Archaea and Bacteria are two kinds of microorganisms that fall under the category of prokaryotes. Earlier, archaea were classified as bacteria, but now it is outdated as it has been found that they both have different biochemistry and different evolutionary history.
Archaea and Bacteria do not possess membrane-bound organelles or a nucleus.
Archaea: They are single-celled organisms that comprise cells with distinct properties that make them unique from the other two domains of life, namely Eukaryota and Bacteria. They can thrive in extreme environmental conditions, such as hot springs, salt lakes, etc.
They use numerous sources of energy and display a diverse array of chemical reactions in metabolism. Based on reactions, they are categorized into nutritional groups depending on carbon sources and energy. One group of archaea uses sunlight as a source of energy. They are termed phototrophs. But none of these organisms show oxygenic photosynthesis.
The other forms of archaea use inorganic compounds as a source of energy, namely ammonia or sulphur. They are called chemotrophs. They either include anaerobic methane oxidizers, nitrifiers, and methanogens. This reaction involves two compounds where one compound acts as an electron acceptor and the other as an electron donor. The energy that is released during the reaction releases ATP – adenosine triphosphate. It is one of the basic processes that can be found in some eukaryotic cells.
Bacteria: They are single-celled organisms that usually live in diverse environments. Bacterial DNA called the nucleoid are a twisted thread-like mass. They even possess a cellular structure that executes a range of circular functions that involves the transfer of energy to the transportation of proteins. Bacteria consist of plasmids which are circular pieces of extra-chromosomal DNA.
Bacterial cells consist of an inner cell membrane and an outer cell wall. Wherein some of the bacteria do not possess cell wall such as mycoplasmas. In some cases, bacteria may consist of a third protective outer layer in a cell called a capsule.
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Bacteria and Archaea – The Major Differences
| Archaea | Bacteria |
| Types | |
| Methanogens, Thermophiles, and Halophiles | Gram-positive and Gram-negative |
| Cell Wall | |
| Pseudopeptidoglycan | Lipopolysaccharide/ Peptidoglycan |
| Metabolism Activity | |
| They perform modified form of glycolysis and citric acid cycle. | They perform glycolysis and citric acid cycle. |
| Cell membrane | |
| Ether-linked lipids | Ester-linked lipids |
| Thriving Habitat | |
| They can sustain in extremely harsh environments such as hot springs, marshlands, deep sea vents, and the gut of humans and ruminants. | They are found everywhere, including soil, organic matter, the earth’s crust, water, bodies of animals and plants, radioactive wastes, hot springs etc. |
For more information and differences on Bacteria, Archaea and other related topics, keep visiting BYJU’S Biology website.
Frequently Asked Questions
1. What is archea? How are they different from bacteria?
Archea is a domain of living organisms containing unicellular prokaryotic organisms. Cell wall in arechea is made up of Pseudopeptidoglycan, whereas in bacteria, it is made up of either Lipopolysaccharide or Peptidoglycan.
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