期刊
ISME JOURNAL
卷 14, 期 1, 页码 104-122出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41396-019-0508-7
关键词
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资金
- Canadian Foundation for Innovation
- DFG Cluster of Excellence 'The Ocean in the Earth System' at MARUM (University of Bremen)
- European Research Council Advanced Grant (BathyBiome) [340535]
- Gordon and Betty Moore Foundation Marine Microbiology Initiative Investigator Award [GBMF3811]
- European Union (EU) Marie Curie Actions Initial Training Network (ITN) SYMBIOMICS [264774]
- NSF [0801741]
- Vienna Science and Technology Fund (WWTF) [VRG14-021]
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- NC State Chancellor's Faculty Excellence Program Cluster on Microbiomes and Complex Microbial Communities
- German Academic Exchange Service DAAD
- Max Planck Society
- Emerging Frontiers
- Direct For Biological Sciences [0801741] Funding Source: National Science Foundation
- European Research Council (ERC) [340535] Funding Source: European Research Council (ERC)
Most autotrophs use the Calvin-Benson-Bassham (CBB) cycle for carbon fixation. In contrast, all currently described autotrophs from the Campylobacterota (previously Epsilonproteobacteria) use the reductive tricarboxylic acid cycle (rTCA) instead. We discovered campylobacterotal epibionts (Candidatus Thiobarba) of deep-sea mussels that have acquired a complete CBB cycle and may have lost most key genes of the rTCA cycle. Intriguingly, the phylogenies of campylobacterotal CBB cycle genes suggest they were acquired in multiple transfers from Gammaproteobacteria closely related to sulfur-oxidizing endosymbionts associated with the mussels, as well as from Betaproteobacteria. We hypothesize that Ca. Thiobarba switched from the rTCA cycle to a fully functional CBB cycle during its evolution, by acquiring genes from multiple sources, including co-occurring symbionts. We also found key CBB cycle genes in free-living Campylobacterota, suggesting that the CBB cycle may be more widespread in this phylum than previously known. Metatranscriptomics and metaproteomics confirmed high expression of CBB cycle genes in mussel-associated Ca. Thiobarba. Direct stable isotope fingerprinting showed that Ca. Thiobarba has typical CBB signatures, suggesting that it uses this cycle for carbon fixation. Our discovery calls into question current assumptions about the distribution of carbon fixation pathways in microbial lineages, and the interpretation of stable isotope measurements in the environment.
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