RESUMO
Objective To investigate the effects of shiga toxin ( Stx ) phage on the expression of type Ⅲsecretion system (T3SS) in E.coli O157 ∶H7.Methods A standard E.coli O157 ∶H7 strain, EDL933 and a natural Stx phage defective mutant of EDL 933 strain, TUV93-0 were used for this study .The expression of T3SS proteins was compared between EDL 933 and TUV93-0 strains.The expression of five operons ( LEE1-LEE5 ) was evaluated by measuring the green fluorescent protein ( GFP ) in five different plasmids with LEE1-LEE5 promoters, respectively.Results The expression of T3SS proteins in TUV93-0 mutant were significantly increased than those in EDL 933 strain.Moreover, the expression of LEE1, LEE2 and LEE5 were also increased in TUV93-0 mutant.Conclusion The deletion of Stx phage might enhance T3SS expression through the regulation of LEE 1.
