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The bacterial orderMagnimaribacterales, previously known as the SAR86 lineage, is among the most abundant groups of planktonic bacteria inhabiting the global surface ocean. Despite their prevalence, our understanding of how this genetically diverse lineage partitions into units with coherent ecology and evolution remains limited. Here we surveyed multiple stations in the tropical Pacific Ocean using shotgun metagenomes and 16S rRNA gene amplicons to resolve distinct habitat preferences forMagnimaribacteraleslineages across nearshore, offshore, and open-ocean environments. The comprehensive collection of genomes that captured a large fraction of the known evolutionary breadth ofMagnimaribacterales, revealed patterns of ecotypic differentiation manifested primarily among genus-level clusters with specific clear preferences for distinct marine habitats. Enrichment analyses identified several functional genes associated with genomes from genera abundant in the nearshore environment, including those associated with sugar metabolism, peptide transport, and glycerophospholipid biosynthesis. Such metabolic adaptations likely facilitate the predominance of specificMagnimaribacteralesgenera in nearshore environments, promoting ecological partitioning across marine habitats.
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Isolate-anchored comparisons reveal evolutionary and functional differentiation across SAR86 marine bacteria
Abstract SAR86 is one of the most abundant groups of bacteria in the global surface ocean. However, since its discovery over 30 years ago, it has remained recalcitrant to isolation and many details regarding this group are still unknown. Here, we report the cellular characteristics from the first SAR86 isolate brought into culture, Magnimaribacter mokuoloeensis strain HIMB1674, and use its closed genome in concert with over 700 environmental genomes to assess the phylogenomic and functional characteristics of this order-level lineage of marine Gammaproteobacteria. The SAR86 order Magnimaribacterales invests significant genomic resources into the capacity for $$\beta$$-oxidation, which is present in most genomes with high gene copy numbers. This cyclical set of reactions appears to be fed by components of cell membranes that include lipids such as phosphatidylcholine, phosphatidylethanolamine, glycolipids, and sulfolipids. In addition to the widespread capacity to degrade the side chain of steroidal compounds via $$\beta$$-oxidation, several SAR86 sublineages also appear able to fully degrade the steroid polycyclic ring structure as well as other aromatic, polycyclic, and heterocyclic molecules. Read recruitment from publicly available metagenomes reveals that the Magnimaribacterales compose up to 6% of the global surface ocean microbial community. Only a subset of genera drives these high relative abundances, with some more globally dominant and others restricted to specific oceanic regions. This study provides an unprecedented foundation through which to understand this highly abundant yet poorly understood lineage of marine bacteria and charts a path to bring more representatives of this order into laboratory culture.
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- Award ID(s):
- 2149128
- PAR ID:
- 10556365
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- The ISME Journal
- Volume:
- 18
- Issue:
- 1
- ISSN:
- 1751-7362
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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