.
Thermoacidophiles
The thermoacidophiles are organisms that can survive in extremely high temperatures and low pH. They can survive in 100° Celsius with a pH of 2. Most of these organisms are anaerobic in nature.
Importance of Archaebacteria
Archaebacteria are important for the following reasons:
- Their ability to tolerate extreme conditions helps researchers learn about the climatic conditions, environment and their survival on ancient earth.
- Methanogens can grow in biogas fermentors and decompose cow dung into methane gas as a by-product. Thus, they are used for production of domestic gas for cooking.
- Organisms like Methanobacterium ruminantium are present in the guts of ruminating animals, helping them digest the cellulose.
- Archaebacteria are also used as biosensors.
- Archaebacteria have an important role in many chemical cycles, like carbon cycle, nitrogen cycle, sulfur cycle, etc.
- Due to their extremophilic nature, archaebacteria have proven to be of great help in the field of Bioechnology, by helping in the production of enzymes that work at very high temperatures, as well as in the production of some antibiotics.
Examples of Archaebacteria
- Methanobacterium
- Methanococcus
- Methanospirillum
- Halococcus
- Halobacterium
- Thermoplasma
- Thermoproteus
- Sulfolobus
- Pyrolobus fumarii
- Methanococcus jannaschii
- Nanoarchaeum equitans
- Ignicoccus