Archaebacteria are one of the oldest living organisms (to be known) on Earth. They are classified as bacteria because many of their features resemble the bacteria when observed under a microscope. They belong to the kingdom Archaea and hence are named Archaebacteria. They share slightly common features with eukaryotes but are completely different from prokaryotes. They are known as extremophiles as they can easily survive under typically harsh conditions, for example, the bottom of the sea and the vents of a volcano.
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Following listed are some of the basic as well as important characteristics of archaebacteria:-
They are obligate anaerobes, i.e., they grow abundantly in the absence of oxygen which is the reason why they are the only one who can go under the process of methanogenesis.
The cell membrane of an archaebacterium is the composition of lipids.
Under hypotonic conditions, the rigid cell wall protects it from bursting, and also provides shape and support to the archaebacteria.
The cell wall of pathogenic bacteria can be dissolved by the enzyme named lysozyme, which is released by the immune system of the host but the cell wall of archaebacteria is made up of Pseudomurein, which protects it from the adverse effect of the lysozyme.
Membrane-bound organelles such as nuclei, endoplasmic reticulum, mitochondria, lysosomes, or chloroplast are found in archaebacteria. It has thick cytoplasm which contains all the essential compounds which are required for nutrition and metabolism.
Pressure upto 200 atmospheres can be withstood by them.
They reproduce asexually, through binary fusion.
They diverged from both prokaryotes and eukaryotes which is clearly depicted by the difference in their ribosomal RNA.
They can live under specifically harsh conditions, such as in acidic and alkaline aquatic regions, and can also survive in temperature above the boiling point.
Archaebacteria can be categorized on the basis of their phylogenetic relationship. Following listed are some of the major kinds of archaebacteria:-
Crenarchaeota:- The crenarchaeota are the kind of archaea which are found in a broad range of habitats. They can bear extreme heat and high temperatures due to a fact that they contain a special kind of protein that helps them to function at an absolute high temperature such as 230 degrees celsius. They are also found deep in the sea vents and also in hot springs. These consist of thermophiles, hyperthermophiles, and thermoacidophiles.
Euryarchaeota:- Unlike any living being on earth, they have the ability to produce methane and can survive under heavy alkaline conditions. This comprises methanogens and halophiles.
Korarchaeota:- They are believed to be the oldest living organisms on earth. They possess the genes that are common to Crenarchaeota and Euryarchaeota, hence all three are said to be descended from a common ancestor. They comprise hyperthermophiles.
Thaumarchaeota:- These are the typical kind of archaea that oxidize ammonia.
Nanoarchaeota:- It is the obligate symbiont of archaea and it belongs to the genus ignicoccus.
Following points determine the importance of archaebacteria:-
Archaebacteria have made the scientists reconsider the definition of species. Species are defined as a group with gene flow within its members whereas archaebacteria exhibit gene flow across its species.
Archaebacteria have the capability to produce methane, i.e., are methanogens. They do this by acting on the organic matter and hence decomposing it to release methane. Methane can hence for cooking and lighting purposes, therefore, these bacteria act as primary producers.
Archaebacteria can not perform photosynthesis.
They do not produce spores, unlike bacteria.
20% of all microbial cells living in the ocean are archaebacteria.
Archaea was discovered by Carl Woese in 1978.
Archaebacteria can only reproduce through the asexual mode.
1. Explain Archaebacteria with Help of Some Examples.
Following listed below are some examples of archaebacteria:-
Lokiarchaeota:- This is a thermophilic archaebacteria and is Generally found in the deep sea vents, which are known as Loki’s castle. Lokiarcheota has a unique genome, some of the genes of the genome are involved in phagocytosis. It is assumed that Lokiarcheota and eukaryotes shared a common ancestor billions of years ago, maybe due to which it also possesses eukaryotic genes that are used by eukaryotes to maintain their shapes.
Methanobrevibacter Smithii:- This bacteria produces methane and is usually found in the human gut. It plays an important role in the breakdown of plant sugar, and also helps us to extract energy and also helps us to extract energy from the food consumed by us. The chances of this bacteria being present in our gut increases for the people suffering from obesity and colon cancer.
2. How does an Archaebacterium get Energy?
A:- An archaebacterium gets energy in several different ways depending upon the type it is. Some archaea are lithotrophs, i.e, they obtain their energy from inorganic compounds such as sulfur or ammonia, and use an electron transport chain for the production of ATP. Other archaea which are phototrophs and obtain their energy from sunlight, however photosynthesis does not occur.