Investigating the Antimicrobial Potential of Cultivable High Arctic Bacteria
Notice bibliographique
Résumé
Antimicrobial resistance (AMR) is one of the most pressing healthcare and environmental challenges of the 21st century. In agricultural settings, the increased prevalence of resistant pathogens infecting livestock are being transmitted to humans and spreading through the food chain causing foodborne illness, while resistant phytopathogens are causing crop losses worldwide. Within this framework, the goal of this doctoral project was to isolate, screen, characterize, and apply cultivable Arctic bacteria exhibiting antimicrobial functions. The first part of this project involved employing two cultivation approaches to isolate and subsequently screen bacterial isolates derived from Canadian high Arctic habitats for antibacterial activities. The first approach included engineering and deploying an in situ cultivation device - the cryo-iplate. The second involved crowdsourcing standard bulk soil plating of twelve different Arctic sample types to a cohort of undergraduate researchers. Through these culturing approaches, bacterial isolates pertaining to Pseudomonas and Paenibacillus spp. exhibiting antibacterial activity against clinically relevant pathogens including methicillin resistant and susceptible Staphylococcus aureus (MRSA and MSSA), Listeria monocytogenes, Salmonella enterica Escherichia coli O157:H7, Acinetobacter baumanii, Enterococcus faecium, and Enterococcus faecalis were identified. Given that these isolates were cultured from a diverse set of Arctic habitats spanning permafrost, saline spring sediments, and cryptoendoliths, our findings suggest that high Arctic environments could potentially represent an untapped reservoir for novel antibacterial metabolites.Since resistant fungal pathogens are increasingly playing a role in the global AMR crisis, the second part of this doctoral project was to characterize the antifungal properties of a putatively novel Arctic species, Pseudomonas sp. B1.1W. This isolate was initially cultured using the cryo-iplate within an active layer permafrost site on Gypsum Hill located at Expedition Fjord, Axel Heiberg Island, Nunavut, Canada and was found to inhibit the growth of the second most prevalent phytopathogenic mold species, Botrytis cinerea, responsible for global crop losses. By mining its genome for antimicrobial BGCs and by biochemically analyzing organic extracts derived from liquid culture supernatants, this B1.1W was found to produce an antifungal molecule part of the viscosin group.The final component of this doctoral project evaluated B1.1W as a potential biocontrol agent against B. cinerea in Cannabis sativa. Cellular inoculants and bioactive extracts prepared from liquid culture supernatants of B1.1W were tested as foliar biocontrol treatments on C. sativa challenged with B. cinerea. Cannabis leaves that were treated with cellular inoculants and organic extracts of B1.1W challenged with B. cinerea featured 43.79% and 89.83% (respectively) less total mold cells. Furthermore, whole cannabis plants that received B1.1W treatments displayed fewer counts of symptomatic foliage throughout the course of a 14-day observation period post B. cinerea challenge compared to untreated controls. Targeted 16S amplicon sequencing of C. sativa leaves treated with cellular inoculants revealed that B1.1W dominates the foliar bacterial community, suggesting that it colonized leaf tissue. By evaluating its antifungal effect in planta and its potential to colonize leaf tissue, B1.1W exhibited biocontrol potential against B.cinerea in cannabis. The studies presented in this thesis ultimately demonstrate how high Arctic bacteria represent a source of potentially novel antimicrobial specialized metabolites with biotechnological applicability
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».