*Article* **New Intranuclear Symbiotic Bacteria from Macronucleus of** *Paramecium putrinum***—"***Candidatus* **Gortzia Yakutica"**

**Alexandra Y. Beliavskaia 1,\*, Alexander V. Predeus 2, Sofya K. Garushyants 3, Maria D. Logacheva 4, Jun Gong 5,6, Songbao Zou 5, Mikhail S. Gelfand 3,4 and Maria S. Rautian 1,\***


Received: 6 April 2020; Accepted: 12 May 2020; Published: 15 May 2020

**Abstract:** *Holospora*-like bacteria (HLB) are obligate intracellular *Alphaproteobacteria*, inhabiting nuclei of *Paramecium* and other ciliates such as "*Candidatus* Hafkinia" is in *Frontonia*. The HLB clade is comprised of four genera, *Holospora*, *Preeria*, "*Candidatus* Gortzia", and "*Candidatus* Hafkinia". These bacteria have a peculiar life cycle with two morphological forms and some degree of specificity to the host species and the type of nucleus they inhabit. Here we describe a novel species of HLB—"*Candidatus* Gortzia yakutica" sp. nov.—a symbiont from the macronucleus of *Paramecium putrinum*, the first described HLB for this *Paramecium* species. The new endosymbiont shows morphological similarities with other HLB. The phylogenetic analysis of the SSU rRNA gene places it into the "*Candidatus* Gortzia" clade.

**Keywords:** symbiosis; intranuclear bacteria; *Holospora*; Gortzia; *Paramecium*
