Abstract：Flagella is the major organelles for motility, is also an important pathogenic factor. Chemotaxis is the movement of an organism in response to a chemical stimulus, bacteria direct their movements according to certain chemicals in their environment. The chemotaxis gene (cheA) mutants caused significant reduction in virulence. In order to study the roles of cheA and flagellin gene (fliC) double mutant in Acidovorax citrulli, The double mutant strain ΔcheAΔfliC and his complemented strain were constructed by homologous recombination approach. Meanwhile, ΔfliC for control and his complemented strain were constructed. The influence of ΔcheAΔfliC illustrated by testing the biological characteristics. The results showed that the pathogenicity, motility, growth ability and seed adhesion of ΔcheAΔfliC were significantly decreased and the biofilm formation ability was significantly enhanced. Compared with ΔfliC and ΔcheA, the virulence of ΔcheAΔfliC was dropped significantly, biofilm formation ability significantly increased. The effect of fliC and cheA on the ability of the pathogenic and biofilm formation of watermelon were even more significant. The movement ability of ΔcheAΔfliC, ΔcheA, ΔfliC were basically consistent, indicating that fliC deletion and cheA deficiency also affect the athletic ability of A. citrulli, and further explain the chemotaxis core gene cheA of A. citrulli by regulating the movement of flagellum and thus affect the movement of A. citrulli ability. The adhesion ability of ΔfliC and ΔcheAΔfliC were significantly lower than that of ΔcheA, indicating that fliC played an important role in adhesion, and it would provide a basis for the prevention and control of the disease and its effective control agents' development.
