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Monera

Monera

Overview
Monera is a superseded kingdom that contains unicellular organisms without a nucleus (i.e., a prokaryotic
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 organization), such as bacteria.

The taxon Monera was first proposed as a phylum by Ernst Haeckel in 1866; subsequently, the taxon was raised to the rank of kingdom in 1925 by Édouard Chatton, gaining common acceptance, and the last commonly accepted mega-classication with the taxon Monera was the five-kingdom classification system established by Robert Whittaker in 1969.
Under the three-domain system
Three-domain system
The three-domain system is a biological classification introduced by Carl Woese in 1977 that divides cellular life forms into archaea, bacteria, and eukaryote domains. In particular, it emphasizes the separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria...

 of taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

, which was established in 1990 and reflects the evolutionary history of life as currently understood, the organisms found in kingdom Monera have been divided into two domains
Domain (biology)
In biological taxonomy, a domain is the highest taxonomic rank of organisms, higher than a kingdom. According to the three-domain system of Carl Woese, introduced in 1990, the Tree of Life consists of three domains: Archaea, Bacteria and Eukarya...

, Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

and Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

(with Eukarya as the third domain).
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Encyclopedia
Monera is a superseded kingdom that contains unicellular organisms without a nucleus (i.e., a prokaryotic
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

 cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 organization), such as bacteria.

The taxon Monera was first proposed as a phylum by Ernst Haeckel in 1866; subsequently, the taxon was raised to the rank of kingdom in 1925 by Édouard Chatton, gaining common acceptance, and the last commonly accepted mega-classication with the taxon Monera was the five-kingdom classification system established by Robert Whittaker in 1969.
Under the three-domain system
Three-domain system
The three-domain system is a biological classification introduced by Carl Woese in 1977 that divides cellular life forms into archaea, bacteria, and eukaryote domains. In particular, it emphasizes the separation of prokaryotes into two groups, originally called Eubacteria and Archaebacteria...

 of taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

, which was established in 1990 and reflects the evolutionary history of life as currently understood, the organisms found in kingdom Monera have been divided into two domains
Domain (biology)
In biological taxonomy, a domain is the highest taxonomic rank of organisms, higher than a kingdom. According to the three-domain system of Carl Woese, introduced in 1990, the Tree of Life consists of three domains: Archaea, Bacteria and Eukarya...

, Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

and Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

(with Eukarya as the third domain). Furthermore the taxon Monera is paraphyletic. The term "moneran" is the informal name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...

 of members of this group and is still sometimes used (as is the term "prokaryote") to denote a member of either domain.

Despite most bacteria being classified under Monera, the bacterial phylum Cyanobacteria (the blue-green algae) was not classified under Monera, but under Plantae given the ability of its members to photosynthesise.

Haekel's classification



Traditionally the natural world was classified as animal, vegetable, or mineral as in Systema Naturae
Systema Naturae
The book was one of the major works of the Swedish botanist, zoologist and physician Carolus Linnaeus. The first edition was published in 1735...

. After the discovery of microscopy
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...

, attempts were made to fit microscopic organisms into either the plant or animal kingdoms.
In 1676, Antonie van Leeuwenhoek discovered bacteria and called them "animacules," assigning them to the class Vermes of the Animalia. Due to the limited tools — the sole references for this group were shape, behaviour, and habitat — the description of genera and their classification was extremely limited, which was accentuated by the perceived lack of importance of the group.

Ten years after The Origin of Species
The Origin of Species
Charles Darwin's On the Origin of Species, published on 24 November 1859, is a work of scientific literature which is considered to be the foundation of evolutionary biology. Its full title was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the...

by Darwin, in 1866 Ernst Haeckel
Ernst Haeckel
The "European War" became known as "The Great War", and it was not until 1920, in the book "The First World War 1914-1918" by Charles à Court Repington, that the term "First World War" was used as the official name for the conflict.-Research:...

, a supporter of evolution, proposed a three-kingdom system which added the Protista as a new kingdom that contained most microscopic organisms. One of his eight major divisions of Protista was composed of the monerans (called Moneres in German) and defines them as completely structureless and homogeneous organisms, consisting only of a piece of plasma. Haeckel's Monera included not only bacterial groups of early discovery but also several small eukaryotic organisms; in fact the genus Vibrio
Vibrio
Vibrio is a genus of Gram-negative bacteria possessing a curved rod shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in saltwater, Vibrio are facultative anaerobes that test positive for oxidase and do not form...

 is the only bacterial genus explicitly assigned to the phylum, while others are mentioned indirectly, which has led Copeland to speculate that Haeckel considered all bacteria to belong to the genus Vibrio, ignoring other bacterial genera. One notable exception were the members of the modern phylum Cyanobacteria, such as Nostoc
Nostoc
Nostoc is a genus of cyanobacteria found in a variety of environmental niches that forms colonies composed of filaments of moniliform cells in a gelatinous sheath.The name "Nostoc" was invented by Paracelsus...

, which were placed in the phylum Archephyta of Algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

(vide infra: Blue-green algae).

The Neolatin noun Monera and the German noun Moneren/Moneres are derived from the ancient Greek noun moneres (μονήρης) which Haeckel states to mean "simple", however it actually means "single, solitary". Haeckel also describes the protist genus Monas in the two pages about Monera in his 1866 book. The informal name of a member of the Monera was initially moneron, but later moneran was used.

Due to its lack of features, the phylum was not fully subdivided, but the genera therein were divided into two groups:
  • die Gymnomoneren (no envelope [sic.]): Gymnomonera
    • Protogenes — such as Protogenes primordialis, an unidentified amaeba (eukaryote) and not a bacterium
    • Protamaeba — an incorrectly described/fabricated species
    • Vibrio
      Vibrio
      Vibrio is a genus of Gram-negative bacteria possessing a curved rod shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in saltwater, Vibrio are facultative anaerobes that test positive for oxidase and do not form...

      — a genus of comma-shaped bacteria first described in 1854
    • Bacterium
      Bacterium (genus)
      The genus Bacterium was a taxon described in 1828 by Christian Gottfried Ehrenberg. The type species was later changed from Bacterium triloculare to Bacterium coli as it was lost...

      — a genus of rod-shaped bacteria first described in 1828. Haeckel does not explicitly assign this genus to the Monera.
    • Bacillus
      Bacillus
      Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...

      — a genus of spore-forming rod-shaped bacteria first described in 1835 Haeckel does not explicitly assign this genus to the Monera.
    • Spirochaeta — thin spiral-shaped bacteria first described in 1835 Haeckel does not explicitly assign this genus to the Monera.
    • Spirillum
      Spirillum
      Spirillum in microbiology refers to a bacterium with a cell body that twists like a spiral. It is the third distinct bacterial cell shape type besides coccus and bacillus cells.-Taxonomic:...

      — spiral-shaped bacteria first described in 1832 Haeckel does not explicitly assign this genus to the Monera.
    • etc.: Haeckel does provide a comprehensive list.
  • die Lepomoneren (with envelope): Lepomonera
    • Protomonas — identified to a synonym of Monas, a flagellated protozoan, and not a bacterium. The name was reused in 1984 for an unrelated genus of bacteria.
    • Vampyrella — now classed as a eukaryote and not a bacterium.

Subsequent classifications


Like Protista, the Monera classification was not fully followed at first and several different ranks were used and located with animals, plants, protists or fungi. Furthermore, Häkel's classification lacked specificity and was not exhaustive —it in fact covers only a few pages—, consequently a lot of confusion arose even to the point that the Monera did not contain bacterial genera and others according to Huxley.
The most popular scheme was created in 1859 by C. Von Nägeli who classified non-phototrophic Bacteria as the class Schizomycetes.

The class Schizomycetes was then emended by Walter Migula (along with the coinage of the genus Pseudomonas in 1894) and others. This term was in dominant use even in 1916 as reported by Robert Earle Buchanan, as it had priority over other terms such as Monera. However, starting with Ferdinand Cohn
Ferdinand Cohn
Ferdinand Julius Cohn was a German biologist.Cohn was born in Breslau in the Prussian Province of Silesia. At the age of 10 he suffered hearing impairment. He received a degree in botany in 1847 at the age of nineteen at the University of Berlin. He was a teacher and researcher at University of...

 in 1872 the term bacteria (or in German der Bacterien) became prominently used to informally describe this group of species without a nucleus: Bacterium
Bacterium (genus)
The genus Bacterium was a taxon described in 1828 by Christian Gottfried Ehrenberg. The type species was later changed from Bacterium triloculare to Bacterium coli as it was lost...

 was in fact a genus created in 1828 by Christian Gottfried Ehrenberg
Christian Gottfried Ehrenberg
Christian Gottfried Ehrenberg , German naturalist, zoologist, comparative anatomist, geologist, and microscopist, was one of the most famous and productive scientists of his time.- Early collections :...

  Additionally, Cohn divided the bacteria according to shape namely:
  • Spherobacteria for the cocci
  • Microbacteria for the short, non-filamentous rods
  • Desmobacteria for the longer, filamentous rods and Spirobacteria for the spiral forms.


Successively, Cohn created the Schizophyta of Plants which contained the non-photrophic bacteria in the family Schizomycetes and the phototrophic bacteria (blue green algae/Cyanobacteria) in the Schizophyceae
This union of blue green algae and Bacteria was much later followed by Haeckel, who classified the two families in a revised phylum Monera in the Protista.

Rise to prominence


The term Monora, became well established in the 20s and 30s when to rightfully increase the importance of the difference between species with a nucleus and without, In 1925 Édouard Chatton divided all living organisms into two empires Prokaryotes and Eukaryotes: the Kingdom Monera being the sole member of the Prokaryotes empire.

The anthropic importance of the crown group of animals, plants and fungi was hard to depose consequently several other megaclassification schemes ignored on the empire rank, but maintained the kingdom Monera consisting of bacteria, such Copeland in 1938 and Whittaker in 1969. The latter classification system was widely followed and in which Robert Whittaker
Robert Whittaker
Robert Harding Whittaker was a distinguished American plant ecologist, active in the 1950s to the 1970s.Born in Wichita, Kansas, he obtained a B.A. at Washburn Municipal College in Topeka, Kansas, and, following military service, his Ph.D...

 proposed a five kingdom system for classification of living organisms. Whittaker's system placed most single celled organisms into either the prokaryotic Monera or the eukaryotic Protista. The other three kingdoms in his system were the eukaryotic Fungi, Animalia, and Plantae. Whittaker, however, did not believe that all his kingdoms were monophyletic.
Whittaker subdiveded the kingdom into two branches containing several phyla:
  • Myxomonera branch
    • Cyanophyta, now called Cyanobacteria
    • Myxobacteria
      Myxobacteria
      The myxobacteria are a group of bacteria that predominantly live in the soil. The myxobacteria have very large genomes, relative to other bacteria, e.g. 9-10 million nucleotides. Sorangium cellulosum has the largest known bacterial genome, at 13.0 million nucleotides...

  • Mastigomonera branch
    • Eubacteriae
      Eubacterium
      Eubacterium is a Gram positive bacteria genus in the family Eubacteriaceae....

    • Actinomycota
    • Spirochaetae


Alternative ommonly followed subdivision systems were based on Gram stains. This culminated in the Gibbons and Murray classification of 1978:
  • Gracilicutes (gram negative)
    • Photobacteria (photosynthetic): class Oxyphotobacteriae (water as electron acceptor, includes the order Cyanobacteriales=blue green algae, now phylum Cyanobacteria) and class Anoxyphotobacteriae (anaerobic phototrophs, orders: Rhodospirillales and Chlorobiales
    • Scotobacteria (non-photosynthetic, now the Proteobacteria and other gram negative nonphotosynthetic phyla)
  • Firmacutes [sic] (gram positive, subsequently corrected to Firmicutes)
    • several orders such as Bacillales and Actinomycetales (now in the phylum Actinobacteria)
  • Mollicutes (gram variable, e.g. Mycoplasma)
  • Mendocutes (uneven gram stain, "methanogenic bacteria" now known as the Archaea)

Three-domain system


In 1977, a PNAS
Proceedings of the National Academy of Sciences
The Proceedings of the National Academy of Sciences of the United States of America, usually referred to as PNAS, is the official journal of the United States National Academy of Sciences...

 paper by Carl Woese
Carl Woese
Carl Richard Woese is an American microbiologist and physicist. Woese is famous for defining the Archaea in 1977 by phylogenetic taxonomy of 16S ribosomal RNA, a technique pioneered by Woese and which is now standard practice. He was also the originator of the RNA world hypothesis in 1977,...

 and George Fox
George E. Fox
George Edward Fox is a researcher at the University of Houston and, with Carl Woese in the early 1970s, was the first scientist to classify Archaea as a separate domain of life within the three-domain system. Fox and Woese also introduced the idea of a progenote as a primordial entity in the...

 demonstrated that the archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

 (initially called archaebacteria) are not significantly closer in relationship to the bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 than they are to eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s. The paper received front-page coverage in The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

, and great controversy initially. The conclusions have since become accepted, leading to replacement of the kingdom Monera with the two kingdoms Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and Archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...

. However, Thomas Cavalier-Smith
Thomas Cavalier-Smith
Professor Thomas Cavalier-Smith , FRS, FRSC, NERC Professorial Fellow, is a Professor of Evolutionary Biology in the Department of Zoology, at the University of Oxford...

 has never accepted the importance of the division between these two groups, and has published classifications in which the archaebacteria are part of a subkingdom of the Kingdom Bacteria.

Blue-green algae



Although it was generally accepted that one could distinguish prokaryotes from eukaryotes on the basis of the presence of a nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...

, mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

 versus binary fission as a way of reproducing, size, and other traits, the monophyly
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...

 of the kingdom Monera (or for that matter, whether classification should be according to phylogeny) was controversial for many decades. Although distinguishing between prokaryotes from eukaryotes as a fundamental distinction is often credited to a 1937 paper by Édouard Chatton (little noted until 1962), he did not emphasize this distinction more than other biologists of his era. Roger Stanier
Roger Stanier
Roger Yate Stanier was a Canadian microbiologist who was influential in the development of modern microbiology. As a member of the Delft School and former student of C. B. van Niel, he made important contributions to the taxonomy of bacteria, including the classification of blue-green algae as...

 and C. B. van Niel believed that the bacteria (a term which at the time did not include blue-green algae) and the blue-green algae had a single origin, a conviction which culminated in Stanier writing in a letter in 1970, "I think it is now quite evident that the blue-green algae are not distinguishable from bacteria by any fundamental feature of their cellular organization". Other researchers, such as E. G. Pringsheim
Ernst Pringsheim, Jr.
Ernst Pringsheim, Jr., Ernst Georg Pringsheim jun., or Ernst Georg Pringsheim was a German Natural scientist and plant physiologist .He taught as a professor for biochemistry and botany, in the University of Berlin, University of Prague, and Cambridge...

 writing in 1949, suspected separate origins for bacteria and blue-green algae. In 1974, the influential Bergey's Manual published a new edition coining the term cyanobacteria to refer to what had been called blue-green algae, marking the acceptance of this group within the Monera.

See also

  • Bacterial cell structure
    Bacterial cell structure
    Bacteria, despite their simplicity, contain a well-developed cell structure which is responsible for many of their unique biological properties. Many structural features are unique to bacteria and are not found among archaea or eukaryotes...

  • Endosymbiont
    Endosymbiont
    An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis...

  • Kingdom (biology)
    Kingdom (biology)
    In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...

  • Prokaryote
    Prokaryote
    The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

  • Symbiogenesis
    Symbiogenesis
    Symbiogenesis is the merging of two separate organisms to form a single new organism. The idea originated with Konstantin Mereschkowsky in his 1926 book Symbiogenesis and the Origin of Species, which proposed that chloroplasts originate from cyanobacteria captured by a protozoan...


External links

Woese reviewed the historical steps leading to the use of the term "Monera" and its later abandonment.