Microbiome Changes of Endemic Lake Baikal Sponges during Bleaching Syndrome Development

Valeria Itskovich,Olga Glyzina,George Seghal Kiran,Oxana Kaluzhnaya,Joseph Selvin,Ragothaman Prathiviraj

doi:10.3390/d13120653

Abstract

The sponge (Porifera) microbiome is an indicator of both natural and anthropogenic stressors. Studying Baikal sponge microbial communities could help reveal if there is a connection between bacterial symbionts and a mass sponge bleaching event that was recently detected; 16S rRNA sequencing was performed among healthy and diseased freshwater sponges of Lubomirskia baikalensis and Baikalospongia intermedia, which were collected from Lake Baikal, Russia. A phylum-based taxonomic classification showed that Chlorophyta, Acidobacteria, Bacteroidetes, Actinobacteria and Cyanobacteria were most abundant across samples. When comparing healthy and diseased L. baikalensis samples, large variations in microbial composition were found at the phylum level. Comparative analyses, which were performed for the first time for B. intermedia, showed a decrease in Chlorophyta (unicellular green algae) and an increase in Bacteroidetes and Cyanobacteria in diseased specimens. At the genus level, the Opitutus (Verrucomicrobia), Planctomyces, and Nitrospira content increased in all diseased sponges, which reflected a general tendency toward an increase in Cyanobacteria in diseased sponges. Comparative analysis of the diseased and healthy sponge metagenomes showed that diseased sponges underwent various nonspecific changes in bacterial composition. The bacterial community composition is probably influenced by sponge type and degree of disease affection.

Highlights

We identified that the species count is increased in bleached samples of L. baikalensis (LBB1) upon 360,000 sequence reads
Among healthy L. baikalensis, there are significant differences in the have shown that, among healthy L. baikalensis,there are significant differences in the content of Chlocontent of Chlorophyta, Bacteroidetes, Cyanobacteria and other phyla
With our limited number of samples, we demonstrate a difference in the microbiome of healthy L. baikalensis collected in different seasons, but more samples need to be analyzed

Summary

Introduction

Sponges (Porifera) constitute an important component of marine and freshwater ecosystems because of their species’ richness, abundance, and key functional roles [1,2,3,4].Sponges are inhabited by a wide variety of microorganisms, including archaea, heterotrophic bacteria, cyanobacteria, microscopic algae (green, red, cryptophytic, diatoms), dinoflagellates, and fungi; these microorganisms account for up to 50% of their biomass [5,6,7].Sponge bacterial communities tend to be dominated by Gamma-, Alphaproteo-bacteria, Actinobacteria, Cyanobacteria, Chloroflexi and Poribacteria [8,9,10].Sponge symbiotic communities are based on complex functional relationships that were formed during the adaptation of the entire community to environmental conditions [11,12]. Sponges (Porifera) constitute an important component of marine and freshwater ecosystems because of their species’ richness, abundance, and key functional roles [1,2,3,4]. Sponges are inhabited by a wide variety of microorganisms, including archaea, heterotrophic bacteria, cyanobacteria, microscopic algae (green, red, cryptophytic, diatoms), dinoflagellates, and fungi; these microorganisms account for up to 50% of their biomass [5,6,7]. Sponge bacterial communities tend to be dominated by Gamma-, Alphaproteo-bacteria, Actinobacteria, Cyanobacteria, Chloroflexi and Poribacteria [8,9,10]. Sponge symbiotic communities are based on complex functional relationships that were formed during the adaptation of the entire community to environmental conditions [11,12]. Metagenomic approaches make it possible to investigate complex microbial communities and their interactions with the host and with the environment

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Results

Discussion

Conclusion