Archaebacteria and Eubacteria Difference

For the first half of geological time our ancestors were bacteria. Most creatures still are bacteria, and each one of our trillions of cells is a colony of bacteria.
~ Richard Dawkins

True to the quote above, bacteria have probably been around since as early as Earth thought it could support life. As most of us are aware, bacteria are unicellular micro organisms having prokaryotic cellular structures. There is probably no place on Earth where these primordial citizens of our planet cannot be found. Bacteria come in a vast assortment of shapes that include spherical, spiral and rod-like structures. Based upon their ability to retain crystal violet stain, bacteria are broadly classified as gram positive and gram negative bacteria. Although all unicellular prokaryotic life forms are identified as bacteria, there exist a bifurcation, in terms of biological domain, that separates these single-celled prokaryotes into two distinct life forms - Archaebacteria and Eubacteria (or simply bacteria). The details and differences of these two unicellular prokaryotes are the subjects of discussion of this article.

What is Archaebacteria?

The archaebacteria kingdom constitutes both aerobic bacteria as well as anaerobic bacteria. The most significant distinctions that set this domain of unicellular prokaryotes from other bacteria species can be enlisted as two observations:-

• Archaea have been observed to be equipped with metabolic pathways and several units of heredity that are very close in form and function to eukaryotic organisms. Most significant among these aspects are the enzymes possessed and produced by archaea that are involved in genetic translation and transcription.
• Archaea are also known to be dependent upon ether lipids for all functions relating to polar lipids.

Besides these observations, another characteristic of archaebacteria is that it is capable of extracting energy and nutrition from more sources than eukaryotic life forms. These sources of energy and nourishment include sugars, metal ions, hydrogen as well as sunlight. Some species of archaea can also convert gaseous carbon dioxide to solid carbon compounds, a process which is known as carbon fixation. Archaebacteria can reproduce asexually in by following any of the following three methods - budding, binary fission or fragmentation. Good examples of Archaebacteria are Halobacteria and Methanocella.

What is Eubacteria?

The term Eubacteria is used to denote the generic unicellular prokaryotes that both look like and act as prokaryotes. Almost all types of eubacteria reproduce by undergoing binary fission though some species are known to reproduce by budding. Eubacteria usually derive their nutrition through carbon fixation. There are many different types of bacteria and these include both helpful and harmful types of bacteria. Eubacteria can derive their nutrition from three chief energy sources - sunlight, organic and inorganic compounds.

Difference between Archaebacteria and Eubacteria

The following table shows the basic structural and characteristic differences with relation to archaebacteria vs. eubacteria.

Points of Distinction	Archaebacteria	Eubacteria
RNA Polymerase Composition	Ten subunit core architecture	Four subunit core architecture
Pathogenicity	Nil	Some eubacteria are pathogenic (see pathogenic bacteria list)
Relationship with Other Organisms	Mutual, commensal	Mutual, predatory, pathogenic
Cellular structure	Peptidoglycan absent, ether-liked lipids in the form of branched chains	Peptidoglycan present, ester-linked lipids in the form of a straight chain
Role in Nature	Unknown	Significant role in nutrient recycling

That precisely sums up what Archaebacteria and Eubacteria are along with the most significant points of distinctions that set these two different evolutionary strains of unicellular life-forms apart. Although initially believed to have belonged to the same group of unicellular prokaryotes as Eubacteria, Archaea, as it was later discovered, were identified as a separate group of micro organisms altogether, based upon their rRNA gene sequence. After much research, it was finally concluded that both eubacteria and archaebacteria belong to two separate microbiological domains that descended from a common unicellular ancestor - much the same way as wolves and dogs are believed to have descended from a separate common ancestor.