Archaebacteria are tough organisms that are known to survive even the extremest conditions. Whether this is at the bottom of the sea or in the vents of a volcano.
Consequently, they are considered to be one of the oldest, known, living organisms on the planet – making them extreme survivors of the Universe.
They are considered a form of bacteria due to their features closely resembling that of bacteria when beheld under the microscope.
Hence the name, they belong to the kingdom called Archaea. Below, in this article, you will find everything you need to know about archaebacteria, as well as examples.
What Are Archaebacteria?
Archaebacteria are single-celled organisms that, as previously mentioned, have the capabilities to survive even the harshest of environments. This has aided in their survival, with the organism being approximately 3.5 billion years old.
While archaebacteria are considered similar to bacteria in form, they are, however, different from the typical bacteria biologists may study.
These differences between typical bacteria and archaebacteria are so large that they are even classified separately from other forms of life, thus challenging how scientists classified organisms into their contrasting kingdoms.
Even though regular bacteria and archaebacteria were once examined within the same kingdom, genetics and molecular biology have since discovered that these prokaryotic organisms are extremely unique in their traits that warrant a branch within the phylogenetic tree of life. Whereby this consists of a three-domain system of biological classification.
To make the distinction between these two organisms even more distinct, some texts will refer to archaebacteria only as archaea.
The Classification Of Archaea
One of the most common ways scientists classify life forms is by separating them into contrasting kingdoms, these are interpreted by the organism’s cell structure.
The distinguished kingdoms include Monera, Animalia, Fungi, Planitia, and Protista. This kingdom, Protista, consisted of single-celled eukaryotic organisms, while the kingdom known as Monera was considered to behold all the different variations of the organism prokaryotic.
However, since then, genetic and biochemical studies carried out on bacteria have demonstrated specific groups of prokaryotes, those known as ‘archaebacteria’, show unique biochemistry; creating their division on the tree of life.
The name archaebacteria are derived from the root ‘archaea’, which also means ‘ancient’, this directly corresponds to the theory that all present archaebacteria originated from ancient populations of bacteria that over time evolved and adapted to advance in the high-temperatures, sulfur-rich environments encompassing deep-sea vents.
As a result of advances in genetics and biochemistry, there has been a new order of classification within the phylogenetic tree of life, the notion of domains. Similar to kingdoms; however, domains circumscribe an even larger section of life.
When looking at the system of domains, all organisms of eukaryotic including animals, fungi, plants, and protists are prescribed as part of the Eukaryota domain.
While most bacteria can be found under the ‘eubacteria’ domain. Lastly, archaea/archaebacteria all belong to the ‘archaea’ domain.
Traits Of Archaebacteria
Archaea/ archaebacteria are made up of ancient cells that exhibit a variety of attributes and traits absent from modern classes of cells.
Regular bacteria and eukaryotes contain a cell membrane made up of ester-linked phospholipids; however, when looking at archaebacteria, their cell membranes are composed of ether-linked phospholipids.
Thus, archaea devise a cell membrane with a sugar that is contrasting to cells of traditional bacteria; which are composed of peptidoglycan sugar. Although, both the sugars contain similar compositions.
Similar to bacteria, archaebacteria have a singular round chromosome; however, their gene transcriptions are different. Instead, the gene transcription found in archaebacteria is similar to gene transcription within eukaryotic cells.
To put it simply, eukarya and archaea share similar gene transcription methods, while the cell membranes are more similar between archaea and bacteria.
This unusual distinction between cell membrane creation methods and gene transcription has led some scientists to speculate that a fusion between archaebacteria and bacteria allowed for the evolution of eukaryotic cells.
As a result of this, it is believed that, at one point in time, archaea may have combined with another form of bacteria and started residing within that bacterial cell; which is an example of symbiotic relationships.
Then, eventually, transformed into the nuclei that can be found within other organisms’ cells, or the cells eukaryotes presently have.
Evidence of this evolutionary path may be found within Lokiarcheota, demonstrating a transitional configuration between early eukaryotes and archaea.
Different archaebacteria can survive within environments of exceedingly high salinity (the salt water levels), which generally affect cells by desiccating and killing them.
An example of such salt-tolerant archaebacteria is halobacterium. Found within halobacterium is the pigment bacteriorhodopsin which gives it a purple coloration due to the chemical energy. This pigment is similar to that of rhodopsin which is found within the retinas of vertebrates.
In addition, there are both anaerobic and aerobic species of archaea, this is found within extreme surroundings, as well as in common environments such as regular soil.
Likewise, archaebacteria can practice anaerobic respiration. More specifically, methanogenesis, whereby it produces methane as a byproduct of respiration.
Archaebacteria have been categorized within three different main subgroups; which are based on the extreme environments they are found. They include:
- Halophiles
- Methanogens
- Thermoacidophiles
Example Of Archaebacteria
Halophiles
Halophiles can be found in highly saline waters such as the Dead Sea and the Great Salt Lake. Species of halophiles often contain red/pink pigment which is known as carotenoids.
These halophiles arrange colonies of bacteria that can contain as many as 100 million bacteria per millimeter!
Examples
- Halogeometricum borinquense
- Haloferax volcanii
- Halterrigena turkmenica
- Halococcus dombrowskii
- Haloarcula marismortui
- Halorubrum kocurii
- Haloferax elongans
- Halobacterium salinarum
- Halorubrum saccarovorum
Methanogens
These organisms typically live in marshes and swamps under anaerobic conditions. They can also be found within the gut of some humans and herbivores.
Likewise, they can be found living in decaying and dead matter, too. As previously mentioned, these organisms are anaerobic and strictly anaerobic; any exposure to oxygen will kill them.
Using H2 they reduce carbon dioxide while releasing methane into marshes and swamps, commonly known as marsh gas.
Examples
- Methanothermus fervidus
- Methanosphaera stadtmanae
- Mathanocaldococcus jannaschii
- Methanolinea mesophila
- Methanomicrobium mobile
- Methanotorris igneus
- Methanogenium aquaemaris
- Methanoculleus chikygoensis
- Methanolacinia paynteri
- Methanogenium marisnigri
- Methanocorpusculum labreanurn
- Methanoplanus petrolearius
- Methanosarcina barkeri
- Methanospirillum hungatei
- Methanohalobium evestigatum
- Methanococcoides burtonii
- Methanohalophilus mahii
- Methanosalsum zhilinae
- Methanolobus zinderi
- Methanocaldococcus jannaschii
- Methanosaeta thermoacidophile
- Methanopyrus kandleri
- Methanofollis formosanus
- Methanocella paludicola
- Methanomethylovorans hollandica
- Methanobacterium thermoautotrophicum
- Methanococcus aeolicus
- Methanimicrococcus blatticola
- Methanocalculus taiwanensis
- Methanocalculus chunghsingensis
- Methanothermobacter thermautotrophicus
- Methanothermococcus okinawensis
Thermoacidophiles
Thermoacidophiles, otherwise known as thermophiles, are organisms that can withstand and live in acidic and very hot environments. For instance, they can thrive in sulfur-rick conditions such as geysers and hot springs with temperatures over 50 degrees celsius.
Thermoacidophiles have both anaerobic and aerobic variants, and they are often distinguished by their color, which appears due to photosynthetic pigmentation. You can find these archaebacteria in the Yellowstone National Park.
Examples
- Humicola insolens
- Thermoplasma acidophilum
- Chaetomium thermophilum
- Thermoproteus tenax
- Thermoascus aurantiacus
- Sulfolobus yangmingensis
- Thermomyces lanuginosus
- Brevibacillus levickii
Final Thoughts
Archaebacteria are a mixed class of organisms, with recent studies acknowledging them as a prime element of Earth’s life. Hopefully, this guide has provided you with everything you need to know about Archaebacteria.
Ever since I was a little girl, I have been fascinated by science. Every holiday I would ask for the newest science kit, and spend weeks learning with it.
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