Symbionts of the ciliate Euplotes: diversity, patterns and potential as models for bacteria–eukaryote endosymbioses. Issue 1907 (17th July 2019)

• Record Type: Journal Article
• Authors: Boscaro, Vittorio; Husnik, Filip; Vannini, Claudia; Keeling, Patrick J.
• Is Part Of: Proceedings. Volume 286:Issue 1907(2019)
• Publication Date: 2019-07-17
• Subjects: Devosia -- Euplotes -- Francisellaceae -- Holosporales -- prokaryote–eukaryote symbioses -- Rickettsiales; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2019.0693
• Languages: English
• ISSNs: 0962-8452

Abstract

Abstract : Endosymbioses between bacteria and eukaryotes are enormously important in ecology and evolution, and as such are intensely studied. Despite this, the range of investigated hosts is narrow in the context of the whole eukaryotic tree of life: most of the information pertains to animal hosts, while most of the diversity is found in unicellular protists. A prominent case study is the ciliate Euplotes, which has repeatedly taken up the bacterium Polynucleobacter from the environment, triggering its transformation into obligate endosymbiont. This multiple origin makes the relationship an excellent model to understand recent symbioses, but Euplotes may host bacteria other than Polynucleobacter, and a more detailed knowledge of these additional interactions is needed in order to correctly interpret the system. Here, we present the first systematic survey of Euplotes endosymbionts, adopting a classical as well as a metagenomic approach, and review the state of knowledge. The emerging picture is indeed quite complex, with some Euplotes harbouring rich, stable prokaryotic communities not unlike those of multicellular animals. We provide insights into the distribution, evolution and diversity of these symbionts (including the establishment of six novel bacterial taxa), and outline differences and similarities with the most well-understood group of eukaryotic hosts: insects.