Novel Endosymbionts in Rhizarian Amoebae Imply Universal Infection of Unrelated Free-Living Amoebae by Legionellales

Abstract

Legionellales-infected water is a frequent cause of local outbreaks of Legionnaires’ disease and Pontiac fever. Decontaminations are difficult because Legionellales reproduce in eukaryotic microorganisms (protists). Most often, Legionellales have been isolated from amoebae; however, the culture-based sampling methods are taxonomically biased. Sequencing studies show that amoebae in the cercozoan class Thecofilosea are dominant in soils and wastewater treatment plants, prompting us to screen their capability to serve as potential hosts of endosymbiotic bacteria. Environmental isolates of Thecofilosea contained a surprising richness of endosymbiotic Legionellales, including Legionella. Considering the widespread dispersal of Legionellales in apparently unrelated amoeboid protist taxa, it appears that the morphotype and not the evolutionary origin of amoebae determines their suitability as hosts for Legionellales. We further provide a protocol for gnotobiotic cultivation of Legionellales and their respective hosts, facilitating future genomic and transcriptomic research of host–symbiont relationships.

Characterization of Rosculus vilicus sp. nov., a rhizarian amoeba interacting with Mycobacterium avium subsp. paratuberculosis

“…Most of these findings documented the involvement of amoebozoans and heteroloboseans representative in such interactions (Balczun and Scheid, 2017;Shi et al, 2021). However, recent work has demonstrated that numerous rhizarian FLA could also bear intracellular bacteria, thereby confirming that tight FLA-bacteria interactions indeed occur in all these taxonomic groups (Pohl et al, 2021;Solbach et al, 2021).…”

Fungivorous protists in the rhizosphere ofArabidopsis thaliana– Diversity, functions, and publicly available cultures for experimental exploration

“…Cultures were established with Saccharomyces cerevisiae as prey. Cell sorting as described in Solbach et al (2021) or serial manual washings in sterile medium were used to establish cultures free of environmental bacteria.…”