The consequences of evolutionary adaptation on the sulfur isotope fractionation of sulfate reducing microorganisms
Notice bibliographique
Résumé
Sulfur metabolisms leave behind a record of their activity in the sulfur they utilize. This thesis seeks to advance our understanding of some of these processes with a particular focus on dissimilatory sulfate reduction. The multiple sulfur isotope composition of two porewater sulfate profiles in the anoxic marine sapropel of Mangrove Lake, Bermuda was investigated. The porewater sulfate profiles exhibit the distinct isotopic signatures of microbial sulfate reduction and sulfur reoxidation which simple diagenetic models can reproduce. The reoxidative cycle includes sulfide oxidation to elemental sulfur followed by the disproportionation of the elemental sulfur to sulfate and sulfide, and this process turns over from 50 to 80% of the sulfide produced by sulfate reduction. We suggest that the reoxidative S cycle in any environment can best be identified within two regions of the multiple sulfur isotope fractionation spectrum. Paper 1 is titled Mass-dependent sulfur isotopefractionation during reoxidative sulfur cycling: A case study from Mangrove Lake, Bermuda. The process of evolutionary adaptation has largely been assumed inconsequential on the sulfur isotopic fractionation produced during dissimilatory sulfate reduction and recorded in the isotope rock record. Yet, the diversity of sulfur isotope phenotypes displayed by species of sulfate reducing microorganisms isolated from modern environments amounts to strong evidence that evolutionary adaptation does matter. If this is the case, important information about the evolutionary history of DSR may be preserved in the rock record. However, the relationship between evolutionary adaptation and isotope phenotype is unexplored. To begin addressing this gap in knowledge, the impact of evolutionary adaptation on the fitness and sulfur isotopic phenotype of the dissimilatory sulfate reducer Desulfovibrio vulgaris Hildenborough (DvH) was investigated. The increases in fitness that were observed did not result in a change of the isotopephenotype. At least in the conditions of the experiment this result indicates that the isotopephenotype is not very sensitive to evolutionary adaptation on the hundreds of generations timescale. This suggests that lengthier timescales are necessary for evolutionary-driven divergence of the isotope phenotype. Paper 2 is titled Evolutionary adaptation of a sulfate reducing bacterium and its sulfur isotope phenotype. To address the issues raised in paper 2, pure cultures of Desulfomicrobium baculatm were evolved in batch culture for 300 generations. A greater than two fold increase in growth rate over the course of the experiment was measured as well as a change in isotope phenotype (??) from 15 to 12 %. The response of ?? to evolutionary adaptation resembles in some ways the isotopic response of physiological adaptations to changing environmental conditions. While in the narrow context of the environment where the evolutionary adaptation took place, the change in isotope phenotype is incontestable, it remains to be seen if this difference in isotope phenotype ismaintained across different growth environments. Paper 3 is titled "Evolutionary response of S isotope fractionation is predicted by phenotypic plasticity".
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 distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,009 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,002 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 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 tête enseignante, 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 ».