AbstractHolospora-like bacteria are obligate intracellularAlphaproteobacteria, inhabiting nuclei ofParameciumciliates and other protists.Alphaproteobacteriahave drawn significant attention, as both closest existing relatives of bacteria that gave rise to mitochondria, as well as a class of intracellular bacteria with numerous important pathogens.HLB clade includes two genera –Holospora(Hafkine 1980) andcandidatusGortzia (Boscaro 2013). These bacteria have a peculiar life cycle with two morphological forms, a strict specificity to the host species and the type of nucleus they inhabit.Here we describe a new species of HLB –candidatusGortzia yakutica sp. nov., a symbiont from macronucleus ofParamecium putrinum, the first known HLB for thisParameciumspecies. The new symbiont shows morphological similarities with other HLB. The phylogenetic analysis of SSU rDNA gene places it intocandidatusGortzia clade.