Difference Between Bacteria and Archaea


Main Difference

Bacteria and Archaea belong to the same family of micro-organisms called prokaryotes. In the beginning, archaea were classified as bacteria and was known as archaebacteria. The reason for this was that both were similar in size and shape. They increase their number with the help of binary fusion and few other similarities. After years of research, scientists were able to conclude that although they both look similar, there are marked differences between the properties of both these organisms. The main difference between these two is that bacteria has a unique rRNA sequence as compared to archaea which although has some unique rRNA sequence but also has a similar series to other eukaryotic organisms. Some parts of genes are not present in bacteria, but non-coding regions such as introns are found in the genes of archaea. In the same way, bacteria are sensitive to antibiotics while archaea are insensitive, and there is no inhabited growth. Histones, which are a critical part of DNA are present in archaea while they are absent in bacteria. Regarding defining both the terms, bacteria are microorganisms which have a bigger range of prokaryotic organisms and have a size of micrometers while Archaea comprise of a smaller variety of organisms which consist of one cell and therefore lack any nucleus in the cell. Bacteria can be of various shapes and sizes depending on their structure, but archaea do not vary much because there are no organelles which support the cells. The type of environment in which both these types of species exist is different. Bacteria are found in places such as soil and the surface of the earth. They can also be found in plants and other animals because they grow in moderate conditions. Archaea, on the other hand, are prone to live in severe environments such as oceans, hot springs, submerged lands and even human beings. Bacteria can also have a longer life than archaea because they have the ability to form spores which can exist for several years. A better explanation of both these types is given in the paragraphs that will follow.

Comparison Chart

Bacteria constitute a large domain of prokaryotic microorganisms.The Archaea constitute a domain or kingdom of single-celled microorganisms.
Carbon chains are branched in bacteria in every case.This chain may or may not be branched in archaea.
Wall Name
Radioactive waste water, Earth’s crustextreme and harsh environments

Definition of Bacteria

The word bacteria is derived from a bacterium, and they are micro-bodies which can neither be termed as animals or plants. Their size varies depending on their structure. Therefore, bacteria can be in many shapes and sizes though their length cannot be more than a few micrometers. There are three primary forms of bacteria which help to differentiate them. Spherical bacteria are the simplest ones, the rod things are called bacilli and can also be known as curved, while spiral bacteria are the last types and have many variations. They are usually found in a moderate climate and cannot exist for long in conditions which are not suitable for them but overall they have a longer life in comparison to other similar organisms. They cannot live in human bodies but are found abundantly in plants, animals, soil, organic material, glaciers and in some cases on hot springs. The cell is different from other cells as they have no nucleus or organelles. It does include ribosomes, plasma membrane, DNA and a cell wall. They are also known as the first organisms to exist on earth several billion years ago.


Definition of Archaea

For several years, archaea were confused and termed as a type of bacteria and were known as a name called archaebacteria, but there were marked differences when the research was done. They are able to exist in conditions where normal life does not exist, they are found in hot springs, oceans, the human body and are sensitive to antibiotic. They are single-celled species and have no cellular nucleus and organelles in their cells. They were evolved differently than other organisms and have existed for several years. They are divided into four different types of phyla which have their own properties. Carbon chains can or cannot be branched in them which helps them exist in different conditions. They are reproduced by the process of binary fusion and have an important role to play in the global chemical cycle since their contribution toward the earth’s biomass is around 25%. They do have a membrane which consists of molecules which are different from other forms of life.

Differences in a Nutshell

  1. The walls of bacteria consist of peptidoglycan while these are not present in archaea because it lacks the cell wall.
  2. The membrane lipid bonding between these two is different from each other. Bacteria has fatty acids which are absent in the archaea.
  3. The sequence of rRNA in the case of bacteria is unique to itself while the rRNA sequence of archaea can be similar to eukaryotic.
  4. Carbon chains are branched in bacteria in every case while this chain may or may not be branched in archaea.
  5. The size of chromosomes is smaller in bacteria while archaea have a larger size of chromosomes.
  6. Bacteria are well suited to moderate climates such as soil and earth surface while archaea are more adapted to harsh environments such as hot springs and even human body.
  7. Bacteria are sensitive to antibiotic bodies while archaea are insensitive to antibiotics.


Although the two terms are related to each other as they are from the same family, still there are many differences between the two which have been detailed here. It gives an idea of how they make changes among themselves to stay unique among their family and exite people who want to know more about microorganisms.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss