Compatible solutes
In cell biology, compatible solutes are the designations for organic compounds of high solubility in water and low molar mass , which thus influence the osmotic state of a cell, but are electrically neutral at a physiological pH value and are compatible with cell metabolism .
properties
The designation compatible solutes refers to the property of these osmolytes not to interfere with the metabolism even at high osmotically effective cytoplasmic concentrations .
Compatible solutes include compounds from different classes of substances, which are characteristic of the different salt tolerance of the respective organism :
-
Sugar (trehalose and sucrose), and sulfur compounds (e.g. dimethyl sulfoniopropionate ) are typical of non- halophilic and halotolerant microorganisms. Solutes of this group are accumulated by synthesis in cytoplasmic concentrations up to about 500 mM . Trehalose, in particular, is considered a general stress metabolite and is also accumulated by E. coli . When trehalose is formed as a stress metabolite in hyperthermophilic archaea, the main compatible solute that occurs is mostly mannosyl glycerate and di-myo-inositol-phosphate.
- Glucosylglycerol
- Glucosyl glycerate in mycobacteria , some mesophilic bacteria and halophilic archaea
- Mannosyl glycerate in red algae , thermophilic bacteria, and hyperthermophilic archaea
-
Polyols
- Glycerol occurs in halophilic fungi as well as in salt-tolerant plants
- Arabitol occurs in halophilic fungi as well as in salt-tolerant plants
- Inositol occurs in halophilic fungi as well as in salt-tolerant plants
- Cyclic 2,3-bis (di) phosphoglycerate in methanogens
- Diglycerol phosphate in Archaeoglobus fulgidus
- Di-myoinositol-phosphate in hyperthermophilic archaea and bacteria
- Di-mannosyl-di-myo-inositol-phosphate in Thermotoga sp.
-
Amino acids and amino acid derivatives are characteristic of organisms with increased salt tolerance and can be accumulated in concentrations above 500 mM. This includes
- Glutamic acid and β-glutamic acid
- Proline
- the tetrahydropyrimidine derivatives ectoine and hydroxyectoine
- Glycine betaine
- acetylated diamino acids and glutamine derivatives.
The enrichment of the cytoplasmic space with compatible solutes can be done by de novo synthesis or by absorption from the medium. If both options are open, the solute is preferred because it is energetically more favorable. If effective transport systems are available for compatible solutes, the energy required for osmoadaptation is significantly reduced if useful connections are available in the environment. Both mechanisms, de novo synthesis and uptake from the medium, are realized by both halotolerant and halophilic organisms. Efficient glycine betaine transporters could be detected in glycine betaine-producing cyanobacteria. Similar glycine betaine transporter systems were also found in Halorhodospira halochloris and in salt-tolerant and salt-dependent methanogenic archaea.
Individual evidence
- ↑ a b c d e f g h i N. Empadinhas, MS da Costa: Diversity and biosynthesis of compatible solutes in hyper / thermophiles. In: International microbiology: the official journal of the Spanish Society for Microbiology. Volume 9, Number 3, September 2006, pp. 199-206, ISSN 1139-6709 . PMID 17061210 .
- ↑ a b c S. Klähn, M. Hagemann: Compatible solute biosynthesis in cyanobacteria. In: Environmental microbiology. Volume 13, Number 3, March 2011, pp. 551-562, ISSN 1462-2920 . doi : 10.1111 / j.1462-2920.2010.02366.x . PMID 21054739 .
- ↑ a b N. Empadinhas, MS da Costa: To be or not to be a compatible solute: bioversatility of mannosylglycerate and glucosylglycerate. In: Systematic and applied microbiology. Volume 31, Number 3, August 2008, pp. 159-168, ISSN 0723-2020 . doi : 10.1016 / j.syapm.2008.05.002 . PMID 18599240 .
- ↑ a b c S. Hohmann, M. Krantz, B. Nordlander: Yeast osmoregulation. In: Methods in Enzymology . Volume 428, 2007, pp. 29-45, ISSN 0076-6879 . doi : 10.1016 / S0076-6879 (07) 28002-4 . PMID 17875410 .