AUTHOR=Jessu Amélie , Delafont Vincent , Moyen Jean-Louis , Biet Franck , Samba-Louaka Ascel , Héchard Yann 

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

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1324985

DOI=10.3389/fmicb.2023.1324985

ISSN=1664-302X

ABSTRACT=<p>Free-living amoebae are described as potential reservoirs for pathogenic bacteria in the environment. It has been hypothesized that this might be the case for <italic>Mycobacterium avium</italic> subsp. <italic>paratuberculosis</italic>, the bacterium responsible for paratuberculosis. In a previous work, we isolated an amoeba from a water sample in the environment of infected cattle and showed that this amoeba was associated with <italic>Mycobacterium avium</italic> subsp. <italic>paratuberculosis</italic>. While a partial 18S rRNA gene has allowed us to suggest that this amoeba was <italic>Rosculus</italic>-like, at that time we were not able to sub-cultivate it. In the present study, we succeeded in cultivating this strain at 20–25°C. This amoeba is among the smallest (5–7 μm) described. The sequencing of the whole genome allowed us to extract the full 18S rRNA gene and propose this strain as a new species of the <italic>Rosculus</italic> genus, i.e., <italic>R. vilicus</italic>. Of note, the mitochondrial genome is particularly large (184,954 bp). Finally, we showed that this amoeba was able to phagocyte <italic>Mycobacterium avium</italic> subsp. <italic>paratuberculosis</italic> and that the bacterium was still observed within amoebae after at least 3 days. In conclusion, we characterized a new environmental amoeba species at the cellular and genome level that was able to interact with <italic>Mycobacterium avium</italic> subsp. <italic>paratuberculosis</italic>. As a result, <italic>R. vilicus</italic> is a potential candidate as environmental reservoir for <italic>Mycobacterium avium</italic> subsp. <italic>paratuberculosis</italic> but further experiments are needed to test this hypothesis.</p>