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Bacteria-protists interactions illustrated by the amoebae Nuclearia spp. and their bacterial symbionts

English title Bacteria-protists interactions illustrated by the amoebae Nuclearia spp. and their bacterial symbionts
Applicant Posch Thomas
Number 159842
Funding scheme Project funding
Research institution Limnologische Station Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Ecology
Start/End 01.07.2015 - 31.10.2018
Approved amount 327'000.00
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Keywords (7)

Ectosymbionts; Opisthokonta; Endosymbionts; Taxonomy; Amoebae; Symbiosis; Nuclearia

Lay Summary (German)

Lead
LeadAlle Tier- und Pflanzenarten leben in enger Beziehung mit Bakterien, wobei das Zusammenleben (Symbiose) von Parasitismus bis zur Kooperation reicht. Symbiosen mit Bakterien treten allerdings schon bei einzelligen Eukaryoten (Einzellern) auf. Die Amöben der Gruppe Nucleariidae haben zahlreiche Bakteriensymbionten und sind zugleich sehr nahe verwandt zu den Tieren. Das macht sie zu idealen Modellorganismen um die Entstehung von Symbiosen zu studieren.
Lay summary

Inhalt und Ziele des Forschungsprojekts

Ziel des Projektes ist es, möglichst viele Nuclearia-Arten und ihre intrazellulären und ektosymbiotischen Bakterien zu isolieren und zu charakterisieren. Dadurch soll geklärt werden, warum gerade diese Einzeller so zahlreiche Symbiosen eingehen. In der ersten Projektphase werden die Diversität und die Verbreitung von Nucleariiden erfasst. Da die Amöben Gewässer mit Massenentwicklungen von giftigen Cyanobakterien bevorzugen, werden entsprechende Seen des Alpenraums beprobt. In der zweiten Phase werden die Amöben und ihre Bakterien morphologisch und molekular charakterisiert. Zudem wird versucht, Bakterienreinkulturen zu gewinnen. In Laborversuchen sollen die Gründe für die Symbiosen der Organismen aufgeklärt werden. Zuletzt wird von einem „Amöben-Bakterien-System“ das Metagenom erstellt.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Obwohl sich das Projekt primär mit Grundlagenforschung beschäftigt, ist das Thema „Symbiose mit Bakterien“ von grösster Relevanz für alle Menschen. Ohne kooperative Symbiosen mit Bakterien könnten wir z. B. keine Nahrung verdauen oder wäre unser Energiestoffwechsel nicht möglich. Daher ist es faszinierend zu verstehen, wie und warum sich Symbiosen bereits zwischen Bakterien und tierischen Einzellern entwickeln und etablieren.

Direct link to Lay Summary Last update: 29.04.2015

Responsible applicant and co-applicants

Employees

Publications

Publication
Grazing of Nuclearia thermophila and Nuclearia delicatula (Nucleariidae, Opisthokonta) on the toxic cyanobacterium Planktothrix rubescens
Dirren Sebastian, Pitsch Gianna, Silva Marisa O.D., Posch Thomas (2017), Grazing of Nuclearia thermophila and Nuclearia delicatula (Nucleariidae, Opisthokonta) on the toxic cyanobacterium Planktothrix rubescens, in European Journal of Protistology, 1.
Promiscuous and specific bacterial symbiont acquisition in the amoeboid genus Nuclearia (Opisthokonta)
Dirren Sebastian, Posch Thomas (2016), Promiscuous and specific bacterial symbiont acquisition in the amoeboid genus Nuclearia (Opisthokonta), in FEMS MICROBIOLOGY ECOLOGY, 92(8), fiw105.

Collaboration

Group / person Country
Types of collaboration
PD Dr. Michael Schweikert / University of Stuttgart Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
37th Kongress der Deutschen Gesellschaft für Protozoologie Individual talk Effects of lake warming on protists and microbial food webs 01.03.2018 Köln, Germany Posch Thomas;
15th Symposium on Aquatic Microbial Ecology (SAME15) Talk given at a conference Grazing of Nuclearia thermophila and Nuclearia delicatula (Nucleariidae, Opisthokonta) on the toxic cyanobacterium Planktothrix rubescens 04.09.2017 Zagreb, Croatia Dirren Sebastian;
5th Meeting of Fresh Blood for FreshWater Talk given at a conference Grazing of Nuclearia thermophila and Nuclearia delicatula (Nucleariidae, Opisthokonta) on the toxic cyanobacterium Planktothrix rubescens 12.04.2017 České Budějovice, Czech Republic Dirren Sebastian;
36th Meeting of the German Society for Protozoology Talk given at a conference Grazing of Nuclearia thermophila and Nuclearia delicatula (Nucleariidae, Opisthokonta) on the toxic cyanobacterium Planktothrix rubescens 22.02.2017 Meissen, Germany Dirren Sebastian;
7th ECOP and ISOP European Congress of Protistology Talk given at a conference Promiscuous and conservative symbiont acquisition in the genus Nuclearia 07.09.2015 Sevilla, Spain Dirren Sebastian;
Embo Conference - SAME14 (Aquatic Microbial Ecology) Talk given at a conference When a lake stops mixing – the fatal effects of warming on microbial food web dynamics 27.08.2015 Uppsala, Sweden Posch Thomas;


Knowledge transfer events



Self-organised

Title Date Place
Tag der offenen Tür - Limnologische Station: Die mikrobielle Welt 02.06.2018 Kilchberg, Switzerland

Communication with the public

Communication Title Media Place Year
Print (books, brochures, leaflets) Protist of the Year 2019 - Nuclearia International 2019

Awards

Title Year
Hydrobiologie-Limnologie-Preis 2018 der Hydrobiologie-Limnologie-Stiftung für Gewässerforschung 2018
Ernennung zum Titularprofessor für Limnologie an der Universität Zürich 2017

Associated projects

Number Title Start Funding scheme
138473 Feeding of ciliates (Ciliophora) on toxic filamentous cyanobacteria in Lake Zurich (Switzerland) 01.08.2012 Project funding

Abstract

All animals and plants live in symbiosis with several, up to thousands of prokaryotic species, however, this phenomenon is not restricted to multicellular organisms. Protists (unicellular eukaryotes) live in intimate contact with bacteria, and this co-occurrence is a potential playground for symbioses (from mutualism to parasitism). Bacteria interacting with protists are either attached to extracellular structures (ectosymbionts) or inside the host itself (endosymbionts). In this project we want to study the diverse symbioses of amoeboid species of the genus Nuclearia (Opisthokonta) with their endo- and / or ectosymbiotic bacteria, also in view of the fact that a few Nuclearia representatives may have no (or lost) symbionts. Nucleariidae are placed at the animal-fungal boundary, and they are unique in that their ectosymbionts (when present) are loosely arranged in a mucous layer, without a direct contact to hosts. So far, eleven Nuclearia morphospecies have been described. However, 18S rDNA sequences were published only for 5 of them, originating from cultures all over the world. A co-existence of two or more Nuclearia spp. in one habitat was not shown until now.In a pilot study conducted in Lake Zurich (Switzerland), we successfully isolated five Nuclearia spp. that covered all four monophyletic branches described so far. We don’t believe that Lake Zurich is a hot-spot of biodiversity, but rather suppose that these tiny organisms have been overlooked in many lakes. Two of our five isolates were found to be associated with bacterial ecto- and endosymbionts, and their taxonomic affiliation could be clarified. Neither ecto- nor endosymbionts of an individual Nuclearia sp. nor symbionts among different Nuclearia spp. seem to be closely related, pointing to a great diversity of prokaryotic partners within this genus. Thus, Nucleariidae are an ideal model group to study the basic principles of symbioses between opisthokonts and prokaryotes.The following scientific questions should be answered in the framework of the proposed project:•Are Nuclearia spp. more common in lakes than previously reported?•Can we indeed find eleven valid morphospecies within Nucleariidae?•Do different morphospecies also reflect phylogenetically distinct taxa?•Is the taxonomic affiliation of bacterial endosymbionts a species specific trait of Nuclearia spp.?•Can two taxonomically different bacterial endosymbionts coexist in one Nuclearia host species?•Are bacterial endosymbionts of Nuclearia spp. phylogenetically only distantly related?•Are there indications for a co-evolution with their hosts?•Can we infect Nuclearia spp. that have no bacterial symbionts with symbionts of other species?•Do endosymbionts remain uncultivable, although ectosymbiotic bacteria may be successfully isolated?•Are ectosymbiotic bacteria in the mucous layer transient rather than permanently interacting partners?•Can the metagenome of Nuclearia sp. Strain N (Dirren et al. 2014) and its symbionts unravel metabolic interconnections between amoebae and prokaryotic symbionts?
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