Objective   Strains of Salmonella typhimurium with yibT and/or csgD deleted were created to observe the effect on its biofilm formation for effective prevention and control of the foodborne pathogen.

  Method   The λ-red homologous recombination technique was applied to create the gene-deleted mutants, WTΔyibTΔcsgD and WTΔcsgD, of WT S. typhimurium (CVCC541). Subsequently, the gene-complemented strains were also obtained using recombinant vector technology. Differences of the mutants in biofilm formation were determined by crystal violet staining, content of exopolysaccharide measured by phenol-sulfuric acid, mobility tested on semi-solid agar plates, and self-aggregation monitored. Under a scanning electron microscope, biofilm structure was observed. Finally, mRNA expressions of the target genes in the biofilm were identified by fluorescence quantitative PCR.

  Result  A double-gene deleted WTΔyibTΔcsgD, a WTΔcsgD without csgD, and their respective complemented strains, WTΔcsgDΔyibT/pcsgD and WTΔcsgD/pcsgD, were successfully obtained. The double-gene deletion significantly reduced the ability in forming biofilm, the content of exopolysaccharide, and the aggregation of the genes to targets, and the mRNA expressions of invF and sdiA in WT S. typhimurium.

  Conclusion  Deletion of yibT and csgD significantly impacted some critical biofunctions of S. typhimurium that could become a new approach for control of the foodborne disease.