A study on prophagic and chromosomal sodC genes involvement in Escherichia coli O157:H7 biofilm  formation and biofilm resistance to H2O2

Raffaella Scotti, Annarita Stringaro, Roberta Gabbianelli

Keywords: biofilm, oxidative stress, hydrogen peroxide, scanning electron microscopy, superoxide dismutase

Introduction. Escherichia coli O157:H7 possesses one chromosomal and two prophagic

sodC genes encoding for Cu,Zn superoxide dismutases. We evaluated the contribution of

sodC genes in biofilm formation and its resistance to hydrogen peroxide.

Methods. The biofilm of sodC deletion mutants has been studied, in presence or absence

of hydrogen peroxide, by crystal violet in 96-well plates and Scanning Electron Microscopy

on glass coverslips.

Results. Deletion of prophagic sodC genes had no effect on biofilm construction, in contrast

to the chromosomal gene deletion. Hydrogen peroxide treatment showed higher

cell mortality and morphological alterations in sodC deletion mutants respect to wild

type. These effects were related to the biofilm development stage.

Conclusion. The role of the three SodCs is not redundant in biofilm formation and the

resistance to oxidative damage. The stage of biofilm development is a crucial factor for

an effective sanitization.