Gelfand, Mikhail S.

Marine bryozoans harbor diverse microbial communities, but not much is known about specificity of bacterial symbionts towards different hosts. We identified potential symbionts and described overall microbial communities of three marine bryozoans, Aquiloniella scabra, Rhamphostomella bilaminata (Gymnolaemata: Cheilostomatida), and Patinella verrucaria (Stenolaemata: Cyclostomatida), revealing that each species maintains a distinct microbial assemblage that differs both from the surrounding environmental microbiome and from other hosts. Previously, the bryostatin-producing gammaproteobacterial genus “ Candidatus Endobugula” was known from only two bryozoan species in the family Bugulidae. Here, we report its first detection in two more cheilostome bryozoans, A. scabra and R. bilaminata , expanding its known host range to two more families.

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.