biostudies-literatureHinzke TGerman Research FoundationNC State UniversityGerman Academic Exchange ServiceInstitut für Marine Biotechnologie e.V.National Institute of Food and AgricultureWoods Hole Oceanographic InstitutionNational Science Foundatione58371https://www.ebi.ac.uk/biostudies/studies/S-EPMC7787665biostudies-literatureUnknown10The hydrothermal vent tubeworm Riftia pachyptila hosts a single 16S rRNA phylotype of intracellular sulfur-oxidizing symbionts, which vary considerably in cell morphology and exhibit a remarkable degree of physiological diversity and redundancy, even in the same host. To elucidate whether multiple metabolic routes are employed in the same cells or rather in distinct symbiont subpopulations, we enriched symbionts according to cell size by density gradient centrifugation. Metaproteomic analysis, microscopy, and flow cytometry strongly suggest that Riftia symbiont cells of different sizes represent metabolically dissimilar stages of a physiological differentiation process: While small symbionts actively divide and may establish cellular symbiont-host interaction, large symbionts apparently do not divide, but still replicate DNA, leading to DNA endoreduplication. Moreover, in large symbionts, carbon fixation and biomass production seem to be metabolic priorities. We propose that this division of labor between smaller and larger symbionts benefits the productivity of the symbiosis as a whole.eLifeBacterial symbiont subpopulations have different roles in a deep-sea symbiosis.PMC7787665DFG Open Access Publication Fund: 393148499Chancellor's Faculty Excellence Program Cluster on Microbiomes and Complex Microbial CommunitiesOCE-1131095The WHOI Investment in Science FundOCE-1559198MA6346/2–1Hatch project 1014212Becher DMarkert SMeister MFelbeck HKleiner MSchluter RPane-Farre JVolker USchweder TSievert SMHildebrandt PHinzke THentschker CBonn FfalseBacterial symbiont subpopulations have different roles in a deep-sea symbiosis.The hydrothermal vent tubeworm Riftia pachyptila hosts a single 16S rRNA phylotype of intracellular sulfur-oxidizing symbionts, which vary considerably in cell morphology and exhibit a remarkable degree of physiological diversity and redundancy, even in the same host. To elucidate whether multiple metabolic routes are employed in the same cells or rather in distinct symbiont subpopulations, we enriched symbionts according to cell size by density gradient centrifugation. Metaproteomic analysis, microscopy, and flow cytometry strongly suggest that Riftia symbiont cells of different sizes represent metabolically dissimilar stages of a physiological differentiation process: While small symbionts actively divide and may establish cellular symbiont-host interaction, large symbionts apparently do not divide, but still replicate DNA, leading to DNA endoreduplication. Moreover, in large symbionts, carbon fixation and biomass production seem to be metabolic priorities. We propose that this division of labor between smaller and larger symbionts benefits the productivity of the symbiosis as a whole.2021-01-01T00:00:00Z2021 Jan2024-10-18T04:47:58.291Z2021-02-20T21:35:49ZS-EPMC77876653340450210.7554/eLife.58371