Teichonic acids

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Teichonic acids are polymeric building blocks of the cell wall of gram-positive bacteria and can make up 20 to 40% of their cell wall dry matter. They are mostly covalently anchored in the peptidoglycan layer ( murein layer ). Teichonic acids consist either of ribitol-phosphate polymers ( ribitol-teichonic acids ) or of glycerol-phosphate polymers ( glycerol-teichonic acids ), which protrude outwards like a chain.

As lipoteichoic acids are called glycerol teichoic acids, covalently bound to glycolipids of the cell membrane are coupled. These are anchored in the cell membrane and penetrate the entire peptidoglycan layer.

Structural example of a teichonic acid
Structural example of a teichonic acid from Micrococcus species

Teichonic acids perform important functions in the interaction of bacteria with host cells, such as adhesion and so-called virulence factors .

Lipoteichoic acids

Lipoteichoic acids ( LTA ) are mainly found in gram-positive bacteria in which the guanine and cytosine content ( GC content ) of the DNA is less than 50%. In gram-positive bacteria with more than 50% GC content, lipoglycans are usually found instead of lipoteichoic acids. Lipoteichoic acids consist of a hydrophilic chain of alditol phosphates and an amphiphilic glycolipid that acts as a membrane anchor. When Staphylococcus aureus is found Polyglycerolphosphat-LTA. This type of WTA is the most widespread and has also been found in genera of the species Bacillus , Enterococcus , Lactobacillus , Lactococcus , Leuconostoc , Listeria and Streptococcus . The polyglycerol phosphate chain of the LTA from S. aureus is made up of 16-40 1,3-linked glycerol phosphate units and bound to the glycolipid via a phosphodiester bond. The glycerol phosphate residues of most LTA are partially modified with D - alanine esters , and glycosyl substituents are also found in many bacteria. D -alanine esters and glycosyl substituents are also found in S. aureus .

The LTA appears to have important functions in the physiology of the cell wall . Various functions have been proposed, such as the binding of magnesium ions, adhesion to host cells or the regulation of autolysins. The biosynthesis of the LTA appears to be a transmembrane process, since all components are lipid. The composition of the LTA begins with a glycerol phosphate transfer from phosphatidylglycerol to the glycolipid, which serves as a lipid anchor , with phosphatidylglycerol also serving as a glycerol phosphate donor for chain extension. Two glycerol phosphate transferases may also be involved. One that recognizes the glycolipid and a second that is responsible for chain elongation. For every glycerol phosphate that is transferred, a diacylglycerol is created on the inner membrane, which is recycled back to phosphatidylglycerol. Part of the diacylglycerol is used for glycolipid synthesis.

Wall teichoic acids

Wandteichoic acids ( WTA ) are localized in the peptidoglycan. Structurally, they are more complex than the AD. The anchor structure, which is bound to the oxygen of the N -acetylmuramic acid of the peptidoglycan via a phosphodiester bond , consists of one molecule of N -acetylglucosamine , one molecule of N -acetyl-mannosamine and three molecules of glycerol phosphate . Modifications to this anchor structure have been reported, but the Glc N Ac-1-phosphate terminus appears to be the same everywhere. A chain of alternating alditol phosphates, which make up the main part of the WTA, is attached to the anchor structure. The most common are chains of glycerol phosphate and ribitol phosphate units. S. aureus produces a WTA that is composed of ~ 40 ribitol phosphate units, whereas other staphylococci also have glycerol phosphate chains. The ribitol phosphate units are partially modified by N -acetylglucosamine and D -alanine.

Effect on humans

Teichoic acids and lipoteichoic acids are strong exogenous pyrogens , ie they are among the substances that cause a febrile reaction in humans after a bacterial infection by gram-positive bacteria. They are recognized by the toll-like receptor TLR-2 , which is expressed on monocytes , dendritic cells , B and T lymphocytes and macrophages . Furthermore, they ensure the release of cytokines and are therefore one of the main factors in the inflammatory reaction after such an infection.

Because of their antigenic properties, they are also of interest for the production of synthetic vaccines.

swell

  • Thomas Kohler: Investigations into the biosynthesis and interaction of the cell wall teichonic acids of Staphylococcus aureus . 2005.

Individual evidence

  1. ↑ a b H. Hof, R. Dörries: Medical Microbiology. 3rd edition, p. 273, 2004, Georg Thieme Verlag, ISBN 3-13-125313-4 .
  2. ↑ a b c d Fischer, W. (1990).
  3. ↑ JM Ghuysen and R. Hakenbeck (Eds), 1994.
  4. ↑ Fischer 1994.
  5. ↑ Baddiley, J. 1988.
  6. ↑ Fischer, W. 1988.
  7. ^ Deutsch, R., Engel, R. and Tropp, BE 1980
  8. ↑ Brisette, JL, Cabacungan, EA and Pieringer, RA 1986th
  9. ↑ Endl, J., Seidl, HP, Fiedler, F. & Schleifer, KH, 1983.
  10. ↑ Araki, Y. and ITO, e. 1989.
  11. ↑ Mikusova, K., Mikus, M., Besrat, GS, Hancock, I. and Brennan, PJ, 1996.
  12. ^ GG Habermehl, HC Krebs, PE Hammann: Naturstoffchemie. S. 390, 2002, Springer-Verlag, ISBN 3-540-43952-8 .