Filtern
Dokumenttyp
- Zeitschriftenartikel (2)
- Buchkapitel (1)
- Vortrag (1)
Sprache
- Englisch (4)
Referierte Publikation
- nein (4) (entfernen)
Schlagworte
- Ectoine (4) (entfernen)
Organisationseinheit der BAM
Eingeladener Vortrag
- nein (1)
The halophilic bacterium Halomonas elongata takes up the compatible solute ectoine via the osmoregulated TRAP transporter TeaABC. A fourth orf (teaD) is located adjacent to the teaABC locus that encodes a putative universal stress protein (USP). By RT-PCR experiments we proved a cotranscription of teaD along with teaABC. Deletion of teaD resulted in an enhanced uptake for ectoine by the Transporter TeaABC and hence a negative activity regulation of TeaABC by TeaD. Atranscriptional regulation viaDNA binding could be excluded. ATP binding to native TeaD was shown by HPLC, and the Crystal structure of TeaD was solved in complex with ATP to a resolution of 1.9 A ° by molecular replacement. TeaD forms a dimer-dimer complex with one ATP molecule bound to each monomer, which has a Rossmann-like R/β overall fold. Our results reveal an ATP-dependent oligomerization of TeaD, which might have a functional role in the regulatory mechanism of TeaD. USP-encoding orfs, which are located adjacent to genes Encoding for TeaABC homologues, could be identified in several other organisms, and their physiological role in balancing the internal cellular ectoine pool is discussed.
Only a few myxobacteria are known to date that are classified as marine, owing to their salt dependency. In this study, the salt tolerance mechanism of these bacteria was investigated. To this end, a growth medium was designed in which the mutated Escherichia coli strain BKA13 served as sole food source for the predatory, heterotrophic myxobacteria. This enabled measurement of the osmolytes without any background and revealed that the closely related strains Enhygromyxa salina SWB007 and Plesiocystis pacifica SIR-1 developed different strategies to handle salt stress. Ple. pacifica SIR-1, which was grown between 1 and 4% NaCl, relies solely on the accumulation of amino acids, while Enh. salina SWB007, which was grown between 0.5 and 3% NaCl, employs, besides betaine, hydroxyectoine as the major compatible solute. In accordance with this analysis, only in the latter strain was a locus identified that codes for genes corresponding to the biosynthesis of betaine, ectoine and hydroxyectoine.
The compatible solute ectoine is a versatile protectant synthesized by many prokaryotes. It is used as an osmolyte helping microorganisms to maintain an osmotic equilibrium. In addition, ectoine acts as a stabilizer and protects proteins, membranes and whole cells against detrimental effects such as freezing and thawing, drying and high temperatures. Its protective effect is explained by the preferential exclusion model, which postulates that ectoine does not directly interact with biomolecules but is excluded from their surface. Interestingly, details on the interaction of ectoine with DNA are still unknown. Therefore, we studied the influence of ectoine on DNA and the mechanisms by which ectoine protects DNA against ionizing radiation. To emulate biological conditions, we used a sample holder comprising a silicon chip with a Si3N4 membrane, which allows for electron irradiation of DNA in aqueous solution. Analysis by atomic force microscopy revealed that without ectoine, DNA was damaged by irradiation with a dose of 1,7 +/-0,3 Gy. With ectoine, DNA remained undamaged, even after irradiation with 15 Gy. Simulations with dsDNA and ectoine in water revealed a preferential binding of the zwitterionic ectoine to the negatively charged DNA. According to the simulations, binding of ectoine will destabilize dsDNA. Destabilizing is probably caused by the transition of B-DNA to A-DNA and will reduce the DNA melting temperature, which was experimentally proven. The preferential binding provides a stable ectoine shell around DNA, which allows ectoine to reduce OH-radicals and electrons near the DNA and thereby mitigating the damaging effect of ionizing radiation.
The compatible solute ectoine: protection mechanisms, strain development, and industrial production
(2020)
Bacteria, Archaea, and Eukarya can adapt to saline environments by accumulating compatible solutes in order to maintain an osmotic equilibrium. Compatible solutes are of diverse chemical structure (sugars, polyols, amino acid derivatives) and are beneficial for bacterial cells not only as osmoregulatory solutes but also as
protectants of proteins by mitigating detrimental effects of freezing, drying, and high temperatures. The aspartate derivative ectoine is a widespread compatible solute in Bacteria and possesses additional protective properties compared with other compatible solutes and stabilizes even whole cells against stresses such as ultraviolet radiation or cytotoxins. Here, it is our intention to go beyond a simple description of effects, but to depict the molecular interaction of ectoine with biomolecules, such as proteins, membranes, and DNA and explain the underlying principles. The stabilizing properties of ectoine attracted industry, which saw the potential to market ectoine
as a novel active component in health care products and cosmetics. In joint efforts of industry and research, a large-scale fermentation procedure has been developed with the halophilic bacterium Halomonas elongata used as a producer strain. The development and application of ectoine-excreting mutants from H. elongata (“leaky” mutants) allow for the annual production of ectoine on a scale of tons. The details of
the strain development and fermentation processes will be introduced.