Osmoadaptation and osmoregulation in archaea

Roberts, Mary F.

doi:10.2741/roberts

Cited by 56 publications

(32 citation statements)

References 82 publications

(32 reference statements)

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“…Hence, the activity of the salt-induced Kcs in D. salina may be required, alongside additional activities, to modify membranes of the endoplasmic reticulum and/or Golgi apparatus so as to optimize vesicular transport in cells grown in high salinity. Adaptations of this sort are not likely to be unique to D. salina because intracellular accumulation of inorganic or organic solutes is a ubiquitous salt-adaptive, osmoregulatory response in taxonomically varied organisms (Roberts, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…The most pronounced biochemical change in the intracellular milieu is the accumulation of high concentrations of glycerol (in excess of 4.0 m) that osmotically balance the external high salinity. Glycerol is generally thought to be fully compatible with the stability and function of cellular components (Roberts, 2000). Yet, one cannot dismiss the possibility that some cellular components may not operate optimally in the presence of such high levels of glycerol and need to D. salina cells collected from 121 cultures grown to ϳ10 6 cells mL Ϫ1 in the indicated NaCl concentrations were used to isolate fraction 1, containing microsomes and plasma membrane, and fraction 2, containing purified plasma membrane, as detailed in "Materials and Methods" and "Results."…”

Section: Discussionmentioning

confidence: 99%

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Salt Induction of Fatty Acid Elongase and Membrane Lipid Modifications in the Extreme Halotolerant Alga Dunaliella salina

et al. 2002

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In studies of the outstanding salt tolerance of the unicellular green alga Dunaliella salina, we isolated a cDNA for a salt-inducible mRNA encoding a protein homologous to plant β-ketoacyl-coenzyme A (CoA) synthases (Kcs). These microsomal enzymes catalyze the condensation of malonyl-CoA with acyl-CoA, the first and rate-limiting step in fatty acid elongation. Kcs activity, localized to a D. salina microsomal fraction, increased in cells transferred from 0.5 to 3.5 m NaCl, as did the level of thekcs mRNA. The function of the kcsgene product was directly demonstrated by the condensing activity exhibited by Escherichia coli cells expressing thekcs cDNA. The effect of salinity on kcsexpression in D. salina suggested the possibility that salt adaptation entailed modifications in the fatty acid composition of algal membranes. Lipid analyses indicated that microsomes, but not plasma membranes or thylakoids, from cells grown in 3.5 mNaCl contained a considerably higher ratio of C18 (mostly unsaturated) to C16 (mostly saturated) fatty acids compared with cells grown in 0.5m salt. Thus, the salt-inducible Kcs, jointly with fatty acid desaturases, may play a role in adapting intracellular membrane compartments to function in the high internal glycerol concentrations balancing the external osmotic pressure.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Salt Induction of Fatty Acid Elongase and Membrane Lipid Modifications in the Extreme Halotolerant Alga Dunaliella salina

et al. 2002

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“…We show that this results in a considerable delay of the response of cells to osmotic shocks, and to an extreme cell-to-cell stochastic variations in their response times, despite the large numbers of channels present in each cell. We discuss how our results are relevant for E. coli.Abrupt changes in the osmolarity of the environment is a hazard most organisms are subject to at one time or another [1][2][3][4][5][6]. A sudden drop in osmolarity (an osmotic shock ) will cause water to rush into a living cell, and requires an immediate response by the cell to prevent it from getting damaged or undergoing lysis from the increased tension on the cellular membrane.…”

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confidence: 99%

Cooperative response and clustering: Consequences of membrane-mediated interactions among mechanosensitive channels

2017

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Mechanosensitive (MS) channels are ion channels which act as cells' safety valves, opening when the osmotic pressure becomes too high and making cells avoid damage by releasing ions. They are found on the cellular membrane of a large number of organisms. They interact with each other by means of deformations they induce in the membrane. We show that collective dynamics arising from the inter-channel interactions lead to first and second-order phase transitions in the fraction of open channels in equilibrium relating to the formation of channel clusters. We show that this results in a considerable delay of the response of cells to osmotic shocks, and to an extreme cell-to-cell stochastic variations in their response times, despite the large numbers of channels present in each cell. We discuss how our results are relevant for E. coli.Abrupt changes in the osmolarity of the environment is a hazard most organisms are subject to at one time or another [1][2][3][4][5][6]. A sudden drop in osmolarity (an osmotic shock ) will cause water to rush into a living cell, and requires an immediate response by the cell to prevent it from getting damaged or undergoing lysis from the increased tension on the cellular membrane. Mechanosensitive channels (or MS channels) are ion channels located on the cell membrane, which open when the membrane tension becomes too high [7,8], and play a crucial role in the cell's defence mechanism against osmotic shocks [9,10]. They act as safety valves, releasing ions and decreasing the osmotic pressure and the membrane tension. Mechanosensitive channels are found in many organisms, and have been well characterised in the bacterium E. coli [11-13].The cellular membrane in which the mechanosensitive channels are inserted is a lipid bilayer. The interior of the bilayer is hydrophobic, making it energetically favourable for it to thicken or compress to match the hydrophobic parts of the channel proteins inserted in the membrane [14]. This results in a deformation profile around each channel, with the thickness of the bilayer being a function of position. This deformation mediates a shortrange effective force between two neighbouring channels, similar to the force between two nearby corks floating on water, which interact through the deformation they induce on the surface of water. This interaction can be attractive or repulsive, depending on the shapes of the two molecules. Furthermore, a theoretical analysis suggests that the interaction between two neighbouring channels lowers the tension needed to open them during an osmotic shock [15], raising the possibility that their function could be influenced by their spatial distribution on the membrane (as already noticed for other membrane proteins [16,17]). This is reinforced by the fact that the channels' attractive forces suggest that they may agglomerate into clusters. Our goal in this paper is to determine the consequences that the inter-channel interaction has on the dynamics of this system, focusing in particular on channel clustering and its con...

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“…Generally, these halophilic proteins maintained their stability and activity by increased ion binding and glutamic acid content, both allowing the protein inventory to compete for water at high salt (9). Further, in moderate halophiles, compatible solutes such as glycine, betaine and hydroxyectoine are known to protect protein, at high salt concentration (13,14,17,21,22).…”

Section: Resultsmentioning

confidence: 99%

Characterization and stability of extracellular alkaline proteases from halophilic and alkaliphilic bacteria isolated from saline habitat of coastal Gujarat, India

Dodia¹,

Joshi²,

Patel³

et al. 2006

Braz. J. Microbiol.

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The present study deals with the isolation and characterization of the moderately halophilic-alkaliphilic bacteria from a saline habitat in western India. Eight different bacterial strains were isolated using enrichment techniques at 20% (w/v) NaCl and pH 10. The isolates exhibited diversity towards gram ' s reaction, colony and cell morphology. They were able to grow and produce alkaline protease over a broad range of NaCl, 5-20% (w/v) and pH, 8-10. None of the isolates could grow at pH 7, and one could not grow even at pH 8. Crude and partially purified proteases from strain S5 were subjected to characterization with reference to pH, salt stability and protein folding. Optimum protease activity and stability was recorded at 10% salt and pH 9-9.5. Denaturation kinetics of S5 alkaline protease along with a reference protease was studied at 8M urea followed by renaturation. The S5 alkaline protease could be partially renatured up to 32% of the original activity. Despite of the fact that all the 8 isolates were from the same site, they displayed significant diversity with respect to their salt requirement for growth and enzyme secretion. While the effect of pH was less demarcated on growth, the protease production was significantly affected. Isolate S 5 produced substantial amount of halotolerant and alkaline protease. The activity and stability of the alkaline protease in a broader range of pH and salt would definitely make this enzyme an important candidate for various industrial applications.

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Osmoadaptation and osmoregulation in archaea

Cited by 56 publications

References 82 publications

Salt Induction of Fatty Acid Elongase and Membrane Lipid Modifications in the Extreme Halotolerant Alga Dunaliella salina

Salt Induction of Fatty Acid Elongase and Membrane Lipid Modifications in the Extreme Halotolerant Alga Dunaliella salina

Cooperative response and clustering: Consequences of membrane-mediated interactions among mechanosensitive channels

Characterization and stability of extracellular alkaline proteases from halophilic and alkaliphilic bacteria isolated from saline habitat of coastal Gujarat, India

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