title: Escherichia coli O157 : H7 glutamate- and arginine-dependent acid-resistance systems protect against oxidative stress during extreme acid challenge.
abstract: Micro-organisms may simultaneously encounter multiple stresses in their environment. To investigate the protection that several known Escherichia coli O157 : H7 acid-resistance systems might provide against both oxidative and acid stress, the addition of diamide, a membrane-permeable thiol-specific oxidizing agent, or hydrogen peroxide were used concurrent with acid challenge at pH 2.5 to determine bacterial survival. The addition of either diamide or hydrogen peroxide decreased bacterial survival in a dose-dependent manner for E. coli O157 : H7 during challenge at pH 2.5 following overnight growth in LB MES pH 5.5 (acid-resistance system 1, AR1). In contrast, the presence of either glutamate or arginine during challenge provided significant protection against diamide- and hydrogen peroxide-induced oxidative stress during pH 2.5 acid challenge. Oxidative stress protection during acid challenge required gadC and adiA for the glutamate- (AR2) and arginine- (AR3) dependent acid-resistance systems, respectively. In addition, maximal protection against oxidative stress in the presence of glutamate required a low external pH (pH 2.5), since pH 5.5 did not protect. This study demonstrates that the glutamate- and arginine-dependent acid-resistance systems of E. coli O157 : H7 can simultaneously protect against oxidative stress during extreme acid challenge.
authors.affiliation: Swine Odor and Manure Management Research Unit, USDA, ARS, National Soil Tilth Laboratory, NSRIC-2103, Ames, IA 50011, USA.
authors.forename: Bradley L
authors.initials: BL
authors.lastname: Bearson
authors.affiliation: Department of Biotechnology, Hannam University, Daejeon 305-811, Republic of Korea.|Swine Odor and Manure Management Research Unit, USDA, ARS, National Soil Tilth Laboratory, NSRIC-2103, Ames, IA 50011, USA.
authors.forename: In Soo
authors.initials: IS
authors.lastname: Lee
authors.affiliation: Pre-harvest Food Safety and Enteric Diseases Research Unit, USDA, ARS, National Animal Disease Center, Ames, IA 50010, USA.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Casey
mesh_terms: D000143:Acids / Q000494:pharmacology*; D001120:Arginine / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000378:metabolism; D003958:Diamide / Q000378:metabolism; D019453:Escherichia coli O157 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D018698:Glutamic Acid / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D018384:Oxidative Stress
chemical_list: D000143:Acids; D029968:Escherichia coli Proteins; C491226:GadC protein, E coli; D008565:Membrane Proteins; D003958:Diamide; D018698:Glutamic Acid; D001120:Arginine; D006861:Hydrogen Peroxide; D002262:Carboxy-Lyases; C019722:arginine decarboxylase