title: Listeria monocytogenes relA and hpt mutants are impaired in surface-attached growth and virulence.
abstract: We describe here the identification and characterization of two Listeria monocytogenes (Tn917-LTV3) relA and hpt transposon insertion mutants that were impaired in growth after attachment to a model surface. Both mutants were unable to accumulate (p)ppGpp in response to amino acid starvation, whereas the wild-type strain accumulated (p)ppGpp within 30 min of stress induction. The induction of transcription of the relA gene after adhesion was demonstrated, suggesting that the ability to mount a stringent response and undergo physiological adaptation to nutrient deprivation is essential for the subsequent growth of the adhered bacteria. The absence of (p)ppGpp in the hpt mutant, which is blocked in the purine salvage pathway, is curious and suggests that a functional purine salvage pathway is required for the biosynthesis of (p)ppGpp. Both mutants were avirulent in a murine model of listeriosis, indicating an essential role for the stringent response in the survival and growth of L. monocytogenes in the host. Taken as a whole, this study provides new information on the role of the stringent response and the physiological adaptation of L. monocytogenes for biofilm growth and pathogenesis.
authors.affiliation: School of Biological Sciences, University of Manchester, 1.800 Stopford Bldg., Oxford Road, Manchester, M13 9PT, UK. mqbsspir@fs1.scg.man.ac.uk
authors.forename: Clare M
authors.initials: CM
authors.lastname: Taylor
authors.forename: Mark
authors.initials: M
authors.lastname: Beresford
authors.forename: Harry A S
authors.initials: HA
authors.lastname: Epton
authors.forename: David C
authors.initials: DC
authors.lastname: Sigee
authors.forename: Gilbert
authors.initials: G
authors.lastname: Shama
authors.forename: Peter W
authors.initials: PW
authors.lastname: Andrew
authors.forename: Ian S
authors.initials: IS
authors.lastname: Roberts
mesh_terms: D000220:Adaptation, Biological; D000596:Amino Acids / Q000172:deficiency; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics*; D002455:Cell Division / Q000235:genetics; D005260:Female; D006159:Guanosine Tetraphosphate / Q000096:biosynthesis; D008089:Listeria monocytogenes / Q000472:pathogenicity* / Q000502:physiology; D051379:Mice; D016254:Mutagenesis, Insertional; D016328:NF-kappa B / Q000235:genetics*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics*; D051996:Transcription Factor RelA
chemical_list: D000596:Amino Acids; D016328:NF-kappa B; D051996:Transcription Factor RelA; D006159:Guanosine Tetraphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C063242:hygromycin-B kinase