Archaebacteria Kingdom

Archaebacteria kingdom is a group of bacteria that are anaerobic, as well as aerobic prokaryotes. These bacteria are adapted to living in extreme environmental conditions, like near volcanic activity, deep oceans, etc, and do not need oxygen and light to survive. All living organisms are placed in five kingdom system: plantae animalia, fungi, protist and monera. Not so long ago, before 1977, the archae were considered to be just another group of bacteria. They were thus, placed in Kingdom Plantae. Soon, they were placed under the new kingdom Monera, after the bacteria. Carl Woese and George Fox, were two scientists who proposed in 1977, that archaebacteria should have a different kingdom of their own. By 1990, scientists found out that 16S rRNA and 18S rRNA sequences were totally different in archea from other bacteria. Genome analysis of archae in 2003, confirmed that they are different from bacteria. Thus, finally they were removed from kingdom Monera and the five kingdom of living things was converted into six kingdom system, with the inclusion of the new archaebacteria kingdom. Do you want to know what is the difference between archaebacteria and bacteria? The following characteristics will help you understand the reason for this transition.

Characteristics of Archaebacteria

The term achaio is a Greek word for ancient. This term aptly describes the archaebacteria who are thought to have a common ancestor like the bacteria and eukaryotes. Archaebacteria is similar in structure to eukaryotes than bacteria. There are several archaebacteria kingdom characteristics that help in distinguishing them from eubacteria. These characteristics of archaebacteria are as follows:

• Archaebacteria have no peptidoglycan in their cell walls
• The cell wall is made up of glycoproteins and polysaccarides.
• The cell wall envelopes have a high resistance to antibiotics and lytic agents due to difference in cell wall composition.
• They have a very different lipid bilayer making up the cell membranes
• The RNA polymerase of archae is very similar to that of eukaryotes
• The eukaryotes and archea ribosomal proteins are similar to each other

Archaebacteria are about 1/10th of a micrometer to about 15 micrometer in size. A few are flagellated and the flagella structure is different from the flagella of other bacteria. The archaebacteria are non-pathogenic bateria that live in and around other organism. However, they do not cause any infections or diseases.

Archaebacteria are autotrophs and use CO₂ in atmosphere as a source of carbon for a process called carbon fixation. Archaebacteria are able to survive in extreme conditions and therefore also known as extremophiles. They can survive in conditions that are highly acidic, alkaline, saline aquatic environment. Some are even able to survive in temperatures above 100° Celsius or 212° Fahrenheit. Few can even withstand over 200 atmosphere pressure and live really deep within the earth. They employ different chemical reactions to 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 be killed with exposure to oxygen. They produce marsh gas that one can observe as bubbles in stagnant waters. They are also present in the gut of cattle and termites. Methanogens use carbon dioxide as an electron acceptor to oxidize hydrogen using coenzymes like coenzyme M and methanofuran. These coenzymes 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.

Reproduction in archae is carried out asexually by binary or multiple fission, fragmentation or budding. They do not undergo meiosis and therefore organisms of a species that are present in more than one form share the same genetic matter. Archaebacteria do not form spores and a few species of haloarchae undergoes phenotypic switching. This means it can grow several different cell types that are resistant to osmotic shock. Thus, the organisms can survive in low salt concentration aquatic environment.

Importance of the Archaebacteria Kingdom

The importance of archaebacteria kingdom are as follows:

• They have phylogenic importance that helps in studying their homology and establish their phylogeny.
• Their ability to tolerate extreme conditions helps one learn about the climatic conditions, environment and their survival on ancient earth.
• Methanogens can grow in bio-gas 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 ruminatum are present in the gut of ruminating animals, helping them digest the cellulose.
• Poor ores of molybdenum are microbial leached using Sulfolobus.
• Archaebacteria are also used to synthesize thermophilic enzymes, restriction enzymes and are also used as bio-sensors

Archaebacteria Examples

The following names of organisms are a few archaebacteria examples:

• Methanobacterium
• Methanococcus
• Methanospirillum
• Halococcus
• Halobacterium
• Thermoplasma
• Thermoproteus
• Sulfobolus
• Pyrolobus fumarii
• Methanococcus jannischii

This was some information related to characteristics of archaebacteria kingdom and archaebacteria kingdom examples. These extremophiles prove life can exist anywhere, under any condition. Hope, the above information has helped you gather some useful archaebacteria information.