<p> In enterohemorrhagic <i>E. coli</i> (EHEC) sigma factor N (σ<sup> N</sup>) 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<sup> N</sup>-dependent reduction in the activity of sigma factor S (σ<sup> S</sup>). This study elucidates pathway components and stimuli for σ<sup> N</sup>-directed regulation of GDAR and the LEE in EHEC. Deletion of <i> fliZ,</i> the product of which reduces σ<sup>S</sup> activity, phenocopies <i>rpoN</i> (σ<sup>N</sup>) and <i> ntrC</i> null strains for GDAR and LEE control, acid resistance and adherence. Upregulation of <i>fliZ</i> by NtrC/σ<sup>N</sup> is indirect, requiring an intact flagellar regulator <i>flhDC</i>. Activation of <i>flhDC</i> by NtrC/σ<sup>N</sup> and FlhDC-dependent regulation of GDAR and the LEE is dependent on σ<sup> N</sup>-promoter <i>flhD</i><sub>P2,</sub> 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 <i>rpoN,</i> <i>ntrC</i> and the NtrC sensor kinase <i>ntrB</i>. Altering the availability of NtrC phosphodonor acetyl phosphate by growth without glucose, with acetate addition, or by deletion of acetate kinase, <i>ackA</i>, abrogates NtrC/σ<sup>N</sup>-dependent control of <i>flhDC,</i> <i>fliZ,</i> GDAR and LEE genes. </p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3617860 |
| Date | 10 June 2014 |
| Creators | Mitra, Avishek |
| Publisher | University of South Florida |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
Page generated in 0.0014 seconds