Characterization and immunoprotective efficacy of a fumarate reductase mutant of .

BACKGROUND

has the ability to adapt to variable environments by modulating metabolism. The Tricarboxylic Acid Cycle (TCA), as a core metabolic process, is critical for the environmental adaptation and infection process of . Fumarate reductase FrdA is an important enzyme in the TCA cycle, mainly catalyzing the conversion of fumarate to succinate. But the association between this enzyme and the pathogenicity of has not yet been reported.

METHODS

To determine the role of fumarate reductase FrdA in infection, a -gene deletion strain of () was generated in this study, and the effect of knockout on the biological properties and pathogenicity of . were further examined. Then, the immunoprotective effect of -deficient strain was determined.

RESULTS

The results showed that deletion did not affect the growth properties of but caused a significant decreased survival under environmental stress, as well as a substantial decrease in its motility and biofilm formation ability. The Δ mutant displayed apparently reduced adhesion and invasion to Caco-2 cells and markedly impaired survival and replication in RAW264.7 cells. The animal infection test showed that the gene deletion could lead to a significant decrease in virulence of in mice, with a 64-fold increased LD for mice, and Δ demonstrated significantly decreased colonization in mouse tissues and organs. The transcriptomics results showed that deletion resulted in altered expression of 2163 genes in , and downregulated expression of and other virulence genes were confimed by qPCR. Moreover, immunization of mice with the deletion strain provided promising immune protection for mice.

CONCLUSION

Fumarate reductase FrdA is closely associated with pathogenicity of and that is an attractive candidate target for vaccine design of .