Abstract: Cyclic diguanolate monophosphate (c-di-GMP) is an important bacterial second messenger molecule which was involved in the regulation of various cellular processes. C-di-GMP is synthesized by the diguanylate cyclases (DGCs) from two GTP molecules, and hydrolyzed by the phosphodiesterases(PDEs). A bifA gene was reported to be the c-di-GMP degradation gene in Pseudomonas aeruginosa, and was proposed to involved in adjusting intracellular c-di-GMP concentration. In this work, the role of bifA in c-di-GMP degradation and biofilm formation was investigated in Pseudomonas stutzeri A1501. It was found that the deletion of the bifA gene resulted in an accumulation of intracellular c-di-GMP, and enhanced the capability of biofilm formation in A1501. In addition, excess c-di-GMP produced in the bifA mutant strain leaded swimming motility to repress. The results suggested that bifA is a key gene for c-di-GMP degradation. And the bifA affected the biofilm formation, swimming motility and other physiological phenotypes by regulating intracellular c-di-GMP concentration level. The results provided a theoretical basis for signal transduction and environmental adaptation of root-associate nitrogen-fixing bacteria.

Key words: Pseudomonas stutzeri, c-di-GMP, biofilm formation, phosphodiesterase, bifA gene

摘要： 环二鸟苷酸（c-di-GMP）是细菌中一种重要的第二信使，能够调控多种生理活动。C-di-GMP由两个GTP分子经环化酶（DGCs） 合成，而被磷酸二酯酶（PDEs）降解，在铜绿假单胞菌中bifA基因为降解c-di-GMP的基因，参与了胞内c-di-GMP的浓度调节。 以固氮施氏假单胞菌A1501中的bifA基因为研究对象，构建了bifA基因突变株；鉴定了bifA基因在c-di-GMP降解及生物膜形成 中的功能。结果表明，bifA基因的突变造成了A1501菌中c-di-GMP的积累，同时增强了菌株的生物膜形成能力。此外bifA突变 株运动能力大幅下降。由此推测bifA为c-di-GMP降解的关键基因，通过调节胞内c-di-GMP水平间接参与调控了生物膜形成以及 菌体运动等生理活动。该结果为解析固氮微生物的信号传递及环境适应机制提供了理论基础。

关键词: 施氏假单胞菌, 环二鸟苷酸, 生物膜形成, 磷酸二酯酶, bifA基因