摘要生物膜法可以实现絮凝剂产生菌的全细胞固定化，有助于提高污水处理效率和连续处理污水。但复杂的水体环境会显著影响生物被膜的稳定性，从而降低污水处理效率。环二鸟苷 (c-di-GMP) 是细菌内部重要的信号分子，提高c-di-GMP的含量能促进部分菌株生物被膜的形成。【目的】通过重组质粒外源表达yedQ基因,提高产生物絮凝剂菌L20胞内第二信使c-di-GMP的含量，继而提高菌株生物被膜的形成能力。【方法】以生物絮凝剂产生菌L20为出发菌株，利用结合转移技术将外源质粒pYedQ转入L20，通过抗性平板筛选阳性克隆，并命名为L159。结合96孔板和酶标仪定量分析基因工程菌L159和野生型菌株在12 h和24 h生物被膜形成能力。【结果】与L20野生型菌株相比，基因工程菌L159在12 h和24 h的生物被膜形成量分别提高了62%和59%。【结论】利用外源表达技术提高菌株内部第二信使c-di-GMP的含量能够显著提高菌株生物被膜形成能力，为通过生物膜法实现生物絮凝剂产生菌的固定化，最终提高污水处理效率提供一定的理论基础。75030

该论文有图5幅，表2个，参考文献21篇。

毕业论文关键词：  生物絮凝剂  环二鸟苷  生物被膜  基因工程菌 

The study of cyclic diguanylate( c-di-GMP) enhancing the biofilm formation by bioflocculant producing bacterium

 Abstract   Biofilm formed by bioflocculant producing bacterium can help to the immobilization of cells to carriers, which will contribute to the improvement of the efficiency of wastewater treatment and the continuous treatment of industrial effluents。 However, the toxic environment will decrease the stability of biofilm and thus reduce the efficiency of wastewater treatment。 Bis-(3’-5’)-cyclic dimeric guanosine monophosphate (c-di-GMP) is an important signaling molecule, previous report have shown that elevated c-di-GMP level could simulate the biofilm formation of some bacteria。 [Objective] Constitutively expressing c-di-GMP synthase YedQ from Escherichia coli in L20 was performed to improve the intracellular level of cyclic diguanylate (c-di-GMP) and enhance the biofilm formation ultimately。 [Methods] The construction of L20 harboring the pYedQ2 plasmid was performed by a biparental mating。 LB agar plate containing 15 μg/L gentamycin was used to select for L20 derivative carrying the pYedQ2 plasmid, which was designated as L159。 Consequently, the biofilm formation of L20 and L159 were conducted based on the 96-well plate method。 After 12 h and 24 h incubation, the amount of biofilm biomass was quantified by microplate reader at OD590。 [Results] The pYedQ2 plasmid was transferred into L20 successfully。 At the same time, compared with L20, the biofilm formation of transconjugant L159 at 12 h and 24 h increased 62% and 59% respectively。 [Conclusion] The results indicated that constitutively expressing YedQ in L20 resulted in an elevated c-di-GMP level and the high c-di-GMP level enhanced biofilm formation, which will provide some theoretical basis for the immobilization of bioflocculant producing bacterium and the improvement of wastewater treatment。

Key words:  Bioflocculant  Biofilm  Cyclic diguanylate(c-di-GMP) Conjugation 

目 录

摘  要 I

Abstract II

目 录 III

图清单 IV

表清单 IV

变量注释表 V

1引言 1

2材料与方法 2

2。1