[Identification of rpoE gene associated with biofilm formation of Salmonella pullorum]

In order to identify Sigma factor associated with biofilm formation of Salmonella pullorum, we determined the gene expression in the wild type strain and biological characteristics of deletion mutants.

Biofilm forming ability of S. pullorum strain was detected by crystal violet assay. The rpoS gene-dependent or -independent strain for biofilm formation was determined by catalase test. Real-time PCR was established to compare the expression of six different Sigma factors during biofilm formation. Deletion mutants were constructed using the Red recombination system, and their resistance to environmental stress was determined.

S. pullorum strain S6702 had strong ability of biofilm formation. The result of catalase test was negative, indicating that S6702 was an rpoS-independent strain for biofilm formation. The expression of rpoE gene was the highest during 4 h and 24 h post-incubation. Compared to wild-type strains, ΔrpoS kept the biofilm-forming ability, whereas ΔrpoE mutant could not produce biofilm. Both mutants with deletion of the rpoS and rpoE genes had reduced resistance to environmental stress.

The rpoE gene was identified as one of biofilm formation associated genes in a S. pullorum rpoS-independent strain. The finding may help to elucidate the regulatory mechanism of Salmonella biofilm formation.