“<i>Candidatus</i> Mesochlamydia elodeae” (Chlamydiae: <i>Parachlamydiaceae</i>), a novel chlamydia parasite of free-living amoebae

<i>Vannella</i> sp. isolated from waterweed <i>Elodea</i> sp. was found infected by a chlamydia-like organism. This organism behaves like a parasite, causing the death through burst of its host. Once the vannellae degenerated, the parasite was successfully kept in laboratory within a <i>Saccamoeba</i> sp. isolated from the same waterweed sample, which revealed <i>in fine</i> through electron microscopy to harbor two bacterial endosymbionts: the chlamydial parasite we introduce and another endosymbiont initially and naturally present in the host. Herein, we provide molecular-based identification of both the amoeba host and its two endosymbionts, with special focus on the chlamydia parasite. High sequence similarity values of the 18S rDNA permitted to assign the amoeba to the species <i>Saccamoeba lacustris</i> (Amoebozoa, Tubulinea). The bacterial endosymbiont naturally harbored by the host belonged to <i>Sphingomonas koreensis</i> (Alpha-Proteobacteria). The chlamydial parasite showed a strict specificity for <i>Saccamoeba</i> spp., being unable to infect a variety of other amoebae, including <i>Acanthamoeba</i>, and it was itself infected by a bacteriophage. Sequence similarity values of the 16S rDNA and phylogenetic analysis indicated that this strain is a new member of the family <i>Parachlamydiaceae</i>, for which we propose the name “<i>Candidatus</i> Mesochlamydia elodeae.”