title: The gluconeogenesis pathway is involved in maintenance of enterohaemorrhagic Escherichia coli O157:H7 in bovine intestinal content.
abstract: Enterohaemorrhagic Escherichia coli (EHEC) are responsible for outbreaks of food- and water-borne illness. The bovine gastrointestinal tract (GIT) is thought to be the principle reservoir of EHEC. Knowledge of the nutrients essential for EHEC growth and survival in the bovine intestine may help in developing strategies to limit their shedding in bovine faeces thus reducing the risk of human illnesses. To identify specific metabolic pathways induced in the animal GIT, the transcriptome profiles of EHEC O157:H7 EDL933 during incubation in bovine small intestine contents (BSIC) and minimal medium supplemented with glucose were compared. The transcriptome analysis revealed that genes responsible for the assimilation of ethanolamine, urea, agmatine and amino acids (Asp, Thr, Gly, Ser and Trp) were strongly up-regulated suggesting that these compounds are the main nitrogen sources for EHEC in BSIC. A central role for the gluconeogenesis pathway and assimilation of gluconeogenic substrates was also pinpointed in EHEC incubated in BSIC. Our results suggested that three amino acids (Asp, Ser and Trp), glycerol, glycerol 3-phosphate, L-lactate and C4-dicarboxylates are important carbon sources for EHEC in BSIC. The ability to use gluconeogenic substrates as nitrogen sources (amino acids) and/or carbon sources (amino acids, glycerol and lactate) may provide a growth advantage to the bacteria in intestinal fluids. Accordingly, aspartate (2.4 mM), serine (1.9 mM), glycerol (5.8 mM) and lactate (3.6 mM) were present in BSIC and may represent the main gluconeogenic substrates potentially used by EHEC. A double mutant of E. coli EDL933 defective for phosphoenolpyruvate synthase (PpsA) and phosphoenolpyruvate carboxykinase (PckA), unable to utilize tricarboxylic acid (TCA) intermediates was constructed. Growth competition experiments between EHEC EDL933 and the isogenic mutant strain in BSIC clearly showed a significant competitive growth advantage of the wild-type strain further illustrating the importance of the gluconeogenesis pathway in maintaining EHEC in the bovine GIT.
authors.affiliation: Institut National de la Recherche Agronomique, UR454 Microbiologie, Saint-Genès-Champanelle, France.
authors.forename: Yolande
authors.initials: Y
authors.lastname: Bertin
authors.affiliation: Institut National de la Recherche Agronomique, UMR 1019, Unité de Nutrition Humaine, Centre de Recherche en Nutrition Humaine d'Auvergne, Clermont-Ferrand, France; Clermont Université, Université d'Auvergne, Unité de Nutrition Humaine, BP 10448, Clermont-Ferrand, France.
authors.forename: Christiane
authors.initials: C
authors.lastname: Deval
authors.affiliation: Institut National de la Recherche Agronomique, UMR1213 Herbivores, Plate-Forme d'Exploration du Métabolisme, Saint-Genès-Champanelle, France.
authors.forename: Anne
authors.initials: A
authors.lastname: de la Foye
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec, Canada.
authors.forename: Luke
authors.initials: L
authors.lastname: Masson
authors.affiliation: Laboratory for Foodborne Zoonoses, Public Health Agency of Canada, Lethbridge, Alberta, Canada.
authors.forename: Victor
authors.initials: V
authors.lastname: Gannon
authors.affiliation: Groupe de Recherche sur les Maladies Infectieuses du Porc, Université de Montréal, Faculté de Médecine Vétérinaire, Saint-Hyacinthe, Québec, Canada.
authors.forename: Josée
authors.initials: J
authors.lastname: Harel
authors.affiliation: Institut National de la Recherche Agronomique, UR454 Microbiologie, Saint-Genès-Champanelle, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Martin
authors.affiliation: Institut National de la Recherche Agronomique, UR454 Microbiologie, Saint-Genès-Champanelle, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Desvaux
authors.affiliation: Institut National de la Recherche Agronomique, UR454 Microbiologie, Saint-Genès-Champanelle, France.
authors.forename: Evelyne
authors.initials: E
authors.lastname: Forano
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D017931:DNA Primers; D019453:Escherichia coli O157 / Q000302:isolation & purification* / Q000502:physiology; D005943:Gluconeogenesis; D007422:Intestines / Q000382:microbiology*; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers