Investigation of small RNAs CjNC110 and CjNC140 and the activated methyl cycle in the pathobiology of Campylobacter jejuni
Date
2022-12
Authors
Ruddell, Brandon Scott
Major Professor
Advisor
Kreuder, Amanda J
Plummer, Paul J
Zhang, Qijing
Sahin, Orhan
Burrough, Eric
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Campylobacter jejuni is a zoonotic pathogen and is one of the leading causes of human gastrointestinal disease worldwide. Additionally, C. jejuni sheep abortion clone (SA), represented by isolate IA3902, is the primary causative agent of sheep abortions caused by Campylobacter spp. within the United States. The transcriptomes of Campylobacter species have been demonstrated to differ even among highly syntenic strains, indicating there may be strain-specific differences in gene regulation leading to unique environmental and host adaptations. One emerging class of regulators that could provide the regulatory link to explain transcriptional and phenotypic differences between highly similar strains are non-coding small RNAs (sRNAs). Small RNAs act post-transcriptionally by base-pairing with mRNAs to activate or repress translation initiation or affect mRNA transcript stability. The lack of sRNA homologs in other bacterial species combined with a lack of known binding proteins has delayed both the discovery and characterization of sRNAs in C. jejuni. Curiously, one of the previously studied sRNAs, CjNC110, is located directly downstream of luxS; LuxS is a central enzyme of the activated methyl cycle (AMC), which may indicate the regulatory network of CjNC110 is connected to the AMC. The AMC is critical for C. jejuni central metabolism, whereby it enables the production of L-methionine (L-met) and the recycling of S-adenosylmethionine (SAM). Thus, the work conducted within this dissertation explores the central hypothesis that C. jejuni sRNA CjNC110, along with associated sRNA CjNC140, and the activated methyl cycle (AMC), are critical for the pathobiology and host colonization of C. jejuni. By utilizing natural genomic differences between C. jejuni NCTC 11168 and IA3902, this work demonstrates the critical role of L-met and the AMC in colonization ability by C. jejuni. This work also provides further insight into the sRNA regulatory network of both CjNC110 and CjNC140, which in addition to regulation of several key phenotypes associated with stress, colonization, and pathogenesis, herein are demonstrated to regulate L-met and SAM levels within the AMC. Uniquely, this work also demonstrates for the first time evidence of a direct interaction between both sRNAs that provides a checks-and-balances system to maintain homeostasis of numerous critical functions of C. jejuni. The collective results of these studies strongly support a critical role for not only sRNAs CjNC110 and CjNC140, but also the AMC, in the ability to establish and maintain colonization of the host, indicating a critical frontier to further study the pathobiology of C. jejuni.
Series Number
Journal Issue
Is Version Of
Versions
Series
Academic or Administrative Unit
Type
dissertation