Date Thesis Awarded

5-2020

Document Type

Honors Thesis

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Mark Forsyth

Committee Members

Shantá D. Hinton

Kurt Williamson

Dennis Smith

Abstract

The acid acclimation capabilities of Helicobacter pylori allow it to colonize the gastric biome for decades, causing many adverse health effects for its human host. The Acid Response System (ArsRS) accomplishes much of the H. pylori acid response by inducing the transcription of subunits and accessory genes of the enzyme urease. Hydrolyzing urea into CO2 and NH3 to buffer the periplasm facilitates long term bacterial survival.

We used H. pylori isogenic mutants of ArsRS and other TCS (DarsS, and DarsS-DcrdS-DflgS) to examine TCS-independent pH mediated gene expression. Control and TCS mutants were treated at pH 7 and pH 5 and RNA was sequenced demonstrating the induction of four genes in the Plasticity Zone, including two virB4 Type IV Secretion/Conjugation ATPases (HP0441 and HP0459) and two hypothetical proteins (HP0447 and HP0453) in the TCS mutant strains (DarsS and DarsS-DcrdS-DflgS). The transcriptomic analyses also revealed two genes that were differentially expressed in the control and both TCS H. pylori mutants. HP0897, likely a dnaC homolog, was induced at pH 5 in all three mutants over multiple biological replicates. HP0996, encoding a relaxase, was repressed in all three H. pylori mutants at pH 5, as was an IS605 Transposase B (tnpB) (HP0997) which was repressed in the two TCS mutants.

Transcriptomic analyses were verified using Quantitative Real Timer Polymerase Chain Reaction (qRT-PCR). Early results verified the induction of HP0447, HP0453, and virB4 (HP0459) in the control mutant and DarsS-DcrdS-DflgS. Further qRT-PCR analyses are necessary to better characterize the expression of these genes. qRT-PCR results for HP0996 and tnpB (HP0997) did not verify the transcriptomic data. No consistent trend in differential expression for either gene could be determined by qRT-PCR in any of the mutants studied. These genes require further qRT-PCR analyses to determine their true pH 5 response.

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