(1) 山西农业大学农学院

[Objective] To investigate the phenotypes of Azorhizobium caulinodans ORS57 mutant strains that lacked the flagellar motor proteins FliN and FliM respectively, and the functional mechanism of these proteins. [Methods] The gene knock-out mutant strains (DeltafliN, DeltafliM) were constructed by homologous recombination and triparental conjugation. The phenotypes including cell growth, chemotaxis, exopolysaccharide production, biofilm formation and cell flocculation were investigated. [Results] Mutants DeltafliN and DeltafliM did not shown any difference in cell growth compared with the wild-type strain. However, both mutants lost their flagella when observed under electron microscope. In addition, DeltafliN and DeltafliM were impaired in chemotaxis, exopolysaccharide production, and biofilm formation. To the contrary, the flocculation ratio of both mutants was higher than that of the wild-type strain within the same amount of time. [Conclusion] The flagellar genes fliN and fliM could regulate the flagellum formation, cell motility, exopolysaccharide production, biofilm formation and cell flocculation of Azorhizobium caulinodans ORS571.