Metabolomic and metagenomic study of Lake Baikal diseased sponges

Abstract

Widespread mortality and disease are recognized as growing problems in benthic marine coral and sponge communities across the globe and despite being extensively studied, in most cases the etiology of disease remains unknown. Since 2011, sponge communities in freshwater Lake Baikal, Siberia, Russia have been affected by an unknown agent of disease, which has been causing an array of physical disease manifestations. Unusual microbial patterns have also been noted in the lake, including cyanobacterial bloom development and cyanobacterial biofilm growth on sponges, which have concurrently occurred with the overall decline of sponge communities. We used UPLC-HR-MS/MS and 16S rRNA sequencing to profile healthy and diseased sponges in order to elucidate the role of cyanobacteria in the development of sponge disease. Diseased specimens from the four sponge genera found in the littoral zone, encompassing a broad range of disease manifestations from violet-brown spots and bacterial biofilms to bleaching, were investigated. Within the four sponge genera, we discovered slight intergenera differences between microbial community composition (at the phylum and cyanobacterial genus levels) and metabolic output in the healthy representatives. As expected, most diseased sponges showed differences in their microbial community composition (at the phylum and cyanobacterial genus levels) and metabolic profiles in comparison to their healthy counterparts, and some connections could be drawn within sponges exhibiting similar disease symptoms. Though the association between cyanobacteria and disease etiology was not supported by the results of the metabolomic and metagenomic profiling and cyanotoxins were not discovered, this thesis provides a solid foundation for the ongoing, more in-depth study of the changes occurring in the Lake Baikal littoral sponge community.