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Title:   Author  item
                                            Bearson, Bradley

                                                         - *Brad*item
                                            Bearson, Shawnitem
                                            Casey, Thomas
  Submitted to: American Society for Microbiology
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 2/21/2003
                                    Publication  Date: 5/22/2003
                                    Citation: BEARSON, B.L., BEARSON, S.M., CASEY, T.A. GLUTATHIONE IS REQUIRED FOR ACID RESISTANCE IN E. COLI O157:H7. AMERICAN SOCIETY FOR MICROBIOLOGY. 2003. ABSTRACT P. 365.Interpretive Summary:
                                Technical Abstract: In Escherichia coli, the reduced cytoplasmic environment is maintained by the glutathione- and thioredoxin-dependent reduction systems.  Glutathione is important for the detoxification of an array of toxic substances.  To determine if a reduced intracellular environment provided by glutathione is important during acid stress, glutathione synthase (gshB) mutants of Salmonella typhimurium and E. coli O157:H7 were constructed.  The gshB mutants were assayed for survival during acid challenge in the log phase acid tolerance of S. typhimurium and the stationary phase acid resistance of E. coli O157:H7.  Acid tolerance assays for S. typhimurium were performed by adapting log phase cultures in EG medium to pH 4.4 for 1 hour followed by acid challenge at pH 3.0.  The acid resistance of E. coli O157:H7 was determined using assays for acid-resistance system 1 and system 2.  The acid-resistance system 1 was assayed by growth of an O.N. culture in LB 100 mM MES medium pH 5.5 with acid challenge in EG medium pH 2.5.  The acid-resistance system 2 was assayed by O.N. culture growth in LB glucose medium with acid challenge in EG 2 mM glutamate medium pH 2.5.  Survival of the E. coli O157:H7 gshB mutant was reduced ~ 100-fold for acid-resistance system 1 after a four hour acid challenge, indicating that glutathione is required during acid challenge for E. coli acid-resistance system 1.  However, for acid-resistance system 2, the acid resistance phenotype of the E. coli O157:H7 gshB mutant was similar to wild-type during acid challenge.  For S. typhimurium, the acid tolerance phenotype of the gshB mutant was similar to wild-type.  Thus, glutathione is either not required during acid challenge or an overlapping system compensates for the absence of glutathione in the gshB mutant of S. typhimurium.


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