Osmoprotectant

Compatible solutes are organic compounds. They have a low molar mass, are at physiological pH electrically neutral, but polar, and are characterized by a high solubility in water. The term compatible solutes describes as not to interfere with the cell metabolism the property of osmolytes, even at high cytoplasmic concentrations. Compatible solutes belong to different classes of compounds, which are characteristic of the different salt tolerance of the respective organisms:

  • Sugar ( sucrose and trehalose ) and sulfur compounds (e.g. Dimethylsulfoniopropionat ) are not typical of halophilic and halotolerant microorganisms. Solutes of this group are accumulated by synthesis in cytoplasmic concentrations of up to about 500 mM. Particularly, trehalose is regarded as a general Stressmetabolit and accumulated by E. coli.
  • Polyols ( glycerol, arabitol, inositol ) occur in halophilic fungi as well as in salt - tolerant plants
  • Amino acids and amino acid derivatives are characteristic of organisms with increased salt tolerance and can be accumulated in concentrations above 500 mM. These include proline,
  • The tetrahydropyrimidine ectoine and hydroxyectoine,
  • Glycine betaine,
  • Acetylated diamino acids and glutamine derivatives.

The accumulation is performed by de novo synthesis and by uptake from the medium. The inclusion of the solutes, when both options are open, preferred because it is energetically more favorable. Standing transport systems for compatible solutes available, the energy is reduced significantly, which must be spent on Osmoadaptation once useful compounds in the environment are available. Both mechanisms, de novo synthesis and uptake from the medium can be realized both of halotolerant and halophilic organisms. So efficient glycine betaine transporter could be detected in glycine betaine -producing cyanobacteria. Similar glycine betaine transporter systems could be found in Halorhodospira halochloris and in salt - tolerant and salt- dependent methanogenic archaea.

  • Material
  • Microbiology
  • Biomolecule
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