The gemmules microbiome project

Description of the project:

In order to overcome the changing temperature conditions during the winter, freshwater sponges are able to form internal dormant buds, named gemmules, that can survive colder temperatures, and will grow out to new sponges when the weather becomes more favorable. While the sponge microbiome is known to play an important role for the host functioning, little is known about its acquisition and assembly during the first life stages following the gemmule hatching.

Objectives:

The goal of this study was to get a better understanding of the changes of the microbiome of the freshwater sponge Spongilla lacustris from gemmule to the first stages of cell proliferation, oscula forming and sponge development. Both vertical and horizontal transfer of the microbiome were considered, with possible acquisition of the microbial community from the maternal tissues, and/or planktonic prokaryotes from the surrounding freshwater. To achieve this, the gemmules from S. lacustris were collected in the peri-urban area of Oegstgeest (The Netherlands) and were washed with either Strekal’s medium or hydrogen peroxide before handling. These two first conditions were conducted to investigate the importance of the microbiome from the maternal tissue attached to the gemmules, since the hydrogen peroxide sterilizes the gemmule surface. The gemmules were hatched in a controlled setting, using a set temperature and light/dark cycles and two different growth media. For the media, canal water was filtered with two different pore sizes (0.45 or 0.2 µm) to hatch gemmules with free-living prokaryotes or without prokaryotes, in order to investigate the importance of planktonic prokaryotic colonizers.