title: Identification of metabolic pathways essential for fitness of Salmonella Typhimurium in vivo.
abstract: Bacterial infections remain a threat to human and animal health worldwide, and there is an urgent need to find novel targets for intervention. In the current study we used a computer model of the metabolic network of Salmonella enterica serovar Typhimurium and identified pairs of reactions (cut sets) predicted to be required for growth in vivo. We termed such cut sets synthetic auxotrophic pairs. We tested whether these would reveal possible combined targets for new antibiotics by analyzing the performance of selected single and double mutants in systemic mouse infections. One hundred and two cut sets were identified. Sixty-three of these included only pathways encoded by fully annotated genes, and from this sub-set we selected five cut sets involved in amino acid or polyamine biosynthesis. One cut set (asnA/asnB) demonstrated redundancy in vitro and in vivo and showed that asparagine is essential for S. Typhimurium during infection. trpB/trpA as well as single mutants were attenuated for growth in vitro, while only the double mutant was a cut set in vivo, underlining previous observations that tryptophan is essential for successful outcome of infection. speB/speF,speC was not affected in vitro but was attenuated during infection showing that polyamines are essential for virulence apparently in a growth independent manner. The serA/glyA cut-set was found to be growth attenuated as predicted by the model. However, not only the double mutant, but also the glyA mutant, were found to be attenuated for virulence. This adds glycine production or conversion of glycine to THF to the list of essential reactions during infection. One pair (thrC/kbl) showed true redundancy in vitro but not in vivo demonstrating that threonine is available to the bacterium during infection. These data add to the existing knowledge of available nutrients in the intra-host environment, and have identified possible new targets for antibiotics.
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Lotte
authors.initials: L
authors.lastname: Jelsbak
authors.affiliation: Department of Medical and Biological Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford, United Kingdom.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hartman
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Casper
authors.initials: C
authors.lastname: Schroll
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Jesper T
authors.initials: JT
authors.lastname: Rosenkrantz
authors.affiliation: Center for Systems Microbiology, Department of Systems Biology, Technical University of Denmark, Kongens Lyngby, Denmark.
authors.forename: Sebastien
authors.initials: S
authors.lastname: Lemire
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Inke
authors.initials: I
authors.lastname: Wallrodt
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Line E
authors.initials: LE
authors.lastname: Thomsen
authors.affiliation: Department of Medical and Biological Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Poolman
authors.affiliation: Center for Systems Microbiology, Department of Systems Biology, Technical University of Denmark, Kongens Lyngby, Denmark.
authors.forename: Mogens
authors.initials: M
authors.lastname: Kilstrup
authors.affiliation: Center for Systems Microbiology, Department of Systems Biology, Technical University of Denmark, Kongens Lyngby, Denmark.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Jensen
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: John E
authors.initials: JE
authors.lastname: Olsen
mesh_terms: D000818:Animals; D001216:Asparagine / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003198:Computer Simulation; D005260:Female; D056084:Genetic Fitness; D006801:Humans; D053858:Metabolic Networks and Pathways; D051379:Mice; D008810:Mice, Inbred C57BL; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000472:pathogenicity*; D014364:Tryptophan / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; D001216:Asparagine; D014364:Tryptophan