THE STUDY OF MICROBIAL ASSOCIATIONS HELPS US UNDERSTAND THE LIFESTYLE OF <i>TEREBELLIDES</i> CF. <i>STROEMII</i> (ANNELIDA, TEREBELLIFORMIA, TRICHOBRANCHIDAE) IN THE WHITE SEA

Abstract

Polychaete annelids are one of the main components of oceanic benthos, but little is known about their microbial symbionts. The purpose of this work is to study the microbiome associated with representatives of Terebellides cf. stroemii and to describe their lifestyle in the White Sea. To do this, the worms and their tubes were examined using light and electron microscopy, and the composition of the microbiome was studied by sequencing the hypervariable V4 regions of the 16S rRNA gene. The tubes of Terebellides cf. stroemii are shown to be loose and, most likely, temporary, whereas the worms dig actively into the ground, yet spending part of their time collecting food from the ground surface with the help of tentacles. Bacteria were found neither in integument cells nor in the intestinal epithelium. Phylogenetic and cluster analyses revealed significant differences in the taxonomic composition of the microbiomes of T. cf. stroemii worms from the soil microbiome and allowed us to determine specific components of the microbiomes of intestines and tentacles, whereas the microbiomes of bottom sediments and worm tubes appeared to be similar. The microbiomes of the tubes are dominated by Pseudomonadota, Desulfobacterota and Bacteroidota. While the intestines are home to Pseudomonadota, Actinomycetota, Bacillota, Cyanobacteriota, Chloroflexota and Planctomycetota, this bacterial community is very different from the microbiomes both of the surrounding sediment and the tentacles. The microbiome of the tentacles of T. cf. stroemii differs significantly from that of the surrounding soil, tube and intestine, as it contains Pseudomonadota, Bacillota and Bacteroidota, in addition to a significant number of representatives of the archaeal superfilium DPANN observed in two samples. Modern technologies for studying microbiomes demonstrate the presence of specific communities of microorganisms associated with the study species, with a combination of morphological and molecular methods being promising for studying the microbiomes associated with marine annelids and their functional relationships with the animals.