Characterization of active microbial ecosystems in icy astrobiology analog cryo-environments.
Notice bibliographique
Résumé
Ice environments, characterized by subzero temperatures, low nutrient levels, and low water activity, present unique challenges to microbial life. Studying these microbes helps us understand the cold limits of life on Earth and extraterrestrial bodies. Lava tube ice caves, such as those at Lava Beds National Monument near California's Medicine Lake Volcano, are analogs to Martian lava tubes that may host microbial ecosystems. Similarly, glaciers and ice caps, like those on Jupiter and Saturn's moons, have thick ice crusts and could support microbial life. Despite being some of the best-studied ice masses in the world, the microbial ecology of the Devon Island ice cap, White Glacier in the Canadian High Arctic, and Johnsons Glacier in Antarctica remains largely unexplored. This study uses both culture-dependent and independent methods to investigate the microbial ecosystems in these four environments.In Lava Beds National Monument, 16S rRNA amplicon sequencing identified ice samples primarily consisting of Actinomycetota, Pseudomonadota, Bacteroidota, Bacillota, and Chloroflexota and culture experiments and metabolic activity assays identified a viable and metabolically active microbial community at subzero temperatures. Furthermore, these communities were found to be more closely related to other cryoenvironments than caves suggesting that ice and cold temperatures exert stronger selection pressures on microbial communities than caves.In the Devon Island ice cap, flow cytometry coupled with live/dead staining identified an ultra-low biomass microbial ecosystem containing 3.62 x 10^4 cells/mL with a live fraction of 0.8%. Viable cells were also isolated and found to grow at subzero temperatures, high salinity (> 6%), and low pH (< pH 5), including one isolate capable of growth at -5°C, in 15% NaCl, and pH 3. Metagenomic and metatranscriptomic sequences belonging to diverse metabolic marker genes, including those related to thiosulfate oxidation, aerobic carbon monoxide oxidation, aerobic respiration, fumarate reduction, nitrate and nitrite reduction, nitrogen fixation, oxygenic photosynthesis and carbon fixation, indicating a diverse ecosystem composed of lithoautotrophs, photoautotrophs and heterotrophs. Transcripts involved in cold adaptation were also abundant, including cold shock proteins, transcription and translation factors, and membrane and peptidoglycan-altering proteins.The microbial ecosystems of White Glacier and Johnsons Glacier were compared, and their taxonomy was found to be significantly different from each other but shared an overlap in functional potential. Metatranscriptome sequencing of White Glacier revealed an active microbial ecosystem dominated by Cyanobacteria performing oxygenic photosynthesis and carbon fixation. In addition, lithoautotrophic metabolisms including carbon fixation via the 3-hydroxyproprionate cycle, anoxygenic photosynthesis, sulfide oxidation, and nitrate reduction/denitrification support a heterotrophic community performing aerobic respiration and aerobic carbon monoxide oxidation. Metagenome-assembled genomes were also found to be active including Cyanobacteriota, and novel phyla Armatimonadota, Eremiobacterota, and Gemmatimonadota. Similarly to the Devon Island ice cap, total biomass within White Glacier was 4.75 x 10^4 cells/ml with a live fraction of 0.5%. The majority of cultured isolates were capable of growth at subzero temperatures, high salinity (> 6%) and low pH (< pH 5). This study determined that ice environments contain diverse, active microbial ecosystems which are well adapted to life in ice, providing insights into how microbial life is sustained in some of Earth’s most extreme environments and how it might survive on Mars or the icy moons
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 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| 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 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 ».