Sponges (phylum Porifera) are ancient, marine and inland water, filter feeding metazoans. In recent years, diseased sponges have been increasingly occurring in marine and freshwater environments. Endemic freshwater sponges of the Lubomirskiidae family are widely distributed in the coastal zone of Lake Baikal. The strain Janthinobacterium sp. SLB01 was isolated previously from the diseased sponge Lubomirskia baikalensis (Pallas, 1776), although its pathogenicity is still unknown. The aim of this study was to confirm whether the Janthinobacterium sp. strain SLB01 is the pathogen found in Baikal sponge. To address this aim, we infected the cell culture of primmorphs of the sponge L. baikalensis with strain SLB01 and subsequently reisolated and sequenced the strain Janthinobacterium sp. PLB02. The results showed that the isolated strain has more than 99% homology with strain SLB01. The genomes of both strains contain genes vioABCDE of violacein biosynthesis and floc formation, for strong biofilm, in addition to the type VI secretion system (T6SS) as the main virulence factor. Based on a comparison of complete genomes, we showed the similarity of the studied bacterial strains of Janthinobacterium spp. with the described strain of Janthinobacterium lividum MTR. This study will help expand our understanding of microbial interactions and determine one of the causes in the development of diseases and death in Baikal sponges.
Keywords: Janthinobacterium sp. strain SLB01; biofilm; complete genomes; pathogen; sponge L. baikalensis; violacein.