Understanding the role of iron in biofilm formation, characterization, and viable but non-culturable state induction and resuscitation in Salmonella spp.
Bibliographic record
Abstract
Non-typhoidal strains of Salmonella spp. are one of the greatest bacterial contributors to food-borne illness in Canada. Until the 1990’s, reports of food-borne illness were mainly associated with contaminated meat products; however, raw or minimally cooked produce is now being identified as a major source of food-borne outbreaks. Salmonella are able to persist on crop plants through biofilm formation, and existing in a viable but non culturable (VBNC) state; currently, little is known about the effect of iron on these processes. Using wildtype and iron mutants of Salmonella Typhimurium and Salmonella Enteritidis, the effect of iron was investigated. The first objective was to determine the effect of iron on Salmonella biofilm formation in vitro. Crystal violet (CV) biofilm assays, cell surface hydrophobicity assays, aggregation assays, motility, Congo red (CR) and calcofluor plates were used to characterize and quantify biofilm formation. In vitro work showed that the S. Typhimurium ton B mutant had significantly (p<0.05) greater hydrophobicity, significantly (p<0.05) reduced motility and biomass measured in the CV assay compared to the wildtype strain. The CR plates showed S. Enteritidis ton B mutant lacked curli, a key component, in its biofilm. The second objective was to determine the effect of iron on Salmonella biofilm formation on spinach using scanning electron microscopy (SEM) and CV biofilm assays. The SEM images showed the wildtype strains had stronger biofilm formation when compared to the ton B mutants; however, only the S. Enteritidis ton B mutant had reduced biofilm formation compared to the wildtype in the CV assays. The third objective was to determine the effect of iron on VBNC state induction and resuscitation of S. Typhimurium in vitro. To assess induction and resuscitation, 7% salt solution and nutrient broth supplemented with Ferrioxamine E were used, respectively. S. Typhimurium wildtype induced within 26 days and resuscitated within 22 hours, whereas, the ton B mutant did not. The results of this study suggest that iron does influence Salmonella biofilm formation, and VBNC induction. This study has further increased our understanding of how Salmonella can exist in the environment on plants with the potential to cause food-borne illnesses.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".