Nejvíce citovaný článek - PubMed ID 38365254
Flexible genomic island conservation across freshwater and marine Methylophilaceae
The SAR11-IIIb genus Fontibacterium within the order 'Ca. Pelagibacterales' is recognized for its ubiquitous presence in freshwater environments. However, cultivation limitations have hampered deeper ecophysiological understanding of this genus, with most data limited to lakes in the Northern Hemisphere. Here we present seven isolates representing two previously undescribed species, along with 93 high-quality metagenome-assembled genomes (MAGs) derived from a global survey across five continents. Phylogenomic analysis revealed 16 species forming nine distinct biogeographic clusters, indicating speciation patterns linked to water temperature and latitude. We observed endemic species restricted to African lakes, and quasi-endemic species confined to the Northern or Southern Hemisphere, which co-exist alongside cosmopolitan species. Metabolic profiling and growth experiments uncovered species- and strain-specific adaptations for nutrient uptake, along with unique pathways for sulfur metabolism. These findings provide a global-scale genomic and ecological overview for this underexplored lineage of freshwater SAR11.
- MeSH
- fylogeneze MeSH
- fylogeografie MeSH
- genom bakteriální MeSH
- jezera mikrobiologie MeSH
- metagenom MeSH
- RNA ribozomální 16S genetika MeSH
- sladká voda * mikrobiologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- RNA ribozomální 16S MeSH
Axenic cultures are essential for studying microbial ecology, evolution, and genomics. Despite the importance of pure cultures, public culture collections are biased towards fast-growing copiotrophs, while many abundant aquatic prokaryotes remain uncultured due to uncharacterized growth requirements and oligotrophic lifestyles. Here, we applied high-throughput dilution-to-extinction cultivation using defined media that mimic natural conditions to samples from 14 Central European lakes, yielding 627 axenic strains. These cultures include 15 genera among the 30 most abundant freshwater bacteria identified via metagenomics, collectively representing up to 72% of genera detected in the original samples (average 40%) and are widespread in freshwater systems globally. Genome-sequenced strains are closely related to metagenome-assembled genomes (MAGs) from the same samples, many of which remain undescribed. We propose a classification of several novel families, genera, and species, including many slowly growing, genome-streamlined oligotrophs that are notoriously underrepresented in public repositories. Our large-scale initiative to cultivate the "uncultivated microbial majority" has yielded a valuable collection of abundant freshwater microbes, characterized by diverse metabolic pathways and lifestyles. This culture collection includes promising candidates for oligotrophic model organisms, suitable for a wide array of ecological studies aimed at advancing our ecological and functional understanding of dominant, yet previously uncultured, taxa.
Telonemia are one of the oldest identified marine protists that for most part of their history have been recognized as a distinct incertae sedis lineage. Today, their evolutionary proximity to the SAR supergroup (Stramenopiles, Alveolates, and Rhizaria) is firmly established. However, their ecological distribution and importance as a natural predatory flagellate, especially in freshwater food webs, still remain unclear. To unravel the distribution and diversity of the phylum Telonemia in freshwater habitats, we examined over a thousand freshwater metagenomes from all over the world. In addition, to directly quantify absolute abundances, we analyzed 407 samples from 97 lakes and reservoirs using Catalyzed Reporter Deposition-Fluorescence in situ Hybridization (CARD-FISH). We recovered Telonemia 18S rRNA gene sequences from hundreds of metagenomic samples from a wide variety of habitats, indicating a global distribution of this phylum. However, even after this extensive sampling, our phylogenetic analysis did not reveal any new major clades, suggesting current molecular surveys are near to capturing the full diversity within this group. We observed excellent concordance between CARD-FISH analyses and estimates of abundances from metagenomes. Both approaches suggest that Telonemia are largely absent from shallow lakes and prefer to inhabit the colder hypolimnion of lakes and reservoirs in the Northern Hemisphere, where they frequently bloom, reaching 10%-20% of the total heterotrophic flagellate population, making them important predatory flagellates in the freshwater food web.
- Klíčová slova
- CARD-FISH, Telonemia, freshwater lakes, metagenomics, microbial food webs, predatory flagellate,
- MeSH
- biodiverzita MeSH
- fylogeneze * MeSH
- hybridizace in situ fluorescenční * MeSH
- jezera mikrobiologie parazitologie MeSH
- metagenom MeSH
- metagenomika MeSH
- RNA ribozomální 18S * genetika MeSH
- sladká voda * mikrobiologie parazitologie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- RNA ribozomální 18S * MeSH
