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What Is Archaebacteria In Biology

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Habitats Of The Archaea

Class 11th â Archaebacteria â Introduction | Biological Classification | Tutorials Point

Archaea are microorganisms that define the limits of life on Earth. They were originally discovered and described in extreme environments, such as hydrothermal vents and terrestrial hot springs. They were also found in a diverse range of highly saline, acidic, and anaerobic environments.

The cultured representatives of the Crenarchaeota are from high-temperature environments, such as hot springs and submarine hydrothermal vents. Likewise, cultured members of the Euryarchaeota include organisms isolated from hot environments, organisms that are methanogenic, and organisms that grow vigorously in high-salt environments . Organisms in the Korarchaeota lineage and the proposed Nanoarchaeota lineage also inhabit high-temperature environments however, the nanoarchaea are highly unusual because they grow and divide on the surface of another archaea, Ignicoccus. Nanoarchaea, which were discovered in 2002, contain both the smallest known living cell and the smallest known genome . Members of the Korarchaeota and Nanoarchaeota have not been detected in pure culture rather, they have been detected only in mixed laboratory cultures.

Molecular Biological Probes Of The Evolution Of The Sulfur Biome

7.1Molecular Phylogenies as Evidence for Relative Microbial Age

Using molecular phylogenies of the type illustrated by the eponymous SSU rRNA tree-of-life it might be possible to obtain a relative stratigraphy of the evolution of the sulfur biome comparable with the Victorian approach to geologic time before absolute age dating was discovered. In this analogy, molecular phylogenetic relationships are equivalent to Stenos Law of Succession . The process gives the apparent order of appearance of the various strata but no indication of their absolute age. The science is still in its infancy and even these qualitative approaches to the evolution of the microbial sulfur cycle are very controversial. As with rock strata, which may be tectonically inverted, there are potential traps in the literal interpretation of the molecular phylogenies. These include horizontal gene transfer, splicing of mobile elements and the problem that the phylogenies may be limited to the < 1% of the total microbial population which has been cultured. The consequence is that this is one of the most exciting research areas in current Earth and biological sciences.

Archaea were originally called Archaebacteria by Woese and Fox on the grounds that

the apparent antiquity of the methanogenic phenotype plus the fact that it seems well suited to the type of environment presumed to exist on earth 34 billion years ago.

7.2Molecular Clocks


Chuanshu He, … Zhengbo Yue, in, 2019

Three Domains Of Life On Earth

DNA sequence comparisons and structural and biochemical comparisons consistently categorize all living organisms into 3 primary domains: Bacteria, Archaea, and Eukarya . Both Bacteria and Archaea are prokaryotes, single-celled microorganisms with no nuclei, and Eukarya includes us and all other animals, plants, fungi, and single-celled protists all organisms whose cells have nuclei to enclose their DNA apart from the rest of the cell. The fossil record indicates that the first living organisms were prokaryotes , and eukaryotes arose a billion years later.

Study Tip: It is suggested that you create a chart to compare and contrast the three domains of life as you read.

The information below was adapted from OpenStax Biology 22.2

Archaea and Bacteria share a number of features, but are also distinct domains of life:

  • Prokaryotes, especially Archaea, can survive in extreme environments that are inhospitable for most living things.
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    Biochemical And Microbiological Aspects Of Methanogenesis

    Most of the CH4 in the atmosphere is of biogenic origin, as determined by its 14C dating. Biological production of CH4, methanogenesis, is performed by methanogenic archaebacteria. All known methanogens share some characteristics, including high intracellular concentrations of coenzyme F420 , the presence of the enzyme methyl coenzyme M methylreductase, and the presence of unique phospholipid membrane components.

    CH4 production is a strictly anaerobic process relying on a limited number of low molecular weight substrates. The two principal pathways of production are acetotrophic methanogenesis and hydrogenotrophic methanogenesis. In the former case, acetate is cleaved into CH4 and carbon dioxide . During hydrogenotrophic methanogenesis, H2 reacts with CO2 forming CH4 and H2O. Other low molecular weight organic molecules, such as formate, methanol, dimethyl sulfide , tri-, di-, and monomethylamines, and ethylamine, can also be used for methanogenesis, but acetate or H2 and CO2 are believed to be the quantitatively most important substrates.

    Table 1. Examples of redox reactions used in the microbial degradation of OMa


    Comparison With Other Domains

    six Kingdoms

    The following table compares some major characteristics of the three domains, to illustrate their similarities and differences.

    Resistant to diphtheria toxin Sensitive to diphtheria toxin

    Archaea were split off as a third domain because of the large differences in their ribosomal RNA structure. The particular molecule 16S rRNA is key to the production of proteins in all organisms. Because this function is so central to life, organisms with mutations in their 16S rRNA are unlikely to survive, leading to great stability in the structure of this polynucleotide over generations. 16S rRNA is large enough to show organism-specific variations, but still small enough to be compared quickly. In 1977, Carl Woese, a microbiologist studying the genetic sequences of organisms, developed a new comparison method that involved splitting the RNA into fragments that could be sorted and compared with other fragments from other organisms. The more similar the patterns between species, the more closely they are related.

    This difference in biochemical structure of Bacteria and Archaea has been explained by researchers that they originated at deep sea alkaline hydrothermal vents, where they independently developed lipid biosynthesis and cell wall biochemistry during their transition to Archaea and Bacteria. It has been suggested that the last universal common ancestor was a not free-living organism. However this view has been challenged by other researchers and is currently in dispute.

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    Archaebacteria: Definition General Account Classification

    Kingdom monera are divided into two major groups. One is Archaebacteria and the other one is Eubacteria.

    Archaebacteria are ancient and most primitive forms of bacteria living in extreme environments. They appear to be the oldest of the living fossils.

    Archaebacteria are an ancient and primitive group of bacteria living in extreme environmental conditions.

    Phylogenetic Relationships Between Archaea Bacteria And Eukarya

    While the term prokaryote is widely used to describe both Archaea and Bacteria, you can see from the phylogenetic Tree of Life below that this term does not describe a monophyletic group:

    In fact, Archaea and Eukarya form a monophyletic group, not Archaea and Bacteria. These relationships indicate that archaea are more closely related to eukaryotes than to bacteria, even though superficially archaea appear to be much more similar to bacteria than eukaryotes.

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    Placing Key Events On The Geologic Time Scale

    How do each of these events map onto geologic time? Most of them are not instantaneous events, and so they span multiple time periods as follows:

    • Hadean eon : No life present on Earth
    • Origin of life , 2.8-2.6 BYA
    • First cyanobacteria, capable of producing oxygen through photosynthesis, ~2.5 BYA
  • Proterozoic eon
  • Oxygen revolution and formation of Banded Iron Formations, occurs over a period from 2.5 to 1.9 BYA
  • First single-celled eukaryotes, ~1.6 BYA
  • First multicellular algaes, ~1.4 BYA
  • First multicellular animals, ~635 MYA
  • Phanerozoic eon
  • Cambrian explosion , 542 MYA
  • Obviously many other events occur in the Phanerozoic, and well spend most of the rest of this module discussing them
  • Iiaprinciple Properties Of Bacteria

    Archaebacteria (Part-1) – Biological Classification | Class 11 Biology

    The prokaryotes include two major groups of life: the archaebacteria and the eubacteria, which are differentiated by numerous genetic and biochemical traits. Structurally and functionally, however, they show so many similarities that it is appropriate to discuss them together. In contrast to eukaryotic cells, bacteria do not have a cytoskeleton and almost all bacteria are enclosed by a rigid cell wall. These features result in certain general properties. The limitation of diffusional solute transport from the surrounding water and within the cell typically constrains bacterial size to 1 or 2 m. Certain giant bacteria measure 510 m or more, but they usually include a large internal vacuole. Bacteria take up only low-molecular-weight solutes from their surroundings. Bacteria that depend on high-molecular-weight polymeric compounds as a source of energy and organic carbon must first hydrolyze their substrates extracellularly, using membrane-bound enzymes, before the resulting monomers can be transported into the cell. This transport may be passive or active . The small size of bacteria means that they can exploit and grow in extremely dilute substrate solutions .

    D. Bastviken, in, 2009

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    Archaeabacteria: Characteristics Types And Phylogeny


    In this article we will discuss about:- 1. Taxonomy of Archaebacteria 2. General Characteristics of Archaebacteria 3. Representative Types 4. Phylogeny.

    Taxonomy of Archaebacteria:

    The domain Archaea has been divided into two Phyla:

    1. Crenarchaeota and


    2. Euryarchaeota. The first includes the extreme thermophiles, acidophiles and sulfur-metabolizing archaebacteria. They are mostly anaerobic and they occur generally in geo-thermallyheated environment, like sulfur hot springs and sea-floors.

    The members of the second phylum, Euryarchaeota, are more diverse and includes anaerobic methanogens, extreme halophiles and extreme thermophiles. The two phyla have been divided mainly on the basis of differences in the 16S r-RNA sequences.

    General Characteristics of Archaebacteria:

    Archaebacteria may be Gram-positive or Gram-negative. Cells are generally invested with a cell- wall, except those of Thermo plasma, a wall-less mycoplasma-like genus. Archaebacterial cells may be spherical, rod-shaped, spiral, irregularly lobed as in Sulfolobus, or filamentous. Cell diameter ranges between 0.1 m and 1.5 m. Cells multiply by several means, like binary fission, budding, fragmentation etc.


    Some Representative Types of Archaeabacteria:

    A. Crenarchaeota:

    The Phylum Crenarchaeota is a comparatively small one consisting of a single class.

    Thermoprotei divided into three orders:

    i. Thermoproteales,

    ii. De-sulfurococcales and

    iii. Sulfolobales.

    Main Difference Archaebacteria Vs Eubacteria

    Archaebacteria and eubacteria are two domains of the kingdom: Monera, which contains the least organized unicellular prokaryotic microorganisms on earth. Both archaebacteria and eubacteria are single-celled microorganisms, which are usually called prokaryotes. The main difference between archaebacteria and eubacteria is that archaebacteria are usually found in extreme environmental conditions whereas eubacteria are found everywhere on earth.

    This article examines,

    3. What is the difference between Archaebacteria and Eubacteria

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    Links To Human Health And Environmental Processes

    The information below was adapted from OpenStax Biology 22.4 Some prokaryotic species can harm human health as pathogens: Devastating pathogen-borne diseases and plagues, both viral and bacterial in nature, have affected humans since the beginning of human history, but at the time, their cause was not understood. Over time, people came to realize that staying apart from afflicted persons tended to reduce ones chances of getting sick. For a pathogen to cause disease, it must be able to reproduce in the hosts body and damage the host in some way, and to spread, it must pass to a new host. In the 21st century, infectious diseases remain among the leading causes of death worldwide, despite advances made in medical research and treatments in recent decades. The information below was adapted from OpenStax Biology 22.5 Not all prokaryotes are pathogenic pathogens represent only a very small percentage of the diversity of the microbial world. In fact, our life would not be possible without prokaryotes. Some prokaryotic species are directly beneficial to human health:

    Other prokaryotes indirectly, but dramatically, impact human health through their roles in environmental processes:

    Gene Transfer And Genetic Exchange

    Archaebacteria Inner and Outer Anatomical Bacteria Structure Outline ...

    Haloferax volcanii, an extreme halophilic archaeon, forms cytoplasmic bridges between cells that appear to be used for transfer of DNA from one cell to another in either direction.

    When the hyperthermophilic archaea Sulfolobus solfataricus and Sulfolobus acidocaldarius are exposed to DNA-damaging UV irradiation or to the agents bleomycin or mitomycin C, species-specific cellular aggregation is induced. Aggregation in S. solfataricus could not be induced by other physical stressors, such as pH or temperature shift, suggesting that aggregation is induced specifically by DNA damage. Ajon et al. showed that UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency in S. acidocaldarius. Recombination rates exceeded those of uninduced cultures by up to three orders of magnitude. Frols et al. and Ajon et al. hypothesized that cellular aggregation enhances species-specific DNA transfer between Sulfolobus cells in order to provide increased repair of damaged DNA by means of homologous recombination. This response may be a primitive form of sexual interaction similar to the more well-studied bacterial transformation systems that are also associated with species-specific DNA transfer between cells leading to homologous recombinational repair of DNA damage.

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    A Brief Introduction Of Archaebacteria

    Archaebacteria is called a primitive bacteria microorganism. It owns only a single cell and it lives in an environment where there is severity. The examples are extremely hot or salty . In other words, Archaebacteria is not only a primitive but also a microorganism with single-cell (these are known as prokaryotes having zero cell nucleus. Every archaeon owns the capability of living in an extreme environment.

    Archaebacteria: Definition Types And Uses


    In this article we will discuss about:- 1. Definition of Archaebacteria 2. Types of Archaebacteria 3. Uses.

    Definition of Archaebacteria:

    They are a group of most primitive prokaryotes which are believed to have evolved immediately after the evolution of the first life. They have been placed in a separate subkingdom or domain of Archaea by a number of workers.

    Archaebacteria are characterised by absence of peptidoglycan in their wall. Instead the wall contains protein and non-cellulosic polysaccharides. It has pseudomurein in some methanogens. The cell membranes are characterised by the presence of a monolayer of branched chain lipids. Their 16S rRNA nucleotides are quite different from those of other organisms.


    Many archaebacteria even now live under extremely hostile conditions where very few other organisms can dare subsist, e.g., salt pans, salt marshes, hot sulphur springs. The archaebacteria are of two broad categories, obligate anaerobes and facultative anaerobes.

    Obligate anaerobes can live under anaerobic conditions only. They get killed in the presence of oxygen, e.g., methanogens. Facultative anaerobes are actually aerobic archaebacteria which can bear anaerobic conditions comfortably. They are represented by thermoacidophiles and halophiles.

    Types of Archaebacteria:

    1. Methanogens:


    2. Halophiles :

    Halophiles are able to live under high salt conditions due to four reasons:


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    Structure Composition Development And Operation

    Archaea and bacteria have generally similar cell structure, but cell composition and organization set the archaea apart. Like bacteria, archaea lack interior membranes and organelles. Like bacteria, the cell membranes of archaea are usually bounded by a cell wall and they swim using one or more flagella. Structurally, archaea are most similar to gram-positive bacteria. Most have a single plasma membrane and cell wall, and lack a periplasmic space the exception to this general rule is Ignicoccus, which possess a particularly large periplasm that contains membrane-bound vesicles and is enclosed by an outer membrane.

    Significance In Technology And Industry

    Archaebacteria | Biology | NEET | Concept of the day | Pushpendu Sir

    Extremophile archaea, particularly those resistant either to heat or to extremes of acidity and alkalinity, are a source of enzymes that function under these harsh conditions. These enzymes have found many uses. For example, thermostable DNA polymerases, such as the Pfu DNA polymerase from Pyrococcus furiosus, revolutionized molecular biology by allowing the polymerase chain reaction to be used in research as a simple and rapid technique for cloning DNA. In industry, amylases, galactosidases and pullulanases in other species of Pyrococcus that function at over 100 °C allow food processing at high temperatures, such as the production of low lactose milk and whey. Enzymes from these thermophilic archaea also tend to be very stable in organic solvents, allowing their use in environmentally friendly processes in green chemistry that synthesize organic compounds. This stability makes them easier to use in structural biology. Consequently, the counterparts of bacterial or eukaryotic enzymes from extremophile archaea are often used in structural studies.

    Archaea host a new class of potentially useful antibiotics. A few of these archaeocins have been characterized, but hundreds more are believed to exist, especially within Haloarchaea and Sulfolobus. These compounds differ in structure from bacterial antibiotics, so they may have novel modes of action. In addition, they may allow the creation of new selectable markers for use in archaeal molecular biology.

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    Bacteria Living In Submarine Hydrothermal Areas

    Archaebacteria are a group of microorganisms considered to be an ancient form of life that evolved separately from the bacteria and blue-green algae, and they are sometimes classified as a kingdom. Hyperthermophilic archaebacteria, found in submarine hydrothermal areas , thrive at temperatures in the range 80-110°C, and they are unable to grow below 60°C. Various extremely thermophilic archaebacteria exhibit optimum growth at above 80°C. Pyrodictium is the most thermophilic of these organisms, growing at temperatures of up to 110°C and exhibiting optimum growth at about 105°C. All of these organisms grow by diverse types of anaerobic and aerobic metabolism .

    These high-temperature-loving bacteria represent life at the known upper temperature limit. Within the marine environment, hyperthermophilic archaebacteria have been found in shallow-water hydrothermal fields as well as in deep hot sediments and vents . Sulfur-dependent archaebacteria can be assigned to two distinct branches: the aerobic, sulfur-oxidizing Sulfolobales and the strictly anaerobic sulfur-reducing Thermoproteales . Archaebacteria are important as primary producers and consumers of organic matter within high-temperature ecosystems. Their distribution and possible modes of dissemination are at present largely unknown.

    Paul V. Dunlap, in, 2001

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