(1) 山西农业大学农学院

[Objective] To study the phenotypes of Azorhizobium caulinodansORS571 mutant strain lacking the diguanylate cyclase AZC-2412, and to explore its functional mechanism. [Methods] We constructed the gene knockout system of rhizobia based on the homologous recombination of cre-loxp, and the mutant strain was constructed by the triparental conjugation. Growth rate, chemotactic ability, exopolysaccharide production, biofilm formation and other phenotypes of the wild type and mutant strains were studied. [Results] The mutant strain had almost the same growth rate as the wild type. Compared with the wild type, the mutant strain impaired in exopolysaccharide production, chemotaxis behavior and biofilm formation due to lower levels of c-di-GMP in cells. [Conclusion] The deletion of the diguanylate cyclase AZC-2412 reduces level of c-di-GMP levels. It had a regulatory effect on the exopolysaccharide production, bacterial motility, biofilm formation, cell flocculation of Azorhizobium caulinodans ORS571 and its interaction with host plant.