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Salt acclimation of cyanobacteria and their application in biotechnology.

Pade N, Hagemann M - Life (Basel) (2014)

Bottom Line: Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes.Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood.This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water.

View Article: PubMed Central - PubMed

Affiliation: Institut für Biowissenschaften, Abteilung Pflanzenphysiologie, Universität Rostock, Albert-Einstein-Str. 3, D-18059 Rostock, Germany. nadin.pade@uni-rostock.de.

ABSTRACT
The long evolutionary history and photo-autotrophic lifestyle of cyanobacteria has allowed them to colonize almost all photic habitats on Earth, including environments with high or fluctuating salinity. Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes. Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood. Here, we briefly review recent advances in the identification of salt acclimation processes and the essential genes/proteins involved in acclimation to high salt. This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water. In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

No MeSH data available.


Comparison of growth of the Synechocystis sp. PCC 6803 wild type and the mutant defective in the gene for glucosylglycerol (GG) synthesis (ggpS) in medium supplemented with 3.5% NaCl. The wild type can grow, whereas the mutant cannot grow at this salinity. Supplementation of the salt medium with 5 mM GG restores the salt tolerance of the mutant, because the compatible solute is taken up by the mutant cells and becomes accumulated to levels comparable to wild-type cells.
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life-05-00025-f002: Comparison of growth of the Synechocystis sp. PCC 6803 wild type and the mutant defective in the gene for glucosylglycerol (GG) synthesis (ggpS) in medium supplemented with 3.5% NaCl. The wild type can grow, whereas the mutant cannot grow at this salinity. Supplementation of the salt medium with 5 mM GG restores the salt tolerance of the mutant, because the compatible solute is taken up by the mutant cells and becomes accumulated to levels comparable to wild-type cells.

Mentions: Heterotrophic bacteria preferentially accumulate compatible solutes from the environment. Many transport systems have been characterized in a variety of heterotrophic bacteria [12,53,54,55]. The activity and expression of these uptake systems are controlled by the salinity of the external medium [56]. It is also known that E. coli and B. subtilis can accumulate many more compatible solutes via transport from the environment than they can synthesize de novo. Many of the well-characterized transport systems belong to the group of primary active ATP-binding-cassette-(ABC)-type transporters [11]. Despite a preference for de novo synthesis of compatible solutes, cyanobacteria also possess transporters for compatible solutes. Initially, an uptake system for glycine betaine was identified, which occurred only in strains able to synthesize this osmolyte de novo [57,58]. Subsequently, the existence of an active-transport system for exogenous GG was found in the cyanobacterium Synechocystis sp. PCC 6803, which also transports the solutes sucrose and trehalose, albeit with a lower affinity [59,60]. The transporter belongs to the ABC transporter family and consists of four subunits, three of which are coded by genes organized in an operon [61,62]. The identification of these genes allows the generation of mutants to analyze the function of the transporter. Interestingly, a transport mutant of Synechocystis sp. PCC 6803 did not show an alteration in growth at high salinity but continuously lost GG to the medium [61]. These experiments revealed that the compatible solute transporters among cyanobacteria are principally necessary to prevent leakage of these compounds from the cells to save organic carbon and energy. Recently, the genome of Synechocystis sp. PCC 6714 was published [63]. This strain is very closely related to Synechocystis sp. PCC 6803 but lacks the genes for the GG transporter. Correspondingly, cells of Synechocystis sp. PCC 6714 continuously lost GG into the medium and showed a lower salt tolerance limit than Synechocystis sp. PCC 6803 [63]. The existence of the GG transporter in Synechocystis sp. PCC 6803 also allowed experiments in which the defect in GG synthesis was complemented by the addition of external GG (Figure 2). As expected, GG supplementation allowed successful salt acclimation via the uptake of externally added GG [60] and proved that the accumulation of compatible solutes is sufficient for the reestablishment of cellular metabolism in salt-stressed cells [60,64]. Interestingly, the uptake of trehalose caused a decrease in the cellular content of previously synthesized GG [60]. This decrease indicates that a yet unknown pathway for degradation or modification of the endogenous GG pool may be involved in the salt acclimation of Synechocystis sp. PCC 6803.


Salt acclimation of cyanobacteria and their application in biotechnology.

Pade N, Hagemann M - Life (Basel) (2014)

Comparison of growth of the Synechocystis sp. PCC 6803 wild type and the mutant defective in the gene for glucosylglycerol (GG) synthesis (ggpS) in medium supplemented with 3.5% NaCl. The wild type can grow, whereas the mutant cannot grow at this salinity. Supplementation of the salt medium with 5 mM GG restores the salt tolerance of the mutant, because the compatible solute is taken up by the mutant cells and becomes accumulated to levels comparable to wild-type cells.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390839&req=5

life-05-00025-f002: Comparison of growth of the Synechocystis sp. PCC 6803 wild type and the mutant defective in the gene for glucosylglycerol (GG) synthesis (ggpS) in medium supplemented with 3.5% NaCl. The wild type can grow, whereas the mutant cannot grow at this salinity. Supplementation of the salt medium with 5 mM GG restores the salt tolerance of the mutant, because the compatible solute is taken up by the mutant cells and becomes accumulated to levels comparable to wild-type cells.
Mentions: Heterotrophic bacteria preferentially accumulate compatible solutes from the environment. Many transport systems have been characterized in a variety of heterotrophic bacteria [12,53,54,55]. The activity and expression of these uptake systems are controlled by the salinity of the external medium [56]. It is also known that E. coli and B. subtilis can accumulate many more compatible solutes via transport from the environment than they can synthesize de novo. Many of the well-characterized transport systems belong to the group of primary active ATP-binding-cassette-(ABC)-type transporters [11]. Despite a preference for de novo synthesis of compatible solutes, cyanobacteria also possess transporters for compatible solutes. Initially, an uptake system for glycine betaine was identified, which occurred only in strains able to synthesize this osmolyte de novo [57,58]. Subsequently, the existence of an active-transport system for exogenous GG was found in the cyanobacterium Synechocystis sp. PCC 6803, which also transports the solutes sucrose and trehalose, albeit with a lower affinity [59,60]. The transporter belongs to the ABC transporter family and consists of four subunits, three of which are coded by genes organized in an operon [61,62]. The identification of these genes allows the generation of mutants to analyze the function of the transporter. Interestingly, a transport mutant of Synechocystis sp. PCC 6803 did not show an alteration in growth at high salinity but continuously lost GG to the medium [61]. These experiments revealed that the compatible solute transporters among cyanobacteria are principally necessary to prevent leakage of these compounds from the cells to save organic carbon and energy. Recently, the genome of Synechocystis sp. PCC 6714 was published [63]. This strain is very closely related to Synechocystis sp. PCC 6803 but lacks the genes for the GG transporter. Correspondingly, cells of Synechocystis sp. PCC 6714 continuously lost GG into the medium and showed a lower salt tolerance limit than Synechocystis sp. PCC 6803 [63]. The existence of the GG transporter in Synechocystis sp. PCC 6803 also allowed experiments in which the defect in GG synthesis was complemented by the addition of external GG (Figure 2). As expected, GG supplementation allowed successful salt acclimation via the uptake of externally added GG [60] and proved that the accumulation of compatible solutes is sufficient for the reestablishment of cellular metabolism in salt-stressed cells [60,64]. Interestingly, the uptake of trehalose caused a decrease in the cellular content of previously synthesized GG [60]. This decrease indicates that a yet unknown pathway for degradation or modification of the endogenous GG pool may be involved in the salt acclimation of Synechocystis sp. PCC 6803.

Bottom Line: Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes.Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood.This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water.

View Article: PubMed Central - PubMed

Affiliation: Institut für Biowissenschaften, Abteilung Pflanzenphysiologie, Universität Rostock, Albert-Einstein-Str. 3, D-18059 Rostock, Germany. nadin.pade@uni-rostock.de.

ABSTRACT
The long evolutionary history and photo-autotrophic lifestyle of cyanobacteria has allowed them to colonize almost all photic habitats on Earth, including environments with high or fluctuating salinity. Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes. Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood. Here, we briefly review recent advances in the identification of salt acclimation processes and the essential genes/proteins involved in acclimation to high salt. This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water. In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

No MeSH data available.