View source for Monera

{{Short description|Biological kingdom that contains unicellular organisms with a prokaryotic cell organization}}
{{Redirect|Monora|the Romanian village of Mănărade, called Monora in Hungarian|Blaj}}
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{{paraphyletic group
| image = E. coli Bacteria (7316101966).jpg
| image_caption = [[Scanning electron microscope|Scanning electron micrograph]] of ''[[Escherichia coli]]'' [[bacillus (shape)|rods]]
| parent = Life
| auto = yes
| includes = [[Bacteria]] and [[Archaea]]
| excludes = Domain [[Eukaryota]]
}}

'''Monera'''  ({{IPA|/məˈnɪərə/}}) (Greek: {{lang|grc|μονήρης}} ({{transliteration|grc|monḗrēs}}), "single", "solitary") is historically a [[Kingdom (biology)|biological kingdom]] that is made up of unicellular [[prokaryote]]s. As such, it is composed of single-celled organisms that lack a [[Cell nucleus|nucleus]].
 
The taxon Monera was first proposed as a phylum by [[Ernst Haeckel]] in 1866. Subsequently, the phylum was elevated to the rank of kingdom in 1925 by [[Édouard Chatton]]. The last commonly accepted mega-classification with the taxon Monera was the [[Kingdom (biology)#Five kingdoms|five-kingdom]] classification system established by [[Robert Whittaker (ecologist)|Robert Whittaker]] in 1969.

Under the [[three-domain system]] of [[Taxonomy (biology)|taxonomy]], introduced by [[Carl Woese]] in 1977, which reflects the evolutionary history of life, the organisms found in kingdom Monera have been divided into two [[domain (biology)|domains]], [[Archaea]] and [[Bacteria]] (with [[Eukarya]] as the third domain). Furthermore, the taxon Monera is [[paraphyletic]] (does not include all descendants of their most recent common ancestor), as [[Archaea]] and [[Eukarya]] are currently believed to be more closely related than either is to [[Bacteria]]. The term "moneran" is the [[Common name|informal name]] of members of this group and is still sometimes used (as is the term "prokaryote") to denote a member of either domain.<ref name="Britannia">{{Citation|title=Encyclopædia Britannica|url=http://www.britannica.com/EBchecked/topic/389114/moneran|date=2018-02-01|contribution=Moneran|access-date=2018-11-13}}</ref>

Most bacteria were classified under Monera; however, some [[Cyanobacteria]] (often called the blue-green algae) were initially classified under [[Plantae]] due to their ability to [[photosynthesize]].

==History==
{{See also|Bacterial taxonomy}}

===Haeckel's classification===
[[File:Haeckel arbol bn.png|thumb|Tree of Life in ''Generelle Morphologie der Organismen'' (1866)<ref name=Haeckel67/>]]
Traditionally the natural world was classified as animal, vegetable, or mineral as in [[Systema Naturae]]. After the development of the [[microscope]], attempts were made to fit microscopic organisms into either the plant or animal kingdoms. In 1675, [[Antonie van Leeuwenhoek]] discovered bacteria and called them "animalcules", assigning them to the class Vermes of the Animalia.<ref>{{cite journal |doi=10.1098/rstl.1684.0030 |author=van Leeuwenhoek A |title=An abstract of a letter from Mr. Anthony Leevvenhoek at Delft, dated Sep. 17, 1683, Containing Some Microscopical Observations, about Animals in the Scurf of the Teeth, the Substance Call'd Worms in the Nose, the Cuticula Consisting of Scales |journal=Philosophical Transactions |volume=14 |pages=568–574 |year=1684 |issue=155–166 |doi-access=free |url=https://zenodo.org/records/1432130/files/article.pdf }}</ref><ref>{{cite journal |author=van Leeuwenhoek A |title=Part of a Letter from Mr Antony van Leeuwenhoek, concerning the Worms in Sheeps Livers, Gnats, and Animalcula in the Excrements of Frogs|journal=Philosophical Transactions |volume=22 |pages=509–518 |year=1700|doi=10.1098/rstl.1700.0013 |issue=260–276|bibcode=1700RSPT...22..509V|doi-access=free }}</ref><ref>{{cite journal |author=van Leeuwenhoek A |title=Part of a Letter from Mr Antony van Leeuwenhoek, F. R. S. concerning Green Weeds Growing in Water, and Some Animalcula Found about Them |url=http://www.journals.royalsoc.ac.uk/link.asp?id=fl73121jk4150280 |journal=Philosophical Transactions |volume=23 |pages=1304–11 |year=1702 |access-date=2007-08-19 |doi=10.1098/rstl.1702.0042 |issue=277–288 |url-status=dead |archive-url=https://web.archive.org/web/20070214025417/http://www.journals.royalsoc.ac.uk/link.asp?id=fl73121jk4150280 |archive-date=2007-02-14 |bibcode=1702RSPT...23.1304V |s2cid=186209549 |url-access=subscription }}</ref> 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.<ref name="Bergey_2B">{{cite book |series=Bergey's Manual of Systematic Bacteriology|volume=2A|title=Introductory Essays|editor=George M. Garrity |author1=Don J. Brenner |author2=Noel R. Krieg |author3=James T. Staley |publisher=Springer|location= New York |edition=2nd|isbn=978-0-387-24143-2 |pages=304 |url=https://www.springer.com/life+sciences/book/978-0-387-24143-2 |date=July 26, 2005| orig-year =1984(Williams & Wilkins)|id=British Library no. GBA561951}}</ref><ref name="Copeland1938"/><ref name="woese87">{{Cite journal
| last1 = Woese | first1 = C. R.
| title = Bacterial evolution
| journal = Microbiological Reviews
| volume = 51
| issue = 2
| pages = 221–271
| year = 1987
| doi = 10.1128/MMBR.51.2.221-271.1987
| pmid = 2439888
| pmc = 373105
}}</ref>

Seven years after ''[[The Origin of Species]]'' by [[Charles Darwin]], in 1866 [[Ernst Haeckel]], a supporter of evolutionary theory, proposed a three-kingdom system that added the Protista as a new kingdom that contained most microscopic organisms.<ref name=Haeckel67>{{cite book|author = Ernst Heinrich Philipp August Haeckel|title = Generelle Morphologie der Organismen|publisher = Reimer, Berlin|year = 1867|isbn = 978-1-144-00186-3|url=https://archive.org/details/generellemorpho00haecgoog}}</ref> One of his eight major divisions of Protista was composed of the monerans (called Moneres by Haeckel), which he defined as completely structure-less 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]]'' is the only bacterial genus explicitly assigned to the phylum, while others are mentioned indirectly, which led [[Herbert Copeland (biologist)|Copeland]] to speculate that Haeckel considered all bacteria to belong to the genus ''Vibrio'', ignoring other bacterial genera.<ref name="Copeland1938"/> One notable exception were the members of the modern phylum [[Cyanobacteria]], such as ''[[Nostoc]]'', which were placed in the phylum Archephyta of [[Algae]] (vide infra: [[#Blue-green algae|Blue-green algae]]).

The Neolatin noun Monera and the German noun Moneren/Moneres<!--German common nouns have capital letter--> are derived from the ancient Greek noun ''moneres'', which Haeckel stated meant "simple";<ref name=Haeckel67/> however, it actually means "single, solitary".<ref>{{LSJ|monh/rhs|μονήρης|ref}}.</ref> Haeckel also describes the protist genus [[Monas (genus)|Monas]] in the two pages about Monera in his 1866 book.<ref name=Haeckel67/><!--It is not the type species or similar, though!--> The informal name of a member of the Monera was initially moneron,<ref name=Pascoe>{{cite book|url=https://archive.org/details/zoologicalclassi00pasc|author=Francis Polkinghorne Pascoe|year=1880|title=Zoological classification; a handy book of reference with tables of the subkingdoms, classes, orders, etc., of the animal kingdom, their characters and lists of the families and principal genera|publisher=London, J. Van Voorst}}</ref> but later moneran was used.<ref name=Britannia/>

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 <nowiki>[sic.]</nowiki>): Gymnomonera
** ''Protogenes'' — such as ''Protogenes primordialis'', an unidentified amoeba (eukaryote) and not a bacterium
** ''Protamaeba''— an incorrectly described/fabricated species
** ''[[Vibrio]]'' — a genus of comma-shaped bacteria first described in 1854<ref>PACINI (F.): Osservazione microscopiche e deduzioni patologiche sul cholera asiatico. Gazette Medicale de Italiana Toscano Firenze, 1854, 6, 405-412.</ref>
** ''[[Bacterium (genus)|Bacterium]]'' — a genus of rod-shaped bacteria first described in 1828. Haeckel does not explicitly assign this genus to the Monera.
** ''[[Bacillus]]'' — a genus of spore-forming rod-shaped bacteria first described in 1835<ref>EHRENBERG (C.G.): Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes. Physikalische Abhandlungen der Koeniglichen Akademie der Wissenschaften zu Berlin aus den Jahren 1833-1835, 1835, pp. 143-336.</ref> Haeckel does not explicitly assign this genus to the Monera kingdom.
** ''[[Spirochaeta]]'' — thin spiral-shaped bacteria first described in 1835 <ref>EHRENBERG (C.G.): Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes. Abhandlungen der Preussischen Akademie der Wissenschaften (Berlin) aus den Jahre 1833-1835, pp. 143-336.</ref> Haeckel does not explicitly assign this genus to the Monera.
** ''[[Spirillum]]'' — spiral-shaped bacteria first described in 1832<ref>EHRENBERG (C.G.): Beiträge zur Kenntnis der Organization der Infusorien und ihrer geographischen Verbreitung besonders in Sibirien. Abhandlungen der Koniglichen Akademie der Wissenschaften zu Berlin, 1832, 1830, 1-88.</ref> 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 (genus)|Monas]]'', a flagellated protozoan, and not a bacterium.<ref name=Pascoe/> The name was reused in 1984 for an unrelated genus of bacteria.<ref>{{lpsn|p/protomonas|Protomonas}}</ref>
** ''[[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, Haeckel'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.<ref name=Pascoe/> They were first recognized as a kingdom by Enderlein in 1925 (Bakterien-Cyclogenie. de Gruyter, Berlin).

The most popular scheme was created in 1859 by [[C. Von Nägeli]] who classified non-phototrophic Bacteria as the class Schizomycetes.<ref name=nageli>{{cite journal
| author      = C. Von Nägeli
| editor      =R. Caspary
| year        = 1857
| title       =Bericht über die Verhandlungen der 33. Versammlung deutscher Naturforscher und Aerzte, gehalten in Bonn von 18 bis 24 September 1857
| trans-title =Report on the negotiations on 33 Meeting of German Natural Scientists and Physicians, held in Bonn, 18 to 24 September 1857<!--Google translate!-->
| journal      =Botanische Zeitung
| volume       =15
| pages        =749–776
}}</ref>

The class Schizomycetes was then emended by [[Walter Migula]] (along with the coinage of the genus ''Pseudomonas'' in 1894)<ref>{{cite journal | author = Migula W | year = 1894 | title = Über ein neues System der Bakterien | journal = Arb Bakteriol Inst Karlsruhe | volume = 1 | pages = 235–328 }}</ref> and others.<ref>{{cite journal | author = CHESTER F. D. | year = 1897 | title = Classification of the Schizomycetes | journal = Annual Report Delaware College Agricultural Experiment Station | volume = 9 | page = 62 }}</ref> This term was in dominant use even in 1916 as reported by [https://www.ncbi.nlm.nih.gov/books/NBK8814/ Robert Earle Buchanan], as it had priority over other terms such as Monera.<ref>{{cite journal | author = Buchanan R E|title=Studies in the Nomenclature and Classification of Bacteria: The Problem of Bacterial Nomenclature |date=Nov 1916 | journal = J Bacteriol | volume = 1 | issue = 6| pages = 591–6 |doi=10.1128/JB.1.6.591-596.1916 | pmc=378679 | pmid=16558720}}</ref> However, starting with [[Ferdinand Cohn]] in 1872 the term ''bacteria'' (or in German ''{{lang|de|Bacterien}}'') became prominently used to informally describe this group of species without a nucleus: [[Bacterium (genus)|Bacterium]] was in fact a genus created in 1828 by [[Christian Gottfried Ehrenberg]]<ref>{{cite book|author=Ferdinand Cohn|year=1872|chapter=Untersuchungen u<!--umlaut-->ber Bakterien|title=Beiträge zur Biologie der Pflanzen|volume=1|issue=1|pages=127–224|chapter-url=https://books.google.com/books?id=wnyHvEtfRrQC&q=COHN%2C%20FERDINAND%201872%20.%20Beitr%C3%A4ge%20zur%20Biologie%20der%20Pflanzen&pg=RA1-PA127}}</ref> 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<ref>{{cite book|author=Ferdinand Cohn|year=1875|chapter=Untersuchungen u<!--umlaut-->ber Bakterien|title=Beiträge zur Biologie der Pflanzen|volume=1|issue=3|pages=141–208}}</ref> 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.<ref>Ernst Haeckel. The Wonders of Life. Translated by Joseph McCabe. New York and London. I904.</ref>

Stanier and van Neil (1941, The main outlines of bacterial classification. J Bacteriol 42: 437- 466) recognized the Kingdom Monera with two phyla, Myxophyta and Schizomycetae, the latter comprising classes Eubacteriae (3 orders), Myxobacteriae (1 order), and Spirochetae (1 order); Bisset (1962, Bacteria, 2nd ed., Livingston, London) distinguished 1 class and 4 orders: Eubacteriales, Actinomycetales, Streptomycetales, and Flexibacteriales; Orla-Jensen (1909, Die Hauptlinien des naturalischen Bakteriensystems nebst einer Ubersicht der Garungsphenomene. Zentr. Bakt. Parasitenk., II, 22: 305-346) and Bergey et al (1925, Bergey's Manual of Determinative Bacteriology, Baltimore : Williams & Wilkins Co.) with many subsequent editions) also presented classifications.

===Rise to importance===
The term Monera 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 sections, Prokaryotes and Eukaryotes: the Kingdom Monera being the sole member of the Prokaryotes section.<ref name=Chatton1925 />

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.<ref name="Copeland1938"/><ref name="Whit1969"/> The latter classification system was widely followed, in which [[Robert Whittaker (ecologist)|Robert Whittaker]] proposed a five kingdom system for classification of living organisms.<ref name="Whit1969">{{cite journal | author = R H Whittaker | year= 1969 | title = New concepts of kingdoms or organisms. Evolutionary relations are better represented by new classifications than by the traditional two kingdoms | journal = [[Science (journal)|Science]] | volume = 163 | pages = 150–160 | pmid = 5762760 | doi = 10.1126/science.163.3863.150 | issue = 3863 |bibcode = 1969Sci...163..150W | citeseerx= 10.1.1.403.5430 }}</ref> 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.<ref name="sapp" />
Whittaker subdivided the kingdom into two branches containing several phyla:
* Myxomonera branch
** Cyanophyta, now called [[Cyanobacteria]]
** [[Myxobacteria]]
* Mastigomonera branch
** [[Eubacterium|Eubacteriae]]
** [[Actinomycota]]
** [[Spirochaetae]]

Alternative commonly followed subdivision systems were based on Gram stains. This culminated in the Gibbons and Murray classification of 1978:<ref>GIBBONS (N.E.) and MURRAY (R.G.E.): Proposals concerning the higher taxa of bacteria. International Journal of Systematic Bacteriology, 1978, 28, 1-6.</ref>
* '''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) eg. ''Pseudomonas aeruginosa, Salmonella enterica, E.coli.'' 
* '''Firmacutes''' [sic] (gram positive, subsequently corrected to Firmicutes<ref>MURRAY (R.G.E.): The higher taxa, or, a place for everything...? In: N.R. KRIEG and J.G. HOLT (ed.) Bergey's Manual of Systematic Bacteriology, vol. 1, The Williams & Wilkins Co., Baltimore, 1984, p. 31-34</ref>)
**several orders such as Bacillales and Actinomycetales (now in the phylum Actinobacteria) eg. ''Bacillus cerus, Streptococcus, Staphylococcus.'' 
* '''Mollicutes''' (gram variable, e.g. Mycoplasma)
* '''Mendocutes''' (uneven gram stain, "methanogenic bacteria" now known as the Archaea)

===Three-domain system===
{{Main|Three-domain system}}
{{For|current subdivision of Bacteria|Bacterial phyla}}
In 1977, a [[Proceedings of the National Academy of Sciences|PNAS]] paper by [[Carl Woese]] and [[George E. Fox|George Fox]] demonstrated that the [[archaea]] (initially called archaebacteria) are not significantly closer in relationship to the [[bacteria]] than they are to [[eukaryote]]s. The paper received front-page coverage in ''[[The New York Times]]'',<ref>{{Cite news
|newspaper=The New York Times
|title=Scientists Discover a Form of Life That Predates Higher Organisms
|author=Lyons, Richard D.
|date=Nov 3, 1977
|pages=A1, A20
}}</ref> and great controversy initially. The conclusions have since become accepted, leading to replacement of the kingdom Monera with the two domains [[Bacteria]] and [[Archaea]].<ref name="sapp" /><ref>{{cite journal
|author=Holland L.
| title=Woese, Carl in the forefront of bacterial evolution revolution
| journal      = Scientist
| volume       =4
| issue        =10
| date        = 22 May 1990}}</ref> A minority of scientists, including [[Thomas Cavalier-Smith]], continue to reject the widely accepted division between these two groups. Cavalier-Smith has published classifications in which the archaebacteria are part of a subkingdom of the Kingdom Bacteria.<ref>{{Citation |last=Cavalier-Smith |first=T. |year=2004 |title=Only six kingdoms of life |journal=Proc. R. Soc. Lond. B |volume=271 |pages=1251–62 |url=http://www.cladocera.de/protozoa/cavalier-smith_2004_prs.pdf |access-date=2010-04-29 |doi=10.1098/rspb.2004.2705 |pmid=15306349 |issue=1545 |pmc=1691724}}</ref>

*Blue-green algae*
{{Main|cyanobacteria}}
Although it was generally accepted that one could distinguish prokaryotes from eukaryotes on the basis of the presence of a [[Cell nucleus|nucleus]], [[mitosis]] versus [[binary fission]] as a way of reproducing, size, and other traits, the [[monophyly]] 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.<ref name="sapp"/> [[Roger Stanier]] 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 that 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".<ref>Roger Stanier to Peter Raven, 5 November 1970, National Archives of Canada, MG 31, accession J35, vol. 6, as quoted in Sapp, 2005</ref> Other researchers, such as [[Ernst Pringsheim Jr.|E. G. Pringsheim]] 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.<ref name="sapp">{{cite journal | title = The Prokaryote-Eukaryote Dichotomy: Meanings and Mythology | author = Jan Sapp | journal = Microbiology and Molecular Biology Reviews | date = June 2005 | pages = 292–305 | volume = 69 | issue = 2 | doi = 10.1128/MMBR.69.2.292-305.2005 | pmid = 15944457 | pmc = 1197417}}</ref>

== Summary==
{{Biological kingdom classification}}
Monerans are a group of organisms having prokaryotic structure.
Archaea differ from Bacteria in having a different 16S srna.
They also have a different cell wall structure.

== See also ==
* [[Bacterial cell structure]]
* [[Endosymbiont]]
* [[Kingdom (biology)]]
* [[Prokaryote]]
* [[Eukaryote]]
* [[Symbiogenesis]]

==References==
{{Reflist}}

== External links ==
*{{cite journal |author=Woese CR |title=Bacterial evolution |journal=Microbiol. Rev. |volume=51 |issue=2 |pages=221–71 |date=June 1987 |doi=10.1128/MMBR.51.2.221-271.1987 |pmid=2439888 |pmc=373105 }} Woese reviewed the historical steps leading to the use of the term "Monera" and its later abandonment.
* [http://www.thebigger.com/section/biology/monera/ What is Monera? A descriptive details of the entire kingdom]

{{Taxonbar|from1=Q97263158}}

[[Category:Obsolete bacteria taxa]]