Brucella abortus is a bacterial species that infects cattle, elk, and bison herds worldwide and is a causative agent of brucellosis. B. abortus is a common form of zoonosis, as incidental spillover into the human population results in millions of infections annually. Current treatment options are limited to culling infected animals and treating humans with a rigorous antibiotic regimen, which still results in up to a 30% relapse rate. Detection of the pathogen is difficult due to the replicative niche residing within the host's immune cells, specifically macrophages and dendritic cells. Numerous small regulatory RNAs (sRNAs) were found to be expressed by B. abortus, and it was hypothesized that they may be important for virulence. One sRNA, when deleted, was shown to be linked to outer membrane stress resistance and was named MssR (membrane sensitivity sRNA). When the ΔmssR strain was tested in both macrophage and mouse models of infection, there were no virulence defects. Additionally, proteomic and transcriptomic studies of the ΔmssR strain showed very few dysregulated targets. Expression of mssR was tested under numerous biologically relevant conditions, and it was shown to be expressed significantly more during exponential phase of growth, compared to stationary phase. Initial microscopical analysis of mutant cells after treatment with sodium dodecyl sulfate (SDS_ did not reveal any morphological differences. It is unknown what contributes to the observed phenotypes and additional experiments are required to determine what is causing the perturbations in the outer membrane of the ΔmssR strain. / Master of Science / Brucella abortus is a bacterial species that causes the disease brucellosis in cattle and humans worldwide. To understand how B. abortus establishes infection, we are studying how the bacteria control the expression of genes during the process of infection. One method of bacterial gene regulation is the use of small regulatory RNAs (sRNAs). These small transcripts are similar to mRNAs but are shorter in length and typically do not encode for a protein. One such sRNA in B. abortus was shown to be linked to sensitivity to outer membrane stress and was named Membrane Sensitivity sRNA (MssR). After engineering a strain of B. abortus that does not produce MssR, there were no differences in the ability of the bacteria to infect macrophages or mice. Additionally, there were no noticable differences in the structure of the bacterial cells. When sRNAs regulate gene expression, differences can be seen at the mRNA and protein levels when the sRNAs are deleted. Very few targets were found be dysregulated at the transcript and protein level within the ΔmssR mutant. It is unknown what is causing the mutant to be more sensitive to outer membrane perturbations and additional tests are necessary to determine how MssR is linked to this phenotype.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/117201 |
| Date | 14 December 2023 |
| Creators | Stoyanof, Stephen Tristan |
| Contributors | Biomedical and Veterinary Sciences, Caswell, Clayton Christopher, Scharf, Birgit, Lahmers, Kevin K., Allen, Irving Coy |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Page generated in 0.0014 seconds