AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na＋/H＋ antiporter crucial for the bacterium＇s resistance to salt/alkali stresses. However, it remains unknown whether this t...AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na＋/H＋ antiporter crucial for the bacterium＇s resistance to salt/alkali stresses. However, it remains unknown whether this type of bacterial gene may be able to increase the tolerance of flowering plants to salt/alkali stresses. To investigate the use of extremophile genetic resources in higher plants, transgenic tobacco BY-2 cells and plants harboring AaNhaDwere generated and their stress tolerance was evaluated. Ectopic expression of AaNhaD enhanced the salt tolerance of the transgenic BY-2 cells in a pH-dependent manner. Compared to wild-type controls, the transgenic cells exhibited increased Na＋ concentrations and pH levels in the vacuoles. Subcellular localization analysis indicated that AaNhaD-GFP fusion proteins were primarily localized in the tonoplasts. Similar to the transgenic BY-2 cells, AaNhaD.overexpressing tobacco plants displayed enhanced stress tolerance when grown in saline-alkali soil. These results indicate that AaNhaD functions as a pH-dependent tonoplast Na＋/H＋ antiporter in plant cells, thus presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance.展开更多
One Gram-positive bacteria,Bacillus sp.strain BG-CSN,was isolated from the muds with hypersaline and alkaline water at the beach of Banger Soda Lake in Tibet,China.After cultivating in liquid medium for 48 hours,an ex...One Gram-positive bacteria,Bacillus sp.strain BG-CSN,was isolated from the muds with hypersaline and alkaline water at the beach of Banger Soda Lake in Tibet,China.After cultivating in liquid medium for 48 hours,an extracellular α-amylase AmyBGC from the strain BG-CSN was purified 23-fold reaching to electrophoretic homogeneity by sequentially ammonium sulfate precipitation,Octyl-Sepharose CL-4B column chromatography,DEAE-Sepharose Fast Flow chromatography,DEAE-Toyopearl 650M chromatography and Sephadex G-100 chromatography.The enzyme had a molecular mass of 87 kD estimated by SDS-PAGE.The enzyme was optimally active at pH 10.5 and 52.5℃ and showed stability at pH range of 5.0 to 11.5 at the temperature below 35℃. The enzyme activity was inhibited by Hg+ and Fe 3+.The activity was not prevented at all by chelating reagents EDTA and SDS at high concentrations.This enzyme efficiently hydrolyzed starch to yield a series of maltooligosaccharides,including maltose after completion of the reaction.These results indicate that AmyBGC is classified as a liquefying endo-1,4-D-α-amylase(EC-3.2.1.1).展开更多
The novel alkaliphilic strain, designated as Bacillus sp. IB-OR17 and isolated from soda lake sediments, was identified and characterized. Isolated strain demonstrated slight antifungal activity against some plant pat...The novel alkaliphilic strain, designated as Bacillus sp. IB-OR17 and isolated from soda lake sediments, was identified and characterized. Isolated strain demonstrated slight antifungal activity against some plant pathogen fungi that are capable to grow under alkaline conditions. Based on its morphological, physiological and biochemical characteristics as well as on 16S rRNA gene analysis data, Bacillus sp. IB-OR17 were related to alkaliphilic species B. mannanilyticus. Such as type species, Bacillus sp. IB-OR17 produced extracellular β-mannanase but additionally it displayed also chitinolytic activity which is a new property reported for this species. Bacillus sp. IB-OR17 grew in pH range 8.0 - 11.0 with maximal intensity under 9.0 - 10.0 but not showed halophilic properties (growth limit under NaCl concentrations < 5%). Maximal production of chitinase is observed at the same pH interval after 96 h of submerged cultivation of the strain. Bacillus sp. IB-OR17 produced chitinase(s) in presence of colloidal chitin as main carbon source and sodium carbonate (0.25% - 1.0%) demonstrating high enzyme yield under enough low concentrations of the substrate (0.20%). Unlike chitinase, β-mannanase was constitutively produced by Bacillus sp. IB- OR17 in presence of various substrates including crab shell chitin. Probable involvement of the enzymes in antifungal activity of Bacillus sp. IB-OR17 is discussed shortly in terms of further researches and application of this strain.展开更多
The putrefaction of alkaline silica sol was investigated in this paper. The total colony numbers in three alkaline silica sol samples were 1.47 ×^ 105, 1.25× 10^4, and 9.45 × 10^4 cfu. mL 1, respectivel...The putrefaction of alkaline silica sol was investigated in this paper. The total colony numbers in three alkaline silica sol samples were 1.47 ×^ 105, 1.25× 10^4, and 9.45 × 10^4 cfu. mL 1, respectively. The salt- and alkalitolerant strains were isolated and selected using nutrient agar medium at 2.5% salinity and pH 9.5. Basic morphological, physiological and biochemical tests were conducted to confirm the preliminary characterizations of the strains. Based on API 50 CH test and 16S rDNA gene sequence analysis, the isolated strains were finally identified as Exiguobacterium aurantiacum, Cyclobacteriaceae bacterium, Microbacterium sp., Acinetobacter sp., Stenotrophomonas maltophilia and Bacillus thuringiensis. The survivability of the strains under different conditions such as salinities, acidities and temperatures was also studied. Some suitable methods for degerming, such as product pipe steam sterilization and regular canister cleaning, were proposed. To explore the possibility of isolates in industrial application, their alkaline protease and amylase production abilities were preliminarily studied. Five strains produced alkaline protease, whereas two strains produced alkaline amylase. Thus, understanding of the putrefaction on alkaline silica sol would be beneficial for improving industrial production.展开更多
基金supported by grants from the National Natural Science Foundation(30771162)the Ministry of Agriculture of China(2009ZX08009-096B)
文摘AaNhaD, a gene isolated from the soda lake alkaliphile Alkalimonas amylolytica, encodes a Na＋/H＋ antiporter crucial for the bacterium＇s resistance to salt/alkali stresses. However, it remains unknown whether this type of bacterial gene may be able to increase the tolerance of flowering plants to salt/alkali stresses. To investigate the use of extremophile genetic resources in higher plants, transgenic tobacco BY-2 cells and plants harboring AaNhaDwere generated and their stress tolerance was evaluated. Ectopic expression of AaNhaD enhanced the salt tolerance of the transgenic BY-2 cells in a pH-dependent manner. Compared to wild-type controls, the transgenic cells exhibited increased Na＋ concentrations and pH levels in the vacuoles. Subcellular localization analysis indicated that AaNhaD-GFP fusion proteins were primarily localized in the tonoplasts. Similar to the transgenic BY-2 cells, AaNhaD.overexpressing tobacco plants displayed enhanced stress tolerance when grown in saline-alkali soil. These results indicate that AaNhaD functions as a pH-dependent tonoplast Na＋/H＋ antiporter in plant cells, thus presenting a new avenue for the genetic improvement of salinity/alkalinity tolerance.
文摘One Gram-positive bacteria,Bacillus sp.strain BG-CSN,was isolated from the muds with hypersaline and alkaline water at the beach of Banger Soda Lake in Tibet,China.After cultivating in liquid medium for 48 hours,an extracellular α-amylase AmyBGC from the strain BG-CSN was purified 23-fold reaching to electrophoretic homogeneity by sequentially ammonium sulfate precipitation,Octyl-Sepharose CL-4B column chromatography,DEAE-Sepharose Fast Flow chromatography,DEAE-Toyopearl 650M chromatography and Sephadex G-100 chromatography.The enzyme had a molecular mass of 87 kD estimated by SDS-PAGE.The enzyme was optimally active at pH 10.5 and 52.5℃ and showed stability at pH range of 5.0 to 11.5 at the temperature below 35℃. The enzyme activity was inhibited by Hg+ and Fe 3+.The activity was not prevented at all by chelating reagents EDTA and SDS at high concentrations.This enzyme efficiently hydrolyzed starch to yield a series of maltooligosaccharides,including maltose after completion of the reaction.These results indicate that AmyBGC is classified as a liquefying endo-1,4-D-α-amylase(EC-3.2.1.1).
文摘The novel alkaliphilic strain, designated as Bacillus sp. IB-OR17 and isolated from soda lake sediments, was identified and characterized. Isolated strain demonstrated slight antifungal activity against some plant pathogen fungi that are capable to grow under alkaline conditions. Based on its morphological, physiological and biochemical characteristics as well as on 16S rRNA gene analysis data, Bacillus sp. IB-OR17 were related to alkaliphilic species B. mannanilyticus. Such as type species, Bacillus sp. IB-OR17 produced extracellular β-mannanase but additionally it displayed also chitinolytic activity which is a new property reported for this species. Bacillus sp. IB-OR17 grew in pH range 8.0 - 11.0 with maximal intensity under 9.0 - 10.0 but not showed halophilic properties (growth limit under NaCl concentrations < 5%). Maximal production of chitinase is observed at the same pH interval after 96 h of submerged cultivation of the strain. Bacillus sp. IB-OR17 produced chitinase(s) in presence of colloidal chitin as main carbon source and sodium carbonate (0.25% - 1.0%) demonstrating high enzyme yield under enough low concentrations of the substrate (0.20%). Unlike chitinase, β-mannanase was constitutively produced by Bacillus sp. IB- OR17 in presence of various substrates including crab shell chitin. Probable involvement of the enzymes in antifungal activity of Bacillus sp. IB-OR17 is discussed shortly in terms of further researches and application of this strain.
文摘The putrefaction of alkaline silica sol was investigated in this paper. The total colony numbers in three alkaline silica sol samples were 1.47 ×^ 105, 1.25× 10^4, and 9.45 × 10^4 cfu. mL 1, respectively. The salt- and alkalitolerant strains were isolated and selected using nutrient agar medium at 2.5% salinity and pH 9.5. Basic morphological, physiological and biochemical tests were conducted to confirm the preliminary characterizations of the strains. Based on API 50 CH test and 16S rDNA gene sequence analysis, the isolated strains were finally identified as Exiguobacterium aurantiacum, Cyclobacteriaceae bacterium, Microbacterium sp., Acinetobacter sp., Stenotrophomonas maltophilia and Bacillus thuringiensis. The survivability of the strains under different conditions such as salinities, acidities and temperatures was also studied. Some suitable methods for degerming, such as product pipe steam sterilization and regular canister cleaning, were proposed. To explore the possibility of isolates in industrial application, their alkaline protease and amylase production abilities were preliminarily studied. Five strains produced alkaline protease, whereas two strains produced alkaline amylase. Thus, understanding of the putrefaction on alkaline silica sol would be beneficial for improving industrial production.
