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当前位置: 首页 > 文章 > 光强和氮源对念珠藻胞外多糖分泌的影响 水生生物学报 2014 (3) 480-486
Position: Home > Articles > EFFECTS OF LIGHT AND NITROGEN SOURCE ON THE SECRETION OF EXTRACELLULAR POLYSACCHARIDES FROM NOSTOC SP. Acta Hydrobiologica Sinica 2014 (3) 480-486

光强和氮源对念珠藻胞外多糖分泌的影响

作  者：
葛红梅;周旭萍;夏令;张德禄;胡春香
单  位：
武汉理工大学生命科学与技术学院;中国科学院水生生物研究所
关键词：
胞外多糖;光强;氮源;生物结皮;Nostoc sp.;蔗糖
摘  要：
胞外多糖(EPS)是结皮蓝藻形成生物结皮的胶结剂,为了理解常球状存在的丝状蓝藻——Nostoc胶结沙粒的机理,探讨了光强[40、80μE/(m2?s)]和氮源(气态氮,硝态氮)对结皮优势种Nostoc sp.分泌EPS(包括荚膜多糖CPS和释放多糖RPS)的影响规律及其内在机理。结果发现:Nostoc sp.在气态氮和硝态氮下都有相似的快速生长,但其分泌的RPS、CPS及EPS量,在硝态氮下均随光强的增加而增加,在气态氮下却与光强没有关系。相关代谢研究发现,在硝态氮下细胞内有更高含量的可溶性糖和蔗糖。进一步的相关分析发现,在两种氮源下,蔗糖量与RPS量或CPS量间的显著正相关都只发生在80μE/(m2?s)下,在气态氮中,两光强下的胞内总糖量都与CPS量显著负相关。以上结果说明,Nostoc sp.在氮源利用和光强适应方面都有明显优势,它即使在快速生长的对数期,也可同时分泌相当量的EPS,这使其在球状藻殖段形成之前胶结沙粒成为可能。由此可推知,Nostoc sp.在贫瘠沙土表面的最初生长过程中,其胞外的EPS均来自胞内的固碳产物,在高光强下,蔗糖很可能是其EPS合成的原料。
译  名：
EFFECTS OF LIGHT AND NITROGEN SOURCE ON THE SECRETION OF EXTRACELLULAR POLYSACCHARIDES FROM NOSTOC SP.
作  者：
GE Hong-Mei;ZHOU Xu-Ping;XIA Ling;ZHANG De-Lu;HU Chun-Xiang;Key Laboratory of Algal Biology,Institute of Hydrobiology,Chinese Academy of Sciences;University of Chinese Academy of Sciences;Department of Biological Science and Biotechnology,Wuhan University of Technology;
关键词：
Extracellular polysaccharides;;Light intensity;;Nitrogen source;;Biological soil crust;;Nostoc sp.;;Sucrose
摘  要：
Extracellular polysaccharides(EPS) play an essential role in adhesion for crust cyanobacteria to form the biological soil crust.The mechanisms of how the normally ball-shape filamentous cyanobacteria Nostoc sp.cements sand grains remains to be elucidated.To understand the mechanisms we investigated the effects of light intensity and nitrogen source on the the secretion of EPS [including releleased exopolysaccharides(RPS) and capsular polysaccharides(CPS)] in the subtype of Nostoc sp.that dominates the formation of the biological soil crust.We tested two forms of nitrogen source – N2 and nitrate,and the light intensities at 40 and 80 μE/(m2·s).The results showed that the biomass of Nostoc sp.in diazotrophic condition was almost the same to that in non-diazotrophic condition.The production of RPS,CPS and EPS in Nostoc sp.was elevated along with the increase in light intensity in nitrate-grown cultures.However,light intensity did not affect the yields of RPS,CPS and EPS in N2-fixing cultures.Studies in Nostoc sp.metabolism showed that the intracellular contents of soluble sugar and sucrose were significantly higher in the presence of nitrate compared to N2.Interestingly a positive correlation between the sucrose content and RPS/CPS production was only observed at the light intensity of 80 μE/m2?s,whereas in the N2-fixing cultures,the total contents of intracellular carbohydrate were negatively correlated with CPS production at both tested light intensities.These results suggested that Nostoc sp.had the advantages of utilizing nitrogen and adapting to the light intensity.Although Nostoc sp.in the logarithmic phase displays a rapid growth rate,they are able to secrete a considerable amount of EPS which enables them to cement sand grains before forming the spherical hormogonium.Thus,these results further suggested that,during the early stage of the growth of Nostoc sp.in the poor soil surface,the secreted extracellular EPS may originate from the intracellular products of fixing carbon,and sucrose was probably the source for the EPS biosynthesis under high intensity of light.

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