Archaebacteria

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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A Brief Introduction of Archaebacteria

Archaebacteria is called a primitive bacteria microorganism. It owns only a single cell and it lives in an environment where there is severity. The examples are extremely hot or salty (the most common instance is methanogens). In other words, Archaebacteria is not only a primitive but also a microorganism with single-cell (these are known as prokaryotes having zero cell nucleus. Every archaeon owns the capability of living in an extreme environment. 

Characteristics of Archaebacteria

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 up to 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 temperatures above the boiling point.

Types of Archaebacteria

Archaebacteria can be categorized on the basis of their phylogenetic relationship. Following listed are some of the major kinds of archaebacteria:-

• Crenarchaeota:- The crenarchaeal is the kind of archaea that are found in a broad range of habitats. They can bear extreme heat and high temperatures due to the 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 gonococcus.

Importance of Archaebacteria

Following points determine the importance of archaebacteria:-

• Archaebacteria have made 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.

Did you Know?

• 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.

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