Abstract: The motility of E. coli is mainly driven by flagella, which is one of the important virulence factors of pathogenic E. coli. In this paper, the influences of Fur and its negatively regulated non-coding RNA-RyhB on the motility of avian pathogenic E. coli (APEC) AE17 strain were investigated to provide scientific basis for exploring potential targets for prevention and control of avian E. coli. The Red homologous recombination method was used to construct AE17△Fur and AE17△Fur/RyhB, then the motility characteristics of the absent and original strains were compared, and the effects of Fur and RyhB on the formation of APEC flagellum and biofilm in combination were explored with transcriptome data. The results showed that the AE17△Fur and AE17△Fur/RyhB were constructed successfully. Transcriptome results showed that the absence of Fur basically down-regulated all flagella-related genes. The absence of Fur significantly weakened the movement of APEC, and RyhB had no significant influence on the movement of APEC. △Fur/RyhB has increased its movement ability compared with △Fur. Biofilm formation ability of △Fur and △Fur/RyhB were significantly enhanced, and that of △RyhB was weakened, which were consistent with the trend of movement. Fur plays a very important role in flagellum assembly of pathogenic E. coli, and its negatively regulated RyhB can inhibit the effect of this mechanism to some extent, and further affect the formation of biofilm, so as to provide a possibility for finding relevant drug targets.

Key words: avian pathogenic Escherichia coli, Fur, RyhB, motility, iron homeostasis