Exopolysaccharides,comprised of colanic acid (CA) or cellulose (Cel) are produced by STEC.Previous studies showed that cells producing CA have greater tolerance to adverse environmental conditions.The goal of this study is to define the role of Cel,and Cel in conjunction with CA in protecting STEC against stress.STEC cells producing solely Cel (Cel+CA-) or Cel in conjunction with CA (Cel+CA+) and their Cel-deficient mutants (Cel-CA-or Cel-CA+) were subjected to oxidative (10,20 and 30 mM H202),osmotic (1,2 and 3 M NaC1) and acidic (pH 3.0,3.5 and 4.5) stress.