Dissertation/Thesis Abstract

Sigma Factor N: A Novel Regulator of Acid Resistance and Locus of Enterocyte Effacement in Escherichia coli O157:H7
by Mitra, Avishek, Ph.D., University of South Florida, 2014, 192; 3617860
Abstract (Summary)

In enterohemorrhagic E. coli (EHEC) sigma factor N (σ N) regulates glutamate-dependent acid resistance (GDAR) and the locus of enterocyte effacement (LEE), discrete genetic systems 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 σS activity, phenocopies rpoNN) and ntrC null strains for GDAR and LEE control, acid resistance and adherence. Upregulation of fliZ by NtrC/σN is indirect, requiring an intact flagellar regulator flhDC. Activation of flhDC by NtrC/σN and FlhDC-dependent regulation of GDAR and the LEE is dependent on σ N-promoter flhDP2, and a newly described NtrC upstream activator sequence. While the addition of ammonium significantly alters GDAR and LEE expression, acid resistance and adherence, it does so 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, abrogates NtrC/σN-dependent control of flhDC, fliZ, GDAR and LEE genes.

Indexing (document details)
Advisor: Riordan, James
Commitee: Scott, Katie, Shaw, Lindsey, Stevens, Stanley
School: University of South Florida
Department: Biology (Cell Biology, Microbiology, Molecular Biology)
School Location: United States -- Florida
Source: DAI-B 75/08(E), Dissertation Abstracts International
Subjects: Molecular biology
Keywords: Acid resistance, Enterohemorrhagic E. coli, Glutamate-dependent acid resistance, Locus of enterocyte effacement, Sigma factor N
Publication Number: 3617860
ISBN: 978-1-303-85693-8
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