title: Impact of nutritional factors on the proteome of intestinal Escherichia coli: induction of OxyR-dependent proteins AhpF and Dps by a lactose-rich diet.
abstract: To study the impact of nutritional factors on protein expression of intestinal bacteria, gnotobiotic mice monoassociated with Escherichia coli K-12 were fed three different diets: a diet rich in starch, a diet rich in nondigestible lactose, and a diet rich in casein. Two-dimensional gel electrophoresis and electrospray-tandem mass spectrometry were used to identify differentially expressed proteins of bacteria recovered from small intestine and cecum. Oxidative stress response proteins such as AhpF, Dps, and Fur, all of which belong to the oxyR regulon, were upregulated in E. coli isolates from mice fed the lactose-rich diet. Luciferase reporter gene assays demonstrated that osmotic stress caused by carbohydrates led to the expression of ahpCF and dps, which was not observed in an E. coli ΔoxyR mutant. Growth of ahpCF and oxyR deletion mutants was strongly impaired when nondigestible sucrose was present in the medium. The wild-type phenotype could be restored by complementation of the deletions with plasmids containing the corresponding genes and promoters. The results indicate that some OxyR-dependent proteins play a major role in the adaptation of E. coli to osmotic stress. We conclude that there is an overlap of osmotic and oxidative stress responses. Mice fed the lactose-rich diet possibly had a higher intestinal osmolality, leading to the upregulation of OxyR-dependent proteins, which enable intestinal E. coli to better cope with diet-induced osmotic stress.
authors.affiliation: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany.
authors.forename: Monique
authors.initials: M
authors.lastname: Rothe
authors.forename: Carl
authors.initials: C
authors.lastname: Alpert
authors.forename: Wolfram
authors.initials: W
authors.lastname: Engst
authors.forename: Stephanie
authors.initials: S
authors.lastname: Musiol
authors.forename: Gunnar
authors.initials: G
authors.lastname: Loh
authors.forename: Michael
authors.initials: M
authors.lastname: Blaut
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis*; D004032:Diet / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional; D048168:Escherichia coli K12 / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D041981:Gastrointestinal Tract / Q000382:microbiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D007785:Lactose / Q000008:administration & dosage*; D051379:Mice; D009997:Osmotic Pressure; D054464:Peroxiredoxins / Q000032:analysis*; D020543:Proteome / Q000032:analysis*; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013312:Stress, Physiological; D053719:Tandem Mass Spectrometry
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; D020543:Proteome; D012097:Repressor Proteins; C088010:dps protein, E coli; C499299:oxyR protein, E coli; D054464:Peroxiredoxins; C515938:ahpF protein, E coli; D007785:Lactose