Difference Between Bacteria and Archaea

The key difference between Bacteria and Archaea is that genes of Archaea are more similar to Eukarya than Bacteria. In addition, Archaea do not have peptidoglycan in their cell walls while bacteria do.

All living organisms can be classified into 3 major domains: Archaea, Bacteria, and Eukarya. Archaea and Bacteria are prokaryotic organisms that lack membrane-bound organelles and a nucleus. They are single-celled organisms.

What are Archaea?

Archaea are a fascinating group of prokaryotic organisms discovered in the 1970s. Before that, they were considered as a part of bacteria (archaebacteria).  Since Archaea show distinct differences from bacteria, now they are in a separate domain called Archaea. They are the most primitive organisms discovered so far. They are very significant and unique group.  Firstly, they resemble early fossils (dated 2 million years old), confirming that they are the most primitive organisms discovered till today. Secondly, they are able to survive in extreme environmental conditions. They include extremophiles which can survive in extreme environments such as hot springs, rift vents in the deep sea, hyper saline water, petroleum deposits, digestive tracts of cows, termites and marine life.

Archaea are tiny organisms, which are less than 1 micron long. Archaea have a variety of shapes such as coccoid, bacilli and other odd shapes. Based on their physiology, there are three main groups: methanogens, thermophiles, and halophiles. Methanogens are anaerobes that live in the bottom of ponds, sewage lagoons and intestinal tracts of animals. They use hydrogen compounds and carbon dioxide to produce energy. In this process, they release methane. Moreover, extreme thermophiles live in extremely hot waters such as geysers, hot vents on the ocean floor etc. They oxidize sulfur to obtain energy and releases sulfuric acid as a byproduct. Extreme halophiles, however, live in high salt water such as in the Dead Sea.

What are Bacteria?

Bacteria are a group of single-celled prokaryotic organisms that live in diverse environments. They were first observed in 1674. This name originated from the Greek word for “small stick”. They are tiny organisms that are only a few micrometers long. There are free-living bacteria as well as those that may grow attached to a surface. Bacteria exist in different shapes such as coccoid, bacilli, spiral, comma and filamentous.

Bacteria lack membrane-bound organelles such as nucleus, mitochondria, chloroplasts, Golgi bodies, and ER. A single chromosome is present in the cytoplasm. They also have highly coiled DNA. A unique characteristic of the bacterial cell wall is the compound “peptidoglycan”. Gram-positive bacteria possess a thick peptidoglycan layer while Gram-negative bacteria possess a thin peptidoglycan layer. This difference in the thickness is a good characteristic when differentiating bacteria from each other. Bacteria contain extrachromosomal DNA called ‘Plasmid’ that are able to self-replicate. Plasmids are circular small DNA molecules that are used as vectors in recombinant DNA technology. Though plasmids carry genes, they are not essential for the survival of bacteria.

Bacteria may also possess flagella for locomotion. Bacterial capsule is a rigid polysaccharide structure. It provides protection. It also contains polypeptides. Hence, it resists phagocytosis. The capsule is also involved in recognition, adherence, and formation of biofilms and pathogenesis. Some may also produce endospores, which are highly resistant dormant structures.

What are the Similarities Between Archaea and Bacteria?

  • Archaea and Bacteria are microorganisms.
  • Both are prokaryotic.
  • They do not have membrane-bound organelles and nucleus.
  • They share similar shapes.
  • Both groups include very tiny organisms.
  • Both of them are unicellular organisms.
  • They may possess flagella.
  • These organisms have 70S ribosomes.

What is the Difference Between Bacteria and Archaea?

Bacteria vs Archaea: Bacteria are a group of unicellular microorganisms belong to Domain Bacteria. Archaea are a group of unicellular microorganisms belongs to Domain Archaea

Peptidoglycan in Cell Wall: Bacteria Have peptidoglycan in their cell wall. Archaea Do not have peptidoglycan in their cell wall

Eukarya: Bacteria Genes are different from Eukarya. Archaea Genes are more similar to Eukarya

Distinct Processes in Cell Division: Bacteria Cell division does not undergo distinct processes. Archaea Cell division undergoes distinct processes

Membrane Lipid Bonding: Bacteria Form ester bonds between the membrane lipids.  Archaea Have ether bonds between the membrane lipids

RNA Polymerases: Bacteria Have less complex RNA polymerases than eukarya.  Archaea Have more comple RNA polymerases similar to eukarya

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