UV irradiation and desiccation modulate the three-dimensional extracellular matrix of Nostoc commune (Cyanobacteria).
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Cyanobacterium Nostoc commune can tolerate the simultaneous stresses of desiccation, UV irradiation, and oxidation. Acidic WspA, of approximately 33.6 kDa, is secreted to the three-dimensional extracellular matrix and accounts for greater than 70% of the total soluble protein. The wspA gene of N. commune strain DRH1 was cloned and found in a single genomic copy, in a monocistronic operon. Transcription of wspA and sodF (superoxide dismutase), and synthesis and secretion of WspA, were induced upon desiccation or UV-A/B irradiation of cells. Recombinant WspA binds the UV-A/B absorbing pigment scytonemin through non-covalent interactions. WspA peptide polymorphism, and heterogeneity of multiple wspA sequences within cells of a single colony, account for distinct WspA isoforms. WspA has no similarity to entries in the sequence databases and wspA, a possible xenolog, is restricted to a subset of strains in the "form species" N. commune characterized through group I intron phylogeny. We hypothesize that WspA plays a central role in the global stress response of N. commune through modulation of the structure and function of the three-dimensional extracellular matrix, particularly the transport, distribution, and/or macromolecular architecture of mycosporine and scytonemin UV-A/B absorbing pigment complexes. (+info)
Crucial role of extracellular polysaccharides in desiccation and freezing tolerance in the terrestrial cyanobacterium Nostoc commune.
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The cyanobacterium Nostoc commune is adapted to the terrestrial environment and has a cosmopolitan distribution. In this study, the role of extracellular polysaccharides (EPS) in the desiccation tolerance of photosynthesis in N. commune was examined. Although photosynthetic O2 evolution was not detected in desiccated colonies, the ability of the cells to evolve O2 rapidly recovered after rehydration. The air-dried colonies contained approximately 10% (wt/wt) water, and field-isolated, natural colonies with EPS were highly water absorbent and were rapidly hydrated by atmospheric moisture. The cells embedded in EPS in Nostoc colonies were highly desiccation tolerant, and O2 evolution was not damaged by air drying. Although N. commune was determined to be a mesophilic cyanobacterium, the cells with EPS were heat tolerant in a desiccated state. EPS could be removed from cells by homogenizing colonies with a blender and filtering with coarse filter paper. This treatment to remove EPS did not damage Nostoc cells or their ability to evolve O2, but O2 evolution was significantly damaged by desiccation treatment of the EPS-depleted cells. Similar to the EPS-depleted cells, the laboratory culture strain KU002 had only small amount of EPS and was highly sensitive to desiccation. In the EPS-depleted cells, O2 evolution was also sensitive to freeze-thaw treatment. These results strongly suggest that EPS of N. commune is crucial for the stress tolerance of photosynthesis during desiccation and during freezing and thawing. (+info)
Purification and characterization of corrinoid-compounds from the dried powder of an edible cyanobacterium, Nostoc commune (Ishikurage).
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Vitamin B12 content (98.8 +/- 5.6 microg/100 g dry weight) of an edible cyanobacterium, Nostoc commune (Ishikurage) was determined by the Lactobacillus delbrueckii ATCC 7830 microbiological method. Bioautography with vitamin B12-dependent Escherichia coli 215 indicated that N. commune contained two (main and minor) corrinoid-compounds. These corrinoid-compounds were purified to homogeneity from the dried algal cells and characterized. The main and minor purified corrinoid-compounds were identified as pseudovitamin B12 and vitamin B12, respectively, on the basis of silica gel 60 TLC, C18 reversed-phase HPLC, 1H NMR spectroscopy, and UV-visible spectroscopy. These results suggest that the bacterial cells are not suitable for use as a vitamin B12 source, especially in vegetarians. (+info)
Lipid extract of Nostoc commune var. sphaeroides Kutzing, a blue-green alga, inhibits the activation of sterol regulatory element binding proteins in HepG2 cells.
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Nostoc commune var. sphaeroides Kutzing (N. commune), a blue-green alga, has been used as both a food ingredient and in medicine for centuries. To determine the effect of N. commune on cholesterol metabolism, N. commune lipid extract was incubated at increasing concentrations (25-100 mg/L) with HepG2 cells, a human hepatoma cell line. The addition of N. commune lipid extract markedly reduced mRNA abundance of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and LDL receptor (LDLR) (P < 0.05), with a concomitant decrease in their protein expression (P < 0.001). Reduced HMGR activity by 90% with N. commune lipid extract confirmed the inhibitory role of N. commune in cholesterol synthesis (P < 0.006). To elucidate a molecular mechanism underlying the repression of HMGR and LDLR by N. commune lipid extract, expression of sterol regulatory element binding protein 2 (SREBP-2) was assessed. Whereas mRNA for SREBP-2 remained unchanged, SREBP-2 mature protein was reduced by N. commune (P < 0.009). In addition, N. commune lipid extract also decreased SREBP-1 mature protein by approximately 30% (P < 0.002) and reduced the expression of SREBP-1-responsive genes such as fatty acid synthase and stearoyl CoA desaturase 1 (SCD-1) (P < 0.05). Therefore, our results demonstrate that N. commune lipid extract inhibits the maturation process of both SREBP-1 and -2, resulting in a decrease in expression of genes involved in cholesterol and fatty acid metabolism. (+info)
Novel thermostable glycosidases in the extracellular matrix of the terrestrial cyanobacterium Nostoc commune.
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The cyanobacterium Nostoc commune is adapted to the terrestrial environment and forms a visible colony in which the cells are embedded in extracellular polysaccharides (EPSs), which play a crucial role in the extreme desiccation tolerance of this organism. When natural colonies were immersed in water, degradation of the colonies occurred within 2 days and N. commune cells were released into the water. The activities that hydrolyze glycoside bonds in various N. commune fractions were examined using artificial nitrophenyl-linked sugars as substrates. A beta-D-glucosidase purified from the water-soluble fraction was resistant to 20 min of boiling. The beta-D-glucosidase, with a molecular mass of 20 kDa, was identified as a cyanobacterial fasciclin protein based on its N-terminal amino-acid sequence. The 36-kDa major protein in the water-soluble fraction was purified, and the N-terminal amino-acid sequence of the protein was found to be identical to that of the water-stress protein (WspA) of N. commune. This WspA protein also showed heat-resistant beta-D-galactosidase activity. The fasciclin protein and WspA in the extracellular matrix may play a role in the hydrolysis of the EPSs surrounding the cells, possibly as an aid in the dispersal of cells, thus expanding the colonies of this cyanobacterium. (+info)
In vitro and in vivo safety assessment of edible blue-green algae, Nostoc commune var. sphaeroides Kutzing and Spirulina plantensis.
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Antioxidative activity and chemical constituents of edible terrestrial alga Nostoc commune Vauch.
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The extract of terrestrial alga Nostoc commune Vauch. has high antioxidative activity. Our study on N. commune Vauch. resulted in the isolation of two beta-ionone derivatives, nostocionone and 3-oxo-beta-ionone, together with four indole alkaloids, scytonemin, reduced scytonemin, N-(p-coumaroyl)tryptamine, and N-acetyltryptamine. The structures of the isolated compounds were determined on the basis of 1D and 2D NMR and MS analyses. Among these isolates, nostocionone and reduced scytonemin demonstrated strong antioxidative activities which were assessed by using a beta-carotene oxidation assay. (+info)
Isolation and purification of an axenic diazotrophic drought-tolerant cyanobacterium, Nostoc commune, from natural cyanobacterial crusts and its utilization for field research on soils polluted with radioisotopes.
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