16S rRNA Gene Amplicon Sequencing Data of Bacterial Community of Freshwater Sponge Lubomirskia baicalensis.

Our study was devoted to investigating the mass disease and mortality of freshwater sponges (Lubomirskiidae) in Lake Baikal. The first sights of the disease were discovered in 2011 and were associated with a shift in sponge microbial diversity. To study the microbiome, we performed sequencing of the 16S rRNA amplicon DNA extracted from the freshwater sponges.

Genome Analysis of the Janthinobacterium sp. Strain SLB01 from the Diseased Sponge of the Lubomirskia baicalensis.

The strain Janthinobacterium sp. SLB01 was isolated from the diseased freshwater sponge Lubomirskia baicalensis (Pallas, 1776) and the draft genome was published previously. The aim of this work is to analyze the genome of the Janthinobacterium sp. SLB01 to search for pathogenicity factors for Baikal sponges. We performed genomic analysis to determine virulence factors, comparing the genome of the strain SLB01 with genomes of other related J. lividum strains from the environment. The strain Janthinobacterium sp. SLB01 contained genes encoding violacein, alpha-amylases, phospholipases, chitinases, collagenases, hemolysin, and a type VI secretion system. In addition, the presence of conservative clusters of genes for the biosynthesis of secondary metabolites of tropodithietic acid and marinocine was found. We present genes for antibiotic resistance, including five genes encoding various lactamases and eight genes for penicillin-binding proteins, which are conserved in all analyzed strains. Major differences were found between the Janthinobacterium sp. SLB01 and J. lividum strains in the spectra of genes for glycosyltransferases and glycoside hydrolases, serine hydrolases, and trypsin-like peptidase, as well as some TonB-dependent siderophore receptors. Thus, the study of the analysis of the genome of the strain SLB01 allows us to conclude that the strain may be one of the pathogens of freshwater sponges.

Draft Genome Sequence of the Green Microalga Chlorella sp. Strain BAC9706, Isolated from Lake Baikal, Russia.

Green algae of the phylum Chlorophyta are the most widespread autotrophic picoplankton in Lake Baika (Russia). To expand our molecular biological knowledge of these microalgae and compare them in the future with an endosymbiotic strain, we present here the draft genome sequence of Chlorella sp. strain BAC9706.

Draft Genome Sequence of Flavobacterium sp. Strain SLB02, Isolated from the Diseased Sponge Lubomirskia baicalensis.

There are significant changes in the consortium of microorganisms of freshwater Baikal sponges during their mass death, which began in 2011. The alleged cause of disease is a significant increase in the number of opportunistic microorganisms. Here, we report the draft genome sequence of Flavobacterium sp. strain SLB02.

Draft Genome Sequence of Janthinobacterium sp. Strain SLB01, Isolated from the Diseased Sponge Lubomirskia baicalensis.

The draft genome sequence of Janthinobacterium sp. strain SLB01, a violacein-producing psychrotolerant bacterium isolated from the diseased sponge Lubomirskia baicalensis, was determined. We identified five genes encoding VioA, VioB, VioC, VioD, and VioE proteins related to violacein biosynthesis that were like those identified in published Janthinobacterium lividum strains MTR and RIT308.

First report on chitinous holdfast in sponges (Porifera).

A holdfast is a root- or basal plate-like structure of principal importance that anchors aquatic sessile organisms, including sponges, to hard substrates. There is to date little information about the nature and origin of sponges' holdfasts in both marine and freshwater environments. This work, to our knowledge, demonstrates for the first time that chitin is an important structural component within holdfasts of the endemic freshwater demosponge Lubomirskia baicalensis. Using a variety of techniques (near-edge X-ray absorption fine structure, Raman, electrospray ionization mas spectrometry, Morgan-Elson assay and Calcofluor White staining), we show that chitin from the sponge holdfast is much closer to α-chitin than to ß-chitin. Most of the three-dimensional fibrous skeleton of this sponge consists of spicule-containing proteinaceous spongin. Intriguingly, the chitinous holdfast is not spongin-based, and is ontogenetically the oldest part of the sponge body. Sequencing revealed the presence of four previously undescribed genes encoding chitin synthases in the L. baicalensis sponge. This discovery of chitin within freshwater sponge holdfasts highlights the novel and specific functions of this biopolymer within these ancient sessile invertebrates.

Long-term cultivation of primmorphs from freshwater Baikal sponges Lubomirskia baikalensis.

The work was aimed at performing long-term cultivation of primmorphs in vitro from freshwater sponge Lubomirskia baikalensis (Pallas 1776), collected from Lake Baikal, obtaining its long-term primmorph culture in both natural (NBW) and artificial (ABW) Baikal water and at identifying the impact of different environmental factors on formation and growth of primmorphs. The first fine aggregates of L. baikalensis are formed in vitro 10-15 min after dissociation of sponge cells. Epithelization of aggregates begins 4 h later after the dissociation. Young primmorphs are formed 1 or 2 days later. The surface of primmorphs is covered with a layer of exopinacocytes. The primmorphs remain viable for more than 10 months at 3-6 °C. Over 50% of primmorphs in NBW and 25% in ABW are attached to the substrate and grow like adult sponges. Thus, the long-term primmorph cultivation in vitro allows the creation of a controlled live model system under experimental conditions. The results of this work will allow the creation of a cell culture collection of Baikal freshwater sponges for studying morphogenesis of primmorphs during cultivation at different stages and transdifferentiation of their cells, physiological functions of sponge cells, processes of spiculogenesis, identification of proteins involved in biomineralization process, decoding of their genes, as well as a spectrum of secondary metabolites.