Difference between Archaea and Bacteria

Introduction

Archaea and bacteria are both unicellular prokaryotic cells and both can survive in extreme conditions. Despite that, they have different structures and different reproduction methods. Archaea are not pathogenesis but there are many bacteria that can cause illness. Archaea and bacteria do not have a nucleus or membrane-possessed organelles. They are almost similar in shapes and sizes.

Overview of Archaea

Archaea is part of single cell prokaryotic organisms. Earlier archaea was known as archaebacteria. Their cell wall elements are different from bacteria. They are mainly observed in utmost natural conditions such as marshy areas, hot springs and utmost salty areas and they are familiar as methanogens, thermoacidophiles and halophiles. They are observed in skin, mouth and gut in humans. They play a great role in the ecosystem.

Characteristics of Archaea

Some features of archaea are as follows −

• Different archaea have different sizes and structures. The range of sizes is from 0.1 μm to over 15 μm. They are found in different shapes like rod, spiral and sphere.

• Archaea’s cell wall does not have peptidoglycan; it is made with pseudopeptidoglycan.

• Archaea’s cell wall contains ether lipid bond where glycerol and fatty acids are linked by ether bonds.

• Membrane-bound nucleus is not seen in them.

• They have plasmid and single circular chromosomes.

• Archaea’s RNA polymerase is more complicated than bacteria and contains many polypeptides.

• Archaea replicate by polypeptides.

• Protein synthesis is similar to eukaryotic.

Types of Archaea

Archaea are mainly categorised into three types, namely −

• Methanogens − Methanogens are anaerobes that are normally found in marshy places and in some ruminating animals’ guts. They can produce methane so they are commercially used to make biogas from animals’ dung. Examples are − Methanococcus, Methanobacterium and so on.

• Thermoacidophiles − They can survive in utmost hot temperatures as well as in acidic situations. They are mainly seen in hot sulphur springs and deep-sea vents. Example − Thermoplasma.

• Halophiles − They can grow in extreme salt concentration and they fall under the Halobacteriaceae family. Example − Halococcus, Halobacterium.

Overview of Bacteria

Bacteria are also single cell prokaryotic organisms and nucleus and some organelles are absent in bacteria. Bacteria is considered the eldest form of life on the planet. They are very necessary for human survival. Bacteria are very flexible organisms and can survive in utmost nature. This type of organism is familiar as extremophiles and they are again classified as − Thermophiles, Alkaliphiles, Osmophiles, Acidophiles, Cryophiles and Barophiles.

Bacteria’s cell walls are manufactured by peptidoglycan protein. This protein is not noticed in nature except in bacteria’s cell wall and this protein helps bacteria to multiply.

Classification of Bacteria

Bacteria are classified depending on their characteristics and feature, such as

Depending on shape

They are classified into four types depending on shape −

• Sphere or Coccus − Example, Streptococcus pneumoniae

• Rod-shaped or Bacillus − Example, Escherichia coli

• Comma-shaped or Vibrio − Example, Vibrio cholerae

• Spiral or Spirilla or spirochete − Example, Spirillum volutans.

Depending on cell wall composition

Bacteria are categorised into two types depending on cell wall composition such as −

• Lipopolysaccharide cell wall − Example, Gram-negative bacteria

• Peptidoglycan cell wall − Example, Gram-positive bacteria.

Depending on nutrition mode

They are categorised into two types such as

• Heterotrophic Bacteria − Example, every disease-causing bacteria

• Autotrophic Bacteria − Example, Cyanobacteria.

Depending on respiration mode

They are categorised into two types such as

• Aerobic Bacteria − Example, Mycobacterium

• Anaerobic Bacteria − Example, Actinomyces.

Difference between Archaea and Bacteria

The common differences between Archaea and Bacteria are discussed below −

Archaea	Bacteria
Archaea are unicellular. They are simple microorganisms and can survive in extreme conditions. It is thought that they are oldest cells that arise four billion years ago onplanet.	Bacteria are also unicellular. Their structure is more complicated than archaea. Except for archaea every type of bacteria are fall under it.
They are noticed in unusual nature like salt brine, hot spring, ocean depth.	They are noticed everywhere like water, soil, living and non-living organisms.
The cell wall is known as pseudopeptidoglycan.	The cell wall is constructed with peptidoglycan and lipopolysaccharide
Archaea’s lipid membrane has ether bonds with aliphatic branch acid	They have lipid membrane with ester bonds with acids.
Glycolysis or Krebs cycle is not seen in them but they follow a similar pathway.	Glucose is divided by glycolysis and Krebs cycle
They are mainly three types: Halophiles, Methanogens and Thermoacidophiles	They are two types: gram-positive and gram-negative
Archaea reproduce asexually through binary fission, fragmentation or through the budding method.	Bacteria reproduce through spore generation that allows them to survive in extreme conditions.
Thymine is absent in tRNA	Thymine is present in tRNA.
Introns are seen.	Introns are missing.
RNA polymerase carries 10 subunits and it is complex.	RNA polymerase carries 4 subunits and it is simple.
They are non-pathogens	Some of them are pathogens.

Conclusion

Archaea are single cell microorganisms and their cell wall contains pseudopeptidoglycan. Bacteria are also single cellular microorganisms but their cell wall is made with peptidoglycan and lipopolysaccharide. Both can survive in extreme nature like hot spring water. Before it was believed that archaea are one kind of bacteria but later it is seen that they are totally different. Archaea do not cause any illness but bacteria can be harmful and cause diseases. There are also some good bacteria which help humans in different ways.

FAQs

Qns 1. What are prokaryotic cells?

Ans. A cell that does not contain a nucleus and membrane-bound organelles is known as prokaryotic cells. Examples: bacterial cells, archaeal cells and so on.

Qns 2. What are eukaryotic cells?

Ans. Eukaryotic cells refer to cells that have nucleus and membrane-bound organelles. Example: protozoa, fungal cells, plant cells, animal cells and so on.

Qns 3. What is Krebs cycle?

Ans. Krebs cycle refers to a sequence of enzyme catalysed reactions that happens in mitochondrial matrix. In this cycle carbon dioxide is produced by oxidation of acetyl-CoA that produces ATP in electron transport chain.