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© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hinzke, T., Kleiner, M., Meister, M., Schlueter, R., Hentschker, C., Pane-Farre, J., Hildebrandt, P., Felbeck, H., Sievert, S. M., Bonn, F., Voelker, U., Becher, D., Schweder, T., & Markert, S. Bacterial symbiont subpopulations have different roles in a deep-sea symbiosis. Elife, 10, (2021): e58371, https://doi.org/10.7554/eLife.58371., 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., This work was supported by the German Research Foundation DFG (grant MA 6346/2–1 to SM), fellowships of the Institute of Marine Biotechnology Greifswald (TH, MM), a German Academic Exchange Service (DAAD) grant (TH), the NC State Chancellor’s Faculty Excellence Program Cluster on Microbiomes and Complex Microbial Communities (MK), the USDA National Institute of Food and Agriculture, Hatch project 1014212 (MK), the U.S. National Science Foundation (grants OCE-1131095 and OCE-1559198 to SMS), and The WHOI Investment in Science Fund (to SMS). We furthermore acknowledge support for article processing charges from the DFG (Grant 393148499) and the Open Access Publication Fund of the University of Greifswald.

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hinzke, T., Kleiner, M., Breusing, C., Felbeck, H., Häsler, R., Sievert, S. M., Schlüter, R., Rosenstiel, P., Reusch, T. B. H., Schweder, T., & Markert, S. Host-microbe interactions in the chemosynthetic Riftia pachyptila symbiosis. Mbio, 10(6), (2019): e02243-19, doi:10.1128/mBio.02243-19., The deep-sea tubeworm Riftia pachyptila lacks a digestive system but completely relies on bacterial endosymbionts for nutrition. Although the symbiont has been studied in detail on the molecular level, such analyses were unavailable for the animal host, because sequence information was lacking. To identify host-symbiont interaction mechanisms, we therefore sequenced the Riftia transcriptome, which served as a basis for comparative metaproteomic analyses of symbiont-containing versus symbiont-free tissues, both under energy-rich and energy-limited conditions. Our results suggest that metabolic interactions include nutrient allocation from symbiont to host by symbiont digestion and substrate transfer to the symbiont by abundant host proteins. We furthermore propose that Riftia maintains its symbiont by protecting the bacteria from oxidative damage while also exerting symbiont population control. Eukaryote-like symbiont proteins might facilitate intracellular symbiont persistence. Energy limitation apparently leads to reduced symbiont biomass and increased symbiont digestion. Our study provides unprecedented insights into host-microbe interactions that shape this highly efficient symbiosis., This work was supported by the German Research Foundation DFG (grant MA 6346/2-1 to S.M., grant BR 5488/1-1 to C.B.), the German Academic Exchange Service DAAD (T.H.), a fellowship of the Institute of Marine Biotechnology Greifswald (T.H.), the Canada Foundation for Innovation, the Government of Alberta and the Natural Sciences and Engineering Research Council of Canada NSERC through a Banting Fellowship (M.K.), the U.S. National Science Foundation (grants OCE-0452333, OCE-1136727, OCE-1131095, and OCE-1559198 to S.M.S.), and the WHOI Investment in Science Fund (S.M.S.). P.R. was supported by a grant from the DFG CCGA Comprehensive Center for Genome Analysis, Kiel, and the DFG CRC1182 “Origin and Function of Metaorganisms.” R.H. and T.B.H.R. were supported by the DFG CRC1182 “Origin and Function of Metaorganisms,” subprojects B2, Z3, and INF.

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Environmental Microbology, (2018), 21: 244-258, doi:10.1111/1462-2920.14452, Chemoautotrophic bacteria belonging to the genus Sulfurimonas (class Campylobacteria) were previously identified as key players in the turnover of zero‐valence sulfur, a central intermediate in the marine sulfur cycle. S. denitrificans was further shown to be able to oxidize cyclooctasulfur (S8). However, at present the mechanism of activation and metabolism of cyclooctasulfur is not known. Here, we assessed the transcriptome and proteome of S. denitrificans grown with either thiosulfate or S8 as the electron donor. While the overall expression profiles under the two growth conditions were rather similar, distinct differences were observed that could be attributed to the utilization of S8. This included a higher abundance of expressed genes related to surface attachment in the presence of S8, and the differential regulation of the sulfur‐oxidation multienzyme complex (SOX), which in S. denitrificans is encoded in two gene clusters: soxABXY 1Z 1 and soxCDY 2Z 2. While the proteins of both clusters were present with thiosulfate, only proteins of the soxCDY 2Z 2 were detected at significant levels with S8. Based on these findings a model for the oxidation of S8 is proposed. Our results have implications for interpreting metatranscriptomic and ‐proteomic data and for the observed high level of diversification of soxY 2Z 2 among sulfur‐oxidizing Campylobacteria., NSF. Grant Number: OCE‐1559198 The Investment in Science Fund at WHOI Institute of Marine Biotechnology e.V., 2019-01-31