Streptococcus sobrinus

from Wikipedia, the free encyclopedia
Streptococcus sobrinus
Systematics
Department : Firmicutes
Class : Bacilli
Order : Lactic acid bacteria (Lactobacillales)
Family : Streptococcaceae
Genre : Streptococcus
Type : Streptococcus sobrinus
Scientific name
Streptococcus sobrinus
Coykendall 1983

Streptococcus sobrinus is a type of bacteria from the genus Streptococcus ( German : Streptococci). These are gram-positive bacteria, the cells are facultatively anaerobic , they can live with or without oxygen. Streptococcus sobrinus and the related species Streptococcus mutans are pathogenic and increase the formation of tooth decay in humans. The ability of Streptococcus sobrinus toproduce acids during lactic acid fermentation that attack tooth enamel and the production of glucans is important here . These are polysaccharides that adhere to the surface of the tooth and form a biofilm in which the bacteria can multiply.

Streptococcus sobrinus was initially considered a subspecies of Streptococcus mutans , but was established as a separate species in 1983 . The species includes numerous strains of bacteria . The genome of the strain Streptococcus sobrinus 6715 was completely sequenced in 2003 .

features

Appearance

The cells of Streptococcus sobrinus are cocci-shaped , with a diameter of 0.5  µm . They are arranged in pairs or in chains. Streptococcus sobrinus , like all species of the genus , does not form endospores . The species cannot move on its own, so it is not motile . The Gram stain is positive.

After incubation , the cells grow into colonies of about 1 mm in size on solid culture media containing sucrose . They are rounded, convex colonies with a granulated surface. Often small drops containing glucans can be seen on the surface or at the edge of the colonies. Most bacterial strains show α- hemolysis on blood agar , which can be detected by the green color of the blood.

Growth and metabolism

The metabolism and energy change of Streptococcus sobrinus is chemo - heterotrophic , it does not perform photosynthesis . The species can reproduce in the presence and absence of oxygen , the metabolism is thus facultatively anaerobic . The growth occurs best when the oxygen content is reduced. An atmosphere enriched with carbon dioxide , with 5% CO 2 , is often used for cultivation . The temperatures usually used for cultivation are in the range of 30-40 ° C, so the bacterium is one of the mesophilic organisms. Growth ceases at 10 ° C or below. Although S. sobrinus belongs to the Viridans subgroup of streptococci, it no longer grows at a temperature of 45 ° C, unlike most of the associated species. The cultivation works optimally on tryptone soy agar (TSA) with the addition of yeast extract at a pH value in the neutral range and a temperature of 37 ° C.

S. sobrinus is one of the lactic acid bacteria and can use various carbohydrates for energy in a fermentation . A characteristic of fermentation ( fermentation ) is that the substrates are broken down without oxygen. The typical fermentation product for lactic acid bacteria is lactic acid , which is why this metabolic pathway is called lactic acid fermentation . Since lactic acid or lactate , the lactic acid anion , is the main product of this fermentation, S. sobrinus is counted among the homofermentative species. It is able to utilize the monosaccharides glucose and fructose , the disaccharides sucrose and trehalose as well as the sugar alcohols mannitol and sorbitol with acid formation, whereas this is not the case with the disaccharide melibiose and the trisaccharide raffinose . Other sources indicate that the results for sorbitol, melibiose and raffinose are variable; H. they do not always lead to a positive test result. A positive result for mannitol is confirmed and also listed for the disaccharide maltose .

The formation of extracellular polysaccharides (abbreviated as ecp from the English extracellular polysaccharide ) when sucrose is present is of importance for the pathogenicity . The polysaccharides produced are glucans made up of D- glucose molecules. For S. sobrinus typically is Mutan , a water-insoluble glucan whose glucose units by a α-1,3 glycosidic bond are linked. The name of the polysaccharide was given after the related S. mutans , only later it turned out that S. sobrinus is the producer.

Some enzymes that are used in the metabolism to break down certain substrates are detected as part of a " colorful series " in order to identify a bacterium. S. sobrinus behaves negatively in the catalase and oxidase test . It has the enzyme α-glucosidase , which causes the splitting of α-glucose from glucose chains. He does not have the enzyme urease to urea to exploit. In addition, the enzyme arginine dihydrolase ( EC  3.5.3.6 ) is not present, so that no ammonia is split off from the amino acid arginine . In contrast to S. mutans, it is able to form hydrogen peroxide (H 2 O 2 ). The Voges-Proskauer test is positive, so acetoin is formed. He is resistant to bacitracin .

Chemotaxonomy

The murein layer in the cell wall contains the diamino acid L - lysine as a diagnostically important amino acid in position 3 of the peptide bridge. The peptidoglycan type is A3α, in addition to lysine, the amino acids glycine and L - alanine are also present.

In order to subdivide the streptococci, their hemolytic behavior and existing antigens are assessed. Streptococcus sobrinus belongs to the Viridans subgroup, which is also known as "oral streptococci" according to their habitat . They are not assigned to the Lancefield groups , which are used to classify the β-hemolytic species. Instead, serological tests are carried out with the so-called Bratthall antisera . S. sobrinus includes serotypes d and g, the type strain not reacting with antibodies of group d or group g.

genetics

The genome of the strain Streptococcus sobrinus 6715 was completely sequenced in 2003 . The bacterial strain used for the study was isolated from the oral cavity of a human. Since then, more than 50 other bacterial strains have been genetically examined, including the type strain S. sobrinus ATCC 33478. Its genome size is 2096 kilobase pairs (kb), which corresponds to about 45% of the genome size of Escherichia coli . Proteins are annotated in 2016 . The result of the sequencing shows a GC content (the proportion of the nucleobases guanine and cytosine ) in the bacterial DNA of 43.5  mol percent for the type strain and between 44 and 46 mol percent for the species. This is comparable to the other Streptococcus species whose GC content in the DNA is between 34 and 46 mol percent. For phylogenetic studies, the nucleotides of the 16S rRNA, a typical representative of ribosomal RNA for prokaryotes , were also determined . This led to a further subdivision of the Viridans group.

In 2012 an extensive comparison of the type strain with the genomes of several strains of S. mutans was carried out . The participating scientists examined the signal transduction system , which is important for bacteria to detect changes in the environment and react to them in order to survive. The signal transduction system consists of two components and is abbreviated as TCS ( two component system ). The two components are the histidine kinase (HK), which acts as a transmembrane sensor, and a response regulator present in the cytoplasm (abbreviated as RR from the English response regulator ). The genes that code for these proteins are usually adjacent to an operon . Analysis of the orthologous genes of the ten bacterial strains examined shows that there are 18 TCS clusters , eight of which are TCS clusters in all strains. However, the HK and RR components differ in their functions so absent in S. sobrinus the TCS, presumably for acid tolerance and fructan - catabolism contribute. These differences are interpreted to the effect that there are different survival strategies of S. sobrinus and S. mutans to the rapidly changing conditions in the oral cavity, which can contribute to an understanding of the pathogenicity.

Occurrence

The habitat of Streptococcus sobrinus is the oral cavity of humans, which is why it is counted among the " oral streptococci". In particular, it can be found on the surface of the teeth . Findings in animals, especially in experimental animals , are not considered to be certain, since the differentiation of the Streptococcus species is laborious, especially the phenotypically similar species that belong to the Mutans group. In addition, the system has changed several times in the second half of the 20th century.

Systematics

External system

The type Streptococcus sobrinus belongs to the family of Streptococcaceae in the order of Lactobacillales (lactic acid bacteria) in the department of Firmicutes . In addition to the genus Streptococcus , the family also includes the genera Lactococcus and Lactovum . The systematics of streptococci changed several times in the second half of the 20th century, initially a division into three genera was made under the aspects of pathogenicity, occurrence ( Enterococcus ) or use in the dairy industry . The species remaining in the genus Streptococcus were assigned to the Pyogenes subgroup or the Viridans subgroup according to their pathogenicity and existing antigens . The latter are also known as "oral streptococci". Phylogenetic studies at the end of the 20th century show a division into four different subgroups within this group, each of which comprises several species and which are named after a typical species. Streptococcus sobrinus belongs to the Mutans group, which was previously described as a single unit and referred to as "Mutans streptococci".

Internal system

Streptococcus sobrinus was initially identified as its subspecies S. mutans subsp. In 1974 by Alan L. Coykendall during a detailed study of various strains of S. mutans . sobrinus . In addition to differences in the GC content, there was also a low level of agreement with the type strain in experiments on DNA-DNA hybridization . As a result, Coykendall proposed in 1977 to raise the subspecies to the rank of a separate species. At this point, however, a type strain of the new species was not available in a common collection of microorganisms , one of the rules of the bacteriological code . Therefore, when the bacterial nomenclature was reorganized in 1980, the species was not included in the Approved Lists of Bacterial Names . With the definition of a type strain and its deposit in several strain collections, he proposed the designation S. sobrinus nom in 1983 . rev. (nom. rev. for nomen revictum , Latin for "resumed name"), which was recognized. The bacterial strain S. sobrinus SL1 is the type strain of the species and has been deposited in the collections of microorganisms in the USA (as ATCC 33478), Great Britain (as NCTC 12279) and Germany (at the DSMZ as DSM 20742). As a result of this first description , which was not successful from the start , the species is referred to as Streptococcus sobrinus (ex Coykendall 1974) Coykendall 1983 by the author's name. Streptococcus mutans subsp. sobrinus is considered a synonym . In addition to the type strain, over 50 bacterial strains are known, most of which were and are the target of genetic studies (as of 2014).

etymology

The genus name Streptococcus refers to the spherical cells strung together in a chain (compare cocci ). The species name S. sobrinus contains the Latin word sobrinus , with which a relative, the maternal cousin , is referred to. This is to indicate the relationship between this species and S. mutans .

Medical importance

Pathogenicity

Streptococcus sobrinus is one of the most important causes of caries and is therefore called pathogenic ("pathogenic"). It is assigned to risk group 2 by the Biological Agents Ordinance in conjunction with the TRBA ( Technical Rules for Biological Agents) 466 .

The pathogen has a number of special properties ( virulence factors ) that assign it a major role in the formation of bacterial plaque :

  • Glucan-mediated adherence: S. sobrinus forms extracellular glucans from the sucrose ( table sugar) contained in the chyme , with which the bacteria are able to adhere to the tooth enamel . So a biofilm is formed on the surfaces of the teeth . The formation of glucans is mediated by glucosyltransferases (enzymes for the transfer of glucose units). The activity of the glucosyltransferases is the benchmark for the virulence of the pathogen. As a result, S. sobrinus is able to colonize smooth tooth surfaces, and the biofilm it produces offers S. mutans the opportunity to multiply there.
  • Lactic acid production: S. sobrinus breaks down carbohydrates into lactic acid (lactate) in the course of a fermentative energy metabolism. The resulting drop in pH leads to demineralization of the tooth substance.
  • Acid tolerance: By actively excreting protons , S. sobrinus is able to survive even in a strongly acidic environment.

Studies with genetically modified bacterial strains of S. sobrinus and S. mutans confirm the influence of these virulence factors. Mutants with reduced production of the ecp show in animal experiments a reduced potential to induce caries. The same applies if the bacteria produce less acid or are less acid-tolerant.

Diseases

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

Streptococcus sobrinus and the related species Streptococcus mutans increase the formation of tooth decay in humans. The biofilm is a mixture of sugar and plaque and forms a suitable environment for the growth of S. sobrinus , which is even more closely linked to the prevalence of caries than S. mutans . S. sobrinus is also responsible for early childhood tooth decay, which causes much of the tooth damage and toothache in children. Children usually acquire S. sobrinus strains from their mothers, but the relatively high consumption of sugar by minors facilitates the growth of bacteria and promotes the onset of early childhood caries. S. sobrinus has also been detected on the teeth of rats.

swell

literature

  • Jeremy M. Hardie, Robert A. Whiley: The Genus Streptococcus - Oral (Chapter 1.2.2) . In: Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt (eds.): The Prokaryotes. A Handbook on the Biology of Bacteria, Volume 4: Bacteria: Firmicutes, Cyanobacteria . 3. Edition. Springer-Verlag, New York 2006, ISBN 978-0-387-25494-4 , pp. 76-107 , doi : 10.1007 / 0-387-30744-3_2 .
  • Michael T. Madigan, John M. Martinko, Jack Parker: Brock Microbiology. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 978-3-8274-0566-1 .

Individual evidence

  1. ↑ a b c d e f g h i j k l Alan L. Coykendall: Streptococcus sobrinus nom. rev. and Streptococcus ferus nom. rev .: Habitat of These and Other Mutans Streptococci. In: International Journal of Systematic Bacteriology. Volume 33, No. 4, October 1983, pp. 883-885, doi : 10.1099 / 00207713-33-4-883 .
  2. ^ Richard R. Facklam: Physiological differentiation of viridans streptococci. In: Journal of clinical microbiology. Vol. 5, No. 2, February 1977, pp. 184-201, PMID 845245 . PMC 274561 (free full text).
  3. ↑ Jeremy M. Hardie, Robert A. Whiley: The Genus Streptococcus - Oral. In: The Prokaryotes. A Handbook on the Biology of Bacteria, Volume 4: Bacteria: Firmicutes, Cyanobacteria. Edited by M. Dworkin, S. Falkow, E. Rosenberg, K.-H. Schleifer, E. Stackebrandt. 3. Edition. Springer Verlag, New York 2006, ISBN 978-0-387-25494-4 , pp. 77-79.
  4. ↑ a b Streptococcus sobrinus 6715. In: Website Genomes Online Database (GOLD). Retrieved July 9, 2014 .
  5. ↑ a b c d e f Michael T. Madigan, John M. Martinko, Jack Parker: Brock Mikrobiologie. German translation edited by Werner Goebel, 1st edition. Spectrum Akademischer Verlag GmbH, Heidelberg / Berlin 2000, ISBN 978-3-8274-0566-1 , pp. 559-563, 868-870.
  6. ↑ Catalog of microorganisms. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved July 9, 2014 .
  7. ↑ a b c d e f g h J. M. Hardie, RA Whiley: The Genus Streptococcus - Oral. Pp. 80-83.
  8. ↑ a b c J. M. Hardie, RA Whiley: The Genus Streptococcus - Oral. Pp. 92-94.
  9. ↑ K.-H. Schleifer, O. Kandler: Peptidoglycan types of bacterial cell walls and their taxonomic implications. In: Bacteriological reviews. Volume 36, No. 4, December 1972, pp. 407-477, PMID 4568761 . PMC 408328 (free full text). (Review).
  10. ↑ a b c d Streptococcus sobrinus. In: National Center for Biotechnology Information (NCBI) Genome website. Retrieved July 9, 2014 .
  11. ↑ L. Song, P. Sudhakar et al. a .: A genome-wide study of two-component signal transduction systems in eight newly sequenced mutans streptococci strains. In: BMC genomics. Volume 13, April 2012, p. 128, doi : 10.1186 / 1471-2164-13-128 . PMID 22475007 . PMC 3353171 (free full text).
  12. ↑ a b J. M. Hardie, RA Whiley: The Genus Streptococcus - Oral. P. 76.
  13. ↑ a b c d Jean Euzéby, Aidan C. Parte: Genus Streptococcus. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved July 8, 2014 .
  14. ↑ AL Coykendall: Four types of Streptococcus mutans based on their genetic, antigenic and biochemical characteristics. In: Journal of general microbiology. Volume 83, No. 2, August 1974, pp. 327-338, PMID 4427102 .
  15. ^ AL Coykendall: Proposal to Elevate the Subspecies of Streptococcus mutans to Species Status, Based on Their Molecular Composition. In: International Journal of Systematic Bacteriology. Volume 27, No. 1, January 1977, pp. 26-30, doi : 10.1099 / 00207713-27-1-26 .
  16. ↑ Approved Lists of Bacterial Names . In: VBD Skerman, Vicki McGowan, PHA Sneath (Eds.): International Journal of Systematic Bacteriology . tape 30 , no. 1 , 1980, p. 225-420 , doi : 10.1099 / 00207713-30-1-225 ( PDF, 17.0 MB [accessed April 13, 2014]). PDF, 17.0 MB ( Memento of the original from January 22, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / ijs.sgmjournals.org
  17. ↑ a b Taxonomy Browser Streptococcus sobrinus. In: National Center for Biotechnology Information (NCBI) website . Retrieved July 10, 2014 .
  18. ↑ TRBA (Technical Rules for Biological Agents) 466: Classification of prokaryotes (Bacteria and Archaea) into risk groups. In: Website of the Federal Institute for Occupational Safety and Health (BAuA). April 25, 2012, p. 212 , accessed April 30, 2014 .
  19. ↑ a b c Friedrich Burkhardt : Microbiological diagnostics. Bacteriology, mycology, virology, parasitology . Thieme, 2009, ISBN 978-3-13-743602-7 , p. 323 .