Archaea Vs Bacteria: Differences And Similarity

Archaea and bacteria are two different domains of cellular life. They are both prokaryotes, as they are unicellular and lack a nucleus. They also look similar (even under a microscope). Then What is the difference between these two microorganisms? and why they are placed in two different domains in the tree of life?

In this article, we will discuss the Differences and Similarities Between Archaea and  Bacteria.

Difference Between Archaea And Bacteria

Bacteria contain peptidoglycan in the cell wall; archaea do not. The cell membrane in bacteria is a lipid bilayer; in archaea, it can be a lipid bilayer or a monolayer. Bacteria contain fatty acids on the cell membrane, whereas archaea contain phytanyl.

Complicated subject, isn’t it? Let’s make it simple to understand the key differences between these two microorganisms.

Like Eubacteria (True Bacteria), Archaea contain a cell wall composed of various polysaccharides and glycoconjugates.

However, the Bacterial Cell wall Is mainly made up of Peptidoglycan. Which consists of N-acetyl muramic acid and D-amino Acids. While the Archaeal Cell walls lack peptidoglycan and have membranes that enclose lipids with hydrocarbons rather than fatty acids (not a bilayer).

These Lipids In the Membranes of Archaea are unique and contain ether linkages between the glycerol backbones rather than ester linkages which are present in the bacterial cell walls.

Archaea Vs Bacteria

Archaea resembles eukaryotes more than bacteria. Their ribosomes work more like eukaryotic ribosomes than bacterial ribosomes. because both bacteria and archaea have different Ribosomal RNAs (rRNA). Archaea have three RNA polymerases like eukaryotes, but bacteria have only one.

RNA polymerase in archaea is complex with more than eight polypeptides While Bacterial RNA polymerase is simple, with four polypeptides.

Archaeal and bacterial DNA and RNA are quite different from one another due to their chemical makeup. In Archaeal t-RNA Thymine is absent While In bacteria it is present. In archaea tmRNA (transfer messenger RNA) is found while absent in bacteria.

These two microorganisms also differ in genetic and biochemical ways. Archaea have been recognized as a distinct domain of life, Only within the last couple of decades.

They have similar ecological roles as bacteria. Both of these organisms react to various antibiotics in different ways.

Many types of bacteria can perform photosynthesis (generating oxygen from sunlight), while Archaea cannot but are phototrophs, that use sunlight as a source of energy.

Archaea do not use glycolysis or Kreb’s cycle for glucose oxidation but follow metabolic pathways similar to these while Glycolysis and Kreb’s cycle are important metabolic pathways in bacteria for glucose oxidation.

Archaeal and bacterial flagella are constructed differently. Bacterial flagella are hollow and are assembled by adding subunits moving from the central pore towards the tip of the flagella While Archaeal flagella, also termed archaea, are synthesized by adding subunits at the base.

Archaea reproduce by fission while some bacteria produce spores. Some bacteria are Might be pathogenic (cause disease) or non-pathogenic while no archaea are pathogenic.

Even their Chromosome is also different from each other, In Archaeal chromosomes Introns are present while in Bacterial Chromosomes Introns are absent.

Similarities Between Archaea And Bacteria

  • Archaea and Bacteria are prokaryotic microorganisms.
  • Do not have membrane-bound organelles and nucleus.
  • They share similar shapes Such as Sphere, rod, spiral.
  • They may possess flagella and Pili.
  • Both have Long circular form of Chromosomal DNA.
  • These organisms have 70S ribosomes.
  • They may Posses plasmid.
  • Both bacteria and archaea have cell membranes and they both contain a hydrophobic portion.
  • They are extremophiles, meaning they thrive in physically or geochemically extreme conditions.

Previously this was different because most of the Archaea are extremophiles But bacteria might be or are not extremophiles. However, archaea are not restricted to extreme environments; new research is showing that archaeans are also quite abundant in the plankton of the open sea. So now you can consider this as a habitual similarity.


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