title: Syntrophic linkage between predatory Carpediemonas and specific prokaryotic populations.
abstract: Most anoxic environments are populated by small (<10 μm) heterotrophic eukaryotes that prey on different microbial community members. How predatory eukaryotes engage in beneficial interactions with other microbes has rarely been investigated so far. Here, we studied an example of such an interaction by cultivating the anerobic marine flagellate, Carpediemonas frisia sp. nov. (supergroup Excavata), with parts of its naturally associated microbiome. This microbiome consisted of so far uncultivated members of the Deltaproteobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia and Nanoarchaeota. Using genome and transcriptome informed metabolic network modeling, we showed that Carpediemonas stimulated prokaryotic growth through the release of predigested biomolecules such as proteins, sugars, organic acids and hydrogen. Transcriptional gene activities suggested niche separation between biopolymer degrading Bacteroidetes, monomer utilizing Firmicutes and Nanoarchaeota and hydrogen oxidizing Deltaproteobacteria. An efficient metabolite exchange between the different community members appeared to be promoted by the formation of multispecies aggregates. Physiological experiments showed that Carpediemonas could also benefit from an association to these aggregates, as it facilitated the removal of inhibiting metabolites and increased the availability of prey bacteria. Taken together, our results provide a framework to understand how predatory microbial eukaryotes engage, across trophic levels, in beneficial interactions with specific prokaryotic populations.
authors.affiliation: Department of Geoscience, University of Calgary, Calgary, AB, Canada.|Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Emmo
authors.initials: E
authors.lastname: Hamann
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.|Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
authors.forename: Halina E
authors.identifier: 0000-0003-1970-4457
authors.initials: HE
authors.lastname: Tegetmeyer
authors.affiliation: Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Riedel
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Sten
authors.initials: S
authors.lastname: Littmann
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Soeren
authors.initials: S
authors.lastname: Ahmerkamp
authors.affiliation: Department of Geoscience, University of Calgary, Calgary, AB, Canada.|Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Jianwei
authors.initials: J
authors.lastname: Chen
authors.affiliation: Max Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: Philipp F
authors.initials: PF
authors.lastname: Hach
authors.affiliation: Department of Geoscience, University of Calgary, Calgary, AB, Canada.|Max Planck Institute for Marine Microbiology, Bremen, Germany.|Institute for Genome Research and Systems Biology, Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Strous
mesh_terms: D001419:Bacteria / Q000378:metabolism; D020564:Deltaproteobacteria / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D053858:Metabolic Networks and Pathways / Q000235:genetics; D056265:Microbial Interactions; D064307:Microbiota; D046588:Nanoarchaeota / Q000378:metabolism