Identification of OxyR as an activator of type 1 fimbriae ( <i>fim</i> ) in <i>Salmonella enterica</i> serovar Typhi
Bibliographic record
Abstract
ABSTRACT Salmonella enterica serovar Typhi ( S . Typhi) encodes 14 fimbrial gene clusters, including the mannose-binding type 1 fimbriae known as Fim. Type 1 fimbriae have been implicated in biofilm formation and adhesion to host cells in Salmonella . However, their regulation in S . Typhi remains largely unknown. To identify genes affecting the regulation of fim in S . Typhi, we employed both a targeted and a genome-wide transposon-based screening approach. Overall, we identified 18 potential regulators of fim expression: 10 activators and 8 repressors. Two genes involved in the electron transport chain, yqiC and ndh, which encode the type II NADH dehydrogenase NDH-2, were identified. Both YqiC and NDH-2 contribute to the production of reactive oxygen species, prompting an investigation into the roles of oxidative stress response regulators OxyR and SoxR. We found that only OxyR regulates fim expression, which was specific to S . Typhi. OxyR acts by directly binding to the fimA promoter region. This study paves the way for future development of anti-adhesion strategies through the identification of 14 novel regulators for the most prominent fimbriae of S . Typhi. IMPORTANCE Adhesion mediated by fimbriae is one of the critical steps in the infection process. Therefore, it is essential to better understand the regulation of type 1 fimbriae ( fim ) in the human-specific pathogen Salmonella enterica serovar Typhi, the etiologic agent of typhoid fever. In this study, we identified 18 distinct mutants with altered regulation of fim . Furthermore, we confirmed that the DNA-binding protein OxyR directly regulates fim expression. Importantly, we also demonstrated regulatory differences in fim expression between S . Typhi and S . Typhimurium, as six of the genes identified altering fim expression in S . Typhi either did not affect fim expression in S . Typhimurium or had the contrary effect. This highlights fundamental differences between these serovars and emphasizes the need to investigate and compare aspects of gene regulation in S . Typhi.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".