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Difference Between Archaea and Bacteria

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About Archaea and Bacteria

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Archaea and bacteria are the two kinds of microorganisms and they fall under the category of prokaryotes. But all the archaea and bacteria are not prokaryotes. Both archaea and bacteria have different biochemistry and different evolutionary history. They both have similar shapes and sizes. 

Archaea: These are the organisms that are single-celled and comprise the cells which are of distinct properties and that make them unique from the other domains of life. The term ‘Archaea’ is derived from a Greek word, ‘archaios’ which means  primitive or ancient, which indicates the primitive structure of these organisms. Usually, these organisms inhabit very extreme environments like deep-sea vents, saline waters, hot springs, below petroleum deposits etc. Archaea are mostly anaerobic and live in environments that have low oxygen. As most of the archaea cannot be cultured in laboratories and that is why they have to be identified through culture-independent techniques only. The organisms which are in this domain might share some characteristics of both the bacteria and eukaryotes. They have a membrane-less nucleus like bacteria but they share some genes, enzymes and metabolic pathways which are also observed in eukaryotes. However, these organisms that are archaea, also have some unique characteristics. 

Bacteria: A single-celled organism that exists in the millions in environments, inside and outside of other organisms and is microscopically known as bacteria. Bacterias are harmful but also have some useful purposes. They are prokaryotes that have a membrane-less nucleus and which lack many cell organelles, which makes them simple in their structure and function. The domain Bacteria includes the organisms which are found in the different forms of life from the high mountains to inside the body of other organisms. Some bacterias are beneficial and help us for various purposes like antibiotics production, biogeochemical cycles, industrial use, etc. However, some bacterias are pathogenic organisms that result in mild to severe diseases. Bacterias are microscopic and they are the smallest living entities in the world. These organisms can be observed under a microscope by performing a number of staining techniques.

Bacterias are divided into gram-positive bacteria and gram-negative bacteria, based on the staining techniques. Almost all the bacterias have a cell wall that is made up of peptidoglycan and that protects the bacteria against harmful chemicals. 

Types and Features of Archaea And Bacteria

Archaea form an area of single-celled microorganisms. These microbes (archaea; singular archaeon) are prokaryotes, which indicates they do not have a cell nucleus. Initially, it was named ad as bacteria, later it came to be known as archaebacteria (in the Archaebacteria kingdom), but this categorization is out-of-date.

Archaeal cells have single properties which separate them from the other two domains of life, Bacteria, and Eukarya. In the further process, archaea is divided into multiple familiar phyla. Categorization is a bit harder because most of it has not been isolated in the laboratory and was only seen by analysis of their nucleic acids in samples from their environment.


Both archaea and bacteria are usually the same in size and shape, even though fewer archaea have shapes quite unique that of bacteria, for example, the flat and square-shaped cells of  Haloquadratum walsbyi.  Regardless of this morphological likeness to bacteria, archaea have genes and quite a few metabolic pathways that are even more very much related to those of eukaryotes, notably for the enzymes involved in transcription and translation. Other aspects of archaeal biochemistry are single, for instance, their dependence on ether lipids in their cell membranes, with archaeols. Archaea use a higher amount of energy sources than eukaryotes: these range from organic compounds, such as sugars, to ammonia, metal ions or even hydrogen gas. Salt-tolerant archaea (the Haloarchaea) make use of sunlight as an energy source and additional species of archaea fix carbon, but unlike plants and cyanobacteria, no identified species of archaea does both. Archaea replicate asexually by binary fission, fragmentation, or budding; dissimilar bacteria and eukaryotes, no known species form spores.


Initially, experimental archaea were living in unkind environments such as hot springs and salt lakes with no organisms, but enhanced detection tools led to the finding of archaea in almost every habitat, including soils, oceans, and marshlands. Archaea were also part of the human microbiota in the gut, mouth, and skin.  Archaea are mainly abundant in the oceans, and the archaea in plankton is perhaps one of the most plentiful groups of organisms on the planet. Archaea are the main part of Earth's life and play many roles in the carbon cycle and the nitrogen cycle. No clear examples of archaeal pathogens or parasites are identified, but they are frequently mutualists or commensals. One instance is the methane producing strains that inhabit human and ruminant guts, where their enormous numbers aid digestion. Methanogens are also used in biogas manufacture and sewage treatment, and biotechnology exploits enzymes from extremophile archaea that can suffer high temperatures and organic solvents.


Bacteria, common noun bacteria, singular bacterium are a kind of genetic cell. They compose a large domain of prokaryotic microorganisms. In broad-spectrum a little micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were first life form organisms were found on the earth surface and currently they are most of its habitats. Bacteria live in soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic contact with plants and animals. Still, most of the bacteria have not been identified, and only half of the bacterial phyla have species that can be grown easily in the laboratory. According to researchers bacteria is also known as bacteriology, a branch of microbiology.


There are characteristically 40 million bacterial cells in a gram of soil and a million bacterial cells in a milliliter of clean water. There are around 5×1030 bacteria on Earth, forming biomass that exceeds that of all plants and animals. Bacteria are very important in many stages of the nutrient cycle by reproducing nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle contains the decay of dead bodies; in this process, bacteria are responsible for the putrefaction. In the biological community’s immediate hydrothermal vents and cold seeps, extremophile bacteria give the nutrients required to sustain life by converting dissolved compounds, for example, hydrogen sulphide and methane, to energy. According to the data report by researchers in October 2012 and published in March 2013 stated that bacteria increase in the Mariana Trench, with a depth of up to 11 kilometers is the deepest known part of the oceans. Further researchers reported related studies that microbes increase inside rocks up to 580 meters under the seafloor less than 2.6 kilometers of ocean off the shore of the northwestern United States. In addition to that, a microbe can be found anywhere. In any condition, they adapt themselves and also survive where they are.


The well-known idea that bacterial cells in the human body are large in number, human cells by a factor of 10:1 has been debunked. There are about 39 trillion bacterial cells in the human microbiota as coming to life by a "reference" 70 kg male 170 cm tall; 30 trillion human cells are found in the human body. This states that though they do not have the upper hand in actual numbers, it is only by 30%, and not 900%.


The highest number exists in the gut flora and a large number on the skin. The huge majority of the bacteria in the body are rendered harmless by the defensive effects of the immune system, though many are helpful, mostly in the gut flora. On the other hand, several species of bacteria are pathogenic and cause infectious diseases, including cholera, syphilis, anthrax, leprosy, and bubonic plague. The most ordinary fatal bacterial diseases are respiratory infections, with tuberculosis alone killing about 2 million people every year, mostly in sub-Saharan Africa. In urbanized countries, antibiotics are used in farming also to treat human infections. In the making of antibiotics fighting against it is a growing problem. In manufacturing, bacteria are vital in mess curing and the breakdown of oil spills, the creation of cheese and yogurt through fermentation, the healing of gold, palladium, copper and other metals in the mining sector, as well as in biotechnology, and the generating of antibiotics and other chemicals.


Once regarded as plants constituting the class Schizomycetes, bacteria are now known as prokaryotes. However, cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and rarely harbor membrane-bound organelles. Even though the word bacteria is usually built-in all prokaryotes, the technical classification altered after the finding in the 1990s that prokaryotes have two very unusual groups of organisms that progress from an earliest common ancestor. These evolutionary domains are called Bacteria and Archaea.


Difference Between Archaea and Bacteria

Basis for Comparison




Archaea are single-cell, simple microorganisms and are able to survive under hard circumstances. They are considered as the oldest cells, which originate on the earth 4 billion years ago.

Bacteria are also single-cell but have a difficult structure. All types of bacteria except archaea fall under this root.

Found in

Archaea are found in a strange environment like in hot springs, ocean depth, salt brine.

They are found anywhere like in the soil, water, living and nonliving organisms.

Cell Wall

The wall of the cell is called pseudopeptidoglycan .

The wall of the cell is made of peptidoglycan with muramic acid or lipopolysaccharide.

Lipid membrane

Archaea have ether bonds with the branch of aliphatic acids in their lipid membrane.

Eubacteria or bacteria have lipid membranes of ester bonds with acids. 

Metabolic pathway

Archaea do not follow glycolysis or Krebs cycle but use a related pathway.

Follow the glycolysis pathway and Krebs cycle to break down glucose.


Methanogens, Halophiles, Thermoacidophiles.

Gram-positive and gram-negative.


Archaea replicate asexually by binary fission, fragmentation, or by the budding process.

Bacteria can generate spores which allow them to live in critical condition. 

Other features

Thymine is missing in the tRNA (transferase RNA).

Thymine is there in the tRNA.

Introns are present.

Introns are absent.

RNA polymerase is complex and contains 10 subunits.

RNA polymerase is simple and contains 4 subunits.

Archaea are non-pathogens.

Some bacteria are pathogens.


1.Pyrolobus Fumarii. 2.Sulfolobus Acidocaldarius. 3.Pyrococcus Furiosus. 4.Methanobacteriumformicum.

1.Streptococcus Pneumoniae. 2.Yersiniapestis. 3.Escherichia coli (E.coli). 4.Salmonella Enterica.

Other Differences Between Archaea and Bacteria 

  • Archaea goes through asexual reproduction by the process of budding, binary fission and fragmentation whereas bacteria use to produce spore for staying latent for many years. 

  • Archaea has a cell membrane known as Pseudopeptidoglycan. Whereas the cell membrane which bacteria have are Lipopolysaccharide and Peptidoglycan. 

  • Metabolism activities in archaea are methanogenesis. Metabolism activities in bacteria are aerobic and anaerobic respiration, autotrophy, fermentation and photosynthesis. 

  • Archaea consists of three RNA whereas bacteria consists of single RNA. 

  • Archaea can sustain in harsh environments which are extreme such as hot springs, oceans, gut of humans and Marshlands. Bacterias are generally found in organic matter, soil, bodies of animals and plants, water, radioactive waste, etc. 

  • In the chromosomes of archaea introns are present whereas in the chromosomes of bacteria, introns are absent.

  • In the t-RNA of archaea, Thymine is absent whereas in the t-RNA of bacteria, Thymine is present.


Above we reflect the difference between the archaea and bacteria and found them superficially different from each other. However, both are single-celled microorganisms and display morphological similarities, but differ in other properties. They even flourish in a different environment and therefore are kept in a different group.

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