The role of this transporter appears to be recovery of ectoine leaked from the cell. However, they balance the high K + by using different ratios of organic polyanions. The model predicts that alanine should cause an increase in Na influx and the ratio of this extra Na flux to alanine flux should vary with Na concentration. Organisms adapt to high external salinity by accumulating osmolytes, and the same solutes accumulated in vivo can also affect stability of microorganisms to thermal stress. This model, although derived from the general model, is very complicated so that little is gained from presenting explicitly the standard parameters. Evolution of sucrose synthesisPlant Physiol 2002;128:1490—1500.
Some of these transporters are very specific and serve to retrieve any solute released by cells. Thus, to avoid lysis under low-osmolarity or dehydration under high-osmolarity growth conditions, cells must possess active mechanisms that permit timely and efficient adaptation to changes in environmental osmolarity. The change of the latter value is, however, small and may hardly be noticeable. The overall transport rate is strongly limited by the mobility of the unloaded carrier, which is mostly in the less mobile Biochim. The peptide backbone plays a dominant role in protein stabilization by naturally occurring osmolytesBiochemistry 1995;34:12884—12891.
Solutions perfused included distilled water Ringers solution and 1% glucose-Ringers solution. In a previous paper kinetic equations of secondary active transport by cotransport have been derived. A double reciprocal plot of the sodium-dependent component of glycine entry against Na+ 2 also gives a straight line, as though two sodium ions are cosubstrates with glycine at some step in the entry process. The addition of a negative charge is accomplished with carboxylate, phosphate, and sulfate groups. The coupling may occur in different ways, either by increasing the affinity of the carrier to the transported solute or by increasing the velocity of the carrier-solute complex, or by both effects at the same time. Detection of the osmoregulator betaine in methanogensAppl Environ Microbiol 1990;56:563—565. However, when grown at 280 atm, β-hydroxybutyrate and polymers of this solute accumulate and become the major solutes.
With the same electrical potential difference co-transport is as a rule faster if the ternary complex rather than the empty carrier is charged. This organism has a large number of potential biotechnology uses many based on its ability to use uncommon carbon sources , one of which is the production of glucosylglycerol. In order to study the specific modifying effects mentioned above and the con- ditions under which these may lead to coupling by co- and counter-transport, we have started with a general model, in which the two effects are present at the same time. Incubation in Na-free media reduced the mean O2-uptake by 44. Using the initial rate of uptake of the test amino acid 2-aminoisobutyrate as a sensitive monitor of the electrical potential at constant cation distribution between cell and medium, a procedure has been devised to split the overall electrical potential into the diffusional and the pump component. Using this method we have demonstrated that the serosa-to-mucosa flux of Na may be attributed to passive diffusion with no evidence for the presence of carrier-mediated exchange diffusion or the influence of solvent-drag.
This restriction appears reasonable, particularly if one takes into account that, owing to the cytologic heterogeneity of the intestinal epithelium, different types of cells might be involved to different degrees in secretion. These cells accumulate both the anion mannosylglycerate and the neutral α-mannosylglyceramide. For example, modified polyols and carbohydrates are often used by cells that grow at high temperatures as well as high salt. But since this error tends to diminish with increasing pump activity, the true p. In sprue patients glucose sodium and chloride all tended to be transported in equimolar proportions only in the distal region of the gut whereas in normal subjects these elements tended to be transported in equimolar proportions across all regions of the small intestine. Protein hydration, thermodynamic binding, and preferential hydrationBiochemistry 2002;41:13473—13482. Sulfate groups occur in biological molecules in both carbohydrate e.
Innocent, Daniel Heine, Mahmoud Al Bassam, Sarah F. Worsley, Felix Trottmann, Elaine H. Roles of N-acetylglutaminylglutamine amide and glycine betaine in adaptation of Pseudomonas aeruginosa to osmotic stressAppl Environ Microbiol 1993;59:473—478. The respiratory quotient was 0. Betaine Betaine transport is common to a wide variety of halotolerant and halophilic organisms, both bacteria and archaea. Li significantly enhances alanine influx in the absence of Na. In a recent study, the ability of betaine to act as a cryo-protectant during freezing of diverse bacteria was examined.
Finally, the usual assumption of symmetry has been omitted, so that the various parameters important for transport and activation may be different on each side of the membrane. Both enantiomorphs of alanine were absorbed against a concentration gradient and in 60 min little breakdown or incorporation of the L-enantiomorph occurred in the tissue. Synthesis of glycine betaine from exogenous choline in the moderately halophilic bacterium Halomonas elongataAppl Environ Microbiol 1998;64:4095—4097. The influx of 22N+ has also been measured under similar conditions in the presence of Tris+ and K+. Kohlenhydrate in der Form von Mono-, Oligo- und insbesondere Polysacchariden stellen die Hauptenergiequelle in der menschlichen Ernährung dar.
Yet the enzymes responsible for the synthesis of other solutes notably the neutral dipeptide and derivatized amino acid, α-diglycerol phosphate, and sulfotrehalose have not been explored. Chloride is the most prevalent inorganic anion in halophiles that do not accumulate organic anions. Biosynthesis of di- myo-inositol-1,1'-phosphate, a novel osmolyte in hyperthermophilic archaeaJ Bacteriol 1998;180:3785—3792. Inorganic cations K + and in some cells Na + are often key players in osmotic balance and the osmotic response. Diversity of halophilic microorganisms: environments, phylogeny, physiology, and applicationsJ Ind Microbiol Biotechnol 2002;28:56—63. Indeed, at lower external NaCl, many bacteria including H.
In other words, the equilibrium constants Li , the permeability constants P lx, P2x, etc. Net mucosal-to-serosal water transport and water retention within the tissue were simultaneously measured in the isolated, everted rat jejunum and ileum along with time. For example, in halotolerant Brevibacterium sp. Instead, many bacterial and archaeal cells synthesize and accumulate a few zwitterionic molecules derived from amino acids as compatible solutes. However, supplying cells with betaine precursors does not necessarily alter the distribution of osmolytes. However, some of the more uncommon solutes raise interesting questions.