Extracellular polymeric substances

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Extracellular polymer substances (EPS) are long-chain compounds ( polymers ) that v. a. Formed by microorganisms and released by them into their immediate environment, i.e. they are located extracellularly .

Microbial EPS

The EPS enable a structure of microbial agglomerates such as biofilms and bacterial flakes and represent the main part of the dry matter of these agglomerates (also referred to as 'aggregates') , shape the space between the microorganisms embedded in it and hold the agglomerates together in their three-dimensional arrangement.

Composition of EPS

The microbial EPS mainly consist of polysaccharides (e.g. alginate , cellulose , dextran , levan ), a variety of proteins , lipids , phospholipids , glycoproteins , glycolipids , lipopolysaccharides (LPS) and often extracellular DNA (e-DNA), The polysaccharides often consist of the monosaccharide building blocks of uronic acids such. B. D- glucuronic acid , D- galacturonic acid and D- mannuronic acid . The composition of the EPS microbial agglomerates differ, among other things, depending on the species involved in the biofilm . In the case of the polysaccharides, the compounds that are typical for the species for their surface structures of the cell wall, cell membrane or glycocalyx predominate. Sun can be found in the EPS at staphylococci -Biofilmen responsible for the cell wall of Gram-positive typical bacterial teichoic or the unicellular fungus Candida the chitin . However, polysaccharides are also produced that are not primary membrane or cell wall polysaccharides, e.g. B. the alginate of the Gram-negative bacteria Pseudomonas and Azotobacter or the colanic acid and cellulose, which are typical for some enterobacteria such as Escherichia coli . The ability of the microorganisms to produce EPS and thus to form biofilms differs between the species and can also differ significantly between the strains of a species.

The chemical composition of the EPS also changes depending on the location and environmental conditions. Therefore, large differences are usually found in the EPS composition of the biofilms of microorganisms in the natural and of microorganisms in an artificially created environment . The proportion of polysaccharides in natural habitats is often much lower than in laboratory studies. Microorganisms of a species without EPS are to be distinguished from those with EPS, as they react differently to their environment.

The EPS enable the absorption of water , which can be up to 97% by weight of the EPS matrix. The hydrodynamic conditions thus created in the EPS matrix ultimately enable the absorption of further substances (e.g. minerals , detritus , humin and nutrients ) from the environment. The stability of the EPS is primarily ensured by hydrophobic interactions, cross-linking of multivalent cations , e-DNA and the intricacies of the polysaccharide structures.

Importance of EPS

The EPS determine the conditions for the life of the microorganisms in a biofilm through the hydrophobicity , charge, water content, substance absorption, density , porosity and mechanical stability. The presence of an EPS matrix is ​​associated with some advantages for the life of the microorganisms. A space (biofilm matrix) is created which makes it possible to build synergistic interrelationships between the microorganisms of one or different species , e.g. B. by nutrient and oxygen gradients within the EPS matrix. As a rule, the EPS offer a better supply of usable substrates . Long periods of starvation can be survived through constant adsorption and accumulation of substrates. The EPS provide protection against chemical and mechanical influences such as temperature fluctuations, pollutants , UV radiation and promote the exchange of genes. Due to these properties, phenomena such as increased resistance to chemical substances ( disinfectants , antibiotics and antiseptics ) or the synergistic interactions of different species in corrosion processes ( biocorrosion ) can be explained.

Additional note on terminology

The EPS were formerly referred to as e xtrazelluläre P olysaccharid s (expanded) or as tructure glycocalyx designated. However, since these are not all polysaccharides, these descriptions are considered to be incorrect.

EPS in the broader sense (EPS not of microbial origin)

EPS in mammalian cells is called extracellular matrix (ECM) or intercellular substance , which is produced in particular by cells of the connective tissue . These are v. a. Glycosaminoglycans , proteoglycans as well as glycoproteins and laminins .

EPS in plant cells are not described with a separate term. In plants, the “extracellular matrix” is determined in particular by the structure of the cell wall. Here, among other things can cellulose , hemicellulose , xylose , galactose , fructose , pectins and glycoproteins be involved.

Individual evidence

  1. ↑ IW Sutherland: Exopolysaccharides in biofilms, flocs and related structures . In: Water Science and Technology . 43, No. 6, 2001, pp. 77-86.
  2. ↑ a b S. Schulte, H. Flemming: Causes of the increased resistance of microorganisms in biofilms . In: Chemical Engineer Technology . 78, No. 11, 2006, pp. 1683-1689. doi : 10.1002 / cite.200600088 .
  3. ↑ H.-C. Flemming: Biofouling in water systems - cases, causes and countermeasures . In: Applied Microbiology and Biotechnology . 59, No. 6, 2002, pp. 629-640. doi : 10.1007 / s00253-002-1066-9 .
  4. ↑ a b c d e H.-C. Flemming, J. Wingender: The biofilm matrix . In: Nature reviews . 8, No. 9, 2010, pp. 623-633. doi : 10.1038 / nrmicro2415 .
  5. ^ A b I. W. Sutherland: Biofilm exopolysaccharides: a strong and sticky framework . In: Microbiology . 147, 2001, pp. 3-9.
  6. ^ F. Götz: Staphylococcus and biofilms . In: Molecular Microbiology . 43, No. 6, 2002, pp. 1367-1378. doi : 10.1046 / j.1365-2958.2002.02827.x .
  7. ↑ U. Remminghorst, BHA Rehm: Bacterial alginates: from biosynthesis to applications . In: Biotechnology Letters . 28, No. 21, 2006, pp. 1701-1712. doi : 10.1007 / s10529-006-9156-x .
  8. ↑ G. Stevenson, K. Andrianopoulos, M. Hobbs, PR Reeves: Organization of the Escherichia coli K-12 gene cluster responsible for the production of the extracellular polysaccharide colanic acid. . In: Journal of Bacteriology . 178, No. 16, 1996, pp. 4885-4893. PMC 178271 (free full text).
  9. ↑ X. Zogaj, W. Bokranz, M. Nimtz, U. Romling: Production of Cellulose and Curli Fimbriae by Members of the Family Enterobacteriaceae Isolated from the Human Gastrointestinal Tract . In: Infection and Immunity . 71, No. 7, 2003, pp. 4151-4158. doi : 10.1128 / IAI.71.7.4151-4158.2003 .
  10. ↑ G. Laverty, SP Gorman, BF Gilmore: Biomolecular Mechanisms of Pseudomonas aeruginosa and Escherichia coli Biofilm Formation . In: Pathogens . 3, No. 3, 2014, pp. 596–632. doi : 10.3390 / pathogens3030596 .
  11. ↑ A. Jain, A. Agarwal: Biofilm production, a marker of pathogenic potential of colonizing and commensal staphylococci . In: Journal of microbiological methods . 76, No. 1, 2009, pp. 88-92. doi : 10.1016 / j.mimet.2008.09.017 .
  12. ↑ a b c d H.-C. Flemming, TR Neu, DJ Wozniak: The EPS matrix: the “house” of biofilm cells . In: Journal of bacteriology . 189, No. 22, 2007, pp. 7945-7947. doi : 10.1128 / JB.00858-07 .
  13. ↑ D. de Beer, P. Stoodley, F. Roe, Z. Lewandowski: Effects of biofilm structures on oxygen distribution and mass transport . In: Biotechnology and bioengineering . 43, No. 11, 1994, pp. 1131-1138. doi : 10.1002 / bit.260431118 .
  14. ↑ H.-C. Flemming: Biofouling and biocorrosion - the consequences of unwanted biofilms . In: Chemical Engineer Technology . 67, No. 11, 1995, pp. 1425-1430. doi : 10.1002 / cite.330671103 .
  15. ↑ HT Dinh, J. Kuever, M. Mussmann, AW Hassel, M. Stratmann, F. Widdel: Iron corrosion by novel anaerobic microorganisms . In: Nature . 427, No. 6977, 2004, pp. 829-832. doi : 10.1038 / nature02321 .
  16. ^ S. Ayad, RP Boot-Hanford, MJ Humphries, KE Kadler, CA Shuttleworth: The Extracellular Matrix (Facts Book) . Academic Press, 1998, ISBN 0-12-068911-1 .
  17. ↑ Ray F. Evert: Esau's plant anatomy: meristems, cells and tissues of plants - their structure, function and development. De Gruyter, 2009, ISBN 978-311020592-3 ; P. 61 ( limited preview in Google Book search).