Micrococcus

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Micrococcus
Micrococcus luteus (REM)

Micrococcus luteus (REM)

Systematics
Domain : Bacteria (bacteria)
Department : Actinobacteria
Class : Actinobacteria
Order : Micrococcales
Family : Micrococcaceae
Genre : Micrococcus
Scientific name
Micrococcus
Cohn 1872 emend. Wieser et al. 2002

Micrococcus is the name of a genus of gram-positive , usually non- pathogenic , spherical bacteria from the family of Micrococcaceae . His name isspelled“ Germanized ” as micrococcus ( plural : micrococci), and the term “micrococci” is also used colloquially for representatives of the family. At the end of the 20th century, the genus Micrococcus was re-described - with the assignment of previous Micrococcus species to other genera. Studies at the beginning of the 21st century led to a further improved description of the genus.

features

Appearance

The Latinized term Micrococcus is made up of the two ancient Greek components μικρός mikrós "small" and κόκκος kókkos "core", "grain" and refers to the appearance in the light microscope : The cell shape is round to oval, it is cocci , often lying the cells as so-called tetrads before - packets of four connected cocci. In the Gram stain they behave gram-positive, have no flagella for active movement and do not form persistence forms such as endospores .

Growth and metabolism

Micrococcus is strictly aerobic , which means it requires oxygen to grow, this serves as a distinguishing feature to representatives of the family of Staphylococcaceae that glucose also anaerobically in a fermentation with acid forming exploit. Its metabolism can be characterized as chemoorganotrophic and heterotrophic , it uses organic compounds as an energy source and also to build up cellular substances. It is catalase positive and oxidase positive. The temperatures suitable for cultivation are in the range of 20–40 ° C, making it one of the mesophilic organisms. During growth, alkaline pH values up to pH 10.0 are tolerated.

Chemotaxonomy

Branched fatty acids in the cell membrane of the Micrococcus
12-methyltetradecanoic acid, svg
anteiso -pentadecanoic acid
13-methyltetradecanoic acid. Svg
iso- pentadecanoic acid

The murein layer in the cell wall contains the diamino acid L - lysine as a diagnostically important amino acid . The peptidoglycan type is either A2 (an interpeptide bridge connects two tetrapeptides ) or A4α (an aminodicarboxylic acid - an amino acid with two carboxy groups - connects two tetrapeptides). The main menaquinones are either MK-8 and MK-8 (H 2 ) or just MK-8 (H 2 ). The menaquinones present in bacteria are quinones ; they have an important function in the respiratory chain , similar to ubiquinones in the respiratory chain in humans. Micrococcus species have a high proportion of branched fatty acid chains in their membrane lipids . This is v. a. around the fatty acids with the abbreviations anteiso -C 15: 0 ( anteiso - pentadecanoic acid , systematic name : 12-methyltetradecanoic acid ) and iso -C 15: 0 ( iso- pentadecanoic acid, 13-methyltetradecanoic acid), which in addition to the methyl group (-CH 3 ) , which represents the branching, still have the peculiarity that they belong to the odd-numbered fatty acids with a total of 15 carbon atoms .

Micrococcus contains a remarkably high GC content , ie a high proportion of the nucleobases guanine and cytosine in the bacterial DNA ; it is 69–76  mol percent . This proves that it is neither closely related to the genus Sarcina nor to the genus Staphylococcus , which are characterized by a particularly low GC content in the genome (28–31 mol percent and 30–39 mol percent).

Occurrence

Micrococcus is part of the natural skin flora in humans, it can also be found as a commensal on the skin of other mammals . It is ubiquitous, so it can be found almost everywhere, e.g. B. air on dust particles , objects in the upper soil layer , in sea water and fresh water as well as in activated sludge from a wastewater treatment plant .

Systematics

External system

It was not until 1955 that the reliable differentiation between Micrococcus and Staphylococcus was possible , the latter being able to metabolize glucose anaerobically with the formation of acid. As a result, at the beginning of the 21st century, staphylococci and other genera were classified in the newly described family of the Staphylococcaceae, while they were previously combined with the genus Micrococcus in the family of the Micrococcaceae. The morphologically oriented systematics in microbiology in earlier times meant that M. luteus was previously referred to as Sarcina lutea (because of its microscopic appearance). The genus Sarcina , however, belongs to the anaerobic endospore formers with a low GC content in the genome and is not closely related to the genus Micrococcus .

In the past, the systematics of microorganisms was mainly based on appearance, resulting in phenotypically oriented family trees. With a complete description of the DNA structure in 1953 and the molecular biological techniques used since around the 1990s (e.g. DNA sequence analysis and PCR ), genetic characteristics are increasingly being investigated in order to determine the phylogenetic development of the microorganisms ( phylogenetic tree ) and thus also to examine certain relationships in the system. The sequences of the so-called 16S ribosomal RNA (rRNA) are examined in prokaryotes . Investigations based on this and investigations of chemotaxonomic characteristics by Stackebrandt et al. showed in 1995 that multiple until then, the genus Micrococcus associated types to be little in common with M. luteus or M. lylae have, so that the original genus in five independent split was: Micrococcus , Kocuria , Nesterenkonia , Kytococcus and Dermacoccus , wherein the last two genera mentioned were assigned to the newly described family Dermacoccaceae . Both families are representatives of the order Micrococcales, which was introduced in the course of the new systematics of the class Actinobacteria (see there).

Internal system

Studies at the beginning of the 21st century by Wieser et al. led to a further improved description of the genus Micrococcus , as well as the species M. luteus and M. lylae . Micrococcus luteus is considered a typical species for the genus.

In 2000 a new type of bacteria was discovered in the Antarctic , which is named after the habitat as Micrococcus antarcticus (synonym M. psychrophilum ). Comparisons of the 16S rRNA sequences as well as the chemotaxonomic features (including occurrence of certain amino acids in the murein layer, main menaquinones) suggest that the bacterial strain belongs to the genus. The occurrence of branched fatty acids in the membrane lipids in significant proportions also fits the genus. In addition to the saturated fatty acids with the abbreviations anteiso -C 15: 0 and iso -C 15: 0, there is also a monounsaturated fatty acid anteiso -C 15: 1 . Investigations using DNA-DNA hybridization show DNA-DNA agreement values ​​with M. luteus and M. lylae of less than 35%, which is considered a sufficiently large phylogenetic distance that it is a separate species. The morphological characteristics match the genus: They are aerobically growing, gram-positive cocci (0.5 µm in size) that are present as tetrads or diplococci, the cells do not form endospores and are not motile (they have no flagella for active movement). The bacterium has adapted to its cold habitat, the optimal growth temperature is around 16 ° C, growth also takes place at 0 ° C, so it is a psychrophilic organism.

In 2007 a new bacterial species was discovered, this time in the activated sludge from the bioreactor of a wastewater treatment plant. In the plant, the bioreactor is used in batch operation to purify wastewater that contains various nitroaromatics and aniline . The isolated bacterial strain is called Micrococcus flavus ( flavus from Latin means “yellow”) because its colonies are colored yellow. Once again, the results of chemotaxonomic and molecular biological studies show that it belongs to the genus Micrococcus , but that it differs sufficiently from the previously known species. The DNA – DNA agreement values ​​with M. luteus , M. lylae and M. antarcticus are 55%, 48% and 36%, respectively. The amino acids lysine , glutamic acid , alanine , glycine and aspartic acid occur in the murein layer , the main menaquinones are MK-8 (H 2 ) and MK-7 (H 2 ). This species is also characterized by the occurrence of branched fatty acids ( anteiso -C 15: 0 and iso -C 15: 0 ) in the membrane lipids and a high GC content in the DNA of 71 mol percent. The morphological characteristics also correspond to those of the genus: They are aerobically growing, gram-positive cocci (0.7–1.0 µm in size), the cells are not motile (they have no flagella for active movement). The aerobic metabolism is heterotrophic, in this way M. flavus can utilize trehalose , dextrins and glycerine (without acid formation). The optimal growth temperature is around 31 ° C (it is a mesophilic organism), the optimal pH for growth is pH 6.0–6.2.

Currently (2018) nine Micrococcus species are listed by the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH in the Prokaryotic Nomenclature up-to-date ("Prokaryotic nomenclature up-to-date "), as well as other species that are included in other Genera were placed. This compilation includes all names validly published according to the Bacteriological Code and takes into account the validation list of the International Journal of Systematic and Evolutionary Microbiology . The various Micrococcus species, as well as other genera and species in the Micrococcaceae family are listed under the taxonomy of the Micrococcaceae family . The genus Micrococcus has the potential to remain interesting in the future.

swell

literature

  • E. Stackebrandt, C. Koch, O. Gvozdiak, P. Schumann: Taxonomic dissection of the genus Micrococcus: Kocuria gen. Nov., Nesterenkonia gen. Nov., Kytococcus gen. Nov., Dermacoccus gen. Nov., And Micrococcus Cohn 1872 gen. Emend . In: International journal of systematic and evolutionary microbiology . tape 45 , no. 4 , 1995, p. 682-692 , doi : 10.1099 / 00207713-45-4-682 ( PDF [accessed March 23, 2013]).
  • M. Wieser, EB Denner u. a .: Emended descriptions of the genus Micrococcus, Micrococcus luteus (Cohn 1872) and Micrococcus lylae (Kloos et al. 1974) . In: International journal of systematic and evolutionary microbiology . tape 52 , no. 2 , 2002, p. 629–637 , doi : 10.1099 / ijs.0.01901-0 ( PDF, 326kB [accessed on March 23, 2013]).

Individual evidence

  1. ↑ a b c d e f g h i E. Stackebrandt, C. Koch, O. Gvozdiak, P. Schumann: Taxonomic dissection of the genus Micrococcus: Kocuria gen. Nov., Nesterenkonia gen. Nov., Kytococcus gen. Nov. , Dermacoccus gen. Nov., And Micrococcus Cohn 1872 gen. Emend. In: International journal of systematic bacteriology. Volume 45, Number 4, October 1995, pp. 682-692, ISSN  0020-7713 . PMID 7547287 .
  2. ↑ a b c d e M. Wieser, EB Denner u. a .: Emended descriptions of the genus Micrococcus, Micrococcus luteus (Cohn 1872) and Micrococcus lylae (Kloos et al. 1974). In: International journal of systematic and evolutionary microbiology. Volume 52, Number 2, March 2002, pp. 629-637, ISSN  1466-5026 . PMID 11931177 .
  3. ^ Wilhelm Gemoll: Greek-German school and hand dictionary. Munich / Vienna 1965.
  4. ↑ a b c d e f g Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 978-3-8274-0566-1 .
  5. ↑ a b c XY Liu, BJ Wang, CY Jiang, SJ Liu: Micrococcus flavus sp. nov., isolated from activated sludge in a bioreactor. In: International journal of systematic and evolutionary microbiology. Volume 57, Number 1, January 2007, pp. 66-69, ISSN  1466-5026 . doi : 10.1099 / ijs.0.64489-0 . PMID 17220443 .
  6. ↑ Catalog of microorganisms. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved April 7, 2018 .
  7. ^ Jean Euzéby, Aidan C. Parte: Phylum "Actinobacteria". In: List of Prokaryotic names with Standing in Nomenclature, ( LPSN ). Retrieved April 7, 2018 .
  8. ↑ H. Liu, Y. Xu, Y. Ma, P. Zhou: Characterization of Micrococcus antarcticus sp. nov., a psychrophilic bacterium from Antarctica. In: International journal of systematic and evolutionary microbiology. Volume 50, Number 2, March 2000, pp. 715-719, ISSN  1466-5026 . PMID 10758880 .
  9. ↑ Der Kleine Stowasser, Latin-German school dictionary, edited by Dr. Michael Petschenig . B. Freytag Verlag, Munich 1971, ISBN 3-486-13402-7 .
  10. ^ Prokaryotic Nomenclature Up-to-date. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved April 7, 2018 .

Web links

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