title: Characterization of relA and codY mutants of Listeria monocytogenes: identification of the CodY regulon and its role in virulence.
abstract: Listeria monocytogenes is a Gram-positive intracellular parasite and the causative organism of human listeriosis. In this article we demonstrate that L. monocytogenes encodes a functional member of the CodY family of global regulatory proteins that is responsive to both GTP and branched chain amino acids. By transcript analyses we identified the CodY regulon in L. monocytogenes and demonstrated that it comprises genes involved in amino acid metabolism, nitrogen assimilation as well as genes involved in sugar uptake and incorporation, indicating a role for CodY in L. monocytogenes in both carbon and nitrogen assimilation. A DeltarelA mutation reduced expression of the CodY regulon in early stationary phase and introduction of a DeltacodY mutation into a DeltarelA strain restored virulence. These data indicate that the avirulence of the DeltarelA mutant can in part be explained by the continued repression of the CodY regulon. The phenotypes of DeltarelA and DeltacodY mutants were studied in J774.A1 and Caco-2 cells and the DeltarelA mutation shown to effect intracellular growth. These results provide the first direct evidence that the activity of a CodY-type protein influences pathogenesis and provides new information on the physiological adaptation of L. monocytogenes to post-exponential phase growth and virulence.
authors.affiliation: 1.800 Stopford Building, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
authors.forename: Hayley J
authors.initials: HJ
authors.lastname: Bennett
authors.forename: David M
authors.initials: DM
authors.lastname: Pearce
authors.forename: Sarah
authors.initials: S
authors.lastname: Glenn
authors.forename: Clare M
authors.initials: CM
authors.lastname: Taylor
authors.forename: Michael
authors.initials: M
authors.lastname: Kuhn
authors.forename: Abraham L
authors.initials: AL
authors.lastname: Sonenshein
authors.forename: Peter W
authors.initials: PW
authors.lastname: Andrew
authors.forename: Ian S
authors.initials: IS
authors.lastname: Roberts
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D002460:Cell Line; D020895:Enterocytes / Q000382:microbiology; D005260:Female; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D008025:Ligases / Q000235:genetics*; D008089:Listeria monocytogenes / Q000235:genetics* / Q000254:growth & development; D008264:Macrophages / Q000382:microbiology; D008660:Metabolism / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases