根际高效定殖是微生物菌剂发挥植物益生作用的关键步骤。根际促生芽孢杆菌的生物膜形成能力是影响其根际定殖的重要因素。芽孢杆菌组氨酸激酶KinA、KinB、KinC、KinD和KinE能够感受不同信号并使Spo0A磷酸化，进而调控生物膜的形成。芽孢杆菌的生物膜形成受到根系分泌物的影响，但是该5种组氨酸激酶所感受的根系分泌物中的信号分子仍缺乏研究。Bacillus amyloliquefaciens SQR9是本实验室从黄瓜根际分离到的一株根际有益细菌，能够对根系分泌物作出响应，并且能在根际高效定殖。本研究拟以B. amyloliquefaciens SQR9为研究材料，通过外源表达该5种激酶，使其特异性结合根系分泌物中的信号分子，进而鉴定每个激酶所结合的根系分泌物中的配体，并在其中寻找促进SQR9根际定殖的信号分子。研究成果有望对外源调控芽孢杆菌的根际定殖行为、增强其植物生长促进作用提供指导。

Bacillus spp. play important roles in microbial fertilizer as gram-positive beneficial rhizobacteria. Rhizosphere colonization of microbes determines the efficiency of their plant beneficial effects. Biofilm formation of Bacillus spp, which is under the regulation of phosphorylated Spo0A, is a critical factor for their root colonization. Spo0A accepts phosphoryl groups from histine kinases termed KinA, KinB, KinC, KinD and KinE. Biofilm formation of Bacillus is known to be affected by plant root exudates. However, the ligand of the each histine kinase as potential signal affecting biofilm formation in root exudates is poorly known. Bacillus amyloliquefaciens SQR9 is an efficient plant growth-promoting rhizobacteria (PGPR) isolated from cucumber rhizosphere, which has been shown to respond to root exudates of cucumber and form stronger biofilm on root as a consequence. In this research, KinA, KinB, KinC, KinD and KinE of SQR9 will be expressed and purified, and subsequently incubated with cucumber root exudates, respectively. The ligand(s) or signal(s) bind to each kinase will be separated and identified and their effects on the root colonization and biofilm formation of SQR9 will be evaluated. The molecules that enhance colonization of SQR9 will be further characterized. This work would expand knowledge on rhizosphere interaction between bacteria and plant, and theoretically support the regulation of behavior of PGPR in rhizosphere.