title: σ(N) -dependent control of acid resistance and the locus of enterocyte effacement in enterohemorrhagic Escherichia coli is activated by acetyl phosphate in a manner requiring flagellar regulator FlhDC and the σ(S) antagonist FliZ.
abstract: In enterohemorrhagic Escherichia coli (EHEC), sigma factor N (σ(N)) regulates glutamate-dependent acid resistance (GDAR) and the locus of enterocyte effacement (LEE); discrete genetic systems that are required for transmission and virulence of this intestinal pathogen. Regulation of these systems requires nitrogen regulatory protein C, NtrC, and is a consequence of NtrC-σ(N) -dependent reduction in the activity of sigma factor S (σ(S)). This study elucidates pathway components and stimuli for σ(N)-directed regulation of GDAR and the LEE in EHEC. Deletion of fliZ, the product of which reduces σ(S) activity, phenocopied rpoN (σ(N)) and ntrC null strains for GDAR and LEE control, acid resistance, and adherence. Upregulation of fliZ by NtrC-σ(N) was shown to be indirect and required an intact flagellar regulator flhDC. Activation of flhDC by NtrC-σ(N) and FlhDC-dependent regulation of GDAR and the LEE was dependent on σ(N)-promoter flhDP 2 , and a newly described NtrC upstream activator sequence. Addition of ammonium chloride significantly altered expression of GDAR and LEE, acid resistance, and adherence, independently of rpoN, ntrC, and the NtrC sensor kinase, ntrB. Altering the availability of NtrC phosphodonor acetyl phosphate by growth without glucose, with acetate addition, or by deletion of acetate kinase ackA, abrogated NtrC-σ(N)-dependent control of flhDC, fliZ, GDAR, and the LEE.
authors.affiliation: Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, Florida, 33620.
authors.forename: Avishek
authors.initials: A
authors.lastname: Mitra
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Fay
authors.forename: Khoury W
authors.initials: KW
authors.lastname: Vendura
authors.forename: Zimrisha
authors.initials: Z
authors.lastname: Alla
authors.forename: Ronan K
authors.initials: RK
authors.lastname: Carroll
authors.forename: Lindsey N
authors.initials: LN
authors.lastname: Shaw
authors.forename: James T
authors.initials: JT
authors.lastname: Riordan
mesh_terms: D002264:Carboxylic Acids / Q000378:metabolism; D004361:Drug Tolerance; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005971:Glutamates / Q000378:metabolism; D010755:Organophosphates / Q000378:metabolism*; D010750:Phosphoproteins; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D002264:Carboxylic Acids; D029968:Escherichia coli Proteins; C574299:FliZ protein, E coli; D005971:Glutamates; C457340:LEE protein, E coli; D010755:Organophosphates; D010750:Phosphoproteins; D012097:Repressor Proteins; D012808:Sigma Factor; D015534:Trans-Activators; C090552:flhC protein, E coli; C090553:flhD protein, E coli; C011632:acetyl phosphate
keywords: EHEC O157; H7; LEE; NtrC; acid resistance; rpoN; sigma factor N