Niche adaptation in Campylobacter jejuni and Helicobacter pylori

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Thompson, S.R., 2022. Niche adaptation in Campylobacter jejuni and Helicobacter pylori. PhD, Nottingham Trent University.

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Abstract

Campylobacter jejuni and Helicobacter pylori represent two major human pathogens. C. jejuni related gastroenteritis (campylobacteriosis) is considered the leading cause of human bacterial gastroenteritis cases worldwide and H. pylori infection although asymptomatic in the majority of cases can increase the risk of developing peptic ulcers and gastric adenocarcinoma. This thesis investigates different populations within these two bacteria and how they vary phenotypically and genomically from each other and how this may relate to niche adaptation ability.

In C. jejuni, research was focussed on strains belonging to the 403 Clonal-Complex (MLST). The 403CC represents a lineage that seemingly demonstrates a near inability to colonise poultry hosts which is atypical, given poultry are a major zoonotic reservoir for C. jejuni carriage. Phenotypic testing found no significant differences between 403CC isolates and chicken isolates, except that during initial growth at 42oC (6-9 h) chicken isolates grew statistically significantly faster. Genome analysis showed a 403CC lineage specific genome content particularly a restriction-modification system (Hha1m) has been described in previous research and this association still holds true.

In H. pylori the aim was to characterise the phenotypic and genomic properties of antrum/corpus paired strains isolated from the respective regions of patient’s stomachs. No statistically significant differences were observed in phenotypic ability between antrum and corpus strains across a range of assays or genomically. The transcriptional effect of sub-MIC concentrations of menadione on H. pylori 322A was demonstrated by whole RNA-Sequencing. Menadione generates superoxides by redox cycling thus replicating niche oxidative stress in the gastric niche. Treatment with menadione compared to untreated samples caused 1312 significantly differentially expressed genes. 89 metabolic pathways, particularly epithelial cell signalling in H. pylori infection were affected. Major genes cagA, vacA, ureA/B/I luxS, and ruvC were all downregulated.

Niches play an important role in both C. jejuni and H. pylori in the wider context of the organisms as human pathogens. The research presented compares niche adaptation within these organisms and demonstrates for the first time the effect of menadione on the whole H. pylori transcriptome.

Item Type:	Thesis
Creators:	Thompson, S.R.
Date:	October 2022
Rights:	The copyright in this work is held by the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the author.
Divisions:	Schools > School of Science and Technology
Record created by:	Jeremy Silvester
Date Added:	02 Jun 2023 13:28
Last Modified:	02 Jun 2023 13:28
URI:	https://irep.ntu.ac.uk/id/eprint/49105