Extreme acid resistance contributes to the successful transmission of enterohemorrhagic E. coli (EHEC) through acidic food matrices and the stomach, allowing it to gain access to the intestine and elicit disease in humans. Alternative sigma factor N (σN, encoded by rpoN) was previously identified as a novel regulator of extreme acid resistance in EHEC. This study investigated the role for σN and co-expressed products of the rpoN operon in the acid resistance phenotype of EHEC. The results revealed that σN primarily controls acid resistance through repression of the glutamate-dependent acid resistance (GDAR) system through control of the σS-directed GadXW pathway. σN was also determined to repress additional acid resistance systems, including arginine-dependent acid resistance, and an anaerobic acid resistance mechanism. Two gene products of the rpoN operon, hpf and ptsN, were also determined to negatively affect GDAR, as well as expression of the σN dependent genes glnA, astA, and pspA. Mutation of hpf and ptsN did not however alter the transcription of rpoN. Transcript levels of rpoN operon genes were observed to be differential, and inconsistent with the hypothesis of expression as a single transcriptional unit. Together this data signifies the importance of rpoN operon genes in the negative regulation of extreme acid resistance systems, and suggests that the products of hpf and ptsN control the activity of σN at its promoters.
|Advisor:||Riordan, James T.|
|Commitee:||Scott, Kathleen M., Shaw, Lindsey N.|
|School:||University of South Florida|
|Department:||Biology (Cell Biology, Microbiology, Molecular Biology)|
|School Location:||United States -- Florida|
|Source:||MAI 51/01M(E), Masters Abstracts International|
|Subjects:||Molecular biology, Microbiology|
|Keywords:||ADAR, EHEC, Escherichia coli, GDAR, QRT-PCR, rpoN|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be