Baikal endemic sponge disease and anthropogenic factor

This article presents the results of observations of the state of the Baikal endemic sponge fauna (Fam. Lubomirskiidae) in the five-year dynamics against the background of their mass mortality. We indicate the change in the projective bottom cover with healthy and diseased sponges at two sites that are radically different from each other in the level of anthropogenic pressure. We also analyse the types of diseases and sponge species exposed to these at the study sites. We observe a significant decrease in the area of the projective bottom cover with healthy sponges both at the site experiencing heavy anthropogenic pressure and at the site where it is almost absent. However, our data have indicated great influence of the anthropogenic factor on the course of the disease and death of sponges. Degradation of sponges at the anthropogenically unfavourable site began much earlier than that at the site with the minimum anthropogenic impact. The most common species are the most susceptible to all types of diseases. At the same time, there is a catastrophic decrease in the abundance of the only branching species in Lake Baikal, Lubomirskia baikalensis.

Microbiome analysis of healthy and diseased sponges Lubomirskia baicalensis by using cell cultures of primmorphs

Endemic sponges (Demosponges, Lubomirskiidae) dominate the fauna of the littoral zone of Lake Baikal. These freshwater sponges live in symbiosis with diverse eukaryotes and prokaryotes, including chlorophyll-containing microalgae. Within the last 5 years, the incidence of sponge disease and mortality events in Lake Baikal has increased. The etiology and ecology of these events remain unknown, in part because of the lack of models to study sponge-microbe interactions. In this work, we tested the use of primmorph cell cultures of Lubomirskia baicalensis as a tool for investigating the microbiomes of sponges. We infected primmorphs, cultured in vitro, with samples from diseased sponges and observed, by microscopy, disease symptoms, including loss of green symbionts, associated with mass die-off events. Subsequent sequencing of 16S rRNA gene fragments revealed that the microbiome community of healthy sponge and primmorphs formed a group separate from the community of diseased sponges and infected primmorphs. This confirms the suitability of the primmorph cell culture as a model sponge system. We also discovered mass mortality of green symbionts (Chlorophyta) was associated with a shift in the microbial communities of sponges/primmorphs. Microbes in diseased sponges, and infected primmorphs, belonged mainly to the phyla Bacteroidetes and Proteobacteria and these families Flavobacteriaceae, Burkholderiaceae, and Moraxellaceae. Primmorphs cell culture may provide a model to study interactions between these bacteria and their host and elucidate the cause of mass mortality events.

The signs of adaptive mutations identified in the chloroplast genome of the algae endosymbiont of Baikal sponge.

Background: Monitoring and investigating the ecosystem of the great lakes provide a thorough background when forecasting the ecosystem dynamics at a greater scale. Nowadays, changes in the Baikal lake biota require a deeper investigation of their molecular mechanisms. Understanding these mechanisms is especially important, as the endemic Baikal sponge disease may cause a degradation of the littoral ecosystem of the lake. Methods: The chloroplast genome fragment for the algae endosymbiont of the Baikal sponge was assembled from metagenomic sequencing data. The distributions of the polymorphic sites were obtained separately for the genome fragments from healthy, diseased and dead sponge tissues. Results: The distribution of polymorphic sites allows for the detection of the signs of extensive mutations in the chloroplasts isolated from the diseased sponge tissues. Additionally, the comparative analysis of chloroplast genome sequences suggests that the symbiotic algae from Baikal sponge is close to the Choricystis genus of unicellular algae. Conclusions: Mutations observed in the chloroplast genome could be interpreted as signs of rapid adaptation processes in the symbiotic algae. The development of sponge disease is still expanding in Baikal, but an optimistic prognoses regarding a development of the disease is nevertheless considered.

Microbiome analysis of healthy and diseased sponges Lubomirskia baicalensis by using cell cultures of primmorphs

Background. Freshwater sponges (Demosponges, Lubomirskiidae) are dominated in the littoral zone Lake Baikal in the biomass of benthic organisms and represent complex consortia of many species of eukaryotes and prokaryotes. A distinctive feature of sponges from Lake Baikal is their ability to live in symbiosis with various kinds of chlorophyll containing microalgae. Recently there have been massive diseases and the death of freshwater sponges. The etiology and ecology of these events remain unknown. Purpose. The purpose of the research was to use cell culture of primmorphs in vitro to study the microbiomes of healthy and diseased sponges to show the transmission of pathogenic agents from diseased sponges to cell cultures. Methods. The cell culture of primmorphs sponge Lubomirskia baicalensis was used to study microbiome communities in diseased and sick sponges in comparison with healthy sponge with subsequent sequencing of gene 16S rRNA and analysis of changes in microbiomes. Results. Results this study were show that use of cell culture of primmorphs in vitro is equivale of healthy sponge. Microbial community of healthy sponge and primmorphs was grouped separately from the community of diseased sponges and infected primmorphs, which confirms the suitability the cell culture of primmorphs, as a model sponge system. We found the mass death of green symbionts (Chlorophyta) and a shift in the microbial communities of sponges/primmorphs, associated with increase in relative abundant of different phyla Bacteroidetes and Proteobacteria with dominated families Flavobacteriaceae and Burkholderiaceae, Moraxellaceae in diseased sponges and infected cell cultures of primmorphs. Conclusions. This approach allowed us, using the cell culture of primmorphs, to identify potential opportunistic bacteria that can work together, which possibly enhances their action. The primmorphs system described here is a powerful new model system for studying basic mechanisms of the development of sponge disease, which will be valuable in future studies.

Microbiome analysis of healthy and diseased sponges Lubomirskia baicalensis by using cell cultures of primmorphs

Background. Freshwater sponges (Demosponges, Lubomirskiidae) are dominated in the littoral zone Lake Baikal in the biomass of benthic organisms and represent complex consortia of many species of eukaryotes and prokaryotes. A distinctive feature of sponges from Lake Baikal is their ability to live in symbiosis with various kinds of chlorophyll containing microalgae. Recently there have been massive diseases and the death of freshwater sponges. The etiology and ecology of these events remain unknown. Purpose. The purpose of the research was to use cell culture of primmorphs in vitro to study the microbiomes of healthy and diseased sponges to show the transmission of pathogenic agents from diseased sponges to cell cultures. Methods. The cell culture of primmorphs sponge Lubomirskia baicalensis was used to study microbiome communities in diseased and sick sponges in comparison with healthy sponge with subsequent sequencing of gene 16S rRNA and analysis of changes in microbiomes. Results. Results this study were show that use of cell culture of primmorphs in vitro is equivale of healthy sponge. Microbial community of healthy sponge and primmorphs was grouped separately from the community of diseased sponges and infected primmorphs, which confirms the suitability the cell culture of primmorphs, as a model sponge system. We found the mass death of green symbionts (Chlorophyta) and a shift in the microbial communities of sponges/primmorphs, associated with increase in relative abundant of different phyla Bacteroidetes and Proteobacteria with dominated families Flavobacteriaceae and Burkholderiaceae, Moraxellaceae in diseased sponges and infected cell cultures of primmorphs. Conclusions. This approach allowed us, using the cell culture of primmorphs, to identify potential opportunistic bacteria that can work together, which possibly enhances their action. The primmorphs system described here is a powerful new model system for studying basic mechanisms of the development of sponge disease, which will be valuable in future studies.

Recovery of the commercial sponges in the central and southeastern Aegean Sea (NE Mediterranean) after an outbreak of sponge disease

The distribution and biometry of commercial sponges (Porifera) in coastal areas of the central and southeastern Aegean Sea was investigated to estimate the recovery progress of the populations eight years after the first appearance of sponge disease. Signs of the disease were detected only in 1.6% of the harvested sponges. Multivariate analysis on the percentage abundance of sponges showed two distinct groups among the sixteen fishing grounds studied: the eight deep (50-110 m) and the eight shallow ones (<40 m). The group from the deep depths consisted of Spongia officinalis adriatica, S. agaricina and S. zimocca. The infralittoral zone was characterized by the presence of Hippospongia communis, S. officinalis adriatica and S. officinalis mollissima. These bath sponges showed an enhanced abundance in the eastern Cretan Sea (S. Aegean Sea). In addition, their dimensions, particularly height, increased with increasing depth. It is indicated that the hydrographic conditions prevailing in the eastern Cretan Sea affected the repopulating processes of sponge banks. In each species, the biometric characteristics of the experimental specimens were similar to those of the sponges found in the market and harvested at respective depths prior to the appearance of sponge disease.