Defensive symbiosis against giant viruses in amoebae

Protists are important regulators of microbial communities and key components in food webs with impact on nutrient cycling and ecosystem functioning. In turn, their activity is shaped by diverse intracellular parasites, including bacterial symbionts and viruses. Yet, bacteria-virus interactions with...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2022-09, Vol.119 (36), p.e2205856119
Main Authors: Arthofer, Patrick, Delafont, Vincent, Willemsen, Anouk, Panhölzl, Florian, Horn, Matthias
Format: Article
Language:English
Subjects:
amoeba
Amoeba - microbiology
Amoeba - virology
BASIC BIOLOGICAL SCIENCES
Biodiversity and Ecology
Biological Sciences
chlamydia
Ecosystem
Environmental Sciences
giant virus
Giant Viruses - genetics
In Situ Hybridization, Fluorescence
Life Sciences
Microbiology and Parasitology
Mimiviridae - genetics
protective symbiosis
protist
Symbiosis
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Summary:Protists are important regulators of microbial communities and key components in food webs with impact on nutrient cycling and ecosystem functioning. In turn, their activity is shaped by diverse intracellular parasites, including bacterial symbionts and viruses. Yet, bacteria-virus interactions within protists are poorly understood. Here, we studied the role of bacterial symbionts of free-living amoebae in the establishment of infections with nucleocytoplasmic large DNA viruses (Nucleocytoviricota). To investigate these interactions in a system that would also be relevant in nature, we first isolated and characterized a giant virus (Viennavirus, family Marseilleviridae) and a sympatric potential host infected with bacterial symbionts. Subsequently, coinfection experiments were carried out, using the fresh environmental isolates as well as additional amoeba laboratory strains. Employing fluorescence in situ hybridization and qPCR, we show that the bacterial symbiont, identified as , represses the replication of the sympatric Viennavirus in both recent environmental isolates as well as laboratory strains. In the presence of the symbiont, virions are still taken up, but viral factory maturation is inhibited, leading to survival of the amoeba host. The symbiont also suppressed the replication of the more complex and (Mimiviridae). Our work provides an example of an intracellular bacterial symbiont protecting a protist host against virus infections. The impact of virus-symbiont interactions on microbial population dynamics and eventually ecosystem processes requires further attention.
ISSN:0027-8424
1091-6490
1091-6490
DOI:10.1073/pnas.2205856119