Microbial community associated with Baicalian crustacea near gas-oil deepwater discharges

Using scanning electron microscopy we investigated the epibiotic associations of peritrichial sessile ciliates of the Lagenophrys (Ciliophora: Lagenoprydae) and prokaryotes of various morphologies on the surface of endemic amphipods Macropereiopus florii (Dybowsky 1874) and ostracods Candona (Candonidae). We noted biofouling and mineralization in the areas of formation of a bacterial biofilm, which includes Fe, P, and other elements. High-throughput sequencing on the Illumina MiSeq platform showed the presence of such bacterial phyla as Actinobacteria, Gracilibacteria, Cyanobacteria, Proteobacteria, Bacteroidetes in the ostracod microbiome, of which the latter two were dominant. Sequence analysis of the 16S rRNA gene fragment showed epibiotic microorganisms that are related to the colorless sulfur bacteria Thiothrix sp. More than 50% of all sequences were attributed to endosymbiont bacteria of the genus Rickettsia, and the presence of endosymbionts of the genus Ca. Cardinium was shown for the first time for Baikal ostracods.