Study On Extracellular Polysaccharide Of Antarctic Psychrotrophs Psychrobacter Sp. B-3

Marine environment of the Antarctic is cold, results in a high diversity of microbial habitats and microbial communities. Extreme environments are sources of microorganisms that secrete interesting new molecules, including exopolysaccharides. The exopolysaccharides present in very high concentrations appear to play important roles for microorganisms against harsh winter conditions, such as high salinity, pH, potential ice-crystal and other chemical substances damage.Ecologic studies examining the role of exopolysaccharides in marine habitats provide evidence that these substances are abundant in the Antarctic marine environment. Bacteria collected by CTD during Chinese 2th Antarctic Scientific Expedition in the Southern Ocean were studied. Phylogenetic analysis by NCBI demonstrated that Antarctic marine bacteria B-3 was more closely related to the genus Psychrobacter sp.. Then the structure of exopolysaccharides from B-3 was determined by using sugar composition analysis, methylation analysis. The molecular weight, sugar composition, induced resistance against Powdery Mildew and defense enzymes activities related to resistance in cucumber seedlings treated with self-developed Antarctic bacteria B-3 extracellular oligasaccharides were studied. 1 Out of 57 strains of Antarctic marine bacteria,1 were found to produce exopolysaccharides according to morphological characterization and the staining techniques(CHRISTENSEN, CONGO RED and FREEMAN method). Phylogenetic analysis by NCBI demonstrated that bacteria B-3 was related to the genus Psychrobacter.2 The effects of major environmental factors on the growth and exopolysaccharides production of bacteria B-3 were investigated. The results indictde that the optimal conditions for exopolysaccharides production:culture period,60h; growth temperature, 10℃; carbon source,1.0% glucose; NaCl,3.0%; pH 7.0. The results showed Antarctic marine bactria B-3 could grow between 4℃and 25℃. Meanwhile, the conditions of fermentation of 100L fermenter were studied,the exopolysaccharides production was higher than cultured in laboratory.3 After removal of the cells by centrifugation, exopolysaccharides was precipitated by adding ethanol. exopolysaccharides were obtained after purification by Sephadex G-50 ionexchange column. the molecular weight of B-3 extracellular oligasaccharides was determined as 2112Da by the HPLC method,sugar composition reveals that main structure of B-3 was mannose and glucose.4 The molecular weight, sugar composition, induced resistance against Powdery Mildew and defense enzymes activities related to resistance with self-developed Antarctic bacteria B-3 extracellular oligasaccharides were studied. he activities of chinitase,β-1,3-glucanse, phenylanine, ammonialyse(PAL), Superoxide dismutase(SOD), and Peroxidase(POD) in cucumber seedlings stimulated by B-3 increased apparently at defferent times comparent with untreated plants, and B-3 has a similar induction effects with 0.5% of the chitosan;at the same time,0.5% of the B-3 polysaccharide significantly reduced the disease index of cucumber powdery mildew, anti-efficiency reached 24.49%,.B-3 polysaccharide is expected to develop as a new type of resistance elictiors.5 The effect of cryoprotection of exopolysaccharides of Antarctic psychrotrophs sp. B-3 was studied also, at the same concentration the effect of exopolysaccharides was better than glucan. Meanwhile, it could protect the cell from the damage of freeze-thaw cycles. So, the results suggestes exopolysaccharides of Antarctic psychrotrophs sp.B-3 might have an effect of cryoprotection.In a word, the exopolysaccharides of Antarctic B-3 was constitute of mannose and glucose. It has an immunostimulating function and anti-tumor effect. And the exopolysaccharides production of B-3 was higher in lower temperature(10℃) and higher salinity(3%) than room temperature. Meanwhile, exopolysaccharides can protect the microbes against the damage of freeze-thawg. This study will provide insight in adaptation mechanism of Antarctic bacteria and the biotechnological application of Antarctic resource.