ИСТИНА

Annelids are one of the most abundant groups of invertebrates that live in the marine sediments. To identify the role of the microbiome community in the life of different annelids inhabiting the Arctic seas, we examined 8 species from 7 annelid families living in the vicinity of the N.A. Pertsov White Sea Station. By using transmission electron microscopy (TEM), bacteria were found in the cuticles of two annelid species inhabiting the subtidal and tidal zones of the White Sea. Using high-throughput sequencing of amplicons of variable regions of the 16S rRNA gene, the taxonomic affiliation of these microorganisms was determined. In the cuticle of Dipolydora quadrilobata (Spionidae), the gram-negative bacteria of the genera Fulvivirga and Aliivibrio, generally known as common inhabitants of the upper layers of the bottom sediments of the northern seas, were found. In the cuticle of Leitoscoloplos acutus, the bacteria belonging to uncultivated members of the Leptospiraceae and Spirochaetaceae families were identified. These microorganisms were not observed in the bottom sediments where the specimens of L. acutus and D. quadrilobata were collected, as well as in the microbiomes of D. quadrilobate tubes, suggesting these bacteria are specific associates of the bodies of these annelids. Physiological aspects of the interaction between bacteria and annelids remain unclear. In addition to D.quadrilobata and L.acutus, the cuticles of 6 more species of infaunal annelids from the families Travisiidae, Opheliidae, Spionidae, Cossuridae, Lubmrineridae, and Dorvilleidae were studied using TEM, but no bacterial cells were detected. The latter points to the specificity of the microbial associations of Dipolydora quadrilobata and Leitoscoloplos acutus, which strengthens the hypothesis of the symbiotic nature of their interactions. The work was supported by the Ministry of Science and Higher Education of the Russian Federation under grant No. 075-15-2021-1396