{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/140924"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/140924","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Investigating Hfq-dependent Small Regulatory RNA, Bsr34, and Its Roles in Brucella abortus Physiology and Pathogenicity","abstract":"Brucellosis, a debilitating zoonotic disease caused by the facultative intracellular pathogen Brucella, relies on rapid gene regulation for survival within host cells. Small regulatory RNAs (sRNAs), often chaperoned by Hfq, are key post-transcriptional regulators of bacterial virulence and stress adaptation, yet remain largely uncharacterized in Brucella. Following the identification of Hfq-associated sRNA candidates in B. suis, this study provides the first functional characterization of Bsr34, an Hfq-dependent sRNA in B. abortus 2308. We confirmed that Bsr34 expression is entirely Hfq-dependent. Phenotypic analysis of a Δbsr34 mutant revealed no defects in in vitro growth or general stress survival but showed significant attenuation in a murine infection model, indicating a specific role in virulence. While an initial chloramphenicol sensitivity phenotype was inconsistent, expression profiling demonstrated that Bsr34 is specifically downregulated under envelope stress (polymyxin B) and acidic pH, but not under oxidative or nutrient stress. Collectively, these findings establish Bsr34 as a bona fide Hfq dependent sRNA involved in host-specific adaptation and stress response, laying the groundwork for future studies to identify its regulatory targets and elucidate its precise role in Brucella pathogenesis.","abstract_html":"Brucellosis, a debilitating zoonotic disease caused by the facultative intracellular pathogen Brucella, relies on rapid gene regulation for survival within host cells. Small regulatory RNAs (sRNAs), often chaperoned by Hfq, are key post-transcriptional regulators of bacterial virulence and stress adaptation, yet remain largely uncharacterized in Brucella. Following the identification of Hfq-associated sRNA candidates in B. suis, this study provides the first functional characterization of Bsr34, an Hfq-dependent sRNA in B. abortus 2308. We confirmed that Bsr34 expression is entirely Hfq-dependent. Phenotypic analysis of a Δbsr34 mutant revealed no defects in in vitro growth or general stress survival but showed significant attenuation in a murine infection model, indicating a specific role in virulence. While an initial chloramphenicol sensitivity phenotype was inconsistent, expression profiling demonstrated that Bsr34 is specifically downregulated under envelope stress (polymyxin B) and acidic pH, but not under oxidative or nutrient stress. Collectively, these findings establish Bsr34 as a bona fide Hfq dependent sRNA involved in host-specific adaptation and stress response, laying the groundwork for future studies to identify its regulatory targets and elucidate its precise role in Brucella pathogenesis.","abstract_has_math":false,"creators":["Saeed, Tahaa"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Biomedical and Veterinary Sciences","degree_department":"Biomedical and Veterinary Sciences","school":null,"contributors":[],"advisors":[],"committee_chairs":["Caswell, Clayton Christopher"],"committee_members":["Allen, Irving Coy","Gloag, Erin Samantha","Wang, Xiaogang"],"year":2026,"date_issued":"2026-01-21","date_published":"2026-01-21","updated_at":"2026-07-22T22:20:34Z","subjects":["Brucella abortus","sRNA","Hfq","Bsr34","virulence","stress response","pathogenesis"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45645"],"render_values":[{"text":"vt_gsexam:45645","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/140924","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Caswell, Clayton Christopher"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Allen, Irving Coy","Gloag, Erin Samantha","Wang, Xiaogang"]},{"key":"dc:contributor.department","label":"Department","values":["Biomedical and Veterinary Sciences"]},{"key":"dc:creator","label":"Author","values":["Saeed, Tahaa"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-01-22T09:00:12Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-01-22T09:00:12Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-01-21"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biomedical and Veterinary Sciences"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Brucella abortus","sRNA","Hfq","Bsr34","virulence","stress response","pathogenesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45645"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/140924"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Brucellosis, a debilitating zoonotic disease caused by the facultative intracellular pathogen Brucella, relies on rapid gene regulation for survival within host cells. Small regulatory RNAs (sRNAs), often chaperoned by Hfq, are key post-transcriptional regulators of bacterial virulence and stress adaptation, yet remain largely uncharacterized in Brucella. Following the identification of Hfq-associated sRNA candidates in B. suis, this study provides the first functional characterization of Bsr34, an Hfq-dependent sRNA in B. abortus 2308. We confirmed that Bsr34 expression is entirely Hfq-dependent. Phenotypic analysis of a Δbsr34 mutant revealed no defects in in vitro growth or general stress survival but showed significant attenuation in a murine infection model, indicating a specific role in virulence. While an initial chloramphenicol sensitivity phenotype was inconsistent, expression profiling demonstrated that Bsr34 is specifically downregulated under envelope stress (polymyxin B) and acidic pH, but not under oxidative or nutrient stress. Collectively, these findings establish Bsr34 as a bona fide Hfq dependent sRNA involved in host-specific adaptation and stress response, laying the groundwork for future studies to identify its regulatory targets and elucidate its precise role in Brucella pathogenesis."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["Brucellosis is a serious infectious disease transmitted from infected animals to humans, causing debilitating flu-like symptoms and fever. Despite prolonged antibiotic treatment, brucellosis frequently relapses, and no available drug regimen is capable of fully eradicating the infection. The bacterium responsible, Brucella abortus, has a remarkable ability to survive inside host cells where it faces numerous environmental challenges including acidic conditions, nutrient limitation, and attack by the immune system. To rapidly adapt to these hostile conditions, Brucella uses specialized molecular tools called small regulatory RNAs (sRNAs), short nucleotide fragments that act like switches to quickly turn genes on or off in response to stress. Bsr34 is one such small RNA that was discovered in Brucella but has never been studied in detail. We hypothesized that Bsr34 plays an important role in helping the bacteria survive stress and cause disease. To test this, we created a mutant strain of B. abortus lacking Bsr34 and compared its behavior to normal bacteria. Our experiments revealed several important findings: First, we confirmed that Bsr34 requires a helper protein called Hfq to remain stable without Hfq, Bsr34 completely disappears. Second, Bsr34 is present in all Brucella species but not in other bacteria, suggesting a Brucella-specific function. Third, while bacteria lacking Bsr34 grew normally under laboratory conditions, Bsr34 levels dropped dramatically when bacteria faced envelope stress or acidic environments, conditions encountered inside host cells. Most importantly, when tested in mice, Brucella lacking Bsr34 showed significantly reduced ability to colonize and persist in the spleen at both 1 week and 4 weeks post-infection. This demonstrates that Bsr34 is specifically required for survival and disease within the host, even though it isn't essential for basic survival in the laboratory. These discoveries provide the first glimpse into how Bsr34 functions as a specialized tool for infection rather than general bacterial survival. However, many questions remain unanswered. We still don't know exactly which genes Bsr34 controls or the precise molecular mechanisms by which it helps bacteria adapt to the host environment. Future research will focus on identifying Bsr34's target genes and understanding how this small RNA coordinates the bacteria's response to the stresses encountered during infection. Understanding these small RNA regulators could eventually lead to new strategies for treating or preventing brucellosis by targeting the molecular switches that help Brucella survive inside host cells and cause disease."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Investigating Hfq-dependent Small Regulatory RNA, Bsr34, and Its Roles in Brucella abortus Physiology and Pathogenicity"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Caswell, Clayton Christopher"],"dc:contributor.committeemember":["Allen, Irving Coy","Gloag, Erin Samantha","Wang, Xiaogang"],"dc:contributor.department":["Biomedical and Veterinary Sciences"],"dc:creator":["Saeed, Tahaa"],"dc:date.accessioned":["2026-01-22T09:00:12Z"],"dc:date.available":["2026-01-22T09:00:12Z"],"dc:date.issued":["2026-01-21"],"dc:description.abstract":["Brucellosis, a debilitating zoonotic disease caused by the facultative intracellular pathogen Brucella, relies on rapid gene regulation for survival within host cells. Small regulatory RNAs (sRNAs), often chaperoned by Hfq, are key post-transcriptional regulators of bacterial virulence and stress adaptation, yet remain largely uncharacterized in Brucella. Following the identification of Hfq-associated sRNA candidates in B. suis, this study provides the first functional characterization of Bsr34, an Hfq-dependent sRNA in B. abortus 2308. We confirmed that Bsr34 expression is entirely Hfq-dependent. Phenotypic analysis of a Δbsr34 mutant revealed no defects in in vitro growth or general stress survival but showed significant attenuation in a murine infection model, indicating a specific role in virulence. While an initial chloramphenicol sensitivity phenotype was inconsistent, expression profiling demonstrated that Bsr34 is specifically downregulated under envelope stress (polymyxin B) and acidic pH, but not under oxidative or nutrient stress. Collectively, these findings establish Bsr34 as a bona fide Hfq dependent sRNA involved in host-specific adaptation and stress response, laying the groundwork for future studies to identify its regulatory targets and elucidate its precise role in Brucella pathogenesis."],"dc:description.abstractgeneral":["Brucellosis is a serious infectious disease transmitted from infected animals to humans, causing debilitating flu-like symptoms and fever. Despite prolonged antibiotic treatment, brucellosis frequently relapses, and no available drug regimen is capable of fully eradicating the infection. The bacterium responsible, Brucella abortus, has a remarkable ability to survive inside host cells where it faces numerous environmental challenges including acidic conditions, nutrient limitation, and attack by the immune system. To rapidly adapt to these hostile conditions, Brucella uses specialized molecular tools called small regulatory RNAs (sRNAs), short nucleotide fragments that act like switches to quickly turn genes on or off in response to stress. Bsr34 is one such small RNA that was discovered in Brucella but has never been studied in detail. We hypothesized that Bsr34 plays an important role in helping the bacteria survive stress and cause disease. To test this, we created a mutant strain of B. abortus lacking Bsr34 and compared its behavior to normal bacteria. Our experiments revealed several important findings: First, we confirmed that Bsr34 requires a helper protein called Hfq to remain stable without Hfq, Bsr34 completely disappears. Second, Bsr34 is present in all Brucella species but not in other bacteria, suggesting a Brucella-specific function. Third, while bacteria lacking Bsr34 grew normally under laboratory conditions, Bsr34 levels dropped dramatically when bacteria faced envelope stress or acidic environments, conditions encountered inside host cells. Most importantly, when tested in mice, Brucella lacking Bsr34 showed significantly reduced ability to colonize and persist in the spleen at both 1 week and 4 weeks post-infection. This demonstrates that Bsr34 is specifically required for survival and disease within the host, even though it isn't essential for basic survival in the laboratory. These discoveries provide the first glimpse into how Bsr34 functions as a specialized tool for infection rather than general bacterial survival. However, many questions remain unanswered. We still don't know exactly which genes Bsr34 controls or the precise molecular mechanisms by which it helps bacteria adapt to the host environment. Future research will focus on identifying Bsr34's target genes and understanding how this small RNA coordinates the bacteria's response to the stresses encountered during infection. Understanding these small RNA regulators could eventually lead to new strategies for treating or preventing brucellosis by targeting the molecular switches that help Brucella survive inside host cells and cause disease."],"dc:description.degree":["Master of Science"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:45645"],"dc:identifier.uri":["https://hdl.handle.net/10919/140924"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Brucella abortus","sRNA","Hfq","Bsr34","virulence","stress response","pathogenesis"],"dc:title":["Investigating Hfq-dependent Small Regulatory RNA, Bsr34, and Its Roles in Brucella abortus Physiology and Pathogenicity"],"dc:type":["Thesis"],"thesis:degree_discipline":["Biomedical and Veterinary Sciences"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:34Z"}